[Health Tip] Congenital Hydronephrosis with Fluid in Fetal Kidney... "Neglect Can Cause Functional Damage"

Advice has been given on the need for proper diagnosis and treatment of congenital hydronephrosis, one of the most common conditions found in fetuses before birth.

According to Ansan Hospital of Korea University on the 16th, congenital hydronephrosis is a condition affecting about 1 to 5 out of every 100 fetuses and is the most commonly detected urinary system abnormality before birth. The kidney functions as a purification tank and drainage system that removes waste products present in the blood. Blood is filtered in the kidney to produce urine, which temporarily collects in the renal pelvis and calyces, the innermost parts of the kidney, before flowing into the ureter. If any part of the urine flow pathway narrows or becomes blocked, pressure increases upstream, causing expansion due to the elevated pressure.

Hydronephrosis refers to the state where urine produced in the kidney excessively accumulates, causing dilation of the renal pelvis. If left untreated, it can lead to kidney atrophy and loss of kidney function. However, about 80% of fetuses with hydronephrosis show no symptoms or abnormal signs at birth. Among these, about half already experience symptom resolution at birth. Even if hydronephrosis persists after birth, many cases resolve naturally within one year. Nevertheless, some cases worsen, leading to kidney function damage, so regular check-ups are necessary.

The main causes of congenital hydronephrosis are obstructive uropathy and vesicoureteral reflux. Obstructive uropathy refers to a blockage in the urinary tract, often at the junction between the renal pelvis and ureter. Vesicoureteral reflux is a condition where urine flows backward from the bladder into the ureter or kidney. Other known causes of congenital hydronephrosis include polycystic kidney disease and duplicated ureters.

Congenital urinary tract malformations, including congenital hydronephrosis, are the most common causes of chronic kidney disease in children and adolescents. Therefore, congenital hydronephrosis detected during pregnancy requires postnatal evaluation through consultation with a pediatric specialist. Even if the fetus has hydronephrosis, most cases do not pose problems for normal delivery.

Professor Lim Hyeong of the Department of Pediatrics at Korea University Ansan Hospital explained, "After birth, primary kidney and bladder ultrasound examinations are performed. Mild hydronephrosis often improves naturally, so regular ultrasound follow-ups are common." He added, "In infants under two years old, urinary tract infections are frequent, so regular urine tests are conducted. Depending on the severity of hydronephrosis, tests such as vesicoureteral reflux studies and diuretic renal scans may be performed to determine the need for surgery."

In severe cases of hydronephrosis, renal scans are conducted to assess kidney drainage function and urinary tract obstruction. If obstruction is confirmed, kidney function declines on follow-up tests, or recurrent urinary tract infections persist, surgery may be considered. A representative surgical method is pyeloplasty, which involves removing the narrowed segment at the junction of the renal pelvis and ureter and reconstructing the connection between the renal pelvis and ureter.

Professor Lim emphasized, "Since congenital urinary tract malformations, including congenital hydronephrosis, are also the most common causes of chronic kidney disease in children and adolescents, unwarranted optimism is not advisable." He stressed, "Following the primary physician’s recommendations, it is essential to identify the underlying cause of hydronephrosis through accurate testing and receive appropriate treatment and follow-up to preserve kidney function."

Im Hyeong-eun, Professor of Pediatrics and Adolescents at Korea University Ansan Hospital. [Photo by Korea University Ansan Hospital]

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