Postrenal acute kidney injury Quiz: Ace Your Exams

A 66-year-old man presents to the emergency department reporting suprapubic discomfort and an inability to urinate for the past eight hours. The patient's medical history is notable for hypertension, diabetes, and hyperlipidemia. The patient smokes half a pack of cigarettes daily and drinks alcohol socially. Temperature is 37°C (98.6°F), blood pressure is 188/87 mmHg, heart rate is 99 beats per minute, respiratory rate is 20 breaths per minute, and oxygen saturation is 99% on room air. On physical examination, the patient appears uncomfortable and shifts frequently in bed. Cardiopulmonary examination is within normal limits. Suprapubic fullness is noted. Reflexes are normal and symmetric in both upper and lower extremities. Urinalysis and bloodwork are detailed below. Further examination is most likely to reveal which of the following additional findings?

Laboratory Value	Result	Reference Range
Serum Chemistry
Sodium	143 mEq/L	136-146 mEq/L
Potassium	4.5 mEq/L	3.5-5 mEq/L
Chloride	95 mEq/L	95-105 mEq/L
BUN	34 mg/dL	7-18 mg/dL
Creatinine	1.8 mg/dL (baseline 0.9 mg/dL 4 weeks ago)	0.6-1.2 mg/dL
Albumin	3.2 g/dL	3.5-5 g/dL
HbA1c	5.8%	<6%
Urinalysis
Color	Clear	Clear to light yellow
Specific gravity	1.013	1.003-1.035
Glucose	Negative	Negative
Blood	Negative	Negative
Leukocyte esterase	Negative	Negative
Nitrites	Negative	Negative
Leukocytes	1-2/hpf	Negative
Erythrocytes	1-2/hpf	Negative
Casts	None	None