Urinary obstruction can be a presentation of benign or a serious condition. In either case, it has to be brought to medical attention as it may lead to kidney failure if left untreated. Obstruction can occur anywhere in the urinary tract:
- Ureter (the tube between the kidney and the bladder)
- Prostate (in men)
- Urethra (the tube between the bladder and the outside)
Signs and symptoms of urinary obstruction include:
- Inability to pass urine (urinary retention)
- Weak stream of urine
- Interrupted stream
- Blood in the urine
- Pain in either flank (side) or in the back
- Abdominal pain and/or swelling
Causes of urinary obstruction include:
- Prostate enlargement (in men), which may be benign or malignant
- Stones (can be in the kidneys, ureter, or bladder)
- Tumor (can be anywhere in or outside the urinary tract, compressing it)
- Blood clots
- Enlarged uterus in pregnant women
- Weak bladder that cannot push the urine out (due to certain medications or neurologic conditions)
- Abnormal congenital structures (abnormal tissue that blocks the connection between the kidney and the ureter, or within the urethra ), especially seen in children
- Abnormal tissue that results from instrumentation of the urinary tract (also called strictures)
- Foreign body
- Trauma with pelvic fracture
Diagnosis of urinary obstruction is frequently established by a radiologic (x-ray) study. These studies include plain kidney x-rays , kidney ultrasound, CAT scan, intravenous pyelogram ( IVP) and magnetic resonance imaging (MRI). Some of these studies may require administration of oral or intravenous contrast (dye). Other studies that may be necessary, especially for diagnosis of prostate enlargement or strictures of the urethra, include:
- Cystoscopy—passing a scope through the urethra into the bladder
- Urodynamics—tests of the nerve supply to the bladder and pressures within the bladder
- Uroflow studies—tests of the pressure and flow of urine from the bladder
- Ultrasound—measurement of how much urine is left in the bladder after the patient feels like the bladder has been emptied
Treatment of urinary obstruction depends on the cause. Passing a catheter in the bladder may be all that is needed to relieve the obstruction (a catheter is a soft tube that is inserted into the urethra). Medication can sometimes help if the obstruction is due to an infection, or sometimes in the case of an enlarged prostate. If the blockage is in the kidney or ureter, then a tube (also called a stent) can be placed in the ureter between the kidney and the bladder to help the flow of urine. This is placed with the help of a lighted scope that is inserted into the urethra. Another alternative is a tube that is inserted through the back into the kidney. Placing these tubes gives temporary relief of a blockage of the ureter. A second procedure may later be necessary to completely eliminate the cause of such an obstruction. Placing a scope into the kidney through the back or into the ureter through the bladder allows the physician to remove obstructing lesions such as stones (or sometimes tumors). Alternatively, a shock-wave procedure may be used to help break up small stones.
Sometimes open surgery is necessary to relieve an obstruction in the urinary tract. This is occasionally true for very large kidney stones, and relatively frequently for an enlarged prostate. Obstructions of the ureter by fibrous tissue are strictures that may have to be repaired with open surgery. Congenital problems of narrowing of the junction between the kidney and ureter frequently require a small open incision in children to be properly repaired.
Obstruction of only one kidney is usually diagnosed because of pain and possibly infection from that side and does not threaten overall kidney function if the other kidney is normal. Obstruction of both kidneys at the same time, however, may cause kidney failure and is a medical emergency that requires immediate attention. Most often such an obstruction occurs because of an enlarged prostate or bladder failure, or other causes of urethral blockage. The initial treatment will usually consist of placing a bladder catheter for drainage, and treatment of the obstructing disease after the situation has stabilized. The most common operation necessary in this situation is transurethral resection of the prostate (TURP), where a scope is used to visualize the prostate from the inside, and to core out the obstructing tissue piece by piece, just like whittling out an apple from the inside. A similar procedure using a laser is also sometimes used.
In summary, urinary obstruction is most often due to a stone or an enlarged area of normal or malignant tissue. The obstruction can be temporarily relieved by some form of catheter drainage, but surgery is often needed to permanently relieve it. Damage to the kidneys, sometimes temporary and sometimes permanent, can be a result, if the obstruction is left untreated.
Victoria J. Sharp, MD
Department of Urology