Acute Kidney Injury Practice Test

A 60-year-old patient undergoes hip replacement. During surgery, they have transient hypotension to 78/40 mm Hg for 20 minutes after blood loss of 1.2 L; they receive 1 unit packed RBCs and 1 L crystalloid. On post-op day 1, urine output is low despite additional fluids. Vitals: BP 104/66 mm Hg, HR 102/min. Exam shows dry mucous membranes; no edema; lungs clear. Labs: creatinine increases from 1.0 to 1.9 mg/dL, BUN 44 mg/dL. Urinalysis is bland. The team suspects reduced kidney perfusion from perioperative volume loss and low blood pressure.

A 46-year-old patient with no prior renal history starts trimethoprim-sulfamethoxazole for a skin infection 10 days ago. They now present with fatigue, decreased appetite, and reduced urine output. They also note a low-grade fever and diffuse itchy rash. Vitals: T 37.9°C, BP 132/78 mm Hg, HR 92/min. Exam shows a faint maculopapular rash on the trunk; mild flank discomfort to palpation. Labs: serum creatinine 2.6 mg/dL (baseline 0.9), BUN 34 mg/dL. Urinalysis shows mild protein and white cells. The timing after a new medication raises concern for kidney injury related to a drug reaction.