WBR0414

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Renal
Prompt	[[Prompt::A 76-year-old man presents to the physician’s office with complaints of dyspnea at rest and fatigue for the past 2 weeks. The patient has been recently diagnosed with congestive heart failure. Physical examination in the office is remarkable for jugular venous distension and bilateral lower extremity pitting edema. Pulmonary auscultation is significant for crackles at the lung bases bilaterally. The physician prescribes a diuretic to relieve the patient's symptoms. Several weeks later, the patient’s routine work-up demonstrates elevated concentrations of serum calcium and uric acid. 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 convoluted tubule is the site of action of osmotic diuretics, such as mannitol, and carbonic anhydrase inhibitors, such as acetazolamide.
Answer B	AnswerB::B
Answer B Explanation	[[AnswerBExp::The thin descending loop of Henle is not a specific site of action of any diuretic.]]
Answer C	AnswerC::C
Answer C Explanation	AnswerCExp::Thick ascending loop of Henle is the site of action of loop diuretics.
Answer D	AnswerD::D
Answer D Explanation	[[AnswerDExp::Thiazide diuretics inhibit NaCl reabsorption at the level of the distal tubule.]]
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 level of the distal tubule. Thiazides are commonly prescribed to patients with advanced heart failure for relief of symptoms associated with fluid overload. The most common adverse drug reactions associated with thiazide intake are hyperglycemia, hyperlipidemia, hyperuricemia, and hypercalcemia. Educational Objective: Thiazide diuretics inhibit NaCl reabsorption at the level of the distal tubule. References: First Aid 2014 page 425]]
Approved	Approved::Yes
Keyword	WBRKeyword::Thiazide, WBRKeyword::Nephron, WBRKeyword::NaCl channel, WBRKeyword::Congestive heart failure, WBRKeyword::Fluid overload, WBRKeyword::Pharmacologic therapy, WBRKeyword::Hypercalcemia, WBRKeyword::Hyperuricemia
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::