COMSAE PHASE 1 RENAL PHYSIOLOGY
PRACTICE EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1.
A healthy 24-year-old medical student undergoes renal physiology
testing. His plasma inulin concentration is 1 mg/dL, urine inulin
concentration is 125 mg/dL, and urine flow rate is 1.2 mL/min. His
plasma creatinine concentration is 1.0 mg/dL. Which value most
accurately represents his glomerular filtration rate?
A. 75 mL/min
B. 100 mL/min
C. 125 mL/min
D. 150 mL/min
E. 180 mL/min
Answer: C. 150 mL/min
Rationale: Inulin clearance is calculated as C = (U × V)/P. Thus, (125
mg/dL × 1.2 mL/min) ÷ 1 mg/dL = 150 mL/min. Inulin is freely filtered
and neither reabsorbed nor secreted, making its clearance the classic
experimental measure of GFR.
2.
1
,A patient has a sudden reduction in renal perfusion due to severe
hemorrhage. Which intrinsic renal mechanism initially helps preserve
glomerular filtration despite the fall in renal arterial pressure?
A. Increased renin degradation
B. Afferent arteriolar constriction
C. Efferent arteriolar constriction mediated by angiotensin II
D. Increased Bowman capsule hydrostatic pressure
E. Reduced sympathetic activity
Answer: C. Efferent arteriolar constriction mediated by angiotensin
II
Rationale: Moderate concentrations of angiotensin II preferentially
constrict the efferent arteriole, increasing glomerular capillary
hydrostatic pressure and helping maintain GFR when renal perfusion
pressure falls. Severe angiotensin II excess can eventually decrease
renal blood flow and GFR because of marked vascular resistance.
3.
A patient receives a drug that selectively constricts the afferent arteriole.
Which combination of changes is expected?
A. Increased renal blood flow and increased GFR
B. Increased renal blood flow and decreased GFR
C. Decreased renal blood flow and increased GFR
D. Decreased renal blood flow and decreased GFR
E. No change in renal blood flow or GFR
Answer: D. Decreased renal blood flow and decreased GFR
Rationale: Afferent arteriolar constriction reduces blood entering the
glomerular capillaries. Consequently, renal blood flow decreases and
glomerular capillary hydrostatic pressure falls, producing a decrease
in GFR.
2
,4.
A patient with bilateral renal artery stenosis is treated with an
angiotensin-converting enzyme inhibitor. Several days later, his serum
creatinine rises substantially. What is the primary renal mechanism
responsible?
A. Afferent arteriolar constriction
B. Efferent arteriolar dilation
C. Increased mesangial cell contraction
D. Increased renal sympathetic activity
E. Increased proximal sodium reabsorption
Answer: B. Efferent arteriolar dilation
Rationale: Angiotensin II normally constricts the efferent arteriole,
helping maintain glomerular capillary pressure when renal perfusion
is reduced. ACE inhibition decreases angiotensin II formation,
causing efferent dilation and a reduction in glomerular capillary
hydrostatic pressure and GFR.
5.
Which substance is freely filtered by the glomerulus but is normally
completely reabsorbed in the proximal tubule?
A. Inulin
B. Creatinine
C. Glucose
D. Para-aminohippuric acid
E. Albumin
Answer: C. Glucose
3
, Rationale: Glucose is freely filtered and normally almost completely
reabsorbed in the proximal tubule through sodium-glucose
cotransporters. Inulin is neither reabsorbed nor secreted, creatinine is
slightly secreted, PAH is strongly secreted, and albumin is normally
restricted from filtration because of its size and charge.
6.
A patient with poorly controlled diabetes mellitus has a plasma glucose
concentration above the renal transport maximum. Glucose begins
appearing in the urine. Which mechanism best explains this finding?
A. Reduced glomerular filtration of glucose
B. Saturation of proximal tubular sodium-glucose cotransporters
C. Increased distal tubular glucose secretion
D. Increased collecting duct glucose permeability
E. Saturation of glomerular glucose-binding proteins
Answer: B. Saturation of proximal tubular sodium-glucose
cotransporters
Rationale: Filtered glucose is normally reclaimed by proximal tubular
sodium-glucose cotransporters. When the filtered glucose load exceeds
the transport maximum, the transporters become saturated and the
excess glucose remains in the tubular fluid and is excreted.
7.
A substance has a clearance of 150 mL/min in a patient whose GFR is
120 mL/min. Which renal process most likely accounts for this finding?
A. Net reabsorption
B. Net secretion
C. Complete filtration only
4
PRACTICE EXAM WITH ACTUAL
QUESTIONS AND VERIFIED ANSWERS,
PLUS EXPLAINED RATIONALES/EXPERT
VERIFIED FOR GUARANTEED 100% PASS
2026/LATEST UPDATE/INSTANT
DOWNLOAD PDF
1.
A healthy 24-year-old medical student undergoes renal physiology
testing. His plasma inulin concentration is 1 mg/dL, urine inulin
concentration is 125 mg/dL, and urine flow rate is 1.2 mL/min. His
plasma creatinine concentration is 1.0 mg/dL. Which value most
accurately represents his glomerular filtration rate?
A. 75 mL/min
B. 100 mL/min
C. 125 mL/min
D. 150 mL/min
E. 180 mL/min
Answer: C. 150 mL/min
Rationale: Inulin clearance is calculated as C = (U × V)/P. Thus, (125
mg/dL × 1.2 mL/min) ÷ 1 mg/dL = 150 mL/min. Inulin is freely filtered
and neither reabsorbed nor secreted, making its clearance the classic
experimental measure of GFR.
2.
1
,A patient has a sudden reduction in renal perfusion due to severe
hemorrhage. Which intrinsic renal mechanism initially helps preserve
glomerular filtration despite the fall in renal arterial pressure?
A. Increased renin degradation
B. Afferent arteriolar constriction
C. Efferent arteriolar constriction mediated by angiotensin II
D. Increased Bowman capsule hydrostatic pressure
E. Reduced sympathetic activity
Answer: C. Efferent arteriolar constriction mediated by angiotensin
II
Rationale: Moderate concentrations of angiotensin II preferentially
constrict the efferent arteriole, increasing glomerular capillary
hydrostatic pressure and helping maintain GFR when renal perfusion
pressure falls. Severe angiotensin II excess can eventually decrease
renal blood flow and GFR because of marked vascular resistance.
3.
A patient receives a drug that selectively constricts the afferent arteriole.
Which combination of changes is expected?
A. Increased renal blood flow and increased GFR
B. Increased renal blood flow and decreased GFR
C. Decreased renal blood flow and increased GFR
D. Decreased renal blood flow and decreased GFR
E. No change in renal blood flow or GFR
Answer: D. Decreased renal blood flow and decreased GFR
Rationale: Afferent arteriolar constriction reduces blood entering the
glomerular capillaries. Consequently, renal blood flow decreases and
glomerular capillary hydrostatic pressure falls, producing a decrease
in GFR.
2
,4.
A patient with bilateral renal artery stenosis is treated with an
angiotensin-converting enzyme inhibitor. Several days later, his serum
creatinine rises substantially. What is the primary renal mechanism
responsible?
A. Afferent arteriolar constriction
B. Efferent arteriolar dilation
C. Increased mesangial cell contraction
D. Increased renal sympathetic activity
E. Increased proximal sodium reabsorption
Answer: B. Efferent arteriolar dilation
Rationale: Angiotensin II normally constricts the efferent arteriole,
helping maintain glomerular capillary pressure when renal perfusion
is reduced. ACE inhibition decreases angiotensin II formation,
causing efferent dilation and a reduction in glomerular capillary
hydrostatic pressure and GFR.
5.
Which substance is freely filtered by the glomerulus but is normally
completely reabsorbed in the proximal tubule?
A. Inulin
B. Creatinine
C. Glucose
D. Para-aminohippuric acid
E. Albumin
Answer: C. Glucose
3
, Rationale: Glucose is freely filtered and normally almost completely
reabsorbed in the proximal tubule through sodium-glucose
cotransporters. Inulin is neither reabsorbed nor secreted, creatinine is
slightly secreted, PAH is strongly secreted, and albumin is normally
restricted from filtration because of its size and charge.
6.
A patient with poorly controlled diabetes mellitus has a plasma glucose
concentration above the renal transport maximum. Glucose begins
appearing in the urine. Which mechanism best explains this finding?
A. Reduced glomerular filtration of glucose
B. Saturation of proximal tubular sodium-glucose cotransporters
C. Increased distal tubular glucose secretion
D. Increased collecting duct glucose permeability
E. Saturation of glomerular glucose-binding proteins
Answer: B. Saturation of proximal tubular sodium-glucose
cotransporters
Rationale: Filtered glucose is normally reclaimed by proximal tubular
sodium-glucose cotransporters. When the filtered glucose load exceeds
the transport maximum, the transporters become saturated and the
excess glucose remains in the tubular fluid and is excreted.
7.
A substance has a clearance of 150 mL/min in a patient whose GFR is
120 mL/min. Which renal process most likely accounts for this finding?
A. Net reabsorption
B. Net secretion
C. Complete filtration only
4
