Obstructive Acute Kidney Injury in an Older Adult

A large retained bladder volume with anuria is direct evidence of lower urinary tract obstruction and requires immediate drainage. Fractional sodium excretion and proteinuria do not establish the cause of anuria.

ECG changes with potassium 6.3 mmol/L require immediate membrane stabilization with intravenous calcium and potassium-shifting measures. Decompression treats the cause but does not act quickly enough to protect the myocardium.

High urine output after relief of bilateral or prolonged obstruction reflects post-obstructive diuresis from accumulated solute, impaired concentrating ability, and persistent tubular dysfunction.

Post-obstructive diuresis can rapidly cause hypovolemia, hypokalemia, hypomagnesemia, and dysnatremia. Hourly output and serial laboratory and clinical assessment are required.

NSAIDs can worsen renal perfusion, and ACE inhibitors may aggravate the fall in filtration during acute obstruction or hypovolemia. Reassess the indication after recovery.