Renal pelviectasis is a condition where the renal pelvis, the funnel-shaped part of the kidney that collects urine, becomes dilated or swollen. This swelling indicates urine accumulation within the kidney’s collecting system. It is a finding, not a disease itself, often signaling an underlying issue with urine flow.
What is Renal Pelviectasis?
The human body typically has two kidneys, which filter waste from the blood to produce urine. Urine collects in a central area of each kidney called the renal pelvis, before traveling down tubes called ureters to the bladder. Renal pelviectasis occurs when this renal pelvis, and sometimes the calyces (smaller collecting areas within the kidney), expand due to urine buildup.
This condition is classified by its severity (mild, moderate, or severe) based on the renal pelvis’s diameter. Severe cases may show cortical thinning. Renal pelviectasis can affect one kidney (unilateral) or both kidneys (bilateral). It is frequently detected during prenatal ultrasounds or found incidentally during imaging for other conditions.
How Renal Pelviectasis Develops
Renal pelviectasis develops when there is an obstruction or a backflow of urine, causing pressure to build up within the kidney’s collecting system. One common cause is a ureteropelvic junction (UPJ) obstruction, a blockage where the kidney connects to the ureter. This blockage can be present from birth (congenital) or develop later due to scar tissue, a crossing blood vessel, kinking of the ureter, or, rarely, a tumor. When urine cannot pass freely through this junction, it backs up and causes the renal pelvis to swell.
Another common cause is vesicoureteral reflux (VUR), where urine flows backward from the bladder into the ureters and sometimes up into the kidneys. This reverse flow can happen if the valve mechanism at the junction of the ureter and bladder does not close properly. Kidney stones can also obstruct urine flow anywhere along the urinary tract, leading to pelviectasis. During pregnancy, mild renal pelviectasis can also be a physiological finding, occurring in up to 90% of pregnant women due to hormonal changes and the expanding uterus compressing the ureters.
Identifying Renal Pelviectasis
Renal pelviectasis is frequently discovered during routine prenatal ultrasound examinations or found incidentally during imaging for other conditions. Many individuals, particularly fetuses and infants, may not experience symptoms. When symptoms do occur, they are typically related to the underlying cause of the dilation or complications like infection.
Possible symptoms include flank pain or discomfort in the side or back. Urinary changes such as increased frequency, urgency, or changes in urine color might also be observed. If there is a significant obstruction or infection, nausea and vomiting may occur. Diagnostic tests include ultrasound to visualize the kidneys and measure the degree of dilation. For more detailed assessment, a computed tomography (CT) scan or magnetic resonance imaging (MRI) may be used. Specialized kidney function tests, such as a MAG3 scan, can assess for functional obstruction, while a voiding cystourethrogram (VCUG) can detect vesicoureteral reflux.
Managing Renal Pelviectasis
Management of renal pelviectasis varies depending on the underlying cause, the degree of dilation, and whether symptoms or complications are present. For many mild cases, especially those detected prenatally, the condition may resolve on its own before birth or within the first few months of life. A watchful waiting approach is often adopted, involving regular monitoring with follow-up ultrasounds.
If an infection is present or recurs, antibiotics may be prescribed. For cases caused by a significant blockage, such as a ureteropelvic junction obstruction (UPJO), surgical intervention may be necessary to restore normal urine flow. A common procedure for UPJO is pyeloplasty, where the obstructed segment of the ureter is removed, and the healthy ureter is reattached to the renal pelvis. This procedure can often be performed minimally invasively. If vesicoureteral reflux (VUR) is the cause, management may involve continuous low-dose antibiotics or, in some instances, surgery to correct the reflux. Most cases of pelviectasis have a favorable outlook, often resolving spontaneously or being successfully managed without long-term kidney issues.