2025 – PAGE 380 – NEPHROLOGY

VESICOURETERAL REFLUX (VUR)

Vesicoureteral reflux (VUR) is another cause of hydronephrosis. It can be diagnosed by a voiding cystourethrogram (VCUG) by showing reflux of contrast from the bladder into the ureter ± renal calyx. Children are at risk for renal failure, hypertension, and urinary tract infections. The goal of treatment is to prevent hypertension and renal failure. Once diagnosed, patients should be given antibiotic prophylaxis to prevent UTIs (use amoxicillin or trimethoprim). Grade 1–2 VUR usually resolves spontaneously within 5 years and do not need antibiotic prophylaxis. Grade 3–5 VUR requires surgical correction if there is no improvement after a year and requires antibiotic prophylaxis (e.g. Bactrim, nitrofurantoin, or amoxicillin in infants < 2 months of age).

• LOW-YIELD FACT: Deflux is a minimally invasive procedure that is done at the time of diagnosis. If after a year there is no improvement, THEN the true surgical correction is done.

POSTERIOR URETHRAL VALVES (PUV)

When posterior urethral valves (PUV) are present, they are located in the urethra and face the wrong way. This causes bilateral hydronephrosis and an increased risk of UTI. Renal ultrasound shows decreased renal parenchyma. The patient needs a STAT urologic consultation for surgical correction. It’s a bad disease and can go on to cause ESRD in up to one-third of children.

PEARL: This is ONLY IN MALES. Also, remember to think about terminology. This is a urETHRal problem and has nothing to do with the urETERs. Look for a newborn MALE with a midline abdominal mass. If you’re lucky, they just tell you that the bladder is distended and that the child dribbles a weak stream of urine.

• MNEMONIC: Girls have a tiny urethra. Boys have a penis. The longer urethra with multiple PUVs would obviously be the one that is symptomatic.PEARL: This is associated with PRUNE BELLY SYNDROME.

• (DOUBLE TAKE) PRUNE BELLY SYNDROME: Prune belly syndrome results in weak abdominal musculature (due to deficient abdominal muscles), cryptorchidism (undescended or missing testicles), and urinary tract anomalies. The urinary tract anomalies include vesicoureteral reflux (VUR), posterior urethral valves (PUV), and renal dysplasia. The renal anomalies often result in hydronephrosis, oligohydramnios, and pulmonary hypoplasia. Children have a poor prognosis, and, unfortunately, many die within a few months.PEARL: Look for a description of a newborn with weak abdominal muscles, “undescended testes” (may actually be missing), and a midline abdominal mass (distended bladder or hydronephrosis).

ABDOMINAL MASS AT BIRTH

If a newborn is noted to have an abdominal mass at birth, it’s probably due to a retroperitoneal mass of renal origin. Get a renal ultrasound and look for evidence of hydronephrosis and/or multicystic dysplastic kidney (MCDK).

PEARL: If they say MIDLINE lower abdominal mass, they probably mean the BLADDER!

MULTICYSTIC DYSPLASTIC KIDNEY (MCDK)

Multicystic dysplastic kidney (MCDK) is usually a unilateral disease. In most cases, the affected kidney is essentially nonfunctioning. The contralateral kidney has more than a 25% chance of having vesicoureteral reflux (VUR), so once the MCDK diagnosis is made, start antibiotic prophylaxis FIRST and then move on to getting the VCUG to look for VUR. The workup is similar to hydronephrosis, and you do have to eventually also do the MAG3 furosemide scan because there’s about a 50/50 chance that the child has at least some type of issue in the “good” kidney. They could have ureteropelvic junction obstruction (UPJ obstruction), vesicoureteral reflux (VUR) or posterior urethral valves (PUV).