Massive Post-Obstructive Diuresis

Objective: Unusual clinical course Background: The purpose of presenting this case is to demonstrate the degree to which the kidney is capable of selectively excreting a massive load of sodium and water when challenged with both of these, without altering the plasma levels of other ions. Case Report: An 8-year-old boy was admitted in severe renal failure. Workup demonstrated a high grade obstruction of a single kidney. Following dialysis, the patient underwent surgery to correct the obstruction and he developed post-obstructive diuresis. Within one week he was receiving 34 liters of essentially 1/2 Na by IV and by mouth and was excreting 70% of his filtered load of water and 50% of his filtered load of sodium. As soon as the administered fluids and Na were cut back, the kidney responded appropriately. Conclusions: While post-obstructive diuresis is a real phenomenon, very frequently it is magnified by forcing diuresis with the administration of too much water. These patients are best treated by administering fluids to equal out-put for two to three days and then gradually cutting back on fluid intake. If the kidney responds appropriately, then fluids can be given as the patient requests.