Congenital hydronephrosis describes a condition where one or both kidneys become swollen with urine. This swelling occurs because urine cannot drain properly from the kidney to the bladder. While concerning, it is a common finding and often manageable with appropriate medical care.
Understanding Congenital Hydronephrosis
Congenital hydronephrosis refers to the enlargement of the kidney’s urine-collecting system, the renal pelvis and calyces, due to urine accumulation. Normally, urine flows through narrow tubes called ureters into the bladder for storage and eventual elimination. In hydronephrosis, this normal flow is disrupted, often by a blockage in the urinary tract or a backward flow of urine, known as reflux. When urine cannot exit efficiently, it builds up, causing kidney structures to stretch and swell. Severity is typically graded from mild to severe, which helps guide management decisions.
Reasons for Development
Congenital hydronephrosis often stems from an obstruction in the urinary tract or a condition that allows urine to flow backward. Common obstructive causes include ureteropelvic junction (UPJ) obstruction, where the kidney-ureter connection is narrowed, impeding urine drainage, and ureterovesical junction (UVJ) obstruction, occurring at the point where the ureter enters the bladder. In male infants, posterior urethral valves (PUV) are flap-like tissues in the urethra that block urine flow from the bladder. A less common obstructive cause is a ureterocele, a balloon-like swelling of the lower part of the ureter as it enters the bladder. Vesicoureteral reflux (VUR), the backward flow of urine from the bladder into the ureters and kidneys, is a significant non-obstructive cause.
How It Is Identified
Congenital hydronephrosis is most frequently identified before birth through routine prenatal ultrasounds, often during the second or third trimester of pregnancy. This imaging technique allows visualization of the fetal kidneys and detection of swelling. Prenatal detection prompts further evaluation after birth. Following birth, a physical examination and repeat renal ultrasound confirm the diagnosis and assess its current severity. If concerns persist or the hydronephrosis is more pronounced, additional imaging tests may be necessary, such as a voiding cystourethrogram (VCUG) to check for vesicoureteral reflux, or a diuretic renogram, also known as a MAG3 scan, to evaluate kidney function and drainage by tracking a radioactive tracer through the urinary system.
Approaches to Care
The approach to managing congenital hydronephrosis depends on its severity and the underlying cause. For many infants with mild to moderate hydronephrosis, watchful waiting is employed, involving regular ultrasounds to monitor the kidney swelling as the condition often improves or resolves on its own without intervention. In some cases, particularly when vesicoureteral reflux is present, low-dose antibiotics may be prescribed to prevent urinary tract infections (UTIs). Surgical intervention becomes necessary for more severe cases, declining kidney function, recurrent UTIs, or significant obstruction. Common surgical procedures include pyeloplasty (repairs UPJ obstruction), ureteral reimplantation (corrects vesicoureteral reflux by repositioning the ureter), and valve ablation for male infants with posterior urethral valves.
Long-Term Outlook
The long-term outlook for children with congenital hydronephrosis is generally favorable, with many cases resolving spontaneously or being effectively managed without lasting kidney damage. Consistent follow-up with a pediatric urologist or nephrologist is important to monitor kidney health. This monitoring ensures that any changes are identified and addressed promptly. While less common, complications can include kidney damage, scarring, or, in severe unmanaged instances, chronic kidney disease. Early detection and appropriate management are important for achieving the best possible outcomes. Most children with this condition lead full and active lives, with minimal impact on their quality of life.