DISORDERS OF URETER – Causes and Risk Factors, Classification, Pathophysiology, Clinical Manifestations, Diagnostic Evaluations and Management
A ureteral stricture is characterized by a narrowing of the ureteral lumen, causing functional obstruction. The most common cause of ureteral stricture is ureteropelvic junction (UPJ) obstruction, which is characterized by a congenital or acquired narrowing at the level of the UPJ.
CAUSES AND RISK FACTORS
Strictures can have several origins:
Ureteral strictures may be classified as extrinsic or intrinsic, benign or malignant, and iatrogenic or non-iatrogenic. Extrinsic malignant strictures include those caused by primary or metastatic cancer. Primary pelvic malignancies, particularly cancers of the cervix, prostate, bladder, and colon, frequently cause extrinsic compression of the distal ureter. Retroperitoneal lymphadenopathy, caused by a wide range of malignancies, particularly lymphoma, testicular carcinoma, breast cancer, or prostate cancer, may cause proximal to midureteral obstruction. Extrinsic benign compression due to idiopathic retroperitoneal fibrosis may also cause unilateral or bilateral ureteral obstruction, leading to azotemia.
Ureteral strictures are typically due to ischemia, resulting in fibrosis. Wolf and colleagues define a stricture as ischemic when it follows open surgery or radiation therapy, whereas the stricture is considered nonischemic if it caused by spontaneous stone passage or a congenital abnormality. Less commonly, the etiology is mechanical, such as from a poorly placed permanent suture or surgical clip.
Pathologic analysis of the strictures reveals disordered collagen deposition, fibrosis, and varying levels of inflammation, depending on factors such as etiology and interval since the causative insult. The resulting ureteral obstruction may vary widely from mild, causing only asymptomatic proximal ureteral dilation and hydronephrosis, to severe, causing complete obstruction and subsequent loss of renal function.
Some patients with ureteral strictures are asymptomatic others are symptomatic only during periods of diuresis or develop severe renal colic. The degree of symptoms correlates poorly with the degree of obstruction; at times, severe obstruction is asymptomatic or silent. Renal failure and azotemia may be due to bilateral strictures, such as in cases of bilateral ureteroenteric strictures, external compression due to retroperitoneal malignancy, or retro-peritoneal fibrosis; recovery depends on the duration of ureteral obstruction.
No accepted medical treatment of ureteral strictures currently exists. The surgical approach used depends primarily on the location of the ureteral stricture.
To decrease the risk of perioperative infection, the patient should have a sterile urine culture prior to surgical or endoscopic treatment. Perform a preoperative mechanical and antibiotic bowel preparation in patients in whom an ileal ureter substitution is a possibility. Antibiotics are used perioperatively and may be continued for 24 hours or until drains are removed.
Drains are left in place until output is minimal (< 30 ml/d) or the drainage is confirmed to be serum, which is accomplished by checking the drain creatinine level. In patients who received an endoureterotomy, stents are left in place for 4-6 weeks. In patients who received anastomotic repairs, stents are left in place for 10-21 days. If a nephrostomy tube was placed in the patient, it is typically removed last because it can be used to perform antegrade nephrostography to confirm patency.
DISORDERS OF URETER – Causes and Risk Factors, Classification, Pathophysiology, Clinical Manifestations, Diagnostic Evaluations and Management - URETERAL STRICTURE