A ureteropelvic junction (UPJ) obstruction is a blockage where the kidney meets the ureter, the tube that carries urine to the bladder. This condition impedes urine flow, leading to a backup and swelling of the kidney, known as hydronephrosis. A UPJ obstruction can be congenital (present at birth) or develop later in life. If not addressed, the obstruction can lead to progressive deterioration of kidney function.
Anatomy of a Crossing Vessel Obstruction
The kidney’s renal pelvis acts as a funnel, collecting urine before it drains into the ureter. While blood vessels normally travel to and from the kidney without issue, a “crossing vessel” can sometimes pass directly over the ureter at the ureteropelvic junction. This is not an extra vessel but one that supplies blood to the lower portion of the kidney, often a lower pole segmental artery.
This anatomical arrangement is like a garden hose being kinked by a rope. The constant pressure from the pulsating artery or vein compresses the flexible ureter, creating an external blockage. This differs from an “intrinsic” obstruction, where the blockage stems from a problem within the ureter wall itself, such as a narrowing or malformation.
A crossing vessel is a common cause of UPJ obstruction. As a person grows into adulthood, their blood vessels enlarge. A vessel that was not causing an issue in childhood can become large enough to compress the ureter and initiate the obstruction. Because the vessel supplies blood to the kidney, it cannot be simply cut or removed to relieve the pressure.
Recognizing Symptoms and Diagnostic Procedures
The signs of a UPJ obstruction vary by age. In adults and older children, symptoms often include intermittent, sharp pain in the flank, the area between the ribs and hip. This pain can be more noticeable after consuming large quantities of fluids, which increases urine production and pressure. Other symptoms include:
- Nausea
- Vomiting
- Urinary tract infections (UTIs)
- Kidney stones
In contrast, infants with a UPJ obstruction often show no outward symptoms. The condition is most frequently detected during routine prenatal ultrasounds, which reveal a swollen kidney. This early detection allows for monitoring and timely intervention if it becomes necessary.
Confirming a diagnosis involves a series of imaging tests. The initial step is often a renal ultrasound, which uses sound waves to show the extent of kidney swelling. For a more detailed view, a physician may order a computed tomography (CT) urogram. This scan uses contrast dye to provide detailed images of the urinary tract, clearly visualizing the blockage and identifying any crossing vessels. Another test is a MAG3 Lasix renogram, a nuclear medicine scan that assesses both kidney function and drainage to confirm the degree of obstruction.
The Pyeloplasty Procedure
The standard surgical treatment for a UPJ obstruction caused by a crossing vessel is a pyeloplasty. The goal is to remove the blockage and restore the normal flow of urine from the kidney into the ureter. The surgery addresses the compression without compromising the blood vessel causing the issue.
During a pyeloplasty, the surgeon carefully dissects the area to expose the renal pelvis, the ureter, and the crossing vessel. The ureter is then detached from the renal pelvis just above the point of obstruction, and the narrowed segment is typically excised. The surgeon then reattaches the healthy ureter to the renal pelvis in a new position, ensuring it is no longer compressed by the crossing vessel.
This repair is most commonly performed using minimally invasive techniques like robotic-assisted or laparoscopic surgery. These approaches use small incisions, resulting in less pain and a quicker recovery than traditional open surgery. Open surgery involves a larger incision and a longer recovery period but remains a highly successful option.
Post-Surgery Recovery and Prognosis
Following a pyeloplasty, patients require a short hospital stay for monitoring. A temporary ureteral stent is placed during the procedure. This thin, flexible tube runs from the kidney to the bladder, ensuring urine drains freely while the area heals. The stent is removed in the doctor’s office a few weeks after surgery.
Follow-up care is an important part of recovery. Patients will have subsequent appointments that include imaging tests, such as ultrasounds, to confirm that the kidney is draining properly and that swelling has resolved. These check-ups allow the medical team to monitor healing and ensure the procedure’s long-term success.
The long-term outlook for patients who undergo a pyeloplasty is excellent. The procedure has a very high success rate, with most individuals experiencing a complete resolution of their symptoms. This preserves the long-term function of the affected kidney.