Society For Pediatric Urology

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Incidence of pathologic postobstructive diuresis after resolution of ureteropelvic junction obstruction with a normal contralateral kidney
Joshua D. Roth, MD, Jeffrey D. Leiser, MD, PhD, Jessica T. Casey, MD, Konrad M. Szymanski, MD, MPH, Benjamin M. Whittam, MD, MS, Rosalia Misseri, MD, Richard C. Rink, MD, Mark P. Cain, MD.
Riley Hospital for Children at Indiana University Health, Indianapolis, IN, USA.

BACKGROUND: Postobstructive diuresis (POD) after pyeloplasty or percutaneous nephrostomy tube (PCN) insertion for ureteropelvic junction obstruction (UPJO) in patients with a normal contralateral kidney is not well described. We sought to determine its incidence and characteristics.
METHODS: We retrospectively reviewed pediatric UPJO patients treated with pyeloplasty or PCN at our institution from 7/1/2010 to 9/30/2017 to determine the rate of POD (defined as urine output of >300% of calculated maintenance fluid) in patients with a normal contralateral kidney. We excluded patients with a solitary kidney, or those who underwent bilateral pyeloplasty or PCN placement.
RESULTS: 397/429 (92.5%) patients with a normal contralateral kidney had treated UPJO. There were 7 cases (1.8%) of POD following PCN placement (n=3) or pyeloplasty (n=4). Median age at intervention was 1.7 years (range 11 days - 18 years); median weight was 11.4 kg (range 3.7 - 54.2 kg). There was no significant difference in age, gender, affected kidney laterality, differential kidney size or function between those who developed POD and those who did not. Affected patients were managed with additional intravenous fluids and frequent electrolyte monitoring. Median initial post-procedure urine output was 5.9 mg/kg/hr (range 3.2 - 10.0 mg/kg/hr). Five patients had nephrostomy tubes following their procedure, and two patients had indwelling stents. In those with nephrostomy tubes where urine output could be differentiated between kidneys, median initial post-procedure urine output from the affected side was 6.1 mg/kg/hr (range 2.5 - 9.1 mg/kg/hr) and 0.8 mg/kg/hr (range 0.4 - 0.9 mg/kg/hr) from the non-affected side. The median length of time to resolution of POD was 3 days (range 2-4 days). One patient developed significant acidosis, acute renal insufficiency and lethargy that improved with intravenous fluid management. Mild hyponatremia developed in 2, hypokalemia in 1, hypomagnesemia in 0, hypophosphatemia in 1, and hypoglycemia in 1.
CONCLUSIONS: POD after resolution of UPJO with pyeloplasty or PCN with a normal contralateral kidney is a rare event (1.8%). However, these patients should be carefully monitored following these procedures given the potential for significant dehydration and electrolyte disturbances.

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