Ureteropelvic junction obstruction (UPJO) refers to an obstruction at the junction between the renal pelvis and the ureter. This condition may result from congenital defects or external factors, such as compression caused by aberrant blood vessels or fibrous bands. The obstruction prevents the passage of peristaltic waves from the renal pelvis, gradually leading to hydronephrosis. The primary pathological change in congenital UPJO is related to alterations in the spiral arrangement of muscle fibers within the wall.
This condition is generally asymptomatic, though some patients may experience dull pain or mild discomfort in the lumbar region, pain or tenderness along the ureteral area, or symptoms secondary to complications like infection, stones, or tumors. In infants, an abdominal mass may be the sole clinical sign. UPJO is a common cause of abdominal masses or hydronephrosis in children and is more frequently observed on the left side. Ultrasonography can confirm the presence of hydronephrosis, but differentiation from renal cysts is necessary. Intravenous urography (IVU) provides visualization of the location and extent of the obstruction, while also assessing the severity of hydronephrosis. Delayed images typically show delayed emptying of the renal pelvis on the affected side, accompanied by varying degrees of dilation in the renal pelvis and calyces, or even the absence of imaging. Radionuclide renography offers insights into renal blood flow as well as secretory and excretory functions.
Progressive hydronephrosis, sustained deterioration of renal function, or the presence of complications such as infections, stones, or tumors may warrant surgical intervention. Renal preservation should be prioritized in cases where at least one-fifth of renal function remains. The surgical approach may involve pyeloplasty, with procedures such as renal drainage, supporting tube placement at the anastomosis, or renal folding being performed based on intraoperative findings and the surgeon's expertise. Follow-up with intravenous urography is typically conducted at 3 months and 1 year postoperatively in most cases.