Ureteropelvic junction (UPJ) obstruction is a condition characterized by a blockage at the point where the kidney connects to the ureter. This obstruction impedes the normal flow of urine from the kidney to the bladder. When urine flow is reduced or stopped, it can lead to a buildup of fluid pressure within the kidney, potentially affecting kidney function over time.
Understanding the Ureteropelvic Junction
The urinary system includes the kidneys, ureters, bladder, and urethra, all working together to filter waste and produce urine. Each kidney, located on either side of the spine, filters blood to create urine. Urine then collects in a funnel-shaped structure within the kidney called the renal pelvis, which narrows to form the ureter.
The ureter is a long, thin tube that transports urine from the kidney to the bladder through peristalsis, wave-like muscular contractions. The ureteropelvic junction (UPJ) is the area where the renal pelvis transitions into the ureter. When an obstruction occurs at this junction, urine drainage is disrupted, causing urine to accumulate and swell the kidney, a condition known as hydronephrosis.
Causes of UPJ Obstruction
UPJ obstruction can arise from various factors, categorized as congenital or acquired. Most cases are congenital and often detected during prenatal ultrasounds. These obstructions commonly occur due to an intrinsic narrowing of the junction as the kidney and ureter develop. Sometimes, an abnormally positioned blood vessel crossing over the ureter can compress it, leading to a blockage.
Acquired UPJ obstructions, though less common, can result from external factors or conditions that develop over time. Scar tissue formation, often from previous surgeries, injuries, or inflammation, can narrow the ureteropelvic junction. Kidney stones, as they pass through or become lodged at the junction, can also cause an obstruction. In rare instances, inflammation or the presence of a tumor can contribute to an acquired blockage.
Recognizing Symptoms and Diagnosis
The symptoms of a UPJ obstruction vary depending on age and blockage severity. In infants, common signs include a palpable abdominal mass, poor growth, weight gain, blood in the urine, or recurrent urinary tract infections (UTIs). Many cases are now identified before symptoms appear due to increased prenatal imaging.
Older children and adults with UPJ obstruction often experience flank pain, which is pain in the upper abdomen or back on the affected side. This pain can be intermittent and may worsen after consuming large amounts of fluids, alcohol, or caffeine. Nausea and vomiting sometimes accompany the pain. Other possible symptoms include recurrent UTIs, blood in the urine (hematuria), or the formation of kidney stones.
Medical professionals diagnose UPJ obstruction using imaging studies. Ultrasound is frequently the initial diagnostic tool, often revealing a dilated kidney, or hydronephrosis. To further assess kidney function and drainage, specialized nuclear medicine scans are often performed. These tests provide detailed information on urine flow from the kidney. Additional imaging, like CT scans or MRI, may also be used to identify the exact location and cause of the obstruction.
Treatment Options
The approach to treating a UPJ obstruction depends on the severity of the blockage and symptoms. For some mild or asymptomatic cases, particularly in infants, observation may be recommended. The condition might resolve on its own, with serial ultrasounds monitoring kidney dilation and function.
When intervention is necessary, surgical repair is the primary treatment. The most common procedure is pyeloplasty. This surgery removes the obstructed section of the ureteropelvic junction and reattaches the healthy ureter to the renal pelvis, widening the pathway for urine flow. This restores proper urine drainage and preserves kidney function. Pyeloplasty can be performed using traditional open surgery or less invasive techniques like laparoscopic or robotic-assisted surgery.