Renal Pathology Practice Questions

Q: A patient with renal disease undergoes a biopsy. On Congo red staining, the deposits show apple-green birefringence under polarised light. What is the most likely diagnosis?

Amyloidosis. ***Amyloidosis***- This feature is the **pathognomonic microscopic manifestation** of amyloid deposition, where the Congo red stain binds specifically to the parallel **cross-beta sheet** configuration of amyloid fibrils [1].- When viewed under **polarized light**, this interaction results in the classic **apple-green birefringence** due to the ordering of the deposited protein [1], [2]. *Minimal change disease*- The diagnosis of minimal change disease relies primarily on **electron microscopy**, which shows **effacement of podocyte foot processes**.- On **light microscopy**, the glomeruli appear virtually normal, and there are no deposits present that would stain positively with Congo red. *Diabetic nephropathy*- Characteristic findings on light microscopy include **diffuse mesangial expansion** and the formation of **Kimmelstiel-Wilson nodules** (nodular glomerulosclerosis).- The thickening of the glomerular basement membrane and mesangial expansion are due to hyperglycemia and associated metabolic changes, not amyloid deposition. *Membranous nephropathy*- This nephropathy is defined by the presence of **subepithelial immune complex deposits** that result in a uniformly thickened glomerular basement membrane (GBM).- Silver stains often reveal a classic **"spike and dome"** pattern on the GBM, which is distinct from amyloid fibrils. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 533-534.

Q: Tamm-Horsfall mucoprotein is a major component of which of the following?

Renal casts. ***Renal casts*** - **Tamm-Horsfall mucoprotein (THP)**, or **uromodulin**, is a glycoprotein synthesized by the tubular epithelial cells of the **thick ascending limb of the loop of Henle** and the distal tubule. - It forms the fundamental matrix of virtually all **renal casts** (hyaline, granular, waxy, fatty, etc.) when it precipitates in the concentrated, acidic environment of the distal nephron [1]. *Mural thrombi* - These are formed within blood vessels or the heart chambers and consist primarily of aggregated **platelets**, **fibrin**, and entrapped red blood cells. - Mural thrombi are related to circulatory pathology (e.g., atrial fibrillation, myocardial infarction) and are distinct from urinary tract components. *Curschmann spirals* - These spiral-shaped mucoid structures are found in the sputum of patients with conditions like severe bronchial **asthma** or chronic bronchitis. - They represent casts of small bronchi or bronchioles composed mainly of **mucus**, glycoproteins, and cellular debris produced by goblet cells and mucous glands. *Bence-Jones proteins* - These are **free monoclonal light chains** (kappa or lambda) of immunoglobulins that appear in the urine due to overproduction by pathologically proliferating plasma cells, most commonly in **multiple myeloma** [1]. - Bence-Jones proteins are filtered plasma proteins and are distinct from Tamm-Horsfall protein which is secreted by the renal tubular cells [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 942-943.

Q: Least common finding in diabetic kidney is

Armanni-Ebstein. ***Armanni-Ebstein*** - **Armanni-Ebstein lesion** (also known as Armanni-Ebstein change) refers to severe **glycogen accumulation** in the tubular epithelial cells, typically the proximal tubules. - This finding is relatively rare and seen mainly in cases of **poorly controlled acute diabetes mellitus** or acute hyperglycemia, making it the least common routine finding compared to the other structural changes. ***Podocyte loss*** - **Podocyte injury (podocytopathy)** and subsequent loss are a central and early feature in the pathogenesis of diabetic nephropathy, leading to **proteinuria**. - Progressive effacement, detachment, and eventual depletion of these highly specialized cells are constant findings in established **diabetic kidney disease (DKD)**. ***Mesangial widening*** - **Mesangial expansion/widening** is considered the earliest and most specific histological change in **diabetic nephropathy**. - This pathology progresses, leading eventually to **diffuse or nodular glomerulosclerosis** (**Kimmelstiel-Wilson lesions**), making it a universal finding in established DKD. ***GBM thickening*** - **Glomerular basement membrane (GBM) thickening** occurs very early in **diabetic nephropathy**, often preceding clinical proteinuria [1]. - It is a consistent and measurable structural abnormality caused by increased synthesis and altered composition of **extracellular matrix** components in the GBM [1], [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Endocrine System, pp. 1119-1121. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 907-908.

Q: In renal transplant biopsy, which of the following stains is not used to identify organisms?

Congo red. ***Congo red*** - **Congo red** is a special stain primarily used to look for **amyloid deposition**, which appears as an apple-green birefringence under polarized light [1]. - It is a diagnostic stain for **amyloidosis** and has **no role in the identification of infectious organisms** (bacteria, fungi, or parasites) in tissue biopsies [2]. - This is the stain that is **NOT used to identify organisms** in renal transplant biopsies. *Gomori methenamine silver* - This stain, often abbreviated as **GMS**, is excellent for demonstrating the cell walls of **fungi** (e.g., *Pneumocystis*, *Aspergillus*, *Cryptococcus*) which appear as black structures. - It is frequently used in transplant pathology to rule out opportunistic fungal infections. *PAS (Periodic acid-Schiff) stain* - **PAS** stain is used to highlight mucopolysaccharides, basement membranes, and certain cell walls, making it useful for identifying various organisms. - It stains the cell walls of **fungi** and the capsules of some organisms, making it valuable in detecting infections. *Masson Fontana* - **Masson Fontana** stain is primarily used to identify **melanin** pigment in tissues. - While it is not a standard organism identification stain in routine renal transplant pathology, specialized silver-based modifications have been described for detecting certain fungal organisms in research settings. - However, it is not considered a primary stain for organism identification in clinical practice. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 533-534.

Q: A 6-year-old child presents with recurrent urinary tract infections. Urine microscopy findings are shown in the image below. What type of crystalluria is depicted?

Calcium phosphate crystalluria. ***Calcium phosphate crystalluria*** - The image clearly displays **rosette-shaped crystals**, which are characteristic of **calcium phosphate crystalluria** - Calcium phosphate crystals often appear as **starbursts or rosettes** and are typically seen in **alkaline urine** (pH > 7.0) - These crystals are amorphous and can be associated with **urinary tract infections** with urease-producing bacteria *Cysteine crystalluria* - Cysteine crystals are typically described as **hexagonal** in shape, distinctly different from the rosette appearance in the provided image - Their presence is indicative of **cystinuria**, a genetic disorder affecting amino acid reabsorption in the renal tubules - These appear as flat, colorless hexagonal plates *Calcium oxalate crystalluria* - Calcium oxalate crystals classically appear as **envelope-shaped or dumbbell-shaped** structures - They are the most common type of crystals found in normal acidic urine - Associated with **hyperoxaluria**, ethylene glycol poisoning, or dietary factors *Triple phosphate crystalluria* - Triple phosphate (struvite/magnesium ammonium phosphate) crystals have a characteristic **coffin-lid or prism** appearance - These form in **alkaline urine** and are commonly associated with **urease-producing bacterial infections** (Proteus species) - Can contribute to staghorn calculi formation

Q: A 6-year-old child presents with puffy eyes, scanty urination. On examination BP=130/80 mmHg and urine examination shows RBC casts. Kidney biopsy specimen is given below. Which of the following is incorrect about the diagnosis of this child?

Electron microscopy shows sub-endothelial humps. ***Electron microscopy shows sub-endothelial humps*** - This statement is **INCORRECT** and is the answer to this question. In post-streptococcal glomerulonephritis (PSGN), electron microscopy characteristically shows **sub-EPITHELIAL humps** (dome-shaped immune complex deposits), NOT sub-endothelial humps. - These sub-epithelial electron-dense deposits are pathognomonic of PSGN and represent immune complexes that form in situ or deposit from circulation. - The biopsy image shows diffuse endocapillary proliferation with increased cellularity, consistent with acute PSGN. *Anti-hyaluronidase antibodies indicate streptococcal etiology* - This statement is **correct**. Anti-hyaluronidase antibodies are one of several antibodies used to detect recent streptococcal infection. - While **anti-streptolysin O (ASO)** and **anti-DNase B (ADB)** are more commonly used, anti-hyaluronidase is also a valid marker for streptococcal etiology. - Multiple antibody tests increase sensitivity for detecting prior streptococcal infection in PSGN. *95% cases recover with reversal of glomerular changes* - This statement is **correct**. Children with PSGN have an excellent prognosis with **>95% complete recovery**. - Most children show complete clinical and histological resolution, though a small percentage may develop chronic kidney disease. - Adults have a less favorable prognosis compared to children. *Kidneys are bilaterally enlarged and show flea bitten appearance* - This statement is **partially correct but potentially misleading**. The kidneys ARE bilaterally enlarged in acute PSGN due to edema and cellular infiltration. - However, the "flea-bitten appearance" (petechial hemorrhages on kidney surface) is more characteristic of **malignant hypertension** or **hemolytic uremic syndrome**, not typical of PSGN. - In PSGN, kidneys appear swollen and pale rather than showing the classic flea-bitten pattern.

Q: What is the most common extra-renal manifestation in this condition showing small cysts radiating peripherally from the medulla?

Congenital hepatic fibrosis. ***Congenital hepatic fibrosis*** - The image depicts a kidney with **cysts radiating peripherally from the medulla**, which is characteristic of **autosomal recessive polycystic kidney disease (ARPKD)**. - **Congenital hepatic fibrosis** is the most common extra-renal manifestation of ARPKD, often leading to **portal hypertension**. *Hypertension* - While hypertension is a very common complication in both ARPKD and ADPKD, it is a **complication** or a feature, not an extra-renal manifestation in the same category as liver pathologies. - In ARPKD, hypertension typically develops due to **renin-angiotensin system activation** secondary to kidney damage. *Liver cysts* - Liver cysts are more commonly associated with **autosomal dominant polycystic kidney disease (ADPKD)**, rather than ARPKD which usually presents with congenital hepatic fibrosis. - While ARPKD can involve biliary dysgenesis leading to some cystic changes, the predominant pathology is **fibrosis**, not simple cysts. *Berry aneurysm* - **Berry aneurysms** are a classic extra-renal manifestation of **autosomal dominant polycystic kidney disease (ADPKD)**, not ARPKD. - Their presence in ADPKD patients increases the risk of **subarachnoid hemorrhage**.

Q: A 45-year-old male with severe hypertension presents with acute renal failure. A renal biopsy shows the histopathological findings in the image. What is the most likely diagnosis?

Hyperplastic arteriosclerosis. ***Hyperplastic arteriosclerosis*** - This condition is characterized by **onion-skinning** of the arterial walls due to concentric thickening of the smooth muscle cells and reduplication of the internal elastic lamina [1][2]. - It is typically seen in severe **malignant hypertension**, where the rapid and severe elevation in blood pressure leads to these distinctive changes [2]. *Hyaline arteriosclerosis* - This involves **homogeneous, pink, hyaline thickening** of the arteriolar walls, often leading to luminal narrowing. - It is commonly associated with **benign hypertension** and diabetes mellitus, resulting from plasma protein leakage and increased extracellular matrix deposition. *Monckeberg's arteriosclerosis* - This is characterized by **calcific deposits** in the media of medium-sized muscular arteries, without significant luminal narrowing. - It is typically an **incidental finding** in older individuals and is not associated with significant clinical consequences like ischemia. *Fibrinoid necrosis* - This refers to the deposition of **fibrin-like material** in the vessel walls, leading to an amorphous, brightly eosinophilic appearance [1]. - While it can be seen in severe hypertension, it represents a more acute and severe form of vascular damage, often associated with **necrotizing arteriolitis**, and is not the primary description for the "onion-skinning" pattern [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, p. 945. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 498-499.

Question 1

A patient with renal disease undergoes a biopsy. On Congo red staining, the deposits show apple-green birefringence under polarised light. What is the most likely diagnosis?

Accepted Answer

Amyloidosis

Answer

Diabetic nephropathy

Answer

Membranous nephropathy

Answer

Minimal change disease

Question 2

A 5-year-old child presented with a history of edema of the face which later progressed to generalized edema. Urine showed massive proteinuria and light microscopy was normal. Electron microscopy showed effacement of podocyte foot processes. What is the diagnosis?

Accepted Answer

Minimal change disease

Answer

Post streptococcal glomerulonephritis

Answer

Focal segmental glomerulo sclerosis

Answer

Membranous glomerulonephritis

Question 3

Tamm-Horsfall mucoprotein is a major component of which of the following?

Accepted Answer

Renal casts

Answer

Bence-Jones proteins

Answer

Mural thrombi

Answer

Curschmann spirals

Question 4

Least common finding in diabetic kidney is

Accepted Answer

Armanni-Ebstein

Answer

Podocyte loss

Answer

GBM thickening

Answer

Mesangial widening

Question 5

In renal transplant biopsy, which of the following stains is not used to identify organisms?

Accepted Answer

Congo red

Answer

Masson Fontana

Answer

PAS (Periodic acid-Schiff) stain

Answer

Gomori methenamine silver

Question 6

A 6-year-old child presents with recurrent urinary tract infections. Urine microscopy findings are shown in the image below. What type of crystalluria is depicted?

Accepted Answer

Calcium phosphate crystalluria

Answer

Calcium oxalate crystalluria

Answer

Triple phosphate crystalluria

Answer

Cysteine crystalluria

Question 7

On the basis of radiopathological correlation. What is the diagnosis?

Accepted Answer

Metastatic renal cell carcinoma

Answer

Metastatic choriocarcinoma

Answer

Metastatic thyroid carcinoma

Answer

Primary pulmonary tuberculoma

Question 8

A 6-year-old child presents with puffy eyes, scanty urination. On examination BP=130/80 mmHg and urine examination shows RBC casts. Kidney biopsy specimen is given below. Which of the following is incorrect about the diagnosis of this child?

Accepted Answer

Electron microscopy shows sub-endothelial humps

Answer

Anti-hyaluronidase antibodies indicate streptococcal etiology

Answer

95% cases recover with reversal of glomerular changes

Answer

Kidneys are bilaterally enlarged and show flea bitten appearance

Question 9

What is the most common extra-renal manifestation in this condition showing small cysts radiating peripherally from the medulla?

Accepted Answer

Congenital hepatic fibrosis

Answer

Hypertension

Answer

Liver cysts

Answer

Berry aneurysm

Question 10

A 45-year-old male with severe hypertension presents with acute renal failure. A renal biopsy shows the histopathological findings in the image. What is the most likely diagnosis?

Accepted Answer

Hyperplastic arteriosclerosis

Answer

Hyaline arteriosclerosis

Answer

Monckeberg's arteriosclerosis

Answer

Fibrinoid necrosis

Renal Pathology — MCQs

Renal Pathology — MCQs

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