Ureteral Obstruction and Strictures
What is the function of the ureter and what causes blockage of the ureter?
The ureter is a small tube that runs from the kidney to the bladder. The ureter acts to transport urine to bladder. Normally the ureter pushes urine towards the bladder in a wave-like motion called peristalsis. The ureter can become obstructed from a congenital problem with its development, scarring (also called strictures), or external compression.
What is a congenital cause of ureteral obstruction (ureteral pelvic junction obstruction)?
The uretero-pelvic junction is where the kidney meets the ureter in the upper abdomen. The funnel that collects urine from the kidney is referred to as the pelvis of the kidney and the junction with the ureter is referred to as the ureter-pelvic junction. This is a spot that is very prone to obstruction from congenital development of the kidney. Either an artery crosses at this location and kinks the junction or the ureter lacks the normal ability to push urine towards the bladder in this location (the pushing of urine towards the bladder is called peristalsis). Either of these problems lead to swelling of the kidney. This can cause periodic pain episodes, especially with fluid intake. These pain episodes are referred to as Dietl’s crisis. These crisis episodes are classic in young men after consuming beer, but can happen after any fluid intake.
Treatment of uretero-pelvic junction obstruction usually involves surgery. There are many procedures described to resolve this problem, but one of the most successful is referred to as a pyeloplasty. In a pyeloplasty the segment of ureter that is affected (at the connection to the kidney) is removed and the ureter is reconnected to the renal pelvis. This will act to remove a segment that does not drain because of lack of peristaltic waves and also moves the ureter in front of any arteries that are causing kinking of the ureter. This operation is very successful at resolving the obstruction and it also generally fixes the pain that patients feel from swelling to the kidney and the passage of urine through the obstructed area.
White are some other causes of ureteral obstruction?
The other causes of ureteral obstruction include inflammation of the abdomen and the tissues surrounding the ureter (retroperitoneal fibrosis), scarring of the ureters from surgeries, and cancer in the abdomen pushing on the ureters.
Retroperitoneal fibrosis is an inflammatory condition of the abdomen and tissues that surround the ureters as they travel from the kidney to the bladder. This condition is also referred to as Ormond’s syndrome or peri-ureteritis. The cause of the inflammation (also called fibrosis) is unknown. In some patients this can be treated successfully with medicines like steroids to decrease inflammation. The kidneys may have to be drained in order to bypass the area of inflammation during this time while it is seen whether patients respond to medicines. Another way of treating this problem is to surgically free the ureters from the inflammation surrounding them. Once the pressure of the surrounding fibrosis is released the ureters can drain the kidneys without internal or external drains. This operation is called ureterolysis.
Another cause of retroperitoneal fibrosis is vascular problems. The ureters can become entrapped in scar tissue surrounding aneurisms of the arteries in the abdomen. The arteries that usually affect the ureters are the aorta and the iliac arteries. In addition to scarring from the widening of the artery from an aneurism, sometimes when these aneurisms are fixed with surgery than the post operative scarring can also cause obstruction of the ureters. The treatment for these problems is freeing the ureters from the scar tissue so they can drain effectively or the placement of internal drains to allow drainage of the kidney.
Ureteral strictures after surgery:
One of the most common causes of scarring or stricture of the ureters is surgery that was performed close by the ureter. Some surgeries that can commonly lead to obstruction of the ureter from scarring are urologic surgery for kidney stones, vascular surgery on the arteries in the abdomen, surgery on the colon or rectum, and gynecologic or obstetric surgery. Gynecologic surgeries, like removal of the uterus or ovaries, is a very common cause of obstruction of the ureters. The reason for this is that the arteries going to the uterus and ovaries are very close to the ureters. During surgery these arteries are tied off or sealed and the ureter can be easily damaged. When an injury is found during the operation, the ureter can often be repaired at the time. In most cases, however, the injury to the ureter is not found until after the operation is complete. Depending upon when the injury to ureter is discovered the ureter may not be able to be repaired immediately. The reason that the ureter cannot be repaired immediately is that the amount of scarring and inflammation that occurs after surgery can be very dense. In this circumstance it is better to wait 6-12 weeks to allow the inflammation to decrease before fixing the problem with another surgery. During this waiting time patients need to have a drain coming out of the kidney to bypass the area of scarring (this is called a nephrostomy tube).
The type of surgery performed for injury to the ureter depends upon where the location and the length of the scarring has occurred. When the stricture or scar in the ureter is low and near the bladder usually the ureter can be reconnected to the bladder, removing the area of scar (this operation is called neo-cystotomy). If the stricture is longer but still located near the bladder a flap of bladder can be fashioned into a tube and substituted for the scarred ureter (this is called a Boari flap). Occasional strictures are so long that a piece of small bowel needs to be substituted to reconnect the kidney to the bladder (this is called an ileal ureter). These surgeries are only some of the types of reconstruction that can be done for ureteral obstruction and the type of surgery that is needed depends a lot on the condition of the patient, the cause of the ureteral scarring, the length of ureteral scarring, and the location of the scarring.
Ureteral obstruction from cancer
Another cause of obstruction of the ureters is from cancer growing in the abdomen. There are many types of cancers that can cause obstruction of the ureters. Some examples are: gynecologic (cervical, ovarian, uterine), colon cancer, urologic cancers (prostate, bladder), or lymphomas. When a tumor grows in the abdomen it can put pressure on the ureter and block the ureters normal drainage. When this occurs the ureters need to be drained to allow the kidneys to function properly. This is accomplished with either an internal tube running from the kidney to the bladder (ureteral stent), or an external tube draining the kidney to a bag (nephrostomy tube). Sometimes treatment of the cancer, with surgery, chemotherapy or radiation can cause shrinkage of the tumor and allows these tubes to be removed. This is a difficult situation for patients, and one that surgery can rarely cure.