WBR0547
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Physiology |
| Sub Category | SubCategory::Renal |
| Prompt | [[Prompt::Mr Jones is a 48 year old man with history of chronic kidney disease who presents to the nephrology clinic for follow-up. He tells you that he was recently admitted to the hospital for shortness of breath and was diagnosed as having heart failure. You explain to him that with his heart failure, blood flow to the kidneys is likely to decrease causing him to retain salt and water. Which of the following curves best represents the behavior of the substance that can be used to measure this patient's renal blood flow?
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| Answer A | AnswerA:: |
| Answer A Explanation | AnswerAExp:: |
| Answer B | AnswerB:: |
| Answer B Explanation | AnswerBExp:: |
| Answer C | AnswerC:: |
| Answer C Explanation | AnswerCExp:: |
| Answer D | AnswerD:: |
| Answer D Explanation | AnswerDExp:: |
| Answer E | AnswerE:: |
| Answer E Explanation | AnswerEExp:: |
| Right Answer | RightAnswer:: |
| Explanation | [[Explanation::Para-aminohippurate (PAH) is a derivative of hippuric acid that is filtered by the glomeruli and actively secreted by the proximal tubules. At low plasma concentrations, >90% of PAH is cleared from the blood by the kidneys in a single circulation. It is used to measure effective renal plasma flow (ERPF) since it has a high clearance, and is nontoxic at recommended doses. Curve A shows the effective concentration of PAH along the length of the proximal tubule. Notice how it increases more rapidly than creatinine concentration given that creatinine is filtered but only slightly secreted compared to PAH that is significantly secreted by the proximal tubule.
ERPF is analogous to the clearance of PAH and is calculated using the following equation:
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| Approved | Approved::No |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
