The management of UTO is directed by the underlying cause; however, regardless of the cause, relief of a prolonged period of obstruction with anuria is often accompanied by postobstructive diuresis. In most cases, this polyuria is transient and may be an adaptive response to fluid overload from the anuria, possibly compounded by iatrogenic fluid administration prior to the diagnosis of UTO. Routine monitoring of vital signs and serum electrolytes is important to assess possible volume depletion or the development of acquired DI.[14] The mechanism of this latter phenomenon is the same as that of the polyuria of partial UTO, manifesting as hypernatremia resistant to vasopressin. Alternatively, large sodium losses from tubular dysfunction will result in hyponatremia. If tachycardia and/or orthostatic hypotension develop following relief of the obstruction, pathologic hypovolemia secondary to diuresis and tubular damage should be suspected. In either of these instances, fluid and electrolyte correction are warranted; otherwise, fluid administration may only be serving to prolong the diuretic phase of the postobstructive recovery.[3,14]

The prognosis for the recovery of renal function is dependent upon the severity and duration of the obstruction. In addition, patients with obstruction complicated by pyelonephritis generally have a much worse outcome. Longstanding UTO leads to tubulointerstitial damage, which can ultimately result in ESRD. In the pediatric population, congenital urologic anomalies causing obstruction are the major cause of ESRD requiring dialysis.[15] With the exception of these risk factors, there is no way of accurately predicting to what degree renal function will be restored after an obstruction is removed


In the case presented, a Foley catheter was initially inserted, 2200 mL of urine were emptied, and the catheter was clamped. An hour later, 1700 mL were drained and the catheter was again clamped. A third drainage 50 minutes later yielded another 1000 mL. In total, 4900 mL of red-tinged urine was drained. The patient's abdominal distention promptly resolved with evacuation of the bladder, and the lower extremity edema regressed over the course of the patient's 4-day hospital stay. A review of the literature yielded case reports of similarly exaggerated urinary retention, including one case of a patient retaining more than 16 L over a 10-day period of anuria. The patient's creatinine levels dropped dramatically by the time of discharge and were within the normal reference range on follow-up 1 week after discharge.
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