20 MCQs on Diuretics and Kidney Diseases Based on Guyton Principles
Diuretic Mechanisms and Classifications
Which of the following diuretics acts primarily at the loop of Henle?
- A) Hydrochlorothiazide
- B) Spironolactone
- C) Furosemide
- D) Amiloride
Answer: C) Furosemide
Loop diuretics like furosemide act at the loop of Henle by inhibiting the reabsorption of sodium and chloride, increasing sodium excretion up to 20-25% of the filtered load 1.
What is the primary site of action for thiazide diuretics?
- A) Proximal tubule
- B) Loop of Henle
- C) Distal convoluted tubule
- D) Collecting duct
Answer: C) Distal convoluted tubule
Thiazide diuretics act in the distal portion of the tubule, increasing fractional excretion of sodium to 5-10% of the filtered load 1.
Which diuretic class maintains its efficacy even in patients with severely impaired renal function?
- A) Thiazides
- B) Loop diuretics
- C) Potassium-sparing diuretics
- D) Carbonic anhydrase inhibitors
Answer: B) Loop diuretics
Loop diuretics maintain their efficacy unless renal function is severely impaired, whereas thiazides lose effectiveness when creatinine clearance falls below 40 mL/min 1.
Metolazone differs from typical thiazide diuretics because:
- A) It has no effect on calcium excretion
- B) It can produce diuresis in patients with GFR below 20 mL/min
- C) It inhibits carbonic anhydrase
- D) It acts primarily in the loop of Henle
Answer: B) It can produce diuresis in patients with GFR below 20 mL/min
Unlike thiazides, metolazone can produce diuresis in patients with glomerular filtration rates below 20 mL/min 2.
Which statement about spironolactone is correct?
- A) It acts by inhibiting sodium-potassium co-transport
- B) It is a potassium-wasting diuretic
- C) It antagonizes the effects of aldosterone
- D) It is the most potent diuretic for treating pulmonary edema
Answer: C) It antagonizes the effects of aldosterone
Spironolactone is a potassium-sparing diuretic that acts by antagonizing aldosterone in the distal tubule 1.
Clinical Applications and Management
In nephrotic syndrome with resistant edema, which combination therapy is recommended?
- A) Multiple loop diuretics
- B) Loop diuretic plus thiazide diuretic
- C) Thiazide plus potassium-sparing diuretic
- D) Acetazolamide alone
Answer: B) Loop diuretic plus thiazide diuretic
For resistant edema in nephrotic syndrome, loop diuretics with other mechanistically different diuretics like thiazides are recommended for synergistic treatment 1.
What is the preferred dosing schedule for loop diuretics in patients with nephrotic syndrome?
- A) Once daily dosing
- B) Twice daily dosing
- C) Continuous infusion only
- D) Weekly high-dose therapy
Answer: B) Twice daily dosing
Twice daily dosing of loop diuretics is preferred over once daily dosing in nephrotic syndrome, though daily dosing may be acceptable for reduced GFR 1.
Which of the following is NOT a common adverse effect of loop diuretics?
- A) Hypokalemia
- B) Hyperkalemia
- C) Impaired GFR
- D) Volume depletion
Answer: B) Hyperkalemia
Loop diuretics typically cause hypokalemia, not hyperkalemia, which is more commonly associated with potassium-sparing diuretics like spironolactone 1.
In a patient with diuretic resistance, which strategy is NOT recommended?
- A) Adding amiloride
- B) Using loop diuretics with IV albumin
- C) Discontinuing all diuretics for 48 hours
- D) Adding acetazolamide
Answer: C) Discontinuing all diuretics for 48 hours
For diuretic-resistant patients, strategies include adding amiloride, acetazolamide, loop diuretics with IV albumin, or ultrafiltration, but not discontinuing diuretics 1.
What is the recommended dietary sodium restriction for patients on diuretic therapy for glomerular disease?
- A) <1.0 g/d
- B) <2.0 g/d
- C) <3.0 g/d
- D) <4.0 g/d
Answer: B) <2.0 g/d
Dietary sodium should be restricted to <2.0 g/d (<90 mmol/d) for patients with glomerular disease on diuretic therapy 1.
Pathophysiology and Pharmacology
Which mechanism explains the synergistic effect when combining loop diuretics with thiazides?
- A) Both act at the same nephron site
- B) Thiazides inhibit distal sodium reabsorption that would compensate for loop diuretic action
- C) The combination reduces glomerular filtration rate
- D) Both increase potassium retention
Answer: B) Thiazides inhibit distal sodium reabsorption that would compensate for loop diuretic action
Thiazide diuretics, administered with loop diuretics, impair distal sodium reabsorption and improve diuretic response by blocking compensatory mechanisms 1.
The maximum percentage of filtered sodium load that can be excreted with loop diuretics is approximately:
- A) 5-10%
- B) 20-25%
- C) 40-50%
- D) 70-80%
Answer: B) 20-25%
Loop diuretics increase sodium excretion up to 20-25% of the filtered load of sodium 1.
Which diuretic is most appropriate for a patient with heart failure and moderate renal impairment (GFR 35 mL/min)?
- A) Hydrochlorothiazide
- B) Furosemide
- C) Chlorthalidone
- D) Indapamide
Answer: B) Furosemide
Loop diuretics like furosemide are preferred for patients with impaired renal function (creatinine clearance less than 40 mL/min) as thiazides lose their effectiveness in this setting 1.
What is the primary mechanism by which acetazolamide produces diuresis?
- A) Inhibition of sodium-potassium-chloride cotransport
- B) Inhibition of sodium-chloride cotransport
- C) Inhibition of carbonic anhydrase
- D) Antagonism of aldosterone receptors
Answer: C) Inhibition of carbonic anhydrase
Acetazolamide produces diuresis by inhibiting carbonic anhydrase in the proximal tubule, though it is considered a weak diuretic 1.
Which statement about the time course of diuretic action is correct?
- A) Loop diuretics take several days to produce clinical effects
- B) Thiazides produce more rapid diuresis than loop diuretics
- C) Diuretics relieve pulmonary and peripheral edema more rapidly than other heart failure medications
- D) Spironolactone has the fastest onset of action among diuretics
Answer: C) Diuretics relieve pulmonary and peripheral edema more rapidly than other heart failure medications
Diuretics produce symptomatic benefits more rapidly than other drugs for heart failure, relieving pulmonary and peripheral edema within hours or days 1.
Special Populations and Conditions
In children with glomerular disease, what is the target protein-to-creatinine ratio (PCR) goal with diuretic therapy?
- A) <500 mg/g
- B) <350 mg/g
- C) <200 mg/g
- D) <100 mg/g
Answer: C) <200 mg/g
In children with glomerular disease, a PCR of <200 mg/g (<20 mg/mmol) or <8 mg/m²/hour in a 24-hour urine should be the goal 1.
Which diuretic combination should be avoided in patients receiving ACE inhibitors due to increased risk of adverse effects?
- A) Loop diuretic + thiazide
- B) Loop diuretic + spironolactone
- C) Thiazide + amiloride
- D) Metolazone + furosemide
Answer: B) Loop diuretic + spironolactone
The combination of spironolactone with ACE inhibitors increases the risk of hyperkalemia, especially if combined with RAS blockade 1.
In cirrhotic patients with ascites, what is the recommended initial diuretic approach?
- A) Loop diuretics alone
- B) Anti-mineralocorticoids alone
- C) Combined loop and thiazide diuretics
- D) Potassium-sparing diuretics alone
Answer: B) Anti-mineralocorticoids alone
In patients with ascites at first appearance, anti-mineralocorticoids alone (spironolactone, canrenone or K-canrenoate) are recommended as initial therapy 1.
Which statement about diuretic use in acute kidney injury (AKI) is correct?
- A) Diuretics prevent progression of AKI to chronic kidney disease
- B) Diuretics are effective in preventing AKI
- C) Diuretics shorten the duration of AKI
- D) Diuretics have an important role in volume management but do not prevent AKI
Answer: D) Diuretics have an important role in volume management but do not prevent AKI
Diuretics have an important role in volume management in AKI, but they are not recommended for the prevention of AKI 3.
Which diuretic has shown potential benefit in preventing progression from acute kidney injury to chronic kidney disease in experimental models?
- A) Furosemide
- B) Hydrochlorothiazide
- C) Spironolactone
- D) Bumetanide
Answer: C) Spironolactone
Experimental data suggests that spironolactone may prevent AKI once an ischemic insult has occurred and thus prevent the progression to chronic kidney disease 3.