Ureteral Obstruction: Causes, Symptoms & Treatment

What is Ureteral Obstruction?

Ureteral obstruction refers to a partial or complete blockage of the ureter, the tube that carries urine from the kidney to the bladder. When the ureter is obstructed, urine backs up into the kidney, causing the renal pelvis to swell -- a condition known as hydronephrosis. If left untreated, the pressure buildup can cause permanent damage to kidney tissue and impair kidney function.

Causes

Ureteral obstruction can result from a variety of conditions:

• Kidney stones: The most common cause; stones that become lodged in the ureter block the flow of urine.
• Tumors: Malignant or benign growths in or around the ureter, bladder, or adjacent organs can compress or invade the ureter.
• Scar tissue (strictures): Narrowing of the ureter due to scarring from prior surgery, infection, or radiation therapy.
• Congenital abnormalities: Structural defects of the ureter present from birth, such as ureteropelvic junction obstruction.
• Inflammatory conditions: Diseases such as Crohn disease, endometriosis, or retroperitoneal fibrosis can compress the ureter from outside.
• Blood clots or pus: Less common causes that can nevertheless block urine flow.

Symptoms

Symptoms vary depending on whether the obstruction develops suddenly (acute) or gradually (chronic):

• Flank pain: Severe, cramping pain in the side or back, often referred to as renal colic.
• Nausea and vomiting: Commonly accompany acute episodes of pain.
• Changes in urine output: Reduced urine production or, in bilateral obstruction, complete absence of urine (anuria).
• Urinary tract infections: Recurrent infections due to stagnant urine.
• Blood in the urine (hematuria): Particularly common when kidney stones are the cause.
• High blood pressure: May develop as a result of impaired kidney function.

In chronic or one-sided obstruction, symptoms may be mild or absent at first, making early diagnosis challenging.

Diagnosis

Several diagnostic methods are used to identify ureteral obstruction:

• Ultrasound: A quick, radiation-free method to detect hydronephrosis.
• CT urography: Provides detailed images to locate and identify the cause of the blockage.
• MRI urography: A radiation-free alternative, preferred for children and pregnant women.
• Intravenous urography (IVU): An X-ray study using contrast dye to visualize the urinary tract.
• Blood and urine tests: To assess kidney function (e.g., creatinine, urea) and detect infection.
• Renal scintigraphy: A nuclear medicine scan to evaluate the function of each kidney individually.

Treatment

Treatment depends on the cause, severity, and duration of the obstruction:

Conservative Management

Small kidney stones may pass spontaneously with adequate fluid intake and, if needed, pain relief and muscle-relaxing medications such as alpha-blockers to help relax the ureter.

Minimally Invasive and Surgical Procedures

• Ureteral stenting (DJ stent): A flexible plastic tube is inserted into the ureter to maintain urine flow while the underlying cause is treated.
• Percutaneous nephrostomy: A drainage tube is inserted directly into the kidney through the skin to relieve urinary obstruction.
• Ureteroscopy: An endoscope is passed through the urethra into the ureter to remove stones or treat strictures.
• Shock wave lithotripsy (SWL): External shock waves are used to break up kidney stones into smaller fragments that can pass naturally.
• Surgical reconstruction: In cases of severe strictures or tumor involvement, surgical widening or rerouting of the ureter may be required.

Treatment of the Underlying Condition

When the obstruction is caused by a tumor or inflammatory disease, treating the underlying condition is essential to achieve a lasting resolution.

References

1. European Association of Urology (EAU) - Guidelines on Urolithiasis and Obstructive Uropathy, 2023. Available at: https://uroweb.org/guidelines
2. Wein, A.J. et al. - Campbell-Walsh Urology. 11th Edition, Elsevier, 2016.
3. Preminger, G.M. et al. - Diagnosis and Acute Management of Suspected Nephrolithiasis in Adults. UpToDate, 2023.