A 3700-g male infant is born at 38 weeks’ gestation after a pregnancy with limited prenatal care. The infant is noted after birth to have a dribbling urinary stream and a lower abdominal mass. Postnatal ultrasonography reveals bilateral hydronephrosis with bladder wall hypertrophy and an enlarged urethra.
What is the most likely diagnosis?
What is the most appropriate next test?
ANSWERS TO CASE 51: Posterior Urethral Valves
Summary: A term newborn male has evidence of severe urinary obstruction.
• Most likely diagnosis: Posterior urethral valves (PUV).
• Most appropriate next test: Renal ultrasonography (USG).
1. Know the various presentations of patients with PUV.
2. Know the possible long-term sequelae associated with PUV.
3. Be familiar with common abdominal masses in the newborn period.
Many conditions cause abdominal masses in the newborn (Table 51-1). In this infant’s case, the dribbling urinary stream suggests PUV. An abdominal USG is a useful and noninvasive tool to aid in the diagnosis.
Table 51-1 • ABDOMINAL MASSES CAUSING DISTENTION
Posterior Urethral Valves
VESICOURETERAL REFLUX (VUR): Retrograde urine flow from the bladder into the ureter(s) and, if severe, into the kidney. In general this condition is more common in females and may lead to recurrent urinary tract infections (UTI) and diminished renal function. Depending on the degree of reflux, treatment ranges from antibiotic prophylaxis to surgical intervention.
VOIDING CYSTOURETHROGRAM (VCUG): A radiographic study in which a catheter is placed in the bladder and contrast is instilled. Upon voiding, the urethra is visualized and, in cases of vesicoureteral reflux, the ureters are outlined.
Fetal ultrasonography assists in the prenatal diagnosis of urinary tract obstruction. Sonographic findings include bilateral hydronephrosis with bladder distention with a “keyhole” appearance,particularly in a male fetus. In severe cases oligohydramnios is found and may lead to poor fetal lung development with pulmonary insufficiency and congenital contractures. Prenatal ultrasonography leads to the diagnosis in most cases of PUV.
Urethral valves are leaflets of tissue located in the lumen of the distal urethra from the prostate to the external sphincter. Posterior urethral valves are the most common cause of severe urinary tract obstruction in boys,occurring in 1 of every 5000-8000 newborn males; 25% to 30% ultimately have end-stage renal disease or chronic renal insufficiency. Neonates present with distended bladders, poor or dribbling urinary streams, palpable kidneys, reduced renal function, or UTI. Older infants have failure to thrive, renal dysfunction, or UTI. Older boys may present with voiding difficulty, such as diurnal enuresis or frequency. Posterior urethral valve is confirmed with VCUG or postnatal USG. The evaluation of the boy who has UTI includes VCUG and renal USG.
Immediate relief of PUV obstruction includes bladder catheterization through the urethra with a small feeding tube. If UTI is suspected, antimicrobial therapy is initiated. Serum electrolytes, blood urea nitrogen, and creatinine levels are measured with correction as needed. Hemodynamic status is monitored because sepsis or renal failure can lead to cardiovascular collapse.
After acute obstruction is relieved and the patient has been stabilized, endoscopic transurethral valve ablation may be performed if the serum creatinine level is normal and urethral size permits. If the serum creatinine remains elevated, the urethral lumen is too narrow, or the UTI does not respond to antibiotics, emergent vesicostomy may be necessary. Following ablation, VUR and persistent hydroureteronephrosis may occur.
After surgery, patients require surveillance of renal function and for possible UTI. Many patients will have polyuria because of diminished ability to concentrate the urine and are at greater risk for dehydration.
Routine care for boys with a history of PUV includes regular monitoring with urinalysis, renal USG, serum electrolyte levels, blood pressure, and linear growth. They may have prolonged diurnal enuresis and may require urodynamic studies to evaluate their voiding. Renal insufficiency is common, and some may require renal transplantation.
51.1 A 3-month-old boy presents with fever without a source. As part of his evaluation a urinalysis is performed; a UTI is suspected. Which of the following is the best next step?
A. If the urine culture reveals UTI, renal USG and VCUG should be performed.
B. VCUG should be performed only after a second UTI is diagnosed.
C. Antibiotics should be initiated after urine culture and sensitivities are obtained.
D. Renal biopsy should be performed.
E. Preferred methods of collection for urine culture for this infant include midstream clean-catch and bag urine.
51.2 A 1-month-old girl presents with fever and vomiting. Her serum white blood cell (WBC) count is elevated. Urinalysis reveals 100 WBC per high-power field (unspun); it is positive for nitrates and leukocyte esterase. Urine culture results confirm a UTI; renal USG and VCUG show mild to moderate hydronephrosis and grade III VUR on the right. Which of the following is the best next step?
A. She will require surgical reimplantation of her right ureter.
B. Antimicrobial prophylactic therapy should be started when her current course of antibiotics is completed.
C. VCUG should be performed on a monthly basis.
D. Subsequent urine specimen must be obtained only by suprapubic aspiration.
E. Renal arteriography is indicated.
51.3 A 6-month-old infant male presents to your clinic with an abdominal mass, which was discovered by his new foster mother during the child’s bath. On physical examination, you also find macroglossia and right-sided hemihyper-trophy. This infant is likely to have which of the following?
A. Down syndrome with duodenal atresia
B. Alagille syndrome and biliary atresia
C. Beckwith-Wiedemann syndrome with Wilms tumor
D. Neurofibromatosis and abdominal neurofibromas
E. Zellweger syndrome and hepatomegaly
51.4 An 8-year-old boy presents with bedwetting 3 to 4 times per week for “as long as he can remember.” He has a strong urine stream, daytime urine continence, and no UTIs. His physical examination is normal. Which of the following is the most appropriate next course of action?
A. Urodynamic studies.
B. Reassurance; he has secondary nocturnal enuresis.
C. Use of enuresis alarm.
D. Desmopressin acetate can be administered every 6 hours to control enuresis.
E. Behavior modification that includes punishment for wet nights and rewards for dry nights.
51.1 A. For any male infant with a UTI, evaluation of anatomy and function is necessary. The preferred methods of urine collection include bladder catheterization and suprapubic bladder aspiration. Antimicrobial therapy is started empirically while awaiting urine culture and sensitivity results.
51.2 B. Infants and children with VUR as described typically receive prophylactic antimicrobial therapy (although the benefit of this therapy on lower grade disease has been questioned) and close monitoring for infection with urinalysis and urine culture at 3- to 4-month intervals. Sulfamethoxazole-trimethoprim, trimethoprim alone, and nitrofurantoin are commonly used for antimicrobial prophylaxis, VUR is graded from I to V based on the degree of reflux. Higher-grade reflux is less likely to resolve spontaneously and is more likely to result in renal damage.
51.3 C. This infant with features of Beckwith-Wiedemann syndrome is at high risk for developing Wilms tumor, hepatoblastoma, and gonadoblastoma.
51.4 C. Nocturnal enuresis occurs in 15% of 5-year-olds with a resolution rate of 15% per year. Males are more frequently affected, and family history is common. Initial evaluation includes a history of wetting pattern, prior UTI, and developmental, social, and emotional history. Physical examination includes kidney palpation, neurologic examination, and examination of the back looking for sacral dimple or hairy nevus. Some recommend urinalysis and culture to rule out occult infection. The enuresis alarm has a success rate of 70% to 90% and requires parental support. Pharmacologic interventions include nighttime doses of imipramine or oral desmopressin acetate. Intranasal formulations of desmopressin are no longer approved for the treatment of primary nocturnal emuresis. Following use of desmopressin acetate, fluid intake is restricted to avoid hyponatremia. Pharmacologic treatment usually is reserved for special occasions, such as when the child is sleeping over at a friend’s house, summer camp, and so on. Behavior modification does not include punishment.
Posterior urethral valve occurs exclusively in males.
Boys with posterior urethral valve are at risk for end-stage renal disease, even after appropriate therapy.
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