Acute renal failure in urological disease

Definition

Acute kidney injury (AKI) is a rapid decline in kidney function, manifested by rising creatinine and/or reduced urine output.

Of particular importance in urology are postrenal causes: obstruction of the ureters, urethra, or bladder outlet.

Postrenal causes

• Always look for reversible obstruction in unexplained AKI.
• Pay particular attention to anuria, oliguria, hydronephrosis, malignancy, stones, a solitary kidney, and the postoperative setting.

Unilateral obstruction does not usually cause marked AKI when the other kidney functions normally. Severe azotemia requires a search for bilateral disease, a solitary kidney, or an additional cause.

Diagnosis

• Monitor creatinine, urea, potassium, sodium, bicarbonate, acid–base status, and urine output.
• Ultrasonography for hydronephrosis and urinary retention.
• In lower tract obstruction, assess bladder urine volume and catheter patency.

Emergency management

• In postrenal AKI, restore drainage.
• In urinary retention, drain the bladder.
• In upper tract obstruction, perform stenting or nephrostomy.
• In parallel: correct hyperkalemia, acidosis, and fluid overload.

Postobstructive diuresis

• Marked diuresis may follow relief of longstanding obstruction.
• After relief of longstanding or bilateral obstruction, monitor hourly urine output, blood pressure, body weight, sodium, potassium, magnesium, and creatinine. Monitoring frequency depends on the degree of diuresis and the patient's condition.
• Individualize fluid and electrolyte replacement according to losses and clinical status, avoiding hypovolemia and excessive fluid administration. Marked diuresis requires inpatient monitoring.

Indications for nephrology support

• Refractory hyperkalemia.
• Severe metabolic acidosis.
• Pulmonary edema.
• Marked uremia.

Consult a nephrologist and consider renal replacement therapy.

Algorithm