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High-Yield USMLE Renal Questions (Step 1)
Which segment of the nephron is responsible for reabsorbing the largest fraction of the filtered load of water and solutes (Na+, K+, Cl-, HCO3-, glucose, amino acids)?
(A) Proximal convoluted tubule (PCT)
(B) Thick ascending limb of Loop of Henle
(C) Distal convoluted tubule (DCT)
(D) Collecting duct
What is the primary mechanism by which Angiotensin II increases blood pressure?
(A) Vasoconstriction of arterioles and stimulation of aldosterone release
(B) Vasodilation of arterioles and inhibition of ADH release
(C) Increased glomerular filtration rate (GFR) only
(D) Stimulation of renin release
Which hormone directly stimulates the insertion of aquaporin-2 (AQP2) channels into the apical membrane of principal cells in the collecting duct?
(A) Antidiuretic hormone (ADH / Vasopressin)
(B) Aldosterone
(C) Atrial natriuretic peptide (ANP)
(D) Parathyroid hormone (PTH)
What is the effect of Atrial Natriuretic Peptide (ANP) on the kidney?
(A) Increases GFR and decreases Na+ reabsorption
(B) Decreases GFR and increases Na+ reabsorption
(C) Increases ADH release
(D) Stimulates aldosterone secretion
In which segment of the nephron does parathyroid hormone (PTH) primarily stimulate calcium reabsorption?
(A) Distal convoluted tubule (DCT)
(B) Proximal convoluted tubule (PCT)
(C) Thick ascending limb of Loop of Henle
(D) Collecting duct
The calculation of Renal Plasma Flow (RPF) typically uses the clearance of which substance?
(A) Para-aminohippuric acid (PAH)
(B) Inulin
(C) Creatinine
(D) Glucose
What is the main function of the countercurrent multiplication mechanism involving the Loop of Henle?
(A) Generation of a hypertonic medullary interstitium
(B) Secretion of potassium
(C) Reabsorption of glucose
(D) Regulation of acid-base balance
Which diuretic class inhibits the Na+-Cl- cotransporter in the distal convoluted tubule?
Which substance's clearance represents the minimum possible urine osmolarity the kidney can produce?
(A) Free water clearance (CH2O)
(B) Osmolar clearance (Cosm)
(C) Inulin clearance (GFR)
(D) PAH clearance (RPF)
What is the function of the vasa recta in the kidney?
(A) Maintain the medullary osmotic gradient (countercurrent exchange)
(B) Filter blood to form ultrafiltrate
(C) Secrete renin
(D) Reabsorb glucose
Diabetes insipidus (either central or nephrogenic) results in the inability to:
(A) Concentrate urine
(B) Dilute urine
(C) Reabsorb glucose
(D) Secrete potassium
Which part of the nephron is responsible for secreting hydrogen ions (H+) and generating 'new' bicarbonate, particularly important in compensating for acidosis?
(A) Collecting duct (alpha-intercalated cells)
(B) Proximal convoluted tubule
(C) Thick ascending limb
(D) Macula densa
What is the filtration fraction (FF)?
(A) The fraction of renal plasma flow (RPF) that is filtered across the glomerulus (FF = GFR / RPF)
(B) The fraction of cardiac output going to the kidneys
(C) The fraction of filtered water that is reabsorbed
(D) The fraction of filtered Na+ that is excreted
Which diuretic works by blocking epithelial sodium channels (ENaC) in the principal cells of the collecting duct?
(A) Amiloride or Triamterene (Potassium-sparing diuretics)
(B) Spironolactone (Potassium-sparing diuretic)
(C) Furosemide (Loop diuretic)
(D) Hydrochlorothiazide (Thiazide diuretic)
What is the effect of severe sympathetic stimulation (e.g., during hemorrhage) on renal blood flow and GFR?
(A) Decreases RBF and decreases GFR significantly
(B) Increases RBF and increases GFR
(C) Decreases RBF but maintains GFR via efferent constriction
(D) No significant effect
Urea recycling contributes to which important renal process?
(A) Maintaining the hypertonicity of the inner medullary interstitium
(B) Reabsorbing glucose in the PCT
(C) Secreting potassium in the collecting duct
(D) Transporting PAH into the tubule
Acute Tubular Necrosis (ATN) most commonly affects which parts of the nephron due to their high metabolic activity and toxin exposure?
(A) Proximal convoluted tubule and thick ascending limb
(B) Glomerulus
(C) Distal convoluted tubule
(D) Collecting duct
Which force favors filtration across the glomerular capillaries?
What is the primary role of beta-intercalated cells in the collecting duct?
(A) Secrete bicarbonate (HCO3-) and reabsorb H+
(B) Secrete H+ and reabsorb HCO3-
(C) Reabsorb Na+ and secrete K+
(D) Reabsorb water
Which condition would lead to an increase in renin secretion?
(A) Hemorrhage leading to hypotension
(B) High dietary salt intake
(C) Administration of an ACE inhibitor
(D) Volume expansion
The macula densa cells are sensitive to the concentration of which substance in the tubular fluid of the distal tubule?
(A) Sodium chloride (NaCl)
(B) Glucose
(C) Potassium (K+)
(D) Urea
What is the effect of aldosterone on acid-base balance?
(A) Promotes H+ secretion by alpha-intercalated cells
(B) Promotes HCO3- secretion by beta-intercalated cells
(C) Inhibits H+ secretion
(D) Has no direct effect on H+ or HCO3- transport
Erythropoietin (EPO), a hormone essential for red blood cell production, is primarily synthesized by which cells in the kidney?
(A) Interstitial fibroblasts in the cortex
(B) Juxtaglomerular (JG) cells
(C) Podocytes
(D) Mesangial cells
A patient has a GFR of 120 mL/min and a plasma glucose concentration of 150 mg/dL (normal < 100 mg/dL, Tm for glucose ~375 mg/min). What is the approximate rate of glucose filtration?
(A) 180 mg/min
(B) 120 mg/min
(C) 375 mg/min
(D) 0 mg/min
In the context of the previous question (Filtered Load = 180 mg/min, Tm = 375 mg/min), what is the rate of glucose excretion?
(A) 0 mg/min
(B) 60 mg/min
(C) 180 mg/min
(D) 375 mg/min
Which ion's reabsorption in the thick ascending limb drives the reabsorption of other cations (like Ca2+ and Mg2+) via the paracellular pathway?
(A) Sodium (Na+) and Chloride (Cl-) reabsorption creating a lumen-positive potential
(B) Potassium (K+) secretion
(C) Bicarbonate (HCO3-) reabsorption
(D) Phosphate reabsorption
Where in the nephron does ADH exert its primary effect on urea permeability?