COLLEGE) NEWEST 2026 ACTUAL EXAM| N212
PATHOPHYSIOLOGY EXAM 2 REVIEW WITH
COMPLETE REAL EXAM QUESTIONS AND CORRECT
VERIFIED ANSWERS/ ALREADY GRADED A+ (MOST
RECENT!!) — 200 Questions
Section 1: Fluid and Electrolyte Imbalances (Questions 1-20)
1 A patient with Syndrome of Inappropriate Antidiuretic Hormone (SIADH) secretion develops severe
hyponatremia (serum Na+ 118 mEq/L). Which of the following best explains the pathophysiology of the
cerebral edema observed in this condition?
A) Increased intracellular osmolality due to rapid loss of organic osmolytes from neurons
B) Extracellular hypotonicity causing water to shift into neurons via aquaporins
C) Impaired Na+/K+ ATPase activity in astrocytes leading to sodium accumulation
D) Increased permeability of the blood-brain barrier to albumin
Answer: B
Rationale: In SIADH, water retention dilutes extracellular fluid, creating a hypotonic environment relative to
intracellular fluid. Water moves into neurons down its osmotic gradient via aquaporins, causing cerebral edema.
Option A describes adaptation to chronic hyponatremia, not acute swelling. Option C is not primary. Option D
occurs in vasogenic edema, not hyponatremia.
2 A patient with chronic heart failure develops hyperkalemia (K+ 6.2 mEq/L) after starting spironolactone. Which
of the following acid-base disturbances would most likely exacerbate the hyperkalemia?
A) Metabolic alkalosis
B) Respiratory alkalosis
C) Metabolic acidosis
D) Respiratory acidosis
Answer: C
Rationale: Metabolic acidosis causes extracellular hydrogen ions to shift into cells in exchange for potassium,
worsening hyperkalemia. Alkalosis (options A and B) would shift potassium into cells, lowering serum K+.
Respiratory acidosis (option D) has a less pronounced effect on potassium shift compared to metabolic acidosis.
3 A patient with severe vomiting (loss of gastric fluid) develops metabolic alkalosis and hypokalemia. Which of
the following renal compensatory mechanisms contributes to the hypokalemia?
A) Increased aldosterone secretion due to volume contraction
B) Decreased tubular flow rate in the distal nephron
C) Increased hydrogen ion secretion in the proximal tubule
D) Decreased activity of the Na+/K+ ATPase in the collecting duct
Answer: A
Rationale: Volume contraction from vomiting stimulates aldosterone release, which increases Na+ reabsorption and
K+ secretion in the collecting duct, leading to hypokalemia. Option B would decrease K+ secretion. Option C is
not directly related. Option D would reduce K+ secretion, not increase it.
,4 A patient with diabetic ketoacidosis (DKA) presents with an anion gap metabolic acidosis and a serum
potassium of 5.8 mEq/L. Despite total body potassium depletion, why is the serum potassium elevated?
A) Insulin deficiency reduces cellular uptake of potassium
B) Metabolic acidosis promotes intracellular potassium shift
C) Aldosterone resistance in DKA increases renal potassium retention
D) Hyperglycemia causes osmotic diuresis concentrating potassium in plasma
Answer: A
Rationale: Insulin normally drives potassium into cells. In DKA, insulin deficiency impairs cellular uptake, causing
extracellular potassium accumulation despite total body depletion. Option B would shift K+ out, not in. Option C is
not characteristic. Option D does not directly explain hyperkalemia; osmotic diuresis actually increases potassium
loss.
5 Which of the following best explains why hypercalcemia (Ca2+ 13.5 mg/dL) can lead to nephrogenic diabetes
insipidus (NDI)?
A) Calcium deposits in the renal medulla impair the countercurrent multiplier
B) Hypercalcemia inhibits the insertion of aquaporin-2 channels in the collecting duct
C) Calcium activates the calcium-sensing receptor in the thick ascending limb, reducing sodium reabsorption
D) Hypercalcemia increases prostaglandin E2 synthesis, antagonizing vasopressin
Answer: B
Rationale: Hypercalcemia directly interferes with vasopressin action by reducing aquaporin-2 insertion in the
collecting duct, causing resistance to ADH and NDI. Option A describes structural damage but not the acute
mechanism. Option C affects sodium handling, not water. Option D is a secondary mechanism but not primary.
6 A patient with severe hypophosphatemia (1.0 mg/dL) develops acute respiratory failure. Which of the following
mechanisms most directly contributes to respiratory muscle weakness?
A) Decreased 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells impairing oxygen unloading
B) Reduced ATP synthesis in skeletal muscle due to low phosphate substrate
C) Impaired diaphragmatic contractility from decreased intracellular phosphate
D) Phosphate depletion causing rhabdomyolysis and electrolyte shifts
Answer: C
Rationale: Hypophosphatemia directly reduces intracellular ATP and 2,3-BPG, but respiratory failure is primarily
due to diaphragmatic weakness from low phosphate impairing contractile function. Option B is partially correct but
option C is more specific. Option A affects oxygen delivery, not muscle strength. Option D is a consequence, not
direct cause.
7 A patient with chronic renal failure develops hypermagnesemia (Mg2+ 4.5 mEq/L). Which of the following
electrocardiographic findings would be most consistent with this electrolyte disturbance?
A) Peaked T waves and widened QRS complex
B) Prolonged PR interval and widened QRS complex
C) ST segment depression and flattened T waves
D) Prolonged QT interval and U waves
Answer: B
Rationale: Hypermagnesemia slows cardiac conduction, causing PR prolongation and QRS widening. Option A is
typical of hyperkalemia. Option C suggests hypokalemia or ischemia. Option D is seen with hypokalemia or
hypocalcemia.
,8 A patient with hyperparathyroidism has a serum calcium of 12.0 mg/dL and a serum phosphate of 2.0 mg/dL.
Which of the following best explains the hypophosphatemia?
A) Increased renal phosphate reabsorption due to PTH
B) Decreased intestinal phosphate absorption
C) Increased renal phosphate excretion due to PTH
D) Shift of phosphate into bone due to increased osteoclast activity
Answer: C
Rationale: PTH increases renal phosphate excretion by down-regulating sodium-phosphate cotransporters in the
proximal tubule, leading to hypophosphatemia. Option A is opposite. Option B is not directly affected by PTH.
Option D is not the primary mechanism.
9 A patient with cirrhosis develops ascites and hyponatremia (Na+ 125 mEq/L). Despite total body sodium
excess, why is the serum sodium low?
A) Increased aldosterone causing sodium retention and dilution
B) Impaired renal water excretion due to non-osmotic ADH release
C) Decreased sodium intake from anorexia
D) Increased natriuretic peptides promoting sodium loss
Answer: B
Rationale: In cirrhosis, splanchnic vasodilation reduces effective arterial blood volume, stimulating non-osmotic
ADH release, which increases water retention and dilutes serum sodium. Option A contributes to total body sodium
excess but not hyponatremia. Option C is minor. Option D is not typical.
10 A patient receiving total parenteral nutrition (TPN) develops hypokalemia (K+ 3.0 mEq/L) and
hypophosphatemia (2.0 mg/dL) after initiation. Which of the following best explains these findings?
A) Insulin-mediated cellular uptake of potassium and phosphate
B) Increased renal losses due to volume expansion from TPN
C) Dilutional effect from the large volume of TPN
D) Inadequate potassium and phosphate content in the TPN formulation
Answer: A
Rationale: TPN containing glucose stimulates insulin release, which drives potassium and phosphate into cells,
causing rapid declines in serum levels, especially in malnourished patients (refeeding syndrome). Option B may
contribute but is not primary. Option C is less significant. Option D is possible but less likely with standard
formulations.
11 A patient with syndrome of inappropriate antidiuretic hormone secretion (SIADH) has a serum sodium of 120
mEq/L. Which of the following intravenous fluids, if administered, would most likely exacerbate the patient's
condition?
A) 0.9% sodium chloride
B) 3% sodium chloride
C) Lactated Ringer's solution
D) 5% dextrose in water
Answer: D
Rationale: 5% dextrose in water is hypotonic and would further lower serum sodium, worsening hyponatremia. In
SIADH, water retention is the problem; hypotonic fluids increase water load. Hypertonic saline (3%) is used to
correct severe hyponatremia.
, 12 Which of the following mechanisms best explains the development of hypokalemia in a patient with metabolic
alkalosis?
A) Increased renal potassium excretion due to aldosterone suppression
B) Intracellular shift of potassium in exchange for hydrogen ions
C) Decreased dietary intake secondary to nausea
D) Increased gastrointestinal loss from vomiting-induced diarrhea
Answer: B
Rationale: In metabolic alkalosis, hydrogen ions move out of cells to buffer the alkalemia, and potassium moves
into cells to maintain electroneutrality, causing hypokalemia. Aldosterone is typically increased in metabolic
alkalosis, not suppressed. Vomiting directly causes potassium loss, but the intracellular shift is the primary
mechanism.
13 A patient receiving loop diuretics develops a serum calcium of 10.8 mg/dL (normal 8.5-10.5). Which of the
following best explains this finding?
A) Increased renal calcium reabsorption due to thiazide-like effect
B) Decreased ionized calcium due to alkalosis from diuretic use
C) Hemoconcentration from volume depletion
D) Loop diuretics inhibit calcium reabsorption in the thick ascending limb
Answer: D
Rationale: Loop diuretics inhibit the Na-K-2Cl cotransporter, which also impairs calcium reabsorption, leading to
increased urinary calcium excretion and typically hypocalcemia. The elevated calcium here suggests a different
pathology; loop diuretics cause hypocalcemia, not hypercalcemia. The question tests understanding that loop
diuretics lower calcium.
14 Which of the following serum electrolyte changes is most consistent with acute tumor lysis syndrome
following chemotherapy?
A) Hypercalcemia, hypophosphatemia, hypouricemia
B) Hyperkalemia, hyperphosphatemia, hypocalcemia
C) Hypokalemia, hypophosphatemia, hypercalcemia
D) Hypernatremia, hypermagnesemia, hypercalcemia
Answer: B
Rationale: Tumor lysis syndrome releases intracellular contents: potassium, phosphate, and nucleic acids
(metabolized to uric acid). Phosphate binds calcium, causing hypocalcemia. Thus, hyperkalemia,
hyperphosphatemia, and hypocalcemia are classic. Hypercalcemia is not typical.
15 A patient with chronic kidney disease (GFR 25 mL/min) has a serum magnesium of 3.2 mEq/L (normal
1.7-2.2). Which of the following is the most likely cause?
A) Increased gastrointestinal absorption from vitamin D supplementation
B) Decreased renal excretion due to reduced GFR
C) Redistribution from intracellular to extracellular space
D) Excessive intake of magnesium-containing antacids
Answer: B
Rationale: Magnesium is primarily excreted by the kidneys. With reduced GFR, excretion decreases leading to
hypermagnesemia. While excessive intake can contribute, in CKD, impaired excretion is the primary mechanism.
Redistribution is not a typical cause.