Stephen A. Boorjian, MD, FACS

• Carl Rosen Professor of Urology
• Mayo Clinic Rochester, Minnesota

In the early 1980s angiographic and vascular balloons were introduced into urologic practice menopause 3 weeks period generic 70 mg alendronate fast delivery, and the technique of balloon dilation with temporary internal stenting became an accepted mode of treatment (Banner et al breast cancer awareness merchandise buy alendronate line. As for any patient with a ureteral stricture women's health center mount carmel east 70 mg alendronate buy visa, the indications to intervene include functionally significant obstruction women's health big book of exercises hard body workout discount alendronate 70 mg buy line. Contraindications to this approach include active infection or a stricture longer than 2 cm because dilation alone will rarely be successful in this setting menstruation not flowing well buy generic alendronate 35 mg. A retrograde approach is indicated whenever access across the strictured area is easily accomplished using transurethral techniques. In general, the procedure begins with a retrograde pyelogram performed under fluoroscopic control to precisely delineate the site and length of stricture. A floppy-tipped guidewire is passed in a retrograde fashion across the strictured area and coiled proximally in the pyelocalyceal system. This is most easily accomplished by passing an open-ended catheter up to the level of the stricture to use as a guide for the hydrophilic or floppy-tipped wire. Passage of the open-ended catheter through the strictured area over the wire will then aid subsequent passage of a balloon catheter. Techniques for bypassing difficult areas of obstruction have been described in detail (Mata et al. At this point, the open-ended catheter is withdrawn and replaced with a high-pressure, 4-cm­long, 5- to 8-mm balloon. Under fluoroscopic control, the balloon catheter is positioned across the strictured area, with proper position ensured by visualization of radiopaque markers at the tips of the balloon. A guidewire is still in place, and this is used to pass an internal stent, which is left indwelling for 2 to 4 weeks. Follow-up diuretic renography is usually performed approximately 1 month after stent extraction and at 6- to 12-month intervals thereafter. Occasionally, access across the involved area cannot be obtained using fluoroscopic control alone. In such cases direct ureteroscopic visualization can aid initial passage of the guidewire, and the procedure can be continued as described. Alternatively, a low-profile balloon can be passed through the ureteroscope and the stricture dilated under direct vision. In such cases, access can be obtained using an antegrade approach and fluoroscopic control (Banner and Pollack, 1984; Mitty et al. Percutaneous nephrostomy drainage is established; in cases associated with infection or compromised renal function, percutaneous drainage alone is instituted to allow resolution of infection and return to baseline renal function. Once that is accomplished, the percutaneous tract is used for access for a fluoroscopically or ureteroscopically guided approach. Under fluoroscopic guidance, an antegrade contrast agent study is used to definitively define the site and length of the stricture. A waist is evident at the level of the stricture during initial balloon inflation. The balloon catheter is withdrawn over a wire and replaced with an internal stent, and a nephrostomy tube is also left indwelling. A follow-up nephrostogram is obtained within 24 to 48 hours to ensure proper positioning of a functional internal stent, and at that time the nephrostomy tube can be removed. Alternatively, access can be maintained by the use of an internal-external stent, which can be capped to allow internal drainage. Initial reports of retrograde and antegrade balloon dilation of ureteral strictures suggested that results were better when the stricture was anastomotic and of relatively short duration and length (Chang et al. Goldfischer and Gerber (1997) reviewed the literature regarding results of balloon dilation of ureteral strictures and found reported success rates ranging from 50% to 76%. In that review, the best results were obtained in patients with iatrogenic, nonanastomotic strictures such as those who had undergone ureteroscopic instrumentation. In that setting, a success rate of 85% was achieved compared with a rate of 50% for anastomotic strictures. As in other series, balloon dilation was more successful for patients with relatively short strictures. In addition, these authors noted the significance of an intact vascular supply on the success of this procedure. One series of transplant ureteral strictures in which percutaneous balloon dilation was used in 14 transplant patients demonstrated 79% success at 29 months. Notably, these were short, anastomotic strictures in patients on immunosuppression (Voegeli et al. Others report endoureterotomy as the primary treatment option in such cases (Duty et al. In experimental models, balloon dilation created longitudinal incisions similar to endoureterotomy, explaining some of the success seen with use of balloon dilation in ureteral strictures (Nakada et al. Endoureterotomy Endoluminal ureteral incision is a logical extension of balloon dilation for "minimally invasive" management of ureteral strictures. As for balloon dilation, access to and across the strictured area can be obtained in a retrograde or antegrade fashion, although a retrograde approach is preferred because it is less invasive. The procedure is performed under direct vision using ureteroscopic control or it can be guided fluoroscopically using the hot-wire cutting balloon catheter. In general, radiographic follow-up using diuretic renography is recommended for up to 2 years to detect most late failures (Wolf et al. A retrograde study is performed under fluoroscopic control at the outset of the procedure. Whenever possible, a floppy-tipped guidewire or hydrophilic glidewire is passed across the level of obstruction as outlined earlier. If a wire cannot be passed across the strictured area using fluoroscopic control alone, the flexible ureteroscope is passed to the level of obstruction, and the guidewire is advanced through the ureteroscope across the involved area under direct vision. The ureteroscope is then withdrawn, but a safety wire is always left in place across the stricture. The ureteroscope is then reintroduced and passed alongside the guidewire to the level of obstruction. The position for the endoureterotomy incision is chosen as a function of the level of the ureter involved. In general, lower ureteral strictures are incised in an anteromedial direction, taking care to stay away from the iliac vessels. In contrast, upper ureteral strictures are incised laterally or posterolaterally, again away from the great vessels (Meretyk et al. Today, the holmium laser represents the dominant approach to endoscopic incisions. In all cases the incision is made from the ureteral lumen out to periureteral fat in a full-thickness fashion. Proximally and distally, the endoureterotomy should encompass 2 to 3 mm of normal ureteral tissue. Similarly, the strictures may be balloon dilated after endoincision, to enlarge the incision. Once the endoureterotomy incision is complete, the remaining guidewire is used to pass an internal stent. In general, the larger-diameter stents should be considered because larger stents (8 to 12 Fr) have been associated with improved results (Hwang et al. Steroids and other biologic response modifiers may eventually have a role in the future in managing select strictures. There is early evidence that strictures related to stone impaction and prior stone treatment may have lower success rates (56% in one series) than typical benign strictures (Gdor et al. As ureteroscopy and laser lithotripsy continue to grow, more strictures involving impacted stones may be encountered, and this may become a growing clinical problem. The familiarity of ureteroscopy, coupled with relative availability of the holmium laser, makes retrograde laser endoureterotomy an attractive initial management strategy for ureteral strictures less than 2 cm in length. When direct visual ureteroscopic access to the strictured area cannot be accomplished in a retrograde fashion, an antegrade approach may be used. Nephrostomy tube drainage is instituted, and any associated infection or compromised renal function is allowed to resolve before definitive incision. The percutaneous tract is dilated to a size large enough to allow a working sheath through which a flexible ureteroscope is passed. A safety wire should be in place at all times alongside the ureteroscope, across the obstructed area and coiled distally in the bladder. Rarely, a ureteral stricture is associated with an area of complete ureteral obliteration across which a wire cannot be passed to allow subsequent balloon dilation or ureteroscopic endoureterotomy. In cases where surgery is high risk, a combined retrograde and antegrade approach has been described (Beaghler et al. The obstructed area is defined radiographically with a simultaneous antegrade and retrograde pyelogram. Endoscopes are passed simultaneously in a retrograde and an antegrade manner, and the two opposing ureteral ends are localized under fluoroscopic guidance. A working guidewire is then passed from one end of the ureter, through and through to the other lumen, using a combination of fluoroscopic and direct visual control. For completely obliterated ureteral segments, this is most easily accomplished using the stiff end of a guidewire passed through a semirigid ureteroscope via the retrograde approach, although when a semirigid ureteroscope cannot be placed, a flexible ureteroscope or even an open-ended ureteral catheter can be used to stabilize the wire from above or below. The ureteral segments are aligned as closely as possible under endoscopic and fluoroscopic guidance, and the light source to one of the ureteroscopes is turned off. The light from the opposite ureteroscope is then used to aid incisional restoration of urinary continuity. The strictured area is then recannulated using the stiff end of a guidewire, a small electrocautery electrode, or holmium laser. Once throughand-through control is obtained with a guidewire, a stent is passed and left in place for 8 to 10 weeks. As with other endourologic approaches to ureteral strictures, success rates are inversely related to the length of the strictured area. Although success rates may be uncertain, internalization of urinary flow, even when dependent on long-term stent placement, can be a quality-of-life advantage for certain high-risk patients. Surgical Repair Before any surgical repair, it is essential to conduct careful evaluation of the nature, location, and length of the ureteral stricture. Preoperative assessment typically includes an intravenous pyelogram (or antegrade nephrostogram) and a retrograde pyelogram if indicated as the location and length of the stricture heavily influence the options for repair. On the basis of such information, the appropriate surgical procedure can then be planned for the patient (Table 89. On the other hand, a lower ureteral stricture is usually best managed by ureteroneocystostomy with or without a psoas hitch or Boari flap. In the transplant setting, a donor ureteral stricture may be managed by a ureteroureterostomy to a healthy, native ureter. Because tension on the anastomosis almost always leads to stricture formation, only short defects should be managed by end-to-end ureteroureterostomy. Determination of whether enough ureteral mobility can be achieved to allow tension-free ureteroureterostomy usually cannot be made until the time of surgery, and thus the urologist must be prepared to pursue other options. If the patient has sustained an iatrogenic ureteral injury from a previous surgery performed through a Pfannenstiel incision, the same incision may be used for the ureteral reconstruction. It is critical to assess the renal unit for function before starting treatment because endourologic therapies typically require 25% function of the ipsilateral moiety. Innovations in stents and stent techniques have led to long-term success in select patients with malignant ureteral obstruction. Contraindications to this approach include active infection or a stricture longer than 2 cm. In contrast, upper ureteral strictures are incised laterally or posterolaterally, away from the great vessels. Extraperitoneal dissection is usually performed except in cases of transperitoneal surgical ureteral injury. After surgical incision, the retroperitoneal space is developed as the peritoneum is mobilized and retracted medially. A Penrose drain or vessel loop may be placed around the ureter to assist its atraumatic handling. Care should be taken to preserve its adventitia, which loosely attaches the blood supply to the ureter. During ureteral dissection and mobilization, enough mobility must be achieved to avoid tension after the excision of the diseased ureter. With a gunshot injury, devitalized tissue and an adjacent segment of normal-appearing ureter should be excised to eliminate late ischemia and stricture formation from the blast effect. Once both ends of the ureter have been adequately trimmed to healthy areas, mobilized, and correctly oriented, they are spatulated for approximately 5 to 6 mm. If a grossly dilated ureter is involved, it may be transected obliquely and not spatulated to match the circumference of the nondilated segment. A fine, absorbable suture is placed in the corner of one ureteral segment and the apex of the other, and the two ends of the suture are tied outside the ureteral lumen. A double-J ureteral stent should be placed before completion of the anastomotic closure. Stent placement can be facilitated by passing the wire through one of the side holes in the middle of the stent to straighten and stiffen the stent enough to permit it to pass. Intraoperative photograph of a patient undergoing a robotic right ureteral neocystostomy for distal ureteral stricture seen in computed tomography urography (A). A laparoscopic or robotic approach may be offered to patients with ureteral stricture disease. In this case, ureteroureterostomy was performed laparoscopically over a ureteral stent after resection of the obstructed ureteral site. Most of the studies since that time consist of single case reports or small series. Several reports of laparoscopic ureteroureterostomy to unobstruct a duplicated system in the pediatric population have appeared (Piaggio et al.

Calyces arise on either side of the pelvis women's health clinic modesto ca order 70 mg alendronate free shipping, with some of them arising medial to the renal pelvis menopause weight loss alendronate 70 mg purchase online. Computed tomography urography (C) shows malrotation and ectopia of the right kidney menopause refers to 70 mg alendronate fast delivery. The right kidney appears in the right pelvic region and its pelvis appears malrotated with the renal pelvis facing anteriorly with a short ureter menstruation headache causes discount alendronate 35 mg buy on line. Computed tomography angiography with volume-rendered three-dimensional image (A) and axial view (B) of a horseshoe kidney showing the aberrant vasculature menstruation 4 times a month buy generic alendronate on-line. Chapter 84 Inferior vena cava Right and left inferior phrenic arteries Celiac trunk Right superior suprarenal arteries Right middle suprarenal artery Right suprarenal vein Right inferior suprarenal artery Surgical, Radiologic, and Endoscopic Anatomy of the Kidney and Ureter Esophagus Left inferior phrenic vein Left superior suprarenal arteries Left middle suprarenal artery Left suprarenal vein Left inferior suprarenal artery 1869. Note that the posterior segmental artery is usually the first branch of the main renal artery and it extends behind the renal pelvis. The left renal vein traverses the acute angle between the superior mesenteric artery anteriorly and the aorta posteriorly. In thin adolescents, the left renal vein may get compressed between the superior mesenteric artery and aorta, causing nutcracker syndrome. In approximately 15% of the patients, supernumerary renal veins are seen and often are retroaortic when present on the left. Accessory renal veins are more common on the right side, and the most common anomaly of the left renal venous system is the circumaortic renal vein, reported in 2% to 16% of patients. The retroaortic renal vein is less commonly seen than the circumaortic vein, in which the left renal vein bifurcates into ventral and dorsal limbs, which encircle the abdominal aorta. However, the main renal artery is often difficult to identify at baseline ultrasonography. Magnetic resonance arteriography uses no ionizing radiation, does not require arterial access, and includes different imaging techniques to visualize renal vasculature. Contrast material can give faster, better resolution and more accurate images without artifacts. Renal lymphatics are embedded in the periarterial loose connective tissue around the renal arteries and are distributed primarily along the interlobular and arcuate arteries in the cortex. The arcuate lymphatic vessels drain into hilar lymphatic Chapter 84 Surgical, Radiologic, and Endoscopic Anatomy of the Kidney and Ureter 1870. No significant difference in position was observed in each vessel grouping (superior vessel group of right gonadal vein vs. Retroperitoneal lymph node dissection: anatomical and technical considerations from a cadaveric study. Accessory renal arteries are seen in 25% to 28% of patients and are considered the sole arterial supply to a specific portion of the renal parenchyma. Venous drainage of the left kidney showing potentially extensive collateral circulation. As these lymphatics exit the renal hilum, they join branches from the renal capsule, perinephric tissues, renal pelvis, and upper ureter, where they empty into lymph nodes associated with the renal vein. Left lymphatic drainage primarily goes into the left lateral para-aortic lymph nodes (between the inferior mesenteric artery and diaphragm), with occasional additional drainage into the retrocrural nodes or directly into the thoracic duct above the diaphragm. Right renal lymphatic drainage primarily goes into the right interaortocaval and right paracaval lymph nodes (between the common iliac vessels and diaphragm), with occasional additional drainage from the right kidney into the retrocrural nodes or the left lateral para-aortic lymph nodes. The pelvicalyceal system may have the configuration of either a true pelvis or divided double calyceal pelvis. The true pelvis is the classic type in which the calyces drain directly through elongated necks into an elongated pelvis. This pelvis may be completely imbedded within the renal sinus (intrarenal pelvis) or mostly outside it (extrarenal pelvis). The renal pelvis is roughly pyramidal, with the base facing the parenchyma and the apex funneling down into the ureter. In a divided (duplex) pelvis, it is divided at the hilum into upper and lower portions and drains a higher number of calyces than a normal pelvis. Its lower part is usually shorter but larger and often drains the hilar and the lower pole calyces. During percutaneous endoscopic evaluation of the kidney, the existence of a duplex pelvis should be considered if upper or lower pole calyces cannot be accessed through a particular calyceal access. When a duplex system is suspected during ureteroscopy, retrograde pyelography could be performed to illustrate the anomalous pelvicalyceal system. Sympathetic preganglionic nerves originate from the eighth thoracic through first lumbar spinal segments, with contributions mainly from the celiac plexus and a lesser contribution from the greater splanchnic, intermesenteric, and superior hypogastric plexuses. Postganglionic sympathetic nerve fiber distribution generally follows the arterial vessels throughout the cortex and the outer medulla. These postganglionic fibers travel to the kidney via the autonomic plexus surrounding the renal artery. In addition, parasympathetic fibers from the vagus nerve travel with the sympathetic fibers to the autonomic plexus along the renal artery. The renal sympathetics cause vasoconstriction, and the parasympathetics cause vasodilation. These calyces vary considerably not only in numbers but also in size and shape because of the different numbers of papillae they receive. Chapter 84 Anterior vagal trunk Posterior vagal trunk Greater thoracic splanchnic nerve Celiac ganglia and plexus Lesser thoracic splanchnic nerve Superior mesenteric ganglion Least thoracic splanchnic nerve Aorticorenal ganglion Renal plexus and ganglion Second lumbar splanchnic nerve Renal and upper ureteric branches from intermesenteric plexus Intermesenteric (aortic) plexus Surgical, Radiologic, and Endoscopic Anatomy of the Kidney and Ureter 1872. Fifteen minutes after contrast injection, a panoramic radiograph of the whole urinary tract can be obtained; the bladder finally appears 20 to 30 minutes after contrast injection. Absence of contrast excretion 24 hours after intravenous contrast injection indicates a nonfunctioning kidney. The pelvicaliceal anatomy is variable, and no simple rule defines calyceal organization. Congenital variants of the pelvicalyceal system are common, representing approximately 4% of the population. The renal pelvis may be completely intrarenal, completely extrarenal, or a combination of both (Friedenberg and Dunbar, 1990). The infundibula insert directly into the extrarenal pelvis, giving the impression of a dilated pelvis. Receiving the tip of renal papilla, the renal calyx is a concave structure with two side projections, the fornices, which surround the papilla of the renal medulla. Multiple single calyces fail to divide completely, forming a larger compound calyx that normally can be observed in the upper and lower poles of the kidneys. Each kidney contains an average of 7 to 9 calyces, although this number may vary considerably from 4 to 19 or even more. Megacalycosis represents a nonobstructive asymptomatic congenital dilation of some or all renal calyces, while the renal pelvis and ureter are normal. It involves all calyces uniformly and usually is associated with a greater number of calyces than normal. Calyceal diverticula represent a focal extrinsic dilation of a renal calyx that is connected to the calyceal fornix and projects into the renal cortex, not into the medulla. The renoureteral unit may show duplication anomalies, including a bifid renal pelvis and complete or incomplete ureteral duplication. Two separate pyelocalyceal collecting systems may be present in one kidney, ranging from a bifid pelvis to a bifid ureter (ureteropelvic duplication). In the retroperitoneum, the ureter is situated just lateral to the tips of the transverse processes of the lumbar vertebrae. The ureters occupy a sagittal plane that intersects the tips of the transverse processes of these lumbar vertebrae. The ureter is arbitrarily divided into proximal (upper), middle (over the sacrum), and distal (lower) segments. However, according to international anatomic terminology the ureter consists of abdominal (from renal pelvis to iliac vessels), pelvic (from iliac vessels to the bladder), and intramural segments. The abdominal parts of the ureters are adherent to the retroperitoneum throughout their entire course and extend from the renal pelvis to the pelvic brim. From the back, the surface anatomy of the ureter corresponds to a line joining a point 5 cm lateral to the L1 spinous process and the posterior superior iliac spine. The bifurcation of the common iliac vessels is used intraoperatively as a landmark to look for the ureter. The right ureter begins behind the descending part of the duodenum, where it is crossed by the gonadal vessels (testicular or ovarian), which is called "water under the bridge. The gonadal vessels cross the left ureter after running parallel to it for a small distance. The inferior mesenteric artery and its terminal branch, the superior rectal artery, follow a curved course close to the left ureter. Therefore, as the left ureter approaches the pelvis, it is crossed by the left colic vessels, the sigmoid colon, and its mesocolon. Just above the entry to the pelvis, the ureter is still covered by peritoneum by virtue of the ureteral fold. This location at the pelvic brim represents one of the most common areas of ureteral injury. Furthermore, the close relationship of the ureter with the terminal ileum, appendix, right and left colons, and sigmoid colon makes it susceptible for encroachment of inflammatory and malignant processes, resulting in clinical presentations ranging from microhematuria to ureteral obstruction or even fistulae. The pelvic segment of the ureter is approximately 15 cm long-half of its total length. This crossover point is usually at the bifurcation of the common iliac artery into the internal and external iliac arteries, making this a useful landmark for pelvic procedures. The ureter then runs downward and laterally toward the ischial spine on the lateral pelvic wall along the anterior border of the greater sciatic notch, dorsally accompanied by the internal iliac artery and its visceral branches and the venous plexuses as well. At the ischial spine, the ureter turns medially to descend in the endopelvic fascia with branches of the hypogastric nerves. At the lateral wall of the pelvis, this part of the ureter crosses the obturator artery, vein, and nerve. In males, the vas deferens loops medially over this part while the ureter passes the ampulla of the vas deferens and the seminal vesicles just before it enters the bladder. In females, the descending part of the pelvic segment of the ureter courses posterior to the ovary to form the posterior boundary of the ovarian fossa. The ureter then passes through the base of the broad ligament and swings in a convex curve to cross under the uterine vessels ("water under the bridge") in a sagittal direction approximately 1. The terminal ureter runs forward, accompanied by the neurovascular bundle of the bladder and passes the anterior vaginal fornix just before entering the bladder. This close proximity of the ureter to the uterine vessels is the cause of ureteral injuries during gynecologic procedures. In the case of vaginal surgery, there is a high risk for injury, especially for the left ureter that crosses the anterior vaginal fornix closer than the right ureter. The Waldeyer muscle bundles of the ureter coalesce with those of the detrusor muscle of the bladder wall. Therefore reflux of urine from the bladder to the ureter is prevented during increased intravesical pressure, such as during micturition. Another important feature of the 3D course of the ureter that is critical to appreciate and follow during rigid ureteroscopy is the angulation of the ureter as it courses through the retroperitoneum. When approached from the retrograde direction, the ureter courses anterolaterally as it goes along the lateral pelvic wall. Then, as it crosses the pelvic brim, it angulates posteriorly to continue as the proximal ureter. Following the 3D course of the ureter along a safety guidewire reduces the risk for perforation, especially in patients with large impacted stones. Radiologic Anatomy of the Ureter the ureter could be delineated by excretory urography during expiration, because it may be kinked during inspiration as a result of downward movement of the kidney (Friedenberg and Dunbar, 1990). Chapter 84 Surgical, Radiologic, and Endoscopic Anatomy of the Kidney and Ureter 1873. The course of the ureter and its bilateral symmetry are subject to great variability. It may descend laterally away from the margin of the transverse processes or be displaced medial to the renal pedicle. A medially displaced right ureter might normally be seen in young black males (Adam et al. The right ureter may run medially behind the vein at the level of third lumbar vertebra before it returns to its lateral position. The entire length of the ureter is rarely seen in a single film of the excretory urography because of its peristaltic activity. Similarly, crossing vessels may compress the ureter and simulate areas of stricture. Therefore the diagnosis of a ureteral stricture should not be based on a single film of excretory urography with the presence of ureteral dilatation proximal to the site of narrowing. Complete duplication results from the development of a second ureteric bud, and the two ureters are inserted into the bladder separately. The partial type results from redundant duplication of the single ureteric bud in which the two ureters join together above the bladder to from a single stump draining into the bladder. Complete ureteral duplication with a common or ectopic entry of the upper pole moiety is less common than incomplete duplication. The ureter draining the upper segment of the kidney prevalently inserts in the bladder inferior and medial to the ureter draining the lower segment of the kidney (Weigert-Meyer rule). In a standard lateral view, the normal renal collecting system should not project anterior to the spine and the ureter stays behind the anterior margin of the vertebral bodies until the level of L4. After this, the ureter lies anterior to the vertebral body by approximately one-fourth the width of the vertebral body (Friedland et al.

These studies suggest that breast cancer 05 cm discount alendronate 70 mg fast delivery, in the setting of impaired ammonium excretion and increased endogenous acid production resulting from obesity and/ or insulin resistance women's health kilojoule counter buy 70 mg alendronate with amex, titratable acids make up the primary urinary buffer breast cancer yati bahar blogspot order alendronate australia, and although acid-base equilibrium can be maintained lynn women's health center boca raton alendronate 35 mg overnight delivery, it occurs at a lower urine pH than is typically maintained by ammonium breast cancer awareness socks order genuine alendronate line, which has a higher pKa. Lipotoxicity, a process whereby fat is redistributed into nonadipocyte tissues such as the heart, liver, skeletal muscle, and pancreatic beta cells, resulting in cellular injury, has been implicated in impaired insulin sensitivity, cardiac dysfunction, and hepatic steatohepatitis and has been postulated to play a role in the pathogenesis of chronic renal disease (Bagby, 2004; Wahba and Mak, 2007; Weinberg, 2006). Whether lipotoxicity plays a role in impaired ammonium excretion or increased endogenous acid production leading to low urine pH in uric acid stone formers is unknown (Sakhaee, 2009). Potential effects of the insulin-resistant state on the generation and secretion of ammonium in the proximal tubule. Interestingly, recent proteomic analysis of the matrix component of uric acid stones identified 242 unique proteins among five stones, with the largest proportion of proteins involved in the inflammation and complement pathways; the most commonly involved metabolic pathways associated with these proteins were the phospholipid and fatty acid pathways (Jou et al. As the fixed acid content of the diets increased, urinary calcium excretion increased from 103 mg/day on the vegetarian diet to 150 mg/ day on the animal protein diet (P < 0. Moreover, the animal protein­rich diet was associated with the highest excretion of undissociated uric acid and lowest excretion of citrate because of the reduction in urinary pH. Urinary crystallization studies revealed that the animal protein diet, when matched for electrolyte composition and quantity of protein with the vegetarian diet, conferred an increased risk of uric acid stones, but because of opposing factors, not of calcium oxalate or calcium phosphate stones. Urinary Lithiasis: Etiology, Epidemiology, and Pathogenesis 2029 Hyperuricosuria Hyperuricosuria is defined as urinary uric acid exceeding 600 mg/ day. Hyperuricosuria predisposes to uric acid stone formation by causing supersaturation of the urine with respect to sparingly soluble undissociated uric acid. Patients with gout and urinary uric acid levels less than 600 mg/day had significantly fewer stones than those with uric acid levels greater than 1000 mg/day (Hall et al. The causes of hyperuricosuria have been discussed previously but include dietary factors as well as acquired and hereditary diseases and defects in the urate transporter. Several factors determine the solubility of cystine, including cystine concentration, pH, ionic strength, and urinary macromolecules. The main contributor to cystine crystallization is supersaturation because there is no specific inhibitor of cystine crystallization in the urine (Pak and Fuller, 1983). Because of the poor solubility of cystine in urine, precipitation of cystine and subsequent stone formation occur at physiologic urine conditions (Joly et al. The solubility of cystine is highly pH dependent, with solubilities of 300 mg/L, 400 mg/L, and 1000 mg/L at pH levels of 5, 7, and 9, respectively (Dent and Senior, 1955). Ionic strength also influences solubility, and as much as 70 mg of additional cystine can be dissolved in each liter of solution as ionic strength increases from 0. Macromolecules such as colloid also increase cystine solubility, although the mechanism is unclear (Pak and Fuller, 1983). Low Urinary Volume All conditions that contribute to low urinary volume increase the risk of uric acid supersaturation. Likewise, high rates of uric acid stone formation have been found in populations living in warmer climates such as Israel (Shekarriz and Stoller, 2002). The two subunits form a heterodimer that resides in the apical membrane of the proximal tubule cells, and mutations in the genes of either subunit lead to cystinuria. Cystinuria is inherited as an autosomal recessive disorder (or rarely autosomal dominant with incomplete penetrance). Although there is significant loss of other dibasic amino acids, the poor solubility of cystine leads to stone formation. Cystine is a dimer composed of two cysteine molecules linked via a disulfide bond. Cystine is much less soluble than cysteine and is responsible for cystine stone formation. Cystine is reduced intracellularly to cysteine, thereby providing a favorable gradient for continued cystine reabsorption (Broer, 2008). Cystine stones are rare, occurring in the United States and Europe with an incidence of only 1 in 1000 to 1 in 17,000 (Cabello-Tomas et al. Each point represents solubility of cystine determined in a separate urine sample by incubation with an excess of solid cystine. The solubility curve of Dent and Senior (1955) and that obtained in a 5-mM sodium cacodylate solution are plotted for comparison. Homozygotes with the condition exhibit urinary cystine levels as high as 2000 µmol/g of creatinine. Although mean urinary cystine levels are significantly higher in heterozygotes with type B abnormalities (475 µmol/g creatinine) compared with those with type A abnormalities (70 µmol/g creatinine), there is no difference in stone formation between the two groups, and, in fact, stone formation is uncommon (Dello Strologo et al. Although stone formers in general have been found to have a higher likelihood of developing chronic kidney disease (Worcester et al. A potential explanation for this finding is the observation that cystinuric patients undergo more open surgical procedures, including nephrectomy, than their calcium oxalate stone-forming counterparts (Assimos et al. Histologically, these patients have been observed to have dilated ducts of Bellini plugged by cystine crystals as well as evidence of cortical glomerulosclerosis and interstitial fibrosis (Evan et al. A Swedish geologist discovered magnesium ammonium phosphate in guano and named it "struvite" after his mentor, naturalist H. Brown (1901) first theorized that bacteria split urea, thereby setting up the condition for stone formation, and he later isolated Proteus vulgaris from a stone. Hager and Magath (1925) postulated that a bacterial enzyme hydrolyzed urea, and Sumner (1926) isolated urease from Canavalia ensiformis. It is now well established that struvite stones (magnesium ammonium phosphate) occur only in association with urinary infection by urea-splitting bacteria (Griffith and Musher, 1973). Although infection stones are a direct result of persistent or recurrent infection with urease-producing bacteria, they may also be associated with or exacerbated by urinary obstruction or stasis (Bichler et al. Pathogenesis the process of urealysis provides an alkaline urinary environment and sufficient concentrations of carbonate and ammonia to induce the formation of infection stones. Because urease is not present in sterile human urine, infection with urease-producing bacteria is a prerequisite for the formation of infection stones. A cascade of chemical reactions generates the conditions conducive to the formation of infection stones. However, in the presence of urease, ammonia continues to be produced, further increasing urinary pH. The most common urease-producing pathogens are Proteus, Klebsiella, Pseudomonas, and Staphylococcus species, with Proteus mirabilis the most common organism associated with infection stones. Although Escherichia coli is a common cause of urinary tract infections, only rare species of E. It has been proposed that ammonium, generated as a result of urealysis, may alter the glycosaminoglycan layer present on the surface of the transitional cell layer and significantly increase bacterial adherence to normal bladder mucosa, further exacerbating infection risk (Parsons et al. In addition, a study in rats found that injury to the bladder mucosa increased crystal adherence to the bladder wall, a process that was potentiated by the presence of common bacteria such as Proteus, E. Another potential mechanism for increased stone formation in the presence of bacteria is the finding that particular bacteria, such as E. Because infection stones occur most commonly in those prone to frequent urinary tract infections, struvite stones occur more often in women than men by a ratio of 2: 1 (Resnick, 1981). Other populations at risk of recurrent infection include the elderly (Kohri et al. Spinal cord­injured patients are at particular risk for infection and metabolic stones because of neurogenic urinary tract dysfunction and hypercalciuria related to immobility. Patients with a functionally complete cord transection are at highest risk of developing a staghorn calculus (DeVivo et al. Miscellaneous Stones Xanthine and Dihydroxyadenine Stones Autosomal recessive disorders of purine metabolism have been implicated in stone disease. This side effect is distinctly uncommon because Epidemiology Although infection stones account for only 5% to 15% of all stones (Levy et al. However, a recent analysis of the composition of 52 staghorn calculi demonstrated that only 44% of stones were infection stones, whereas 56% of stones were metabolic, with calcium phosphate the most common (Viprakasit et al. This is consistent with recent evidence suggesting a correlation between stone risk and obesity (Powell et al. More than 40 mutations have been described, including Met136Thr, which is common in Japanese individuals (Kamatani et al. Like xanthine stones, 2,8-dihydroxyadenine stones are extremely insoluble at any pH, but stone formation can be averted by the administration of allopurinol. Matrix Stones the association between urinary proteins and stone formation has long been recognized. Early experiments demonstrated that protein suspensions could promote calcium stone formation (Kimura et al. Osteopontin and calprotectin have been shown to play a role in forming the matrix structure of urinary calcium stones (Kleinman et al. However, stones composed predominantly of matrix are rare; these "stones" are typically radiolucent and may be mistaken for tumor or uric acid stones depending on the imaging study obtained (Bani-Hani et al. The literature regarding matrix stones is sparse, consisting mostly of anecdotal case reports (Allen and Spence, 1966; Bani-Hani et al. Boyce and Garvey (1956) determined that the composition of matrix stones was approximately two-thirds mucoprotein and one-third mucopolysaccharide by weight. Furthermore, they found that the matrix substance in crystalline calculi is closely related to the matrix substance found in matrix calculi. Although some have theorized that reduced urinary calcium levels may account for the preferential formation of matrix stones (Allen and Spence, 1966; Boyce and King, 1959), a recent metabolic evaluation of five patients with matrix stones revealed normal urinary calcium excretion (Bani-Hani et al. In renal failure patients undergoing dialysis, proteinuria may contribute to an increased risk of matrix stone formation. In these patients, matrix stones have been shown to include microfibrillar protein (Bommer et al. Recent analysis of the matrix stone from a single patient with Proteus urinary tract infection by scanning electron microscopy revealed fibrous netlike laminations containing bacterial, cellular, and crystalline material (Canales et al. Proteomic analysis identified 33 unique proteins, of which 90% had not been previously reported as components of matrix stones and 70% are considered inflammatory or defensive. Ammonium Acid Urate Stones Ammonium acid urate stones represent about 1% of all stones (Pichette et al. In developing countries, however, endemic ammonium acid urate urolithiasis is still observed because it makes up bladder calculi in children (Vanwaeyenbergh et al. Ammonium urate stones are radiolucent and occur in patients with chronic diarrhea, inflammatory bowel disease, ileostomy bowel diversions, laxative abuse, recurrent urinary tract infection, and recurrent uric acid stone formation (Dick et al. Among these patients, 25% had a history of inflammatory bowel disease, 14% had a history of significant laxative abuse, 41% were morbidly obese, 36% had a history of recurrent urinary tract infections, and 21% had a history of recurrent uric acid stones. The subgroup of patients with inflammatory bowel disease and ileostomy as the sole clinical risk factor had the highest mean ammonium acid urate content (39%), and ammonium acid urate constituted the predominant stone type in seven of eight such patients. Patients with ileostomy after colectomy have markedly reduced urinary volume, pH, and sodium and are not prone to hyperoxaluria as are other individuals with bowel disease because the colon is the main site of dietary oxalate absorption (Kennedy et al. Therefore these patients are prone to ammonium acid urate and uric acid stones rather than calcium oxalate stones. The underlying pathophysiologic mechanism of ammonium acid urate stone formation attributable to laxative abuse has been postulated to be dehydration resulting from gastrointestinal fluid loss, causing intracellular acidosis and enhanced ammonia excretion. Because urinary sodium is low in the setting of laxative use, urate complexes with abundant ammonia, thereby leading to urinary supersaturation of ammonium acid urate. The association of recurrent uric acid stones with ammonium acid urate stones is likely related to the shared risk factors of low urine volume and pH. They theorized that transient fluctuations in urinary acidity and ammonium and sodium levels may shift the balance between uric acid and sodium- or ammonium-bound urate excretion. Medication-Related Stones Drug-induced stones form either directly as a result of precipitation and crystallization of a drug or its metabolite or indirectly by altering the urinary environment, making it favorable for metabolic stone formation (Daudon, 1999). Drugs such as loop diuretics (furosemide, bumetanide) and carbonic anhydrase inhibitors (acetazolamide, topiramate, and zonisamide) contribute to calcium stone formation (Matlaga et al. However, indinavir poses a risk for indinavir stone formation in treated patients, leading to an estimated incidence of 4% to 13% (Wu and Stoller, 2000). Indinavir is rapidly absorbed from the intestine, achieving peak plasma Chapter 91 concentrations in less than 1 hour. The drug is metabolized in the liver and eliminated primarily in the stool, but about half of the ingested dose of indinavir is excreted essentially unchanged in the urine (Sutherland et al. In pure form, indinavir is relatively insoluble in aqueous solution, although the solubility is pH dependent. As such, individuals taking indinavir on a regular basis are at high risk of producing indinavir stones because of the high urinary excretion and poor solubility of the drug at physiologic urinary pH. After the first 2 weeks, indinavir crystalluria remained constant at a frequency of approximately 25% of urine sediments examined at each test point. Indinavir is now an infrequently used antiretroviral agent, replaced with newer generation agents. Kidney stone formation has been associated with a number of newer antiretroviral agents, including lopinavir-ritonavir (Doco-Lecompte et al. Ritonavirboosted atazanavir, currently one of the more widely used agents, has been shown to have a nearly 7% incidence of stone formation, higher than most of the other new agents (Hamada et al. Because stone formation associated with these agents is thought to be the result of high urinary excretion and low solubility of the drug in urine, agents with higher excretion rates are associated with higher rates of stone formation; 7% of ritonavir-boosted atazanavir is excreted in the urine unmetabolized versus less than 3% for nelfinavir and amprenavir, which have lower rates of stone formation. Triamterene is a potassium-sparing diuretic commonly used for the treatment of hypertension. An evaluation of triamterene stone formers revealed no significant differences between patients and matched control subjects with respect to total recovery of the drug, hourly excretion patterns, and urinary concentrations of triamterene and its sulfate metabolite (Ettinger, 1985). Approximately half of all subjects tested demonstrated urine concentrations of the sulfate metabolite that exceeded the observed solubility limit. One investigation determined that triamterene is more likely to become incorporated into existing stones or stone nidi than to promote stone formation independently (Werness et al. This may account for the rarity of this stone in nonrecurrent stone formers, as well as the finding that hospitalization rates for urinary stones did not differ between patients prescribed triamterene and hydrochlorothiazide (Jick et al. Consumption of large quantities of guaifenesin and ephedrine can lead to stones composed of their metabolites (Assimos et al. Most of the patients reported to have these stones are found to have consumed large quantities of over-the-counter preparations of cold medicine for the stimulatory properties of the ephedrine component, and a history of drug abuse is not uncommon (Assimos et al. Herbal ecstasy and ma huang are also popular ephedrine-containing preparations that are abused for stimulatory properties (Mack, 1997). Unfortunately, chronic ephedrine use leads to tachyphylaxis and prompts the use of increasing doses to achieve a comparable effect.

After the harvest of a sheet graft womens health evangeline lilly alendronate 70 mg amex, the sheet is placed on a carrier that cuts systematically placed slits in the graft womens health zone link health purchase alendronate canada. For most genital reconstructive surgery women's health center dickson tn alendronate 35 mg purchase on line, the slits are not for expansion but rather to allow subgraft collections to escape; in some cases women's health center canfield ohio purchase discount alendronate on-line, the slits allow the graft to conform better to irregular graft host beds womens health tacoma cheap alendronate 70 mg buy on line. It has also been proposed that mesh grafts take readily because of increased levels of growth factors, possibly as a function of the slits. Variable characteristics such as color, texture, thickness, extensibility, innate skin tension, and blood supply can be useful in various situations. Mucosa from different sources have been used in genitourinary reconstructive surgery with excellent results. The term tissue transfer implies the movement of tissue for purposes of reconstruction. In contrast to extirpative surgery, the transfer of tissue for reconstruction requires an intimate knowledge of the anatomy of the donor and the recipient sites as well as of the principles that allow the tissue to survive after it is transferred. The dermis has two layers: a superficial layer, the adventitial dermis (also called the papillary or periadnexal dermis, depending on the anatomy), and a deep layer, the reticular dermis. Other tissues commonly transferred for genitourinary reconstruction include bladder and oral mucosa as well as rectal. The bladder epithelium is the superficial layer of the bladder; the deep layer of the bladder is termed the lamina propria, with superficial and deep layers. The oral mucosa is the superficial layer of much of the oral cavity, which also has a deeper layer termed the lamina propria, again with superficial and deep layers. All tissue has physical characteristics: extensibility, inherent tension, and the viscoelastic properties of stress relaxation and creep. The physical characteristics of a transferred unit are primarily a function of the helical arrangement of collagen along with the elastin cross-linkages. The collagen-elastin structure is suspended in a mucopolysaccharide matrix that influences the viscoelastic properties. The epidermal (or epithelial) layer is a covering-the barrier to the "outside"-and is adjacent to the superficial dermis, or superficial lamina. The deep dermis contains most of the lymphatics and greater collagen content than found in the superficial dermal layer. The deep, or reticular, dermis is generally thought to account for the physical characteristics of the tissue. In most cases, the plexus is composed of larger vessels that are more sparsely distributed. A full-thickness unit carries most of the lymphatics, and the physical characteristics are likewise carried with the transferred tissue (Devine et al. There is a difference between genital full-thickness skin (penile and preputial skin grafts) and extragenital full-thickness skin. This is probably a reflection of the increased mass of the graft in extragenital skin grafts. The posterior auricular graft (Wolfe graft) is an exception to the rule concerning extragenital skin. The postauricular skin is thin and overlies the temporalis fascia and is thought to be carried on numerous perforators. The subdermal plexus of this graft mimics the characteristics of the intradermal plexus, and the total mass of the graft is more like that of the splitthickness unit. The term graft implies that tissue has been excised and transferred to a graft host bed, where a new blood supply develops by a process termed take. Dermal Graft the dermal graft has been used for years to augment the tunica albuginea of the corpora cavernosa. When it is harvested, the graft exposes the intradermal plexus and the deep dermal plexus. Cross-sectional diagrams (histologic appearance above, microvasculature below) of the skin. When it is properly prepared, the tunica vaginalis graft is essentially peritoneum. The tendency of peritoneum to take readily is well documented in the literature that examines adhesion formation and in the urology literature concerning the application of peritoneal grafts for reconstruction of the urinary tract. The literature fails to define accurately what the surgeon can expect regarding physical characteristics (Jordan, 1993). The fact that the graft has a "wet epithelial" surface is likewise thought to be a favorable characteristic for many cases of urethral reconstructive surgery. A systematic review of the literature regarding the use of oral mucosa in the reconstruction of urethral defects associated with stricture and hypospadias/epispadias by Markiewicz et al. In that series, 67 patients were described, all with follow-up exceeding 5 years and some with 10 years of follow-up. More recent studies showed equal results with buccal and lingular grafts (Sharma et al. Because the labial mucosal grafts are thin, some surgeons prefer that donor site for reconstruction of the fossa navicularis (Jordan, 1993). Vein Grafts As described in the urologic literature, vein grafts are perhaps not true grafts according to the terminology used in this chapter. The premise is that the vein survives by endothelial direct perfusion and re-establishment of vein wall blood flow by perfusion of the vasa vasorum. At the present time, vein "grafts" are being widely used for replacement of defects of the tunica albuginea of the corpora cavernosa. The pertinent points with regard to the transfer of vein patches to the corpora cavernosa and their long-term behavior have been inferred from the current vascular literature. Dermal grafts have been tried for urethral reconstruction, also with generally poor results. Other Grafts In the bladder epithelial graft, there is a superficial and a deep plexus; however, the plexuses are connected by many more perforators. The arterial perforators have been interrupted, and flap survival depends on the intradermal and subdermal plexuses. B Rectal mucosal grafts also have been proposed for urethral reconstruction, but little is known about their graft take. In general, the vascularity of the bowel mucosa is based on the vascularity of the underlying muscle, with the mucosa carried on perforators. Tunica vaginalis grafts have proven useful for small defects of the tunica albuginea of the corpora cavernosa, but aneurysmal dilation tends to develop when they are used for larger defects. Tunica vaginalis grafts have been tried for urethral reconstruction with uniformly poor results. The free-flap cuticular and vascular connections are interrupted at the base of the flap. Vascular continuity is reconstituted in the recipient area by a microsurgical anastomosis. The term flap implies that the tissue is excised and transferred with the blood supply either preserved or surgically reestablished at the recipient site. Random Flaps A random flap is a flap without a defined cuticular vascular territory. The flap is carried on the dermal or laminar plexuses; the dimensions of random flaps can vary widely from individual to individual and from body site to body site. In genitourinary reconstructive surgical procedures, we tend to use the term island flap. However, the usual case is that a skin island or paddle is elevated either on the muscle, as in the gracilis musculocutaneous flap, or on the fascia, as in local genital skin flaps. The term island flap is not synonymous with the terms skin island and skin paddle. The usefulness of these flaps and grafts is illustrated in the discussion of surgical techniques later in this chapter. There is continued interest in the use of tissuecultured grafts or "manufactured" grafts. The likelihood of someday being able to use off-the-shelf grafts or sheets of cultured material successfully is not far in the future (Atala, 2002; Bhargava et al. Axial Flaps the term axial flap means that there is a defined vessel in the base of the flap. If the muscle alone is carried as a flap, the overlying skin survives as a random unit. However, the deep blood supply is carried on the fascia (deep and superficial layers), and the overlying skin paddle is based again on perforators. One can transfer a fascial flap based on the deep blood supply associated with the flap; the overlying skin, if it is not carried with the flap, remains as a random unit (Cormack and Lamberty, 1984; Ponten, 1981; Tolhurst and Haeseker, 1982). It has been argued that fascia is relatively avascular and cannot serve as the "blood supply" to the fasciocutaneous unit. Actually, the fascial layer acts as a trellis: the vessels are carried much like the limbs of a vine (Jordan, 1993). The septum is correctly illustrated as strands that interweave with the tunica albuginea ventrally and dorsally. Bottom, Diagram of a sagittal section of the penis and perineum illustrating the fascial layers. Proximally, the corpora cavernosa have split into individual crura, with the urethra lying against the triangular ligament. The spongy tissue of the corpus spongiosum has become incorporated as the deep tissues of the glans. The urethra here is relatively ventrally placed in relation to the body of the corpus spongiosum. In Carson C, editor: Topics in clinical urology: complications of interventional techniques, New York, 1996, Igaku-Shoin, pp 86­94. The dartos fascia is contiguous with the Scarpa fascia onto the abdomen, with the tunica dartos of the scrotum, with the Colles fascia on the perineum, and over the thigh-eventually to insert at the fascia lata. The urethra is subdivided into the following sections: 1, fossa navicularis; 2, pendulous or penile urethra; 3, bulbous urethra; 4, membranous urethra; 5, prostatic urethra; and 6, bladder neck. By common usage, the divisions of the fossa navicularis, pendulous urethra, and bulbous urethra compose the anterior urethra, and the divisions of the membranous urethra, prostatic urethra, and bladder neck compose the posterior urethra. Diagrammatic representation of the sphincters surrounding the male posterior urethra. This artery is thought to arborize in the tunica dartos of the scrotum and Colles fascia of the perineum. The perineal artery continues lateral to the groin crease onto the thigh and extends toward the groin. Note the division of the superficial transverse perineal muscle, exposing the deep transverse perineal muscle. The fossa navicularis is contained within the spongy erectile tissue of the glans penis and terminates at the junction of the urethral epithelium with the skin of the glans. The penile urethra lies distal to the investment of the ischiocavernosus musculature but is invested by the corpus spongiosum and maintains a constant lumen size roughly centered in the corpus spongiosum. The bulbar urethra is covered by the midline fusion of the ischiocavernosus musculature and is invested by the bulbospongiosus of the corpus spongiosum. It becomes larger and lies closer to the dorsal aspect of the corpus spongiosum, exiting from its dorsal surface before the posterior attachment of the bulbospongiosus to the perineal body. The bulbous urethra is lined distally with squamous epithelium that gradually changes to the transitional epithelium found in the membranous urethra as it swings upward (Devine and Horton, 1977). The membranous urethra is the portion that traverses the perineal pouch and is surrounded by the external urethral sphincter. This segment of the urethra is unattached to fixed structures, has the distinction of being the only portion of the male urethra that is not invested by another structure, and is lined with a delicate transitional epithelium. The prostatic urethra is the portion of the urethra that is proximal to the membranous urethra and is mostly surrounded by the prostatic stromal and glandular tissue. The bladder neck is the location of the bladder neck musculature, variably surrounded by intravesical protrusion of the prostate. Discussion of the anatomic relationships of the male genitourinary structures in the penis and male perineum must precede discussion of specific reconstructive surgical techniques; for a complete anatomic description, please see Chapters 21 and 68. The corpora cavernosa contain erectile tissue within a dense elastic sheath of connective tissue called the tunica albuginea. The corpora cavernosa are not separate structures but constitute a single space with free communication through an incompetent midline septum that becomes more complete toward the base of the penis. This erectile tissue contains arteries, nerves, muscle fibers, and venous sinuses lined with flat endothelial cells, and these features fill the corpora cavernosa, making its cut surface look like a sponge. This tissue is separated from the tunica albuginea by a thin layer of areolar connective tissue. The third erectile body, the corpus spongiosum, lies in the ventral groove between the two corpora cavernosa. The tunica albuginea (adventitia) of the corpus spongiosum is thinner than the tunica albuginea of the corpora cavernosa, and the corpus spongiosum contains less erectile tissue than the corpora cavernosa. The urethral meatus is slitlike, lying slightly on the ventral aspect of the tip of the glans, with its long axis oriented vertically. At its base, the penis is supported by two ligaments, composed primarily of elastic fibers that are continuous with the fascia of the penis. In the penis, the erectile bodies are surrounded by Buck fascia, dartos fascia, and skin. On the superior aspect of the corpora cavernosa, the deep dorsal vein, paired dorsal arteries, and multiple branches of the dorsal nerves are contained within the envelope of Buck fascia. In the midline groove on the underside of the corpora cavernosa, Buck fascia splits to surround the corpus spongiosum. Attached distally to the undersurface of the glans penis at the corona, Buck fascia extends into the perineum, enclosing each crus of the corpora cavernosa and the bulb of the corpus spongiosum and firmly fixing these structures to the pubis, ischium, and inferior fascia of the perineal membrane (urogenital diaphragm). Distally, the skin of the penis is confluent with the glabrous skin covering the glans.

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