Diuretics Practice Questions

Q: A 35-year-old male experiences headache, nausea, and shortness of breath while trekking. The physician prescribes a drug to alleviate his symptoms. The drug administered primarily acts on which part of the nephron?

Proximal convoluted tubule (PCT). ***Proximal convoluted tubule (PCT)***- The clinical presentation (headache, nausea, shortness of breath while trekking) is consistent with **Acute Mountain Sickness (AMS)**, which is typically prevented or treated with **Acetazolamide**.- **Acetazolamide** is a **carbonic anhydrase inhibitor** that acts primarily in the PCT, reducing bicarbonate reabsorption and inducing metabolic acidosis, which stimulates ventilation to counteract altitude-induced respiratory alkalosis.*Loop of Henle*- This segment is the primary site for **Loop Diuretics** (e.g., **Furosemide**), which inhibit the **Na+-K+-2Cl- cotransporter** in the thick ascending limb.- Loop diuretics promote powerful diuresis but are not the standard pharmacological choice for treating or preventing the symptoms of AMS.*Distal convoluted tubule (DCT)*- The DCT is the target site for **Thiazide Diuretics** (e.g., **Hydrochlorothiazide**), which block the **Na+-Cl- cotransporter**.- Thiazides primarily manage hypertension and edema and lack the necessary mechanism (carbonic anhydrase inhibition) to directly increase ventilation required for AMS treatment.*Collecting duct (CD)*- The collecting duct is where **Potassium-sparing diuretics** and **Aldosterone antagonists** (e.g., **Spironolactone**) exert their effects by controlling final sodium and potassium balance.- While these drugs can influence fluid balance, their primary actions are far removed from the need to induce metabolic acidosis to stimulate central respiratory drives in high-altitude illness.

Q: Which of the following diuretics primarily acts on the part labeled 'D' in the given diagram of a nephron?

Hydrochlorothiazide. ***Hydrochlorothiazide*** - The part labeled 'D' in the diagram is the **Distal Convoluted Tubule (DCT)**. **Thiazide diuretics**, such as hydrochlorothiazide, primarily act on this segment of the nephron. - They work by inhibiting the **Na+/Cl- cotransporter** in the DCT, which reduces the reabsorption of sodium and chloride from the tubular fluid, leading to increased water excretion. *Furosemide* - Furosemide is a **loop diuretic** that acts on the **thick ascending limb of the Loop of Henle** (part of B), not the DCT. - It is a more potent diuretic than thiazides because it inhibits the **Na+-K+-2Cl- cotransporter**, which is responsible for reabsorbing a significant portion of filtered sodium. *Acetazolamide* - Acetazolamide is a **carbonic anhydrase inhibitor** that primarily acts on the **Proximal Convoluted Tubule (PCT)** (labeled 'A'). - Its mechanism involves reducing the reabsorption of **bicarbonate (HCO3-)**, which leads to a mild diuretic effect and can cause metabolic acidosis. *Mannitol* - Mannitol is an **osmotic diuretic** that acts mainly in the **Proximal Convoluted Tubule (PCT)** and the **descending limb of the Loop of Henle**. - It is a pharmacologically inert substance that increases the **osmolarity** of the tubular fluid, thereby preventing water reabsorption.

Q: A 50-year-old woman was prescribed a diuretic by a doctor to manage hypertension. Which of the following diuretics acts on site 'A' as marked in the given image?

Hydrochlorothiazide. ***Hydrochlorothiazide*** - Hydrochlorothiazide is a **thiazide diuretic** that acts on the **Distal Convoluted Tubule (DCT)**, which is indicated by the letter 'A' in the provided diagram. - It works by inhibiting the **Na+/Cl- cotransporter** in the early DCT, leading to increased excretion of sodium and water, which helps lower blood pressure. *Furosemide* - Furosemide is a potent **loop diuretic** that acts on the **thick ascending limb of the loop of Henle** (labeled as 'G'). - It inhibits the **Na+/K+/2Cl- cotransporter**, causing a significant increase in sodium and water excretion, making it more powerful than thiazides. *Acetazolamide* - Acetazolamide is a **carbonic anhydrase inhibitor**, and its primary site of action is the **Proximal Convoluted Tubule (PCT)** (labeled as 'D'). - It is a weak diuretic and is more commonly used for glaucoma, metabolic alkalosis, or altitude sickness rather than as a primary agent for hypertension. *Mannitol* - Mannitol is an **osmotic diuretic** that exerts its effect primarily in the **Proximal Convoluted Tubule (PCT)** and the **descending limb of the loop of Henle**. - It is administered intravenously and is used to reduce intracranial or intraocular pressure, not for the chronic management of hypertension.

Q: A patient on hydrochlorothiazide develops renal stones. What explains this adverse effect?

Decreased urinary citrate. ***Decreased urinary citrate*** - **Hydrochlorothiazide** (HCTZ) can cause hypokalemia associated with **metabolic alkalosis** - Metabolic alkalosis leads to **decreased urinary citrate** excretion (hypocitraturia) - **Citrate is a key inhibitor** of calcium oxalate and calcium phosphate stone formation by complexing with urinary calcium - Hypocitraturia theoretically increases stone formation risk by reducing this protective effect - **Clinical Note:** Despite this mechanism, thiazides are actually used to **prevent** recurrent calcium stones due to their dominant effect of reducing urinary calcium excretion *Increased urinary calcium* - This would promote stone formation, but thiazides actually **decrease** urinary calcium excretion (hypocalciuria) - The calcium-lowering effect is why thiazides are used therapeutically for **preventing** calcium nephrolithiasis - In this question, the mechanism relates to altered citrate, not calcium excretion *Decreased urinary calcium* - Thiazides do decrease urinary calcium, which is **protective** against stones, not causative - This is the primary beneficial effect that makes thiazides useful in preventing recurrent calcium nephrolithiasis - The stone formation in the question stem relates to the **citrate** mechanism, not calcium *Increased urinary citrate* - Increased citrate would be **protective** against stone formation by binding urinary calcium - Thiazides cause the opposite effect: **hypocitraturia** (decreased citrate) due to associated metabolic alkalosis - Higher urinary citrate is actually a therapeutic goal in stone prevention

Q: A patient is started on hydrochlorothiazide for hypertension and later develops renal stones. Which metabolic effect of hydrochlorothiazide is most likely responsible?

Hyperuricemia. ***Hyperuricemia*** * Hydrochlorothiazide causes **hyperuricemia** by competing with uric acid for secretion in the proximal tubule, leading to decreased uric acid excretion. * Elevated serum uric acid levels increase the risk of **uric acid stone formation**, which is a well-recognized adverse effect of thiazide diuretics. * This is why thiazides can precipitate gout attacks and increase uric acid stone risk. *Hypocalciuria* * HCTZ causes **decreased urinary calcium excretion** (hypocalciuria) by enhancing calcium reabsorption in the DCT. * This effect is **stone-PROTECTIVE**, not causative - thiazides are actually used therapeutically to prevent recurrent calcium stones. * This would NOT explain stone formation in this patient. *Hypomagnesemia* * While HCTZ can cause magnesium loss, hypomagnesemia is not a primary mechanism for stone formation with thiazide use. * Magnesium is actually a stone inhibitor, so low levels could theoretically contribute, but this is not the main mechanism. *Hypocitraturia* * HCTZ does not typically cause significant citrate wasting or hypocitraturia. * Hypocitraturia is more characteristic of **carbonic anhydrase inhibitors** and chronic metabolic acidosis, not thiazide diuretics.

Q: The image shows drug 'X' blocking a channel in the renal tubule. Which of the following drugs is 'X'?

Amiloride. ***Amiloride*** - The image shows drug 'X' inhibiting the **epithelial sodium channel (ENaC)** in the kidney tubule. **Amiloride** is a potassium-sparing diuretic that directly blocks ENaC. - By blocking ENaC, amiloride reduces sodium reabsorption and thereby reduces potassium excretion, making it a **potassium-sparing diuretic**. *Eplerenone* - **Eplerenone** is a selective aldosterone receptor antagonist. It blocks the action of aldosterone, not directly the ENaC. - While it has a similar overall effect of potassium-sparing, its mechanism is upstream of the ENaC receptor itself, by preventing aldosterone from increasing ENaC expression. *Canrenone* - **Canrenone** is an active metabolite of spironolactone, which is also an aldosterone receptor antagonist. - Like eplerenone, it works by blocking aldosterone receptors, preventing aldosterone from increasing ENaC activity, rather than directly blocking the channel itself. *Indapamide* - **Indapamide** is a thiazide-like diuretic that acts on the distal convoluted tubule. - It inhibits the **Na+/Cl- symporter**, which is different from the ENaC shown in the image, affecting a different part of the nephron and mechanism of action.

Q: A 66-year-old male presents to the outpatient cardiology clinic for evaluation of suspected primary hypertension. His blood pressure is elevated to 169/96 mm Hg, and his heart rate is 85/min. Physical examination reveals an overweight male with regular heart and lung sounds. Following repeated elevated blood pressure measurements, the diagnosis is made and the patient is started on hydrochlorothiazide. Of the following options, which is a side effect that one could experience from thiazide-like diuretics?

Hyperuricemia. ***Hyperuricemia*** - Thiazide diuretics inhibit the secretion of **uric acid** in the renal tubules. [1] - This can lead to increased serum uric acid levels, potentially exacerbating or precipitating **gout**. [1] *Hyperkalemia* - Thiazide diuretics work by inhibiting the Na+/Cl- cotransporter in the **distal convoluted tubule**, which leads to increased sodium delivery to the collecting duct. [1] - This promotes the excretion of potassium, resulting in **hypokalemia**, not hyperkalemia. *Hypocalcemia* - Thiazide diuretics decrease the excretion of **calcium** by increasing its reabsorption in the distal convoluted tubule. [1], [2] - This effect leads to **hypercalcemia**, not hypocalcemia, and can be beneficial in patients with osteoporosis. [2] *Hypernatremia* - Thiazide diuretics increase the excretion of **sodium** along with water. - This effect tends to cause **hyponatremia**, not hypernatremia, due to increased urinary sodium loss and water retention relative to sodium. [2]

Q: Which of the following is a carbonic anhydrase inhibitor?

Acetazolamide. ***Acetazolamide*** - Acetazolamide is a classic example of a **carbonic anhydrase inhibitor**, primarily used as a diuretic and for managing **glaucoma** and **altitude sickness**. - It works by inhibiting the enzyme **carbonic anhydrase** in the **proximal renal tubule**, reducing bicarbonate reabsorption and thus promoting diuresis. *Hydrochlorothiazide* - Hydrochlorothiazide is a **thiazide diuretic** that acts on the **distal convoluted tubule** to inhibit the reabsorption of sodium and chloride. - It is not a carbonic anhydrase inhibitor. *Mannitol* - Mannitol is an **osmotic diuretic** that works in the **proximal tubule** and **descending limb of Henle's loop** by creating an osmotic gradient. - It is not a carbonic anhydrase inhibitor and functions by drawing water into the renal tubule, leading to increased urine output. *Furosemide* - Furosemide is a **loop diuretic** that acts on the **thick ascending limb of the loop of Henle** by inhibiting the Na+-K+-2Cl- cotransporter. - It is one of the most potent diuretics but does not inhibit carbonic anhydrase.

Q: Hydrochlorothiazide works by inhibiting

Na+ Cl pump in early DCT. ***Na+ Cl pump in early DCT*** - **Hydrochlorothiazide** is a **thiazide diuretic** that acts primarily on the **early distal convoluted tubule (DCT)**. - It inhibits the **sodium-chloride cotransporter (NCC)**, leading to increased excretion of sodium, chloride, and water. *Na+ Cl pump in late DCT* - The **late DCT** and collecting duct are primarily involved in fine-tuning sodium reabsorption, influenced by **aldosterone**, not the primary site of action for thiazides. - The **epithelial sodium channel (ENaC)** and Na+/K+-ATPase are more prominent here. *Na+ K+ 2Cl pump in descending limb of loop of Henle* - The **descending limb of the loop of Henle** is primarily permeable to water, with no active ion pumps like **Na+ K+ 2Cl pump**. - Its main function is to concentrate the urine by allowing water to move out. *Na+ K+ 2Cl pump in ascending limb of loop of Henle* - **Furosemide** and other **loop diuretics** act on the **Na+ K+ 2Cl cotransporter (NKCC2)** in the **thick ascending limb of the loop of Henle**, not hydrochlorothiazide. - Inhibition here prevents significant reabsorption of sodium, potassium, and chloride, leading to potent diuresis.

Question 1

A 35-year-old male experiences headache, nausea, and shortness of breath while trekking. The physician prescribes a drug to alleviate his symptoms. The drug administered primarily acts on which part of the nephron?

Accepted Answer

Proximal convoluted tubule (PCT)

Answer

Loop of Henle

Answer

Collecting duct (CD)

Answer

Distal convoluted tubule (DCT)

Question 2

Which of the following diuretics primarily acts on the part labeled 'D' in the given diagram of a nephron?

Accepted Answer

Hydrochlorothiazide

Answer

Acetazolamide

Answer

Mannitol

Answer

Furosemide

Question 3

A 50-year-old woman was prescribed a diuretic by a doctor to manage hypertension. Which of the following diuretics acts on site 'A' as marked in the given image?

Accepted Answer

Hydrochlorothiazide

Answer

Acetazolamide

Answer

Mannitol

Answer

Furosemide

Question 4

A patient on hydrochlorothiazide develops renal stones. What explains this adverse effect?

Accepted Answer

Decreased urinary citrate

Answer

Increased urinary citrate

Answer

Decrease urinary calcium

Answer

Increase urinary calcium

Question 5

By what primary mechanism does hydrochlorothiazide help prevent the formation of calcium stones?

Accepted Answer

It increases calcium reabsorption in the distal convoluted tubule, leading to a decrease in urinary calcium excretion.

Answer

It directly dissolves existing calcium stones by altering urinary pH and increasing their solubility.

Answer

It increases the urinary excretion of citrate, which acts as a chelating agent.

Answer

It increases the filtration of calcium at the glomerulus, thereby reducing serum calcium levels.

Question 6

A patient is started on hydrochlorothiazide for hypertension and later develops renal stones. Which metabolic effect of hydrochlorothiazide is most likely responsible?

Accepted Answer

Hyperuricemia

Answer

Hypocitraturia

Answer

Hypocalciuria

Answer

Hypomagnesemia

Question 7

The image shows drug 'X' blocking a channel in the renal tubule. Which of the following drugs is 'X'?

Accepted Answer

Amiloride

Answer

Eplerenone

Answer

Canrenone

Answer

Indapamide

Question 8

A 66-year-old male presents to the outpatient cardiology clinic for evaluation of suspected primary hypertension. His blood pressure is elevated to 169/96 mm Hg, and his heart rate is 85/min. Physical examination reveals an overweight male with regular heart and lung sounds. Following repeated elevated blood pressure measurements, the diagnosis is made and the patient is started on hydrochlorothiazide. Of the following options, which is a side effect that one could experience from thiazide-like diuretics?

Accepted Answer

Hyperuricemia

Answer

Hyperkalemia

Answer

Hypocalcemia

Answer

Hypernatremia

Answer

Hypoglycemia

Question 9

Which of the following is a carbonic anhydrase inhibitor?

Accepted Answer

Acetazolamide

Answer

Hydrochlorothiazide

Answer

Mannitol

Answer

Furosemide

Question 10

Hydrochlorothiazide works by inhibiting

Accepted Answer

Na+ Cl pump in early DCT

Answer

Na+ Cl pump in late DCT

Answer

Na+ K+ 2Cl pump in descending limb of loop of Henle

Answer

Na+ K+ 2Cl pump in ascending limb of loop of Henle

Diuretics — MCQs

Diuretics — MCQs

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