Chronic Kidney Disease USMLE Step 1 Practice Question
A 68-year-old man with stage 3b chronic kidney disease (eGFR 34 mL/min/1.73m²) presents for research study participation. Vital signs: BP 142/88 mmHg, HR 76/min, RR 14/min, Temp 37°C. Recent labs show serum creatinine 1.8 mg/dL and BUN 28 mg/dL. Researchers administer para-aminohippuric acid at low plasma concentration to measure renal clearance. The PAH is nearly completely removed during single-pass renal circulation. Which parameter does PAH clearance best approximate under these conditions?
Answer choices
- ARenal plasma flowCorrect answer
- BRenal blood flow
- CFree water clearance
- DGlomerular filtration rate
- EFiltration fraction
- FTubular secretion capacity
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