Postrenal acute kidney injury Quiz: Ace Your Exams

A 66-year-old woman presents to the emergency department with acute onset hematuria and left flank pain. The patient has a history of recurrent kidney stones and states these symptoms feel similar. One year ago, her right kidney was removed due to injuries sustained in a motor vehicle accident. The patient does not drink alcohol. Temperature is 37°C (98.6°F), blood pressure is 190/87 mmHg, heart rate is 88 beats per minute, respiratory rate is 18 breaths per minute, and oxygen saturation is 99% on room air. On physical examination, the patient appears uncomfortable and in mild distress. Cardiopulmonary examination is within normal limits. The patient has left-sided costovertebral angle tenderness, and the rest of the abdominal examination is unremarkable. Initial laboratory studies and a urinalysis are shown below. Post-void residual (PVR) is <100 mL. Computed tomography (CT) of the abdomen and pelvis shows a 1 cm stone at the left ureteropelvic junction with upstream hydronephrosis; the right kidney is absent. Which of the following is the best next step in management?

Laboratory value	Result
Serum chemistry
Sodium	140 mEq/L
Potassium	4.2 mEq/L
Chloride	97 mEq/L
BUN	47 mg/dL
Creatinine	2.4 mg/dL (baseline 1.3 mg/dL six months ago)
Albumin	3.2 g/dL
Urinalysis
Color	Clear
Specific gravity	1.013
Glucose	Negative
Blood	Positive
Leukocyte esterase	Negative
Nitrites	Negative
Leukocytes	1-2/hpf
Erythrocytes	100/hpf
Casts	None