Renal pathology US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Renal pathology. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Renal pathology US Medical PG Question 1: A 22-year-old man comes to the physician because of a 2-week history of cough and decreased urination. The cough was initially nonproductive, but in the last few days he has coughed up small amounts of blood-tinged sputum with clots. He has not had any fevers, chills, or weight loss. He has smoked one pack of cigarettes daily for 5 years. Pulse is 115/min and blood pressure is 125/66 mm Hg. Physical examination shows dried blood around the lips. Serum studies show a creatinine of 2.9 mg/dL. Results of a serum antineutrophil cytoplasm antibody test are negative. A biopsy specimen of the kidney is most likely to show which of the following light microscopy findings?
- A. Thinning of the basement membrane
- B. Fibrin crescents in Bowman space (Correct Answer)
- C. Expansion of the mesangial matrix
- D. Enlarged and hypercellular glomeruli
- E. Neutrophilic infiltration of the capillaries
Renal pathology Explanation: ***Fibrin crescents in Bowman space***
- The patient's presentation with **hemoptysis** (coughing up blood) and **acute kidney injury** (decreased urination, elevated creatinine 2.9 mg/dL) suggests a **pulmonary-renal syndrome**. The **negative ANCA** is a key distinguishing feature pointing towards **Goodpasture syndrome (anti-GBM disease)**.
- Goodpasture syndrome is characterized by **rapidly progressive glomerulonephritis**, classically showing **crescent formation** (fibrin and proliferating parietal epithelial cells) in Bowman's space on light microscopy. The linear IgG deposition on basement membrane would be seen on immunofluorescence.
*Thinning of the basement membrane*
- This finding is characteristic of **Alport syndrome**, a hereditary nephritis presenting with hematuria, sensorineural hearing loss, and ocular abnormalities.
- The patient's acute presentation with hemoptysis and rapidly progressive renal failure is inconsistent with Alport syndrome, which typically has a more chronic course.
*Expansion of the mesangial matrix*
- **Mesangial matrix expansion** is seen in **diabetic nephropathy** and **IgA nephropathy**.
- While IgA nephropathy can cause hematuria and occasionally upper respiratory symptoms, it typically does not present with significant hemoptysis and the acute, severe renal failure seen here.
*Enlarged and hypercellular glomeruli*
- **Glomerular enlargement and hypercellularity** are features of **post-streptococcal glomerulonephritis** (diffuse proliferative glomerulonephritis).
- The absence of preceding infection history and the prominent hemoptysis with negative ANCA make this less likely than Goodpasture syndrome.
*Neutrophilic infiltration of the capillaries*
- **Neutrophilic infiltration** (endocapillary proliferation) is characteristic of **acute post-infectious glomerulonephritis**.
- The pulmonary-renal syndrome presentation without clear evidence of recent infection and negative ANCA makes this diagnosis unlikely.
Renal pathology US Medical PG Question 2: On cardiology service rounds, your team sees a patient admitted with an acute congestive heart failure exacerbation. In congestive heart failure, decreased cardiac function leads to decreased renal perfusion, which eventually leads to excess volume retention. To test your knowledge of physiology, your attending asks you which segment of the nephron is responsible for the majority of water absorption. Which of the following is a correct pairing of the segment of the nephron that reabsorbs the majority of all filtered water with the means by which that segment absorbs water?
- A. Distal convoluted tubule via passive diffusion following ion reabsorption
- B. Distal convoluted tubule via aquaporin channels
- C. Thick ascending loop of Henle via passive diffusion following ion reabsorption
- D. Proximal convoluted tubule via passive diffusion following ion reabsorption (Correct Answer)
- E. Collecting duct via aquaporin channels
Renal pathology Explanation: ***Proximal convoluted tubule via passive diffusion following ion reabsorption***
- The **proximal convoluted tubule (PCT)** is responsible for reabsorbing approximately **65-70% of filtered water**, making it the primary site of water reabsorption in the nephron.
- This water reabsorption primarily occurs **passively**, following the active reabsorption of solutes (especially **sodium ions**), which creates an osmotic gradient.
*Distal convoluted tubule via passive diffusion following ion reabsorption*
- The **distal convoluted tubule (DCT)** reabsorbs a much smaller percentage of filtered water (around 5-10%) and its water reabsorption is largely **regulated by ADH**, not primarily simple passive diffusion following bulk ion reabsorption.
- While some passive water movement occurs, it is not the main mechanism or location for the majority of water reabsorption.
*Distal convoluted tubule via aquaporin channels*
- While aquaporin channels do play a role in water reabsorption in the DCT, particularly under the influence of **ADH**, the DCT is not the segment responsible for the **majority of all filtered water absorption**.
- The bulk of water reabsorption occurs earlier in the nephron, independently of ADH for the most part.
*Thick ascending loop of Henle via passive diffusion following ion reabsorption*
- The **thick ascending loop of Henle** is primarily involved in reabsorbing ions like Na+, K+, and Cl- but is largely **impermeable to water**.
- Its impermeability to water is crucial for creating the **osmotic gradient** in the renal medulla, which is necessary for later water reabsorption.
*Collecting duct via aquaporin channels*
- The **collecting duct** is critically important for **regulated water reabsorption** via **aquaporin-2 channels** under the influence of **ADH**, allowing for fine-tuning of urine concentration.
- However, it reabsorbs only a variable portion (typically 5-19%) of the remaining filtered water, not the **majority of all filtered water**.
Renal pathology US Medical PG Question 3: A 42-year-old man presents to his primary care provider complaining of foamy urine for the last 2 weeks. He has also begun to notice swelling in his hands and feet, and he says that his shoes have not been fitting normally. On exam, the patient has a temperature of 98.8°F (37.1°C), blood pressure is 132/84 mmHg, pulse is 64/min, and respirations are 12/min. The patient has 2+ pitting edema bilaterally up to his shins. A 24-hour urine study is found to contain 9.0 g of protein. The patient is referred to a specialist and undergoes a renal biopsy. On light microscopy, the glomeruli demonstrate basement membrane thickening. On electron microscopy, subepithelial deposits are seen. Which of the following is a characteristic of this patient’s disease?
- A. X-linked condition
- B. Antibodies to alveolar basement membrane
- C. Loss of podocyte foot processes
- D. Antibodies to phospholipase A2 receptor (Correct Answer)
- E. IgA immune complex deposition
Renal pathology Explanation: ***Antibodies to phospholipase A2 receptor***
- The patient's presentation with **foamy urine**, **edema**, and **9.0 g of protein** in a 24-hour urine study indicates **nephrotic syndrome**. Renal biopsy findings of **glomerular basement membrane thickening** on light microscopy and **subepithelial deposits** on electron microscopy are characteristic of **membranous nephropathy**.
- Approximately 70-80% of primary membranous nephropathy cases are associated with **autoantibodies to the M-type phospholipase A2 receptor (PLA2R)**, a protein expressed on podocytes.
*X-linked condition*
- This description is characteristic of **Alport syndrome**, a genetic disorder leading to progressive kidney disease, hearing loss, and eye abnormalities.
- Alport syndrome presents with **hematuria** rather than significant proteinuria, and biopsy would show **laminar splitting of the glomerular basement membrane**.
*Antibodies to alveolar basement membrane*
- This describes **Goodpasture syndrome**, which is characterized by the presence of anti-glomerular basement membrane (anti-GBM) antibodies that target both the kidney and the lung.
- Patients typically present with rapidly progressive glomerulonephritis and pulmonary hemorrhage, and biopsy would show **linear IgG deposition** along the glomerular basement membrane on immunofluorescence.
*Loss of podocyte foot processes*
- This is a characteristic finding in **minimal change disease** and **focal segmental glomerulosclerosis (FSGS)**, two other causes of nephrotic syndrome.
- Minimal change disease typically shows normal glomeruli on light microscopy, while FSGS shows segmental sclerosis. Neither shows subepithelial deposits.
*IgA immune complex deposition*
- This is the hallmark of **IgA nephropathy (Berger's disease)** or **Henoch-Schönlein purpura** in children.
- Patients typically present with **hematuria**, often macroscopic, following an upper respiratory or gastrointestinal infection. Biopsy would show IgA deposits in the mesangium, not subepithelial deposits.
Renal pathology US Medical PG Question 4: A 53-year-old woman presents to her physician for evaluation of sudden onset respiratory distress for the past few hours. The past medical history includes a myocardial infarction 2 years ago. The vital signs include a blood pressure 70/40 mm Hg, pulse 92/min, respiratory rate 28/min, and SpO2 92% on room air. The physical examination reveals bilateral basal crepitations on auscultation. The echocardiogram reveals an ejection fraction of 34%. She is admitted to the medical floor and started on furosemide. The urine output in 24 hours is 400 mL. The blood urea nitrogen is 45 mg/dL and the serum creatinine is 1.85 mg/dL. The fractional excretion of sodium is 2.4%. Urinalysis revealed muddy brown granular casts. Which of the following is the most likely cause of the abnormal urinalysis?
- A. Acute interstitial nephritis
- B. Acute tubular necrosis (Correct Answer)
- C. Acute pyelonephritis
- D. Chronic kidney disease
- E. Acute glomerulonephritis
Renal pathology Explanation: ***Acute tubular necrosis***
- The presence of **muddy brown granular casts** on urinalysis is pathognomonic for **acute tubular necrosis (ATN)**, indicating damage to the renal tubules.
- The patient's history of **cardiogenic shock** (low BP 70/40 mm Hg, respiratory distress, low SpO2, low ejection fraction of 34%) led to **renal hypoperfusion** and ischemic tubular injury.
- The **fractional excretion of sodium (FENa) of 2.4%** (>2%) is characteristic of **intrinsic renal injury** (ATN), as damaged tubules cannot effectively reabsorb sodium.
- **Oliguria** (400 mL/24 hours), elevated **BUN (45 mg/dL)** and **creatinine (1.85 mg/dL)** further support acute kidney injury from ATN.
*Acute interstitial nephritis*
- This condition is typically associated with **drug hypersensitivity** (e.g., NSAIDs, antibiotics, PPIs) or **infections** and is characterized by inflammatory infiltrate in the renal interstitium.
- Urinalysis typically shows **white blood cell casts** and **eosinophiluria**, not muddy brown granular casts.
*Acute pyelonephritis*
- This is an **infection of the kidney** parenchyma, usually caused by bacterial ascension from the urinary tract.
- Symptoms often include **fever, flank pain, dysuria**, and urinalysis reveals **leukocyturia** (white blood cells) and **bacterial casts**, not muddy brown granular casts.
*Chronic kidney disease*
- While the patient has elevated creatinine and BUN, **chronic kidney disease (CKD)** develops over months to years and is characterized by persistent kidney damage or decreased function.
- Urinalysis in CKD often shows **broad waxy casts** and typically does not present with such **acute, sudden onset** of severe renal dysfunction with muddy brown granular casts.
*Acute glomerulonephritis*
- This condition involves inflammation of the glomeruli and typically presents with **hematuria, proteinuria, and red blood cell casts** (dysmorphic RBCs).
- The patient's clinical picture, including the absence of significant hematuria and the presence of **muddy brown granular casts**, does not fit acute glomerulonephritis.
Renal pathology US Medical PG Question 5: A 6-year-old boy is brought to the physician because of increasing swelling around his eyes for the past 3 days. During this period, he has had frothy light yellow urine. He had a sore throat 12 days ago. He appears tired. His temperature is 37°C (98.6°F), pulse is 90/min, and blood pressure is 105/65 mm Hg. Examination shows periorbital edema and pitting edema of the lower extremities. Cardiopulmonary examination shows no abnormalities. Which of the following findings on urinalysis is most likely associated with this patient's condition?
- A. WBC casts
- B. Fatty casts (Correct Answer)
- C. Hyaline casts
- D. RBC casts
- E. Muddy brown casts
Renal pathology Explanation: ***Fatty casts***
- The patient's symptoms of **periorbital edema**, **pitting edema of lower extremities**, and **frothy urine** are classic for **nephrotic syndrome**, characterized by massive **proteinuria** (>3.5 g/day), **hypoalbuminemia**, **hyperlipidemia**, and **edema**.
- **Fatty casts** (also called **oval fat bodies** when in tubular cells) are **pathognomonic for nephrotic syndrome** and result from hyperlipidemia and lipiduria associated with severe proteinuria.
- In a **6-year-old child**, the most common cause of nephrotic syndrome is **minimal change disease**.
*WBC casts*
- **WBC casts** indicate **renal parenchymal inflammation** or **infection**, such as **pyelonephritis**, **acute interstitial nephritis**, or **tubulointerstitial disease**.
- These are not characteristic findings in **nephrotic syndrome**, which primarily affects the **glomerular filtration barrier** leading to protein loss rather than inflammatory cell infiltration.
*Hyaline casts*
- **Hyaline casts** are composed of **Tamm-Horsfall protein** and can be found in **normal urine**, especially with **dehydration**, **exercise**, or **concentrated urine**.
- They are **non-specific** and do not indicate significant kidney pathology or nephrotic syndrome.
*RBC casts*
- **RBC casts** are characteristic of **glomerulonephritis** and **nephritic syndrome** (such as **post-streptococcal glomerulonephritis**), where patients present with **hematuria**, **hypertension**, **mild edema**, and **oliguria**.
- While this patient had a **sore throat 12 days ago** (typical timing for post-streptococcal disease), his clinical presentation is clearly **nephrotic** (massive edema, frothy urine, normal blood pressure) rather than **nephritic**, making RBC casts unlikely.
- The **frothy urine** indicates significant **proteinuria**, not hematuria.
*Muddy brown casts*
- **Muddy brown casts** (granular casts with epithelial cell debris) are highly suggestive of **acute tubular necrosis (ATN)**, typically resulting from **ischemic** or **nephrotoxic injury**.
- This patient's presentation with **gradual onset edema** and **frothy urine** points to a **glomerular disorder** (nephrotic syndrome), not **acute tubular injury**.
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