Integrated Multisystem Clinical Vignettes
Exam 2026 Edition Clinical Reasoning Verified
Answers with Detailed Rationales and pdf
download.
1. A 64-year-old man with a 40-pack-year smoking history
presents with progressive fatigue, proximal muscle weakness,
and difficulty climbing stairs. He has lost 7 kg over 3 months.
Examination reveals dry mucous membranes and mild
hyperpigmentation. Laboratory studies show sodium 124
mEq/L, potassium 4.1 mEq/L, serum osmolality 260 mOsm/kg,
and urine osmolality 500 mOsm/kg. CT of the chest reveals a
hilar mass. Which mechanism best explains this patient's
electrolyte abnormality?
A. Increased aldosterone secretion
B. Ectopic antidiuretic hormone secretion
C. Autoimmune destruction of the adrenal cortex
D. Renal resistance to antidiuretic hormone
Answer: B. Ectopic antidiuretic hormone secretion
Rationale: The patient has hypotonic hyponatremia with
inappropriately concentrated urine, indicating SIADH. Small-cell
,lung carcinoma is a classic cause of ectopic ADH production. The
normal potassium level and absence of significant volume
depletion further support SIADH rather than primary adrenal
insufficiency.
2. A 58-year-old woman with hypertension and type 2 diabetes
presents with sudden right-sided weakness and expressive
aphasia. She was last known to be neurologically normal 90
minutes ago. Blood pressure is 176/98 mm Hg. CT of the head
shows no hemorrhage. Which vessel is most likely occluded?
A. Left middle cerebral artery
B. Right posterior cerebral artery
C. Left anterior cerebral artery
D. Right middle cerebral artery
Answer: A. Left middle cerebral artery
Rationale: Contralateral face and arm weakness accompanied
by aphasia indicates a dominant-hemisphere MCA lesion. In
most individuals, the left hemisphere is dominant for language.
The acute presentation and absence of hemorrhage are
consistent with ischemic stroke involving the left MCA territory.
3. A 72-year-old man presents with fever, productive cough,
confusion, and hypotension. Laboratory studies show elevated
,lactate, leukocytosis, and acute kidney injury. Blood cultures
grow gram-negative rods. Despite intravenous fluids, his blood
pressure remains low. Which mechanism most directly
contributes to his persistent hypotension?
A. Increased systemic vascular resistance
B. Excessive vagal stimulation
C. Nitric oxide-mediated vasodilation
D. Increased circulating aldosterone
Answer: C. Nitric oxide-mediated vasodilation
Rationale: Septic shock is characterized by profound systemic
vasodilation caused partly by increased nitric oxide production
and inflammatory mediator release. The resulting decrease in
systemic vascular resistance causes hypotension and impaired
tissue perfusion despite adequate or increased cardiac output
early in the course.
4. A 45-year-old woman presents with fatigue, weight loss,
abdominal discomfort, and diffuse hyperpigmentation. Blood
pressure is 88/56 mm Hg. Laboratory testing shows sodium 128
mEq/L and potassium 5.9 mEq/L. Which additional finding is
most likely?
A. Increased serum cortisol
B. Decreased ACTH
, C. Increased plasma renin activity
D. Decreased serum potassium
Answer: C. Increased plasma renin activity
Rationale: Primary adrenal insufficiency causes deficient cortisol
and aldosterone production. Reduced aldosterone leads to
sodium loss, hyperkalemia, hypotension, and compensatory
activation of the renin-angiotensin system. Elevated ACTH
causes diffuse hyperpigmentation.
5. A 61-year-old man with a history of atrial fibrillation presents
with severe abdominal pain that began suddenly 3 hours ago.
His abdomen is initially soft with minimal tenderness, but his
lactate is elevated. Which diagnosis is most likely?
A. Acute pancreatitis
B. Mesenteric ischemia
C. Perforated peptic ulcer
D. Acute cholecystitis
Answer: B. Mesenteric ischemia
Rationale: Sudden severe abdominal pain that is
disproportionate to physical examination findings is classic for
acute mesenteric ischemia. Atrial fibrillation predisposes to
embolization of thrombi into the superior mesenteric artery.
Elevated lactate suggests tissue ischemia.
Exam 2026 Edition Clinical Reasoning Verified
Answers with Detailed Rationales and pdf
download.
1. A 64-year-old man with a 40-pack-year smoking history
presents with progressive fatigue, proximal muscle weakness,
and difficulty climbing stairs. He has lost 7 kg over 3 months.
Examination reveals dry mucous membranes and mild
hyperpigmentation. Laboratory studies show sodium 124
mEq/L, potassium 4.1 mEq/L, serum osmolality 260 mOsm/kg,
and urine osmolality 500 mOsm/kg. CT of the chest reveals a
hilar mass. Which mechanism best explains this patient's
electrolyte abnormality?
A. Increased aldosterone secretion
B. Ectopic antidiuretic hormone secretion
C. Autoimmune destruction of the adrenal cortex
D. Renal resistance to antidiuretic hormone
Answer: B. Ectopic antidiuretic hormone secretion
Rationale: The patient has hypotonic hyponatremia with
inappropriately concentrated urine, indicating SIADH. Small-cell
,lung carcinoma is a classic cause of ectopic ADH production. The
normal potassium level and absence of significant volume
depletion further support SIADH rather than primary adrenal
insufficiency.
2. A 58-year-old woman with hypertension and type 2 diabetes
presents with sudden right-sided weakness and expressive
aphasia. She was last known to be neurologically normal 90
minutes ago. Blood pressure is 176/98 mm Hg. CT of the head
shows no hemorrhage. Which vessel is most likely occluded?
A. Left middle cerebral artery
B. Right posterior cerebral artery
C. Left anterior cerebral artery
D. Right middle cerebral artery
Answer: A. Left middle cerebral artery
Rationale: Contralateral face and arm weakness accompanied
by aphasia indicates a dominant-hemisphere MCA lesion. In
most individuals, the left hemisphere is dominant for language.
The acute presentation and absence of hemorrhage are
consistent with ischemic stroke involving the left MCA territory.
3. A 72-year-old man presents with fever, productive cough,
confusion, and hypotension. Laboratory studies show elevated
,lactate, leukocytosis, and acute kidney injury. Blood cultures
grow gram-negative rods. Despite intravenous fluids, his blood
pressure remains low. Which mechanism most directly
contributes to his persistent hypotension?
A. Increased systemic vascular resistance
B. Excessive vagal stimulation
C. Nitric oxide-mediated vasodilation
D. Increased circulating aldosterone
Answer: C. Nitric oxide-mediated vasodilation
Rationale: Septic shock is characterized by profound systemic
vasodilation caused partly by increased nitric oxide production
and inflammatory mediator release. The resulting decrease in
systemic vascular resistance causes hypotension and impaired
tissue perfusion despite adequate or increased cardiac output
early in the course.
4. A 45-year-old woman presents with fatigue, weight loss,
abdominal discomfort, and diffuse hyperpigmentation. Blood
pressure is 88/56 mm Hg. Laboratory testing shows sodium 128
mEq/L and potassium 5.9 mEq/L. Which additional finding is
most likely?
A. Increased serum cortisol
B. Decreased ACTH
, C. Increased plasma renin activity
D. Decreased serum potassium
Answer: C. Increased plasma renin activity
Rationale: Primary adrenal insufficiency causes deficient cortisol
and aldosterone production. Reduced aldosterone leads to
sodium loss, hyperkalemia, hypotension, and compensatory
activation of the renin-angiotensin system. Elevated ACTH
causes diffuse hyperpigmentation.
5. A 61-year-old man with a history of atrial fibrillation presents
with severe abdominal pain that began suddenly 3 hours ago.
His abdomen is initially soft with minimal tenderness, but his
lactate is elevated. Which diagnosis is most likely?
A. Acute pancreatitis
B. Mesenteric ischemia
C. Perforated peptic ulcer
D. Acute cholecystitis
Answer: B. Mesenteric ischemia
Rationale: Sudden severe abdominal pain that is
disproportionate to physical examination findings is classic for
acute mesenteric ischemia. Atrial fibrillation predisposes to
embolization of thrombi into the superior mesenteric artery.
Elevated lactate suggests tissue ischemia.
