The ureter is a tubular structure that transports urine made by the kidney into the bladder. Strictures (or narrowing) of the ureter can lead to flank pain, infection, stone formation, and even kidney failure.
The ureter for each kidney acts as a conduit, actively transporting urine into the bladder. They are about 3 mm in diameter and 22-30 cm long. They have an inner mucosal layer (called transitional epithelium), a middle longitudinal muscle layer, and an outer circular muscle layer. The ureteral blood supply lies in its outermost layer—the adventitia.
In general, the ureter receives small arterial branches from the renal artery, gonadal artery, aorta, and internal iliac vessels as it courses thru the retroperitoneum. Its course and anatomic relationship proceeds as follows: (1) The ureters begin at the ureteropelvic junction (UPJ) where they lie posterior to the renal veins and arteries. (2) The proximal ureters then course behind the ascending colon on the right and the descending colon on the left. (3) The mid ureters begin at the upper border of the sacrum and lie anterior to the psoas muscles, eventually crossing over the common iliac artery bifurcation (a consistent anatomic landmark for pelvic surgery). (4) The distal ureters begin at the lower border of the sacrum and enter the bladder at the ureterovesical junction. The ureters terminate at the ureteral orifices located at the posterior bladder wall near the bladder neck—a region called the trigone.
Throughout its length, the ureter receives nutrients from its adventitia thru a vascular plexus with extensive anastomoses. This allows ligation of small arterial branches to the ureter without compromising ureteral blood supply (as long as the adventitia is not stripped off the ureter during dissection).
Luminal narrowing etiology is generally divided into two categories: extrinsic (external compression of the ureteral lumen) and intrinsic (disease of the ureter itself). Examples of extrinsic compression include UPJ obstruction by a crossing vessel, cancer (i.e. prostate, colon, ovarian, carcinomatosis, etc), retroperitoneal fibrosis, aortic or iliac artery aneurysms, and rarely anatomic anomalies like ureteroceles (dilated segment of the distal ureter than can obstruct the ureteral lumen proximally) or retrocaval ureters (ureters congenitally positioned behind the inferior vena cava with resultant luminal narrowing). Extrinsic obstruction are not true ureteral strictures. Intrinsic causes include anything that can lead to scarring or narrowing of the ureteral lumen; these are true strictures. Examples include radiation, trauma, infection, impacted stones, previous urologic or pelvic surgery, and ureteral cancer. Partial and complete ureteral transections can occur with penetrating trauma or gynecologic surgery (blood supply to the uterus (uterine arteries) lies in close proximity to the distal ureters).
The most common causes of true ureteral strictures are prior surgical intervention for urinary tract disease, including kidney stone treatment, cancer surgery, or radiationi, ii.
Patients with pelvic cancer requiring radical resection may require supravesical urinary diversion surgery like an ileal conduit—a segment of small intestine with one end connected to both ureters and the other end brought out as a stoma. The connection is called an ureterointestinal/ureteroenteric anastomosis and has a 3-5% chance of stricturingiii. Patients with renal transplants also have a transplant ureteral complication rate of 2-10%iv. Complications include stricture, urinary extravasation, necrosis, and fistula formation.
DIAGNOSIS AND EVALUATION
Many patients will present with hydronephrosis (dilation of the renal collecting system). A thorough history and physical, with a focus on prior surgery, will sometimes reveal an iatrogenic etiology. Patients are often asymptomatic but may complain of flank pain, early satiety, nausea, vomiting, and fevers. The necessary workup includes a urinalysis (analysis of the urine to identify presence of infection and/or blood), urine culture, serum creatinine and electrolytes, renal ultrasound and/or computed tomography (CT) of the abdomen and pelvis (radiographic tools that help delineate the anatomy and pathology), and diuretic renal scans (nuclear medicine study that helps determine kidney function and presence of obstruction). More invasive tests include cystoscopy and retrograde pyelogram (RPG: radiographic study that involves injecting contrast thru the ureter). These quickly identify the location, length, number, and severity of ureteral strictures. Cystoscopy and RPG also allows concomitant placement of a ureteral stent.
Management of ureteral strictures varies depending on stricture severity, location, etiology, as well as the patients’ goals and overall health. The least invasive treatments include ureteral stenting, endoscopic dilation and/or ureterotomies, or chronic nephrostomy tubes (tubes that enter the skin and drain the renal pelvis directly). Surgical reconstruction involves open or laparoscopic/robotic repair or excision and tissue replacement of the stricture. Patients unfit for or disinterested in definitive repair are managed with periodic ureteral stent or nephrostomy tube changes. Chronic ureteral stents are changed every 6-12 months and nephrostomy tubes every 3 months. Younger, healthier patients opt for surgical reconstruction because it offers better long-term success rates.
A common initial treatment is retrograde (via cystoscopy from bladder towards kidney) or antegrade (via percutaneous access from kidney towards bladder) ureteral stent placement with balloon or catheter dilation. The short term success rates are good (85-90% at 3 months), but longer term followup reveals recurrent stricture disease in about 50% of patientsv. Success rates are generally better for single and short (<2cm) ureteral strictures than for multiple and longer (>2cm) stricturesvi. Patients with distal ureteral strictures also fared better than those with mid or upper ureteral stricturesvii.
Endoureterotomy can be accomplished via an antegrade, retrograde, or combined approach for benign ureteral and ureteroenteric strictures. Note that endoureterotomy is not appropriate for extrinsic causes of ureteral compression as these are not true strictures. The most important aspect of this treatment is making a full-thickness incision thru the entire ureteral stricture, including 1cm of healthy ureteral tissue proximal and distal to the stricturevi. Caution must be taken for where the stricture is located since proximal strictures have neighboring anteromedial vessels and distal strictures have adjacent posterolateral vessels. Therefore, endoureterotomies are directed posterolaterally in the proximal ureter/UPJ and anteromedially in the distal ureter to avoid major vascular injury. Ureterotomy can be performed with a cold knife, small electrocautery device, or laser fiber with no significant difference. Cautery can help with small vessel bleeding during the procedure. Another tool available is the Acucise (Applied Medical Resources, Laguna Hills, CA) cutting balloon, which cuts and dilates the stricture.
Wolf et al looked at the long term success rates of the Acucise and specially designed ureteroscopic electrodes and knives in treating benign ureteral and ureteroenteric stricturesviii. The overall 3-year success rate for benign strictures was 80%; the success rate for ureteroenteric strictures was lower at about 30%.
For both dilation and ureterotomy, ureteral stenting for 6 weeks postoperatively is recommended since ureteral injuries take that long to healix.
Endoscopic management of ureteroenteric strictures
Ureteroenteric strictures can also be treated with dilation and/or ureterotomy, but with much higher recurrence and complication rates than benign ureteral stricturesviii. Dilation has a lower complication rate, but ureterotomy is more successful than dilation in these stricturesx. Complications include extravasation with urinoma formation, development of urinary fistulas, and severe hemorrhagexi. Retrograde treatment is often difficult, if not impossible, in these patients. The antegrade approach is therefore preferred for the endoscopic treatment of ureteroenteric strictures. Open reconstruction remains the gold standard for definitive treatment of these strictures.
Endoscopic management of renal transplant ureteral strictures
Allograft ureteral strictures can occur at the UPJ, mid ureter, or ureteroneocystostomy. Much like ureteroenteric strictures, a retrograde approach is very difficult since most transplant surgeons place the ureteroneocystostomy at an unfavorable location (anterior bladder wall). Percutaneous antegrade management is more appropriate in these patients. Dilation and ureterotomy have modest success rates ranging from 45-80% over a follow up of about 2 yearsvi. Given the proximity to the iliac vessels, dilation is preferred over ureterotomy.
We must emphasize that open repair of transplant ureteral strictures is extremely difficult given the fibrosis and scarring surrounding the allograft kidney and ureter. It is thus most appropriate to treat these strictures conservatively. Chronic ureteral stents or nephrostomy tubes are reasonable. Patients interested in treatment should be managed first with antegrade dilation. If this fails, consideration can be given to ureterotomy. Open repair is a high risk but high reward endeavor with more successful long-term stricture free rates than dilation or ureterotomy.
Reconstruction is frequently offered after failed endoscopic management. The type of treatment is very much dependent on stricture location, length, severity, etiology, and patient health. Approaches for repair include traditional open, laparoscopic, retroperitoneoscopic, or robotic-assisted laparo-/retroperitoneo-scopic techniques depending on patient preference and surgeon ability. Given the prevalence of laparoscopic and robotic training in urology residencies, as well as patient desire for decreased postoperative pain and earlier return to activity, robotic ureteral reconstruction is becoming more popular.
UPJ strictures or obstruction are treated by pyeloplasty with excellent results (>90% success rates)xii. Dismembered pyeloplasties are the most commonly performed procedure. It is generally conducted by first reflecting the colon and isolating the diseased UPJ and ureter. The strictured segment is then excised, and the proximal ureteral segment spatulated. Of note, extrinsic obstruction does not require segment excision as the ureter itself is not strictured. The most common cause of extrinsic compression is the crossing vessel (usually anterior to the UPJ). The transected and spatulated ureter is then anastomosed to the renal pelvis with absorbable braided suture anterior to the crossing vessel. Prior to completion of the anastomosis, we place a ureteral stent antegrade (some surgeons put in a retrograde stent prior to performing the pyeloplasty) and a retroperitoneal drain is positioned near but not on the anastomosis. Patients are typically discharged in 2 days. The drain is removed prior to discharge if output is low and drain creatinine levels equal serum creatinine levels. Patients return 6 weeks later for cystoscopy and ureteral stent removal. Periodic postoperative ultrasounds are required to verify improvement/stabilization of the hydronephrosis. Postoperative diuretic nuclear renal scans confirm resolution of obstruction and assess for improvement/stabilization of renal function. Complications specific to this procedure include urine leak/extravasation, stent migration, infection, rhabdomyolysis from prolonged flank positioning, and recurrent obstruction.
PROXIMAL/MID URETERAL STRICTURES
Proximal and mid ureteral strictures, if short, can be treated with ureteroureterostomies (UUs). Much like in pyeloplasties, we expose the retroperitoneum, dissect free the ureter, and excise the diseased segment. Ureterolysis and occasional nephrolysis (freeing up adhesions around the kidney) can close the gap between the ureteral segments. The segments are then spatulated and anastomosed end-to-end with absorbable suture. Much of the literature on UUs are for duplication anomalies of the urinary tract. They report a success rate of > 90%xiii. Alternatively, transureteroureterostomy (TUU) can be performed by tunneling the proximal ureteral segment to the contralateral healthy ureter and accomplishing an end-to-side anastomosis. The obvious disadvantage of this is involvement of the contralateral normal kidney and ureter. We rarely perform TUUs.
MID/DISTAL URETERAL STRICTURES
Mid and distal ureteral strictures can be treated with a Boari flap or psoas hitch. Casati and Boari first described the Boari flap technique in 1894xiv. It involves exposing the bladder and identifying healthy ureter. A rectangular flap of bladder tissue is then created anterolaterally and tubularized to replace the diseased ureter. The posterolateral aspect of the bladder is secured to the psoas tendon (psoas hitch) to facilitate a tension free ureter-to-tubularized bladder anastomosis. A ureteral stent is placed and we repair the bladder defect. A psoas hitch is performed by making a transverse incision on the anterior bladder. This faciliates our fixing the dome and posterior aspect of the bladder to the psoas tendon. The transverse bladder incision is then closed longitudinally. A preoperative cystogram to assess bladder capacity is prudent. We heavily favor the psoas hitch over the Boari flap (when possible) for mid and distal ureteral strictures. Postoperatively, patients have a pelvic drain, a urethral catheter, and a ureteral stent. We remove the drain the day of discharge (typically postoperative day 3), the foley catheter in 1-2 weeks (given a normal cystogram), and the ureteral stent is removed in 6 weeks.
Groups are currently performing laparoscopic/robotic Boari flap and psoas hitch procedures with excellent resultsxv.
DISTAL URETERAL STRICTURES
Distal ureteral injuries or transections are treated with refluxing end-to-side ureteroneocystostomies (aka ureteral reimplantation). The ureters in these situations can easily be placed tension-free near the dome of the bladder. Pelvic drains, urethral catheters, and stents are of course recommended.
COMPLEX URETERAL STRICTURES
Pan-ureteral or long ureteral strictures are rare and complex problems caused by upper tract urothelial malignancy, retroperitoneal fibrosis (RPF), infection (tuberculosis), or iatrogenic/traumatic injury (i.e. chemical irritant accidentally injected into the ureter).
Treatment options include renal autotransplantation or ileal ureter interposition. We perform ileal ureters. In general, the diseased ureter is not removed unless it is associated with malignancy. We then harvest a 15-20cm segment of ileum and anastomosis it end-to-side at the renal pelvis and the posterolateral bladder. These are refluxing anastomoses that require normal bladder function preoperatively to minimize the risk of pyelonephritis and renal failure. In general, ileal ureter substitution is a safe and reliable procedure with a low complication rate and satisfactory long-term resultsxvi, xvii, xviii.
For medically refractory RPF associated with vascular aneurysms, bilateral ureterolysis with omental wraps can be helpful. On occasion, however, the dense fibrotic reaction and the proximity of the aneurysm prohibit safe dissection of the ureter away from the RPF. Bilateral ileal ureters can be performed in this setting. Essentially, a longer segment of ileum is harvested and each end is anastomosed to both the left and right renal pelvis. The “vertex” of the segment is then connected to the bladder, creating a “V”-shaped reconstruction.
For strictures associated with renal transplantation, there is often a thick inflammatory reaction around the allograft kidney and ureter. This makes surgical reconstruction difficult. In this situation, we ask the transplant surgeons to assist in dissecting free the allograft kidney and renal pelvis and we isolate the native ureter or create a mini-Boari flap to complete an allograft pyeloureterostomy or pyeloneocystostomy.
Failed endoscopic management of ureteroenteric strictures will require open reconstruction. This will be difficult due to surgical adhesions. Resection of the stricture and creation of a new ureteroenteric anastomosis will frequently suffice.
Ureteral urothelial cancers causing strictures can be treated with: periodic endoscopic resection/ablation; excision with UU, Boari flap/psoas hitch, ureteral reimplant, or gold standard nephroureterectomy (removal of entire kidney and ureter).
Ureteral trauma and intraoperative injury is managed in a similar fashion depending on location and severity of the injury. Unstable trauma patients can be temporized with nephrostomy tube drainage until they are clinically improved. Intraoperative consultation for ureteral injuries are addressed immediately either with ureteral stenting, nephrostomy tube drainage, or definitive repair. Unrecognized ureteral injury can lead to urinoma formation, fistula, ileus, fever, peritonitis, sepsis and even death. Treatment decisions for these patients hinge on their clinical status and usually include immediate percutaneous drainage, urinary diversion, and delayed ureteral reconstruction.
Ureteral strictures, if left untreated, can cause adverse symptoms and renal failure. Management varies greatly and includes minimally invasive procedures like ureteral stent placement, nephrostomy tube placement, and endoscopic dilation/ureterotomy. More invasive techniques include pyeloplasty, UU, Boari flap, psoas hitch, ureteroneocystostomy, and ileal ureter substitution. With the spread of laparoscopic training, the advancement of robotic technology, and patient preference, robotic ureteral reconstruction is increasing in popularity and practice.
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