A blockage in the kidney's renal pelvis (upper end of the ureter) is called a ureteropelvic junction (UPJ) obstruction. Blocking urine flow can damage the kidney.
Ureteropelvic junction (UPJ) obstruction is a blockage in the renal pelvis of the kidney. The renal pelvis is located at the upper end of each ureter (tube that drains urine from the kidneys to the bladder). The renal pelvis, which is shaped like a funnel, collects urine.
In normal cases, each of the two kidneys has one ureter. The kidneys filter the blood of waste matter and excess water, creating urine. The urine is pooled at the UPJ, and then flows down the ureters to the bladder.
In UPJ obstruction, the flow of urine is slowed or stopped completely. This raises the risk of kidney damage. In most cases of UPJ obstruction, only one of the kidneys is affected.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
UPJ obstruction occurs in about one of every 1,500 births, and is responsible for about 80% of all swollen urine-collecting systems. Males are affected at more than double the rate of females, and the left kidney is affected about twice as often as the right.
Most UPJ obstructions are present at birth, an indication that structures of the ureter or kidney did not form correctly as the fetus was developing.
In some cases an inherited tendency to obstructions will run in a family, but usually an obstruction appears in just a single family member.
A number of different types of obstructions may be present at birth, such as:
Less frequently, UPJ obstructions may form in adults as a result of kidney stones, upper urinary tract infections, surgery, an abnormally crossing blood vessel or swelling in the urinary tract.
In many infants with UPJ obstruction, the condition may improve on its own within the first 18 months of life. During this time, repeated ultrasounds and scans are used to monitor the condition to make sure it will not cause lasting harm.
If urine flow doesn’t improve and the obstruction remains after the first 18 months of life, surgery is usually needed to fix the problem. In infants, the surgery most often used is called open pyeloplasty. In this procedure the UPJ is removed, and the ureter is reattached to the renal pelvis but with a wider opening. The goal of the surgery is to allow urine to drain freely, eliminate symptoms and reduce the chances of infection.
Minimally invasive pyeloplasty uses a laparoscope, a long thin tube requiring just a small incision through which the surgeon or a robot operates surgical tools.
Another option is to insert a wire through the ureter to reach the site of the UPJ obstruction internally. The wire is then used to cut the obstruction and a drain is inserted for a few weeks during healing. This procedure doesn’t require any incisions and involves less discomfort than the other two options, but has a lower success rate and may have to be repeated more than once.
Open pyeloplasty usually takes a few hours to complete and has about a 95% success rate. The patient may need to stay in the hospital for two or three days following surgery. A drainage tube may be inserted into the kidney or ureter to assist in urine flow while healing takes place.
The success rate of minimally invasive techniques is on par with open pyeloplasty, but is more technically demanding of the skills of the surgeon and is dependent on patient age and size.
Researchers have not found any link between a pregnant person's diet or nutrition and the formation of UPJ obstruction in a developing fetus There does not appear to be anything one can do to prevent UPJ obstruction when it's a genetic condition.
In adults not born with UPJ obstruction, reducing the chances for later development would depend on avoiding kidney stones, urinary tract infections or trauma to the kidneys.
Last reviewed by a Cleveland Clinic medical professional on 10/06/2020.
Learn more about our editorial process.