Antenatal Hydronephrosis (Case 27)

Chapter 64 Antenatal Hydronephrosis (Case 27)



David J. Sas, DO, MPH




Case


A routine prenatal ultrasound of a 20–weeks’-gestation male fetus reveals bilateral hydronephrosis.




Differential Diagnosis











Multicystic dysplastic kidneys (MCDK)
Vesicoureteral reflux (VUR)
Urinary tract obstruction


Speaking Intelligently


When antenatal hydronephrosis is detected, I assess the degree of hydronephrosis and plan additional evaluation after birth. Although the definition of hydronephrosis is not universally agreed upon, most experts consider an anterior-posterior renal pelvis diameter of >5 mm in a second-trimester ultrasound abnormal. The degree of hydronephrosis predicts the likelihood of significant renal pathology. Patients with antenatal hydronephrosis not detected in utero often present postnatally with urinary tract infection, poor urinary stream, failure to thrive, dehydration, neonatal sepsis, or respiratory distress. It is important to determine the mechanism of hydronephrosis, because some are amenable to surgical intervention. As with all kidney disease, the goal is to protect residual renal function.



Patient Care



Clinical Thinking



• The degree of prenatal hydronephrosis is an important predictor of renal pathology.

• Newborns with enlarged kidneys can have impaired respiratory function either through mass effect or pulmonary hypoplasia secondary to oligohydramnios. Impaired respiratory function is the most important predictor of survival in babies born with renal insufficiency.

• After birth a thorough physical examination is performed, and urine output is carefully monitored.

• There may be excessive water and electrolyte loss, so hydration status is monitored carefully and electrolytes are checked as needed.


History



• Review the prenatal record, including laboratory investigations and ultrasound reports.

• A history of oligohydramnios increases the likelihood of significant postnatal renal impairment and potential respiratory problems at birth.

• A careful family history focusing on cystic kidneys, solitary kidney, or obstructive uropathy should be elicited.


Physical Examination



• The initial assessment should focus on vital signs, as well as respiratory effort and lung auscultation.

• Be particularly wary of masses and abnormal musculature on abdominal examination.

• Carefully note the presence or absence of descended testicles, anatomy of the penile/urethral meatus, and quality of the urinary stream.

• A complete physical examination is performed, looking for other anatomic anomalies that may suggest an associated syndrome.


Tests for Consideration



• Serum electrolytes and measure of kidney function: Should be monitored carefully because abnormalities may develop over time. Initial creatinine values reflect the mother’s renal function rather than the baby’s. This normally persists until about 5 to 7 days of life but varies in babies with renal insufficiency. $174

• Urine culture: Urinary tract abnormalities increase the risk for infection. $148


Imaging Considerations


→ Renal ultrasound: If performed during the first 48 hours of life, renal ultrasound may falsely minimize hydronephrosis because of the normal oliguric state during the newborn period. By 2 to 4 weeks, the infant should be feeding well and gaining weight, and the renal ultrasound will provide accurate assessment of the degree of postnatal hydronephrosis. About one third of babies with mild prenatal hydronephrosis will have an abnormal postnatal ultrasound; the more severe the prenatal hydronephrosis, the more likely the postnatal scan will demonstrate persistence. If anterior-posterior renal pelvis diameter is >10 mm, start antimicrobial prophylaxis with amoxicillin 20 mg/kg once daily. $590


→ Voiding cystourethrogram (VCUG): VCUG is used for detection of vesicoureteral reflux. Start antimicrobial prophylaxis as above if the VCUG reveals grade 4 or 5 reflux; some start prophylaxis for lesser grades. However, the utility of prophylactic antibiotics in prevention of recurrent urinary tract infection (UTI) in infants with VUR is currently under investigation, and many expect it to be demonstrated that there is little utility in prophylaxis. $600


→ Dimercaptosuccinic acid (DMSA) scan: DMSA scan can evaluate renal function vis-à-vis proximal tubule uptake. This test is useful for patients suspected of having little functioning renal parenchyma. $1524


→ Diuretic renography: Like the DMSA, this study can also evaluate renal function but is most useful for evaluating for obstruction. $906

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Jul 18, 2016 | Posted by in PEDIATRICS | Comments Off on Antenatal Hydronephrosis (Case 27)

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