Posterior Urethral Valve Masquerading as Failure to Thrive

Introduction: Only half the cases of posterior urethral valves (PUV) are diagnosed antenatally with dilated kidneys and ureters. The rest, present later in life with failure to thrive (FTT), recurrent urinary tract infections (UTI) and nocturnal enuresis in older boys. Undiagnosed PUVs can have sequelae such as progression to chronic kidney disease, vesicoureteral reflux (VUR) and overactive bladder which can be prevented if picked up early. Case Description: Patient is a 6 month old male, ex-35 weeker born small-for-gestational age with an otherwise normal prenatal course who presented with FTT. Since birth, his weight has been tracking below the 3rd centile. He had been tried from breast milk to various formulae over a period of time with minimal weight gain. He was having frequent spit-ups and took frequent small volume feeds; so was started on a proton pump inhibitor for possible gastroesophaegal reflux. There was also concerns of crying during voiding and stooling. He was admitted to the hospital and was started on scheduled feeds. His labs were unremarkable except for mild hyponatremia (132 mEq/L), 3+ red blood cells and 3+ leukocyte esterase in the urine. His C-reactive protein was moderately elevated. So a catheterized urine sample was obtained which also revealed the same findings and was sent for culture. The next day, his serum sodium dropped further (128 mEq/L) with a 4x rise in serum creatinine (0.8 mg/dL). Physical exam disclosed a new mass in the right iliac fossa. Ultrasonography revealed a massively distended urinary bladder with bilateral moderate-to-severe hydroureteronephrosis. A voiding cystourethrogram revealed dilatation and elongation of the posterior urethra, grade 5 VUR on the left and severe bladder trabeculation concerning for a PUV. An indweling Foley's catheter was placed and his serum sodium and creatinine normalized within the next few hours. Urine culture was sterile, but he was started on prophylactic antbiotics given his severe VUR and was referred to a higher facility for surgical correction. Discussion: PUV is a rare yet serious cause of FTT in male children. This case was a reminder of how PUVs can be present even in babies who did not have oligohydramnios in-utero and have been voiding well. Chronic struggling to void against a tight urethra, fighting recurrent UTIs and a distended bladder which limits food intake can all contribute to poor weight gain in babies.