A Cautionary Tale of Replenishing Fluids in Postobstructive Diuresis

Postobstructive diuresis is a response initiated by the kidneys after relief of a ureteral obstruction to eliminate accumulated salt and fluid. Studies suggest that 0.5% to 52% of patients experience postobstructive diuresis after relief of an obstruction.1 Urine output of 200 mL/h for 2 consecutive hours or 3 L in a 24-hour period after relief of an obstruction is diagnostic.2 In most patients, the diuresis resolves on its own once the kidneys normalize the volume and solute status. However, diuresis will continue in some patients after homeostasis is reached, leading to pathologic postobstructive diuresis, which puts patients at risk for severe dehydration, metabolic acidosis, electrolyte imbalances, hypovolemic shock, and death if fluid and electrolytes are not adequately replaced.