WBR0414

Author	[[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A 76-year-old male, recently diagnosed with heart failure, presents to the physician’s office with complaints of dyspnea upon rest and fatigue. Physical examination reveals jugular venous distension and bilateral lower extremity pitting edema. Pulmonary auscultation reveals crackles at the base of lungs bilaterally. The physician prescribes a diuretic to relieve his symptoms. Several weeks later, the patient’s routine work-up reveals elevated serum calcium and uric acid levels. Based on the image below, the diuretic prescribed to this patient acts at the level of which segment of the nephron? ]]
Answer A	AnswerA::A
Answer A Explanation	[[AnswerAExp::The proximal tubule is the action site of osmotic diuretics such as mannitol and carbonic anhydrase inhibitors, including acetazolamide.]]
Answer B	AnswerB::B
Answer B Explanation	[[AnswerBExp::The thin descending loop of Henle is not the site of action of any diuretic.]]
Answer C	AnswerC::C
Answer C Explanation	[[AnswerCExp::Thick ascending loop of Henle is the action site of loop diuretics.]]
Answer D	AnswerD::D
Answer D Explanation	[[AnswerDExp::Thiazide diuretics inhibit NaCl reabsorption at the level of the distal tubule. Side effects of thiazide diuretics include hypercalcemia and hyperuricemia.]]
Answer E	AnswerE::E
Answer E Explanation	[[AnswerEExp::The collecting duct is the main site of action of aldosterone receptor antagonists, such as spironolactone.]]
Right Answer	RightAnswer::D
Explanation	[[Explanation::Thiazide diuretics inhibit NaCl reabsorption at the distal tubule level. Thiazides are commonly prescribed for patients with heart failure. Frequent side effects are often summarized with the mnemonic hyperGLUC: hyperGlycemia, hyperLipidemia, hyperUricemia, and hyperCalcemia. Educational Objective: Thiazide diuretics inhibit NaCl reabsorption by inhibiting the NaCl channel in the distal tubule. They are commonly prescribed for patients with heart failure. Common side effects include hyperGLUC: hyperGlycemia, hyperLipidemia, hyperUricemia, and hyperCalcemia. References: First Aid 2014 page 425]]
Approved	Approved::Yes
Keyword	WBRKeyword::loop of henle, WBRKeyword::action site, WBRKeyword::kidney, WBRKeyword::cardiology, WBRKeyword::excratory system, WBRKeyword::thiazide diuretics
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::