URETERAL STRICTURES
Ureteral strictures cause narrowing of the ureteral lumen, and they can reflect either ischemic or nonischemic damage to the mucosa with subsequent fibrosis. Ischemic strictures are caused by a devascularization of the periadventitial blood supply, which may occur after surgical mobilization of the ureter, renal transplantation, or radiation therapy. Nonischemic strictures may be caused by ureteral instrumentation, infection (e.g., pyelonephritis, tuberculosis, schistosomiasis), inflammatory periureteral disease, or malignancy.
PRESENTATION AND DIAGNOSIS
Patients with acute ureteral obstructions of any kind
typically have flank pain, which may be accompanied by nausea and vomiting.
Chronic obstructions are often asymptomatic, although some may cause urosepsis
or, if bilateral, renal insufficiency.
The gold-standard imaging study for evaluation of the
ureter is contrast-enhanced CT. If any chronic ureteral obstruction is present,
the more proximal segments will appear dilated. If a stricture is present,
progressive narrowing of the ureter may be seen on delayed urographic phase,
with little or no contrast seen in the distal segment if the narrowing is
severe. If, in contrast, a stone is present, it will be visible as a discrete,
hyperattenuating region in the ureter. If a ureteral mass is present, a filling
defect may be seen.
Once a stricture has been diagnosed, a renal scan can
be performed to quantify the function of each kidney. Such measurements are
especially important if endoscopic treatment is being considered because the
ipsilateral kidney should have at least 25% of normal filtration function for
the intervention to have a high probability of success.
TREATMENT
Once a ureteral stricture has been diagnosed, the
possible ongoing presence of secondary causes (especially malignancy) should be
ruled out. The stricture should then be treated to relieve the pain of
obstruction and prevent upper tract infection.
Endoscopic techniques, which are associated with less
morbidity and faster recovery times than open procedures, should be employed
for strictures that are 1 cm or less in length, located away from the
midureter, present for less than 6 months, nonischemic in etiology, and
associated with at least 25% remaining function in the ipsilateral kidney.
Strictures that do not possess these characteristics should be treated using an
open or laparoscopic surgical approach.
Endoscopic Treatment. A ureteral stent can be deployed as a temporizing measure in patients
with pain or urosepsis. In the occasional patient with significant comorbidities
who is a poor candidate for more invasive procedures, a stent may be used as
definitive management, although it should be changed every 3 to 12 months.
Occasionally, if a very tight obstruction is seen, two side-by-side stents may
be necessary to provide adequate drainage.
Balloon dilation may be performed to recanalize the
strictured segment, but recurrent stricture formation is common. Retrograde
pyeloureterography is first performed to delineate ureteral anatomy and the
precise location of the stricture. Next, a balloon catheter is placed under
fluoroscopic guidance so that it traverses the strictured segment. If placement
is challenging, a ureteroscope
can be used to directly visualize the process (see Plate 10-33). Once
appropriately positioned, the balloon is briefly inflated, which stretches and
dilates the strictured segment.
An endoureterotomy consists of stricture incision
under direct vision through a ureteroscope. Several different technologies can
be employed, including cold knife incision, electrocautery, and holmium laser
ablation. All require a full-thickness cut through the wall of the ureter into
the periureteral fat. The optimal direction of the incision depends on the
level of the ureter that is affected. Incisions into the pelvic ureter should
be made in an anteromedial direction, so as to avoid the iliac vessels.
Meanwhile, incisions into the upper ureter should be made in a posterolateral direction, so as to avoid the aorta
and inferior vena cava.
Surgical Treatment. Open or laparoscopic excision of a ureteral stricture should begin with
careful ureteral mobilization to minimize the risk of damage to the
periureteral blood supply. Debridement of the scarred and fibrotic area should
then proceed until a bleeding edge is reached. Finally, the ureter should be
reconstructed in a manner that is tension-free, spatulated, and water-tight. A
ureteral stent should be placed to ensure adequate postoperative drainage. The
optimal method of reconstruction depends on the location and length of the
excised segment. Several different options are available, as described in Plate 10-36.
