Summary GNRS 610 / GNRS610: Understanding Kidney
Function Disorders A-Comprehensive Guide 4: Latest
Fall 2025/26 EXAM with Questions and Answers/Plus a
Rationale Updated 2026 A+/Instant Download PDF
EXAM COVERAGE
1. Glomerular Pathology and Nephritic/Nephrotic Syndromes
2. Acute Kidney Injury (AKI): Prerenal, Intrarenal, and Postrenal Etiologies
3. Chronic Kidney Disease (CKD) and Mineral-Bone Disorders
4. Electrolyte and Acid-Base Disturbances in Renal Failure
5. Tubulointerstitial Nephritis and Obstructive Uropathies
6. Renal Vascular Disorders and Hypertensive Nephrosclerosis
7. Pharmacokinetics and Nephrotoxic Drug Management in Renal Impairment
8. Renal Replacement Therapy Modalities, Complications, and Management
1. A 45-year-old male with a history of untreated hypertension presents with generalized edema,
severe proteinuria (6 g/24 hours), hypoalbuminemia, and hyperlipidemia. Renal biopsy reveals
effacement of epithelial podocyte foot processes on electron microscopy without immune
complex deposition. Which underlying pathophysiological mechanism is primarily responsible
for this patient's clinical presentation?
A. Immune complex deposition within the subendothelial space leading to complement
activation and leukocyte infiltration.
B. Loss of the negative electrostatic charge of the glomerular filtration barrier, resulting in
selective plasma albumin filtration.
, C. Direct ischemic necrosis of the proximal convoluted tubules secondary to chronic renal artery
hypoperfusion.
D. Interstitial fibrosis and tubular atrophy driven by chronic tubulointerstitial leukocyte
infiltration.
CORRECT ANSWER : B
Rationale: Minimal change disease is characterized by podocyte foot process effacement and
loss of the glomerular basement membrane's negative charge (heparan sulfate), selectively
permitting massive albumin loss. Option A describes membranous or proliferative
glomerulonephritis pathways. Option C outlines acute tubular necrosis mechanisms, and Option
D describes chronic kidney disease scarring.
2. An advanced practice nurse is evaluating a 60-year-old male admitted with acute oliguria
following major cardiac surgery. Laboratory results show a fractional excretion of sodium
(FENa) of less than 1%, a serum BUN-to-creatinine ratio of 22:1, and bland urine sediment with
occasional hyaline casts. Which physiological response accounts for these findings?
A. Primary tubular epithelial cell destruction causing impaired sodium reabsorption and high
urinary sodium excretion.
B. Maximal renal conservation of sodium and water stimulated by decreased effective
circulating arterial blood volume and renin-angiotensin-aldosterone activation.
C. Postrenal mechanical obstruction of the lower urinary tract resulting in elevated tubular
hydrostatic pressure and backflow.
D. Immune-mediated interstitial nephritis triggered by perioperative administration of beta-
lactam antibiotics.
CORRECT ANSWER : B
Rationale: A FENa under 1% and a BUN-to-creatinine ratio exceeding 20:1 reflect prerenal
azotemia, where intact tubules aggressively reabsorb sodium and urea in response to renal
hypoperfusion. Option A describes intrinsic acute tubular necrosis. Option C denotes postrenal
obstruction, and Option D represents acute interstitial nephritis.
3. A 52-year-old female with stage 4 chronic kidney disease presents for routine management. Her
laboratory profile demonstrates a serum calcium of 8.2 mg/dL, serum phosphorus of 6.5 mg/dL,
and an elevated intact parathyroid hormone (iPTH) level. Which underlying pathophysiological
sequence initiated these findings?
A. Primary hypersecretion of parathyroid hormone by a single autonomous parathyroid
adenoma.
, B. Decreased renal alpha-1-hydroxylase activity leading to impaired calcitriol synthesis,
subsequent hypocalcemia, and secondary parathyroid hyperplasia.
C. Enhanced renal tubular reabsorption of calcium driven by excessive aldosterone activity in the
distal nephron.
D. Direct precipitation of calcium-phosphate crystals within the glomerular capillary loops
secondary to hypercalcemia.
CORRECT ANSWER : B
Rationale: In advanced chronic kidney disease, failing kidneys cannot convert 25-
hydroxyvitamin D to active calcitriol ($1,25$-dihydroxyvitamin D), causing intestinal calcium
malabsorption, hypocalcemia, hyperphosphatemia, and secondary hyperparathyroidism. Option
A describes primary hyperparathyroidism. Option C and D do not account for the core bone-
mineral disorder pathway of CKD.
4. A critically ill patient in the intensive care unit develops acute kidney injury with a rapidly rising
serum creatinine and a fractional excretion of sodium (FENa) greater than 2%. Urinalysis reveals
muddy brown granular casts and epithelial cell casts. Which pathologic process has occurred
within the nephron?
A. Functional renal hypoperfusion with intact tubular epithelial architecture.
B. Ischemic or nephrotoxic injury causing sloughing of proximal tubular epithelial cells
into the tubular lumen.
C. Retrograde hydrostatic pressure increase secondary to bilateral ureteral obstruction.
D. Antigen-antibody complex deposition within the mesangium causing localized inflammation.
CORRECT ANSWER : B
Rationale: The presence of muddy brown granular casts, tubular epithelial cells, and a FENa
above 2% are pathognomonic for acute tubular necrosis (ATN) caused by ischemic or
nephrotoxic cellular injury. Option A defines prerenal azotemia. Option C describes postrenal
obstruction, and Option D outlines glomerulonephritis.
5. A 68-year-old male with long-standing type 2 diabetes mellitus and chronic kidney disease
presents with profound weakness. His electrocardiogram displays peaked T waves, prolonged PR
intervals, and widened QRS complexes. Serum potassium is 7.4 mEq/L. Which immediate
therapeutic intervention should the clinician prioritize to stabilize cardiac membrane resting
potential?
A. Administration of oral sodium polystyrene sulfonate to bind intestinal potassium.
, B. Intravenous infusion of calcium gluconate to antagonize the membrane-stabilizing
effects of hyperkalemia on cardiac myocytes.
C. Intravenous administration of regular insulin and 50% dextrose to drive potassium into
intracellular compartments.
D. Initiation of urgent hemodialysis to physically remove excess total body potassium.
CORRECT ANSWER : B
Rationale: Intravenous calcium gluconate does not lower serum potassium but rapidly stabilizes
the cardiac membrane threshold potential, preventing lethal arrhythmias during severe
hyperkalemia. Options A, C, and D lower potassium levels via binding, intracellular shifting, or
removal, but calcium acts first to protect the heart.
6. A 34-year-old female presents with macroscopic hematuria, mild periorbital edema, and
hypertension following a recent pharyngitis infection three weeks ago. Laboratory analysis
reveals elevated antistreptolysin O (ASO) titers, low serum C3 complement levels, and red blood
cell casts in the urine sediment. What is the primary immunopathogenic mechanism?
A. Direct bacterial invasion of the glomerular basement membrane by group A beta-hemolytic
streptococci.
B. Deposition of circulating immune complexes containing streptococcal antigens and
immunoglobulins within the glomerular subepithelial space ("humps").
C. Formation of autoantibodies directed against the alpha-3 chain of type IV collagen in the
glomerular basement membrane.
D. Cell-mediated delayed-type hypersensitivity reaction targeting proximal tubular epithelial
brush borders.
CORRECT ANSWER : B
Rationale: Post-streptococcal glomerulonephritis is an immune complex-mediated disease
characterized by subepithelial immune deposits, low C3 complement levels, and classic
subepithelial "humps" on electron microscopy. Option C describes Goodpasture syndrome, and
Option A and D are incorrect mechanisms.
7. A 55-year-old male with decompensated cirrhosis develops progressive azotemia, oliguria, and a
very low urinary sodium excretion (< 10 mEq/L) despite adequate intravascular volume
resuscitation and absence of tubular injury. What is the pathophysiological driver of this
condition (hepatorenal syndrome)?
A. Direct nephrotoxicity from unconjugated hyperbilirubinemia precipitating acute tubular
necrosis.
Function Disorders A-Comprehensive Guide 4: Latest
Fall 2025/26 EXAM with Questions and Answers/Plus a
Rationale Updated 2026 A+/Instant Download PDF
EXAM COVERAGE
1. Glomerular Pathology and Nephritic/Nephrotic Syndromes
2. Acute Kidney Injury (AKI): Prerenal, Intrarenal, and Postrenal Etiologies
3. Chronic Kidney Disease (CKD) and Mineral-Bone Disorders
4. Electrolyte and Acid-Base Disturbances in Renal Failure
5. Tubulointerstitial Nephritis and Obstructive Uropathies
6. Renal Vascular Disorders and Hypertensive Nephrosclerosis
7. Pharmacokinetics and Nephrotoxic Drug Management in Renal Impairment
8. Renal Replacement Therapy Modalities, Complications, and Management
1. A 45-year-old male with a history of untreated hypertension presents with generalized edema,
severe proteinuria (6 g/24 hours), hypoalbuminemia, and hyperlipidemia. Renal biopsy reveals
effacement of epithelial podocyte foot processes on electron microscopy without immune
complex deposition. Which underlying pathophysiological mechanism is primarily responsible
for this patient's clinical presentation?
A. Immune complex deposition within the subendothelial space leading to complement
activation and leukocyte infiltration.
B. Loss of the negative electrostatic charge of the glomerular filtration barrier, resulting in
selective plasma albumin filtration.
, C. Direct ischemic necrosis of the proximal convoluted tubules secondary to chronic renal artery
hypoperfusion.
D. Interstitial fibrosis and tubular atrophy driven by chronic tubulointerstitial leukocyte
infiltration.
CORRECT ANSWER : B
Rationale: Minimal change disease is characterized by podocyte foot process effacement and
loss of the glomerular basement membrane's negative charge (heparan sulfate), selectively
permitting massive albumin loss. Option A describes membranous or proliferative
glomerulonephritis pathways. Option C outlines acute tubular necrosis mechanisms, and Option
D describes chronic kidney disease scarring.
2. An advanced practice nurse is evaluating a 60-year-old male admitted with acute oliguria
following major cardiac surgery. Laboratory results show a fractional excretion of sodium
(FENa) of less than 1%, a serum BUN-to-creatinine ratio of 22:1, and bland urine sediment with
occasional hyaline casts. Which physiological response accounts for these findings?
A. Primary tubular epithelial cell destruction causing impaired sodium reabsorption and high
urinary sodium excretion.
B. Maximal renal conservation of sodium and water stimulated by decreased effective
circulating arterial blood volume and renin-angiotensin-aldosterone activation.
C. Postrenal mechanical obstruction of the lower urinary tract resulting in elevated tubular
hydrostatic pressure and backflow.
D. Immune-mediated interstitial nephritis triggered by perioperative administration of beta-
lactam antibiotics.
CORRECT ANSWER : B
Rationale: A FENa under 1% and a BUN-to-creatinine ratio exceeding 20:1 reflect prerenal
azotemia, where intact tubules aggressively reabsorb sodium and urea in response to renal
hypoperfusion. Option A describes intrinsic acute tubular necrosis. Option C denotes postrenal
obstruction, and Option D represents acute interstitial nephritis.
3. A 52-year-old female with stage 4 chronic kidney disease presents for routine management. Her
laboratory profile demonstrates a serum calcium of 8.2 mg/dL, serum phosphorus of 6.5 mg/dL,
and an elevated intact parathyroid hormone (iPTH) level. Which underlying pathophysiological
sequence initiated these findings?
A. Primary hypersecretion of parathyroid hormone by a single autonomous parathyroid
adenoma.
, B. Decreased renal alpha-1-hydroxylase activity leading to impaired calcitriol synthesis,
subsequent hypocalcemia, and secondary parathyroid hyperplasia.
C. Enhanced renal tubular reabsorption of calcium driven by excessive aldosterone activity in the
distal nephron.
D. Direct precipitation of calcium-phosphate crystals within the glomerular capillary loops
secondary to hypercalcemia.
CORRECT ANSWER : B
Rationale: In advanced chronic kidney disease, failing kidneys cannot convert 25-
hydroxyvitamin D to active calcitriol ($1,25$-dihydroxyvitamin D), causing intestinal calcium
malabsorption, hypocalcemia, hyperphosphatemia, and secondary hyperparathyroidism. Option
A describes primary hyperparathyroidism. Option C and D do not account for the core bone-
mineral disorder pathway of CKD.
4. A critically ill patient in the intensive care unit develops acute kidney injury with a rapidly rising
serum creatinine and a fractional excretion of sodium (FENa) greater than 2%. Urinalysis reveals
muddy brown granular casts and epithelial cell casts. Which pathologic process has occurred
within the nephron?
A. Functional renal hypoperfusion with intact tubular epithelial architecture.
B. Ischemic or nephrotoxic injury causing sloughing of proximal tubular epithelial cells
into the tubular lumen.
C. Retrograde hydrostatic pressure increase secondary to bilateral ureteral obstruction.
D. Antigen-antibody complex deposition within the mesangium causing localized inflammation.
CORRECT ANSWER : B
Rationale: The presence of muddy brown granular casts, tubular epithelial cells, and a FENa
above 2% are pathognomonic for acute tubular necrosis (ATN) caused by ischemic or
nephrotoxic cellular injury. Option A defines prerenal azotemia. Option C describes postrenal
obstruction, and Option D outlines glomerulonephritis.
5. A 68-year-old male with long-standing type 2 diabetes mellitus and chronic kidney disease
presents with profound weakness. His electrocardiogram displays peaked T waves, prolonged PR
intervals, and widened QRS complexes. Serum potassium is 7.4 mEq/L. Which immediate
therapeutic intervention should the clinician prioritize to stabilize cardiac membrane resting
potential?
A. Administration of oral sodium polystyrene sulfonate to bind intestinal potassium.
, B. Intravenous infusion of calcium gluconate to antagonize the membrane-stabilizing
effects of hyperkalemia on cardiac myocytes.
C. Intravenous administration of regular insulin and 50% dextrose to drive potassium into
intracellular compartments.
D. Initiation of urgent hemodialysis to physically remove excess total body potassium.
CORRECT ANSWER : B
Rationale: Intravenous calcium gluconate does not lower serum potassium but rapidly stabilizes
the cardiac membrane threshold potential, preventing lethal arrhythmias during severe
hyperkalemia. Options A, C, and D lower potassium levels via binding, intracellular shifting, or
removal, but calcium acts first to protect the heart.
6. A 34-year-old female presents with macroscopic hematuria, mild periorbital edema, and
hypertension following a recent pharyngitis infection three weeks ago. Laboratory analysis
reveals elevated antistreptolysin O (ASO) titers, low serum C3 complement levels, and red blood
cell casts in the urine sediment. What is the primary immunopathogenic mechanism?
A. Direct bacterial invasion of the glomerular basement membrane by group A beta-hemolytic
streptococci.
B. Deposition of circulating immune complexes containing streptococcal antigens and
immunoglobulins within the glomerular subepithelial space ("humps").
C. Formation of autoantibodies directed against the alpha-3 chain of type IV collagen in the
glomerular basement membrane.
D. Cell-mediated delayed-type hypersensitivity reaction targeting proximal tubular epithelial
brush borders.
CORRECT ANSWER : B
Rationale: Post-streptococcal glomerulonephritis is an immune complex-mediated disease
characterized by subepithelial immune deposits, low C3 complement levels, and classic
subepithelial "humps" on electron microscopy. Option C describes Goodpasture syndrome, and
Option A and D are incorrect mechanisms.
7. A 55-year-old male with decompensated cirrhosis develops progressive azotemia, oliguria, and a
very low urinary sodium excretion (< 10 mEq/L) despite adequate intravascular volume
resuscitation and absence of tubular injury. What is the pathophysiological driver of this
condition (hepatorenal syndrome)?
A. Direct nephrotoxicity from unconjugated hyperbilirubinemia precipitating acute tubular
necrosis.
