Renal Outlet Stenosis

The condition where there is a narrowing at the junction between the renal pelvis (pelvis) and the ureter (urinary tract) due to congenital developmental defects is called Ureteropelvic Junction Obstruction (UPJ Obstruction or Kidney Outlet Obstruction). This narrowing impairs urine flow, causing dilation (hydronephrosis) of the renal pelvis and the renal ducts due to accumulated urine in the kidney. If this obstruction causes significant disruption in urine flow, it can lead to a decline in kidney function over time, potentially resulting in complete loss of kidney function.

How common is it?

The most common cause of renal enlargement (hydronephrosis) detected in a baby during pregnancy is UPJ Obstruction. It occurs in approximately 1 in 1,500 births. It is typically on the left side and is twice as common in males.

What is the cause

It is often a congenital disorder. It occurs due to abnormalities during the development of the structures that form the kidney and urinary tract, known as the ureteric bud and metanephric blastema. Additionally, abnormally developed renal blood vessels crossing the UPJ or a UPJ with an abnormally high exit point can also be causes of congenital UPJ obstruction.

In addition to congenital disorders, infections (especially tuberculosis), trauma, and surgeries can also be causes of acquired UPJ obstruction.

How is the diagnosis made?

The diagnosis is typically made during routine pregnancy screenings via ultrasound, that is, while still in the womb. Some cases, however, are detected years later or even in adulthood through radiological examinations performed due to pain, urinary infections, or other reasons. In cases where UPJ obstruction is diagnosed radiologically, a renal scintigraphy (DTPA or MAG-3 with diuretic renogram) is performed to assess the severity of the obstruction, and it is determined whether surgery is necessary. Early diagnosis and treatment of severe obstructions are crucial for preserving kidney function.

Who should be treated?

If kidney function is impaired (<40%) or if there is a decrease of more than 10% during follow-up,
If the drainage is poor despite the administration of the drug in the diuretic renogram,
If it leads to persistent pain and infections,

How is it treated?

The treatment of UPJ obstruction is surgical. In a procedure called pyeloplasty, the narrowed UPJ is removed, and the renal pelvis is reattached to the ureter. This procedure can be performed through open, laparoscopic, or robotic surgery. Laparoscopic and robotic surgeries offer advantages over open surgery in terms of cosmetic outcomes and recovery time.

In individuals who have previously undergone pyeloplasty but experienced failure, an endoscopic procedure called endopyelotomy is another surgical technique used in the treatment of this condition.