53 Michael Zhang,1 Ali Fathollahi,1 Joel Hillesohn,1 & Majid Eshghi2 1 Department of Urology, New York Medical College, New York, NY, USA 2 Department of Urology, Westchester Medical Center Health System, New York Medical College, Valhalla, NY, USA A stricture is a short or long narrowing of the ureteral lumen which leads to functional changes causing decreased or complete interruption of urinary flow distally into the bladder or urinary reservoir. Obstruction can be mechanical, with altered anatomy, or functional, with impaired peristalsis without a true narrowing. A narrow lumen at the vesical or pelvic junction is sometimes called stenosis. Strictures of the ureter can be acute, such as postsurgical cases and ischemia, or chronic, as in postradiation therapy. Some varieties of stricture are congenital, with altered histology. The treatment options are influenced by a variety of factors but are often dependent on cause and the patient’s comorbidities and preferences. Knowledge and understanding of ureteral anatomy is an absolute necessity for management of all ureteral diseases and prevention of iatrogenic injuries. The adult ureter ranges from 22 to 30 cm in length and is 6.5–7 cm in neonates [1]. On radiographs, the ureter may be divided into thirds: the upper third is from the ureteropelvic junction (UPJ) coinciding with L2 vertebrae to the brim of the sacrum; the middle third is from the upper to the lower border of the sacrum; and the segment from the lower border of the sacrum to the ureterovesical junction(UVJ) is called lower or distal ureter. The upper ureter is called the lumbar or abdominal ureter and the distal segment is referred to as the pelvic ureter. The intramural ureter is about 1.2–2.5 cm in adults and 0.5–0.8 cm in neonates. The UPJ and UVJ or ureteral orifice have their own characteristics and configurations from normal to abnormal shapes and locations and their own specific procedures. In a contracted bladder the ureteral orifices are 2.5 cm apart, which can increase to 5 cm when distended. The renal pelvis typically lies posterior to the duodenum on the right and the jejunum on the left. The ureter begins posterior to the renal artery and vein then descends in the retroperitoneum, moving anteriorly over the psoas muscle and passing under the gonadal vein at the level of the inferior pole of the kidney. It travels on the pelvic wall and at the ischial spine enters the pelvis, turns anteromedially, medially crossing the iliac vessels. The two ureters are 5 cm apart with physiologic narrowing at this point. The ureters then diverge laterally at the same course in both sexes with gender‐specific differences. In men the ureter travels down medially and lies in the sacrogenital fold; it is dorsal to the vas deferens that crosses it medially. In women, the ureter is initially posterior to the ovary, passes posterior to the round (ureterosacral) ligament with the uterine artery travelling medially. It is about 2 cm lateral to the uterine cervix and courses anterior to the vagina’s lateral border. In both men and women the ureters travel past the dorsal aspect of the medial umbilical ligament and superior vesical artery. The transition of ureter into the bladder causes the lower physiologic narrowing. The three narrow points of the ureter are the UPJ, the crossing point over the iliac vessels, and the UVJ, which is the narrowest. The typical S‐shaped curvatures of the ureter can be appreciated on anteroposterior and cross‐table views of the ureter [2]. See Figure 53.1. Figure 53.1 (a) Anteroposterior view of the abdomen with a catheter in the left ureter showing the S‐shaped (right–left, up–down) curvatures of the ureter. In older women the ureter dips down before turning up cephalad due to bladder or pelvic prolapse whereas in older men the so called J‐hooking is due to elevation of the intramural ureter secondary to prostatic growth. (b) A cross‐table view of the ureter with the patient in supine position shows the anteroposterior curvatures of the ureter. The ureters are have multiple arterial sources as they travel caudally. The proximal ureter is essentially supplied by the lower pole renal arterial branches anteriorly. This section, referred to as the golden triangle, has significant value during donor nephrectomies, to preserve the only arterial supply to the ureter. The gonadal artery and the aorta also contribute to the upper ureter. The gonadal artery and common iliac artery provide the blood supply to the middle third of the ureter. The spermatic artery supplies up to 10% of ureteral blood supply. The distal ureter is supplied by branches of the common iliac and internal iliac arteries, superior vesical artery, and the uterine and vaginal arteries in women and inferior vesical artery in men. Ureteral arterial vessels travel longitudinally within its adventitia and create a branched network, allowing for mobilization without risking its blood supply. The venous drainage is paired with the arteries and drains to the renal, gonadal, and internal iliac veins and vesical venous plexus. Knowledge of this vascular supply is crucial in ureteral surgery, because a devascularized ureter is subject to complications of stricture and leakage. Lymphatic drainage of the upper ureter is into the lumbar and para‐aortic nodes on the left, and the para‐caval and interaortocaval nodes on the right. Lymphatics of the middle ureter drain to the common and internal iliac nodes, while those of the pelvic ureter drain to the internal iliac and vesical nodes. See Figure 53.2. Ureters have a richly innervated plexus arising from T12–L2 segments of the spinal cord with corresponding dermatome referral [3]. The kidney’s sympathetic innervation is from T8 to L1 and travels along arterial branches, causing vasoconstriction, and the parasympathetic fibers arise from the vagus nerve, causing vasodilation. The loss of renal and especially ureteral innervation has significant implication in ureteral strictures. This is seen in transplanted kidneys, patients who have undergone extensive manipulation of the ureter, and procedures such as Boari flap or reimplantation. The lack of ureteral innervation can mask the clinical presentation. Figure 53.2 (a) Vascular supply of the ureter. Note the longitudinal descending pattern of the upper ureteral blood supply, and the medial and lateral vascular supply of the mid and distal ureter [7]. (b) Paraureteral structures. This diagram illustrates the ureteral anatomy, vascular supply, and adjacent organs to help create a virtual anatomy in the operator’s mind. A & V, artery and vein. In an adult the thickness of a nondilated normal ureter and peri‐ureteral adventitia is about 3 mm. In a review of 212 unobstructed ureters on computed tomography (CT) scan 96% of the ureters had a diameter of 3 mm or less [4]. The ureter is lined with transitional cell epithelium, which consists of a short basal layer, one or more layers of columnar cells, and, most apically, umbrella cells. The umbrella cells are specialized to survive bathing in hypertonic urine and to stretch with distention of the lumen. Folds of mucosa help to protect against reflux of urine when the bladder is full [5]. Underneath the epithelial layer is a thick, fibroelastic matrix, known as the lamina propria. It is a packed layer of cells that allows for stretching of the ureteral wall when obstructed. The ureter has no mucosal or submucosal glands, and no submucosa. The thickest layer of the ureter is the muscularis, which is a layer of smooth muscle outside the lamina propria: the upper two‐thirds have two layers of muscle: the inner arranged longitudinally and outer arranged circularly. The muscular layers contribute to peristalsis. The lower third has a thicker urothelium and three layers of muscle: the inner longitudinal, middle circular, and outer longitudinal. See Figure 53.3. The distal end of the ureteral musculature flattens and rolls under to allow the lumen to migrate to the vesical mucosal surface. In the intramural section the muscle layering is lost and all fascicles become oriented longitudinally and fan out to form the trigone. Within the bladder wall the ureter is loose (Waldeyer’s separation) [6]. This anatomic description explains why, during endoscopic meatatomy in the 12 o’clock position, muscular layers are rarely noted [7]. The outer adventitial layer has fibroelastic connective tissue. This layer harbors the blood vessels, lymphatics, and nerves. This histological structure along with the richer vascular supply explain why the distal ureter is more resilient and forgiving as compared to the upper ureter during endoscopy and after iatrogenic injuries. The ureteral lumen is not actually a circle but folded epithelium that is stellate in form, mostly with five or six points. The points of the stars are the last to disappear with ureteral dilation and with further dilation the ureteral lumen takes a square shape and eventually a circle, allowing it to distend up to 17 times when obstructed [8]. Figure 53.3 Histology of the ureter. (a) Upper ureter: note the stellate appearance of the lumen. There are only two muscular layers in this segment; from the inside out: urothelial mucosal folds, lamina propria, longitudinal muscle, outer circular muscle, and adventia. (b) Cross section of the lower ureter showing increased thickness of the urothelium and additional muscular layer. The proximal part of the ureter is prone to higher shear stress during peristalsis compared to the middle and distal parts [9]. Disruption of the ureteral muscle layers during mechanical dilation of the ureter in conjunction with ureteroscopy is one of the main causes of subsequent strictures [10]. Pelvic surgery, skeletonization, and radiation can result in significant vascular compromise of the distal ureter, resulting in secondary strictures. The pattern of ureteral stricture and degree of dilation partly depend on this histological structure. The upper ureter, with fewer muscle layers and loose surroundings, allows for significant dilation which functions as a reservoir in cases of severe obstruction and allows for tortuosity to accommodate urine volume and keep the renal pelvic pressure low. The loose structure, on the other hand, makes this part weaker and more prone to injuries. The majority of ureteral avulsions occur in this segment due to the lesser musculature and no paraureteral support. In the lower ureter the degree of dilation is less due to thicker muscle layers and also rather tighter space. In this segment, strictures from iatrogenic injuries and impacted stones are usually short in length with normal ureter below and above, except for cases of hydronephrosis. In cases of pelvic surgery, radiation, malignancies, and fibrosis the ureter is restricted externally and the obstructed segment is long with the appearance of an irregular piece of string. The ureter additionally loses its mobility and appears fixed, even with placement of a catheter; this is in contrast to a normal ureter that takes the shape of an open‐ended catheter or balloon and looks straight [10–12]. Virtual endoscopic anatomy can be defined as a three‐dimensional reconstruction of the ureter in the mind of the operator. This reconstruction includes what is visualized endoscopically to the regional/vascular/histological information described earlier. The key additional information relates to paraureteral structures. The surgeon can make the best judgment in selecting the procedure and the extent of the intervention, regardless of the nature of the procedure, to achieve the best and safest outcome. There are three layers of information: (i) visible intraluminal findings, (ii) visible and invisible ureteral wall histovascular anatomy, and (iii) invisible regional and paraureteral structures. The combination of these factors creates a three‐dimensional virtual anatomy in the operator’s mind. Figure 53.4 elaborates some of the details and recommendations for safe incisional sites. Figure 53.4 Ureteral and paraureteral structures with the recommended sites of incision. Normal anatomy of the distal ureter can be altered by past surgical procedures, which renders the management of strictures more challenging for the surgeon. Recommendations to overcome them are described here. Ureteral reimplantation is performed using a variety of techniques and in the event of subsequent obstruction it can potentially be difficult to access the relocated neo‐orifice. Figure 53.5 (a) A rotated right lower quadrant transplant kidney (the renal pelvis faces laterally) with ureteral obstruction. (b) A right ureteroureterostomy with stricture and angulation. Since the ureteral anastomosis is at the end of a tubularized flap it is rather far from the bladder neck, especially in male patients with an enlarged prostate. A flexible cystoscope or a semirigid ureteroscope is useful for reaching the obstructed anastomotic site for initial wire placement. Urinary reservoirs present special problems in cases of stricture and obstruction of the implanted ureter. Some of the implants form a chimney structure and some have a short tunnel with direct anastomosis to the bowel mucosa or are inverted with nipple formation. The disadvantage is a lack of normal bladder boundaries to help identify the implant site. Radical prostatectomy, abdominoperineal resection, hystero‐oophorectomy, bladder neck reconstruction, pelvic floor reconstruction, and a variety of bladder neck suspension procedures can, at times, contribute to the development of ureteral strictures. This can be due to anatomic or histological causes such as dissection and cauterization. Figure 53.6 (a) Retrograde pyelogram of a female in the immediate postoperative period after hysterectomy showing leftdistal stricture/obstruction secondary to suturing. The cold‐knife incision intraluminally released the suture with no recurrence on follow‐up. (b) CT urogram image of a female patient 5 weeks postradical hysterectomy and pelvic lymph node dissection with complaint of flank pain and urine leak from the vagina. (c) Radiographic appearance of resistance to balloon dilation with a ring effect (persistent waist). (d) Appearance of the balloon after removal showing persistence of waist: a sign that the stricture is not adequately dilated. Bulky pelvic malignancies create a different type of challenge. A common example is a female patient with bulky uterine mass, postradiation. In these cases obstruction of the distal ureter is a combination of mechanical changes due to anteromedial dislocation and secondary postsurgical/postradiation histological changes. The stenotic ureteral orifice is located centrally on a mound facing the lateral aspect of the bladder: the mirror image of the natural orientation. The ureter then takes a medial and a sharp lateral curve towards the renal pelvis depending on the degree of the ureteral tortuosity. The use of Kumpe, Cobra, and other types of angiographic catheter is very helpful to overcome these angulations and types of tortuosity [22]. See Figure 53.7. Figure 53.7 Obstructed distal ureter due to bulky pelvic tumor. The orifice is medially and anteriorly displaced. A variety of instruments are used to manage ureteral strictures endoscopically or under fluoroscopy. Some are used by interventional radiologists in an antegrade fashion when urologists do not have enough expertise or, at times, desire to do the procedures. The majority of these can easily be used by urologists who have had adequate endourological training or exposure. The instruments used are from the urology and radiology armamentaria. These catheters are used in parts of the ureter that are kinked or angulated. Intubate with a guidewire or Glidewire, rotated clockwise or counterclockwise while simultaneously advancing it. See Figure 53.8. Figure 53.8 Angle‐tipped angiographic catheters for negotiating a stenotic orifice and tortuous ureter. There are multiple types of guidewire which are used in these procedures, with each specific guidewire designed for a certain purpose. The common types are stainless steel, PTF coated, stainless steel‐coated with a hydrophilic tip (Sensor, Boston Scientific, Marlborough, MA, USA), all hydrophilic (Glidewire, Terumo, Somerset, NJ, USA; Roadrunner, Cook Medical, Bloomington, IN, USA), and coated rigid shaft with a floppy tip (Amplatz superstiff). They range in diameter (0.014–0.038 inches), length (140–150 cm), tip shape, and level of stiffness. The most common wires used in urology are 0.035 and 0.038 inches. The floppy soft tip varies from 3 to 5 cm depending on the product. Tip shape may be angled, straight, floppy, or J‐shaped. In general, the ideal endourologic guidewire should be sufficiently flexible and lubricated to negotiate a tortuous ureter and pass possible obstructions with adequate strength against bending for stability to pass the stent over. If guidewires cannot pass the stricture, a hydrophilic guidewire (Glidewire) can be used bypass a strictured area. A disadvantage is that hydrophilic guidewires are very slippery and easily dislodge out of the ureter. An external device clipped to the end of the Glidewire makes it easier to handle and control [23]. Meatotomy scissors, one of the oldest pieces of equipment in the urological armamentarium, is ideal for incising a stenotic ureteral orifice. The very first indication for meatotomy was for facilitating the passage of a stone through a small ureteral orifice. Endoscopic scissors are used to incise the orifice along its intramural course medially, This approach is taken because the distal ureter’s blood supply enters it laterally, from the inferior vesical artery: 12 and 2 o’clock on the right and 10 and 12 o’clock on the left. This is a type of single‐action rigid or flexible scissors with the cutting edge facing outward when passed through a rigid ureteroscope. When the scissors are opened in the stenotic intraluminal portion and withdrawn, with proper orientation the dorsal aspect of the upper blade incises the ureteral stricture. This is called reverse cutting [24]. See Figure 53.9. Figure 53.9 (a) Close up of endoureterotomy scissors. The sharp dorsal aspect of this instrument is ideal for reverse cutting. (b) Radiographic appearance of endoureterotomy. The stricture knife was also designed for semirigid ureteroscopes and is not commonly used. It includes a narrow‐profile catheter with an inner scalpel which is advanced through the area of stricture and slowly withdrawn under direct vision to incise the stenotic area. This 3 Fr needle is inserted into the bed of a stricture to instill triamcinolone to decrease the rate of collagen production and thus decrease recurrence rate. Some studies have reported a 50% response rate at 5 year follow‐up. This 45° angled electrode is used to incise the intramural ureter and obstructed ureterocele using the standard transurethral resection set. If the opening of a ureterocele is accessible then a wide meatotomy can be performed. Most urologists recommend incising the base of the ureterocele horizontally at the medial aspect as this gives the best chance of avoiding reflux afterwards [25]. Neodymium (Nd):YAG and Ho:holmium lasers may be used with semirigid and flexible ureteroscopes to incise stenotic areas under vision. Both 200 and 365 μm fibers may be used depending what size ureteroscope is used. The 365 μm fiber fits the lumen of most semirigid ureteroscopes. The lowest possible energy must be used to minimize thermal injury. YAG should not be used primarily as it may cause necrosis. This 3 Fr angled or straight electrode is used to incise a stricture using an electrical current. The downside is that the added electrical energy can damage an already compromised vascular supply. These sequential or graduated fascial dilators (6–12 and 12–18 Fr) or a variation of Teflon dilators are advanced over a guidewire under fluoroscopic control to dilate a narrow segment of the distal ureter prior to ureteroscopy. This longitudinal force can result in tears and splitting of muscle layers that can potentially cause stricture formation (see Figure 53.10) [26]. Figure 53.10 Tapered 6–12 and 12–18 Fr fascial dilators. The tapered tip matches a 0.038 inch guidewire without any gap, avoiding tissue dragging and decreasing mucosal damage. The larger diameter of the dilator as compared to the smaller ureteral lumen still causes mucosal and muscular injuries. These stainless steel devices are available in single size or graduated size on a single shaft. Their purpose is for dilating stenotic distal ureters. Since the introduction of balloon dilators by Grüntzig in 1978, they have been used to dilate the ureter prior to ureteroscopy. Balloons are the most common form of stricture dilator. Dilated balloon outer diameters (OD) range from 15 to 24 Fr with marked lengths of 4–10 cm and tapered shoulders. The balloons have a set range of pressure tolerance and can rupture if overinflated. Use of a pressure gauge can avoid this problem. If a balloon is placed too close to a dense stricture it has a tendency to slide out of position. In narrow ureters it is often difficult to advance a balloon once it is inflated and deflated; therefore, in long segments, it is best to advance the balloon to the proximal end and withdraw it segmentally. The balloon must be deflated completely, the syringe removed, and the valve open during withdrawal. This maneuver prevents the ureter from being dragged during withdrawal. A balloon’s maximum pressure tolerance is described in atmospheres (atm) or pounds per square inch (psi) and rarely in kilopascals (kPa), where 1 atm = 14.7 psi = 101.3 kPa. A simplified rounded formula is 1 atm = 15 psi = 100 kPa. Uncontrolled overinflation of the ballon can result in rupture and possible disruption of the ureteral wall continuity. If a pressure gauge and Leveen (spiral cylinder)‐type syringes are not available then smaller (2–5 ml) syringes can be used, but produce high pressures. A zero‐tip balloon, which has no shoulder, can be used to dilate the point of obstruction before endoscopy. Balloon dilation causes circumferential histological injury but is less traumatic than fascial dilators. In a study by Schwalb and Eshghi [10], mechanical dilation was found to cause more sites of immediate mucosal trauma. Six weeks later, mechanically dilated ureters showed extensive scarring and muscle loss. There was significantly less damage with balloon dilation and hydraulic dilation for ureteroscopy was atraumatic [10]. The Acucise kit is used for fluoroscopic incision without endoscopy. A 10 Fr balloon, which helps define the area of stenosis, places the cutting wire against the tissue for direct incision. The inflated balloon (which may reach 24 Fr in OD) is left for 10 minutes after incision is made for tamponade. Placing the orientation of the cutting wire away from vessels and paraureteral vital structures is the key factor to avoid incising vital structures. The dilated balloon can create tense pressure and place the ureter directly against adjacent structures such as uterine, iliac gonadal, and lower pole vessels and once the electrical wire is activated it can potentially incise through the ureter and adjacent vessels. This instrument has been used in the treatment of UPJ obstruction as well as ureteral strictures [27–33]. A dedicated endoureterotome is most useful and yet is one of the most underused instruments in the ureteroscopic aramamentorium. There are three models of this rigid instrument with variations in their shape, length, and tip configuration – cutting cold knife, either straight (Storz) or half‐moon‐shaped (Wolf, Olympus) – which are described as follows. This is the most user‐friendly of the three. It is a three‐piece instrument and is part of the ureteroresectoscope set. The working element has a locking mechanism to hold the half‐moon cutting knife in place. The rod lens is inserted through the element and into the sheath which is 41 cm long with an OD of 11 Fr. The rounded beak is at the top of the instrument. The cutting knife also has a hollow channel allowing a 0.025 inch wire which ensures that the blade follows the wire and remains intraluminal at all times. This instrument is also used for endopyelotomy. This device has similar elements to the Wolf but the length is 38 cm and the OD is 13 Fr. The beak is at the bottom. The advantage is that it has a larger half‐moon cutting element that can slide over a 0.038 inch wire and is perfect for very distal strictures. The major disadvantage is the larger OD and so it is not ideal for higher lesions. This instrument is actually a 36.6 cm long ureteroresectoscope with a similar type of working element. It has an OD of 11.5 Fr and an oval insulated tip. A straight or serrated knife is used for cutting. It is hard to advance this instrument to upper nondilated or tight ureters. It may be beneficial to initially stent the ureter to allow for passive dilation and decompression of the upper tract. See Figure 53.11. Figure 53.11 (a) The Wolf and Olympus endoureterotome for cold knife incision with a half‐moon guided knife. (b) The Storz endoureterotome with a straight knife. Stents vary in shape, size, design profile, and material and are almost always needed after any procedure associated with endoscopic or radiological treatment of ureteral stricture. Most stents are for general use while some are designed for stricture disease. Antibiotic‐coated stents have been tested on animals; rifampin‐coated stents showed efficacy against Enterococcus infection. An in vitro study assessed the efficacy of a sustained‐release varnish containing chlorhexidine against three common bacteria in the urinary tract (Enterococcus, Escherichia, Pseudomonas) and was shown to be effective against all three species. Triclosan‐eluting ureteral stents changed every 3 months did not result in reduced infection rates in this chronically colonized group; however, the rate of symptoms and requirement for antibiotics were significantly lower [34–36].
Endoscopic Management of Distal Ureteral Strictures
Definition
Regional, histological, vascular, and endoscopic anatomy
Regional anatomy
Vascular anatomy
Histologic anatomy
Virtual anatomy
Altered anatomy
Ureteral reimplantation
Boari flap
Neobladder
Extirpative and reconstructive pelvic surgery
Some pelvic reconstructive procedures can cause angulation and distortion of the natural course of the intramural ureter as well. The best approach is careful inspection of the area and placement of a guidewire to be followed with either mechanical dilation or incision in long and dense strictures. Posthysterectomy distal ureteral obstructions are mostly above the intramural section and are mechanical or ischemic due to thermal injury to the vasculature and the tissue directly. In such cases the lumen is not actually compromised. An initially valuable instrument is a semirigid ureteroscope, allowing direct access to the orifice. This allows the wire to be inserted, with the scope keeping the wire from curling (bellying) outward. The use of hydrophilic guidewires such as Sensor, Roadrunner, or Glidewire are additionally advantageous. After negotiating and stabilizing the access we generally change the Glidewire into a more stable wire such as the Amplatz superstiff wire or a Sensor wire. In cases of obstruction above the orifice a mini semirigid ureteroscope (6 Fr) is advanced to the area of narrowing to allow for direct and atraumatic insertion of the wire through the compromised lumen without creating any false passages. This can later be incised using a cold‐knife endoureterotome without any thermal injury. See Figure 53.6 and Video 53.1.
Pelvic malignancies
Instruments
Angled angiographic catheters
Guidewires
Meatotomy scissors
Endoureterotomy scissors (Storz)
Stricture knife (Cook Medical)
Greenwald needle
Collin’s knife‐electrode
Laser fiber
Angled Bugbee electrode (Greenwald)
AQ Taper and Nottingham one‐step dilators (Cook Medical/Boston Scientific)
Bugbie dilators (Storz)
Balloon dilators
Acucise endopyelotomy
Endoureterotome (Wolf, Storz, Olympus)
Wolf endoureterotome
Olympus endoureterotome
Storz endoureterotome
Stents
Coating (antibiotic‐eluting stents)
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
