Renal Pathology — MCQs

Renal Pathology Indian Medical PG Practice Questions and MCQs

Question 521: Congenital hepatic fibrosis is a characteristic feature of which of the following conditions?

A. Multicystic renal dysplasia
B. Autosomal Recessive Polycystic Kidney Disease (ARPKD) (Correct Answer)
C. Familial juvenile nephronophthisis
D. Medullary sponge kidney

Explanation: ### Explanation **Correct Answer: B. Autosomal Recessive Polycystic Kidney Disease (ARPKD)** **Why it is correct:** ARPKD is a ciliopathy caused by mutations in the **PKHD1 gene**, which encodes the protein **fibrocystin** [2]. This protein is expressed in the primary cilia of both renal tubular epithelial cells and bile duct epithelium. In ARPKD, there is a constant association between renal cystic disease and developmental biliary abnormalities. This spectrum is known as the **ductal plate malformation**, which histologically manifests as **congenital hepatic fibrosis** (characterized by periportal fibrosis and dilated bile ducts) [1]. In older children, the hepatic manifestations (portal hypertension, splenomegaly) may clinically overshadow the renal disease [1]. **Why incorrect options are wrong:** * **Multicystic renal dysplasia (A):** This is a sporadic developmental anomaly resulting from abnormal metanephric differentiation. It presents as a unilateral multicystic mass and is not associated with congenital hepatic fibrosis. * **Familial juvenile nephronophthisis (C):** While this is a ciliopathy that can be associated with extrarenal features (like retinitis pigmentosa in Senior-Løken syndrome), it typically presents with corticomedullary cysts and tubulointerstitial fibrosis, not the classic congenital hepatic fibrosis seen in ARPKD. * **Medullary sponge kidney (D):** This is a benign condition characterized by cystic dilations of the collecting ducts in the papillae. It is usually asymptomatic and does not involve the liver. **High-Yield Facts for NEET-PG:** * **Potter Sequence:** Severe ARPKD can lead to oligohydramnios, resulting in pulmonary hypoplasia, flattened facies, and clubfoot. * **Imaging:** On ultrasound, ARPKD kidneys appear enlarged and "echogenic" with a loss of corticomedullary differentiation. * **Mnemonic:** "ARPKD = All Recessive, Potter, Kidneys (bilateral), Ductal plate (liver)." * **ADPKD vs. ARPKD:** ADPKD (Adult) is associated with **berry aneurysms** and **liver cysts**, whereas ARPKD (Infantile) is associated with **congenital hepatic fibrosis**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Liver and Gallbladder, p. 868. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 952-953.

Question 522: Which of the following is a feature of autosomal recessive polycystic kidney disease?

A. Can be diagnosed intrauterine (Correct Answer)
B. Progresses to renal failure by school age
C. Can be palpated abdominally
D. Hypertension does not develop until late stages of the disease

Explanation: **Explanation:** **Autosomal Recessive Polycystic Kidney Disease (ARPKD)** is a genetic disorder caused by mutations in the **PKHD1 gene** on chromosome 6, which encodes **fibrocystin** [1]. 1. **Why Option A is correct:** ARPKD can be diagnosed **intrauterine** via prenatal ultrasound. Characteristic findings include bilaterally enlarged, echogenic kidneys and **oligohydramnios** (due to poor fetal urine output). Severe cases present at birth (Potter sequence) with pulmonary hypoplasia [1]. 2. **Why other options are incorrect:** * **Option B:** While some patients survive to school age, the classic "infantile" form often leads to **perinatal or neonatal death** due to respiratory failure [1]. It does not "progress" to failure by school age; rather, those who survive birth usually already have significant renal impairment. * **Option C:** While the kidneys are massively enlarged, they are typically described as **smooth and symmetrical** (due to small, radially arranged cortical cysts), unlike the "bosselated" or "knobby" irregular masses palpated in Autosomal Dominant PKD (ADPKD). * **Option D:** Hypertension is a **very early and severe** feature of ARPKD, often appearing in the neonatal period, and is a major cause of morbidity. **High-Yield Clinical Pearls for NEET-PG:** * **Microscopy:** Characterized by **cylindrical/saccular dilation of collecting ducts** (radial arrangement) [1]. * **Liver Involvement:** 100% of cases have **Congenital Hepatic Fibrosis**. If the patient survives the renal complications, they often present later with portal hypertension and splenomegaly. * **Potter Sequence:** Oligohydramnios → Fetal compression → Clubbed feet, flattened facies, and pulmonary hypoplasia. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 952-953.

Question 523: 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?

A. Diabetic nephropathy
B. Amyloidosis (Correct Answer)
C. Membranous nephropathy
D. Minimal change disease

Explanation: ***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.

Question 524: 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?

A. Post streptococcal glomerulonephritis
B. Minimal change disease (Correct Answer)
C. Focal segmental glomerulo sclerosis
D. Membranous glomerulonephritis

Explanation: ***Minimal change disease*** - **Classic presentation** in children aged 2-6 years with nephrotic syndrome (edema, massive proteinuria) [1] - **Normal light microscopy** is the pathognomonic feature that distinguishes MCD from other glomerular diseases [3] - **Electron microscopy shows effacement of podocyte foot processes** (fusion of foot processes) - the only ultrastructural abnormality [1], [3] - **Most common cause** of nephrotic syndrome in children (~90% of cases <6 years) [1], [3] - Excellent response to corticosteroid therapy (steroid-sensitive) [3] *Post streptococcal glomerulonephritis* - Presents with **nephritic syndrome** (hematuria, hypertension, mild proteinuria), not nephrotic syndrome - Light microscopy shows **hypercellular glomeruli** with neutrophil infiltration - EM shows **subepithelial "humps"** (immune complex deposits), not foot process effacement alone *Focal segmental glomerulosclerosis (FSGS)* - Light microscopy shows **focal and segmental sclerosis** of some glomerular [1] - More common in adults and African Americans - Associated with obesity, HIV, heroin use [4] - Poor response to steroids (steroid-resistant nephrotic syndrome) [1] *Membranous glomerulonephritis* - Light microscopy shows **diffuse thickening of glomerular basement membrane** with "spike and dome" appearance [2], [4] - EM shows **subepithelial immune complex deposits** [2], [4] - More common cause of nephrotic syndrome in **adults**, not children [2] - Associated with autoimmune diseases, infections, and malignancies [2] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 927-928. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 919-921. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 922-923. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 531-532.

Question 525: Tamm-Horsfall mucoprotein is a major component of which of the following?

A. Bence-Jones proteins
B. Renal casts (Correct Answer)
C. Mural thrombi
D. Curschmann spirals

Explanation: ***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.

Question 526: Least common finding in diabetic kidney is

A. Podocyte loss
B. GBM thickening
C. Armanni-Ebstein (Correct Answer)
D. Mesangial widening

Explanation: ***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.

Question 527: In renal transplant biopsy, which of the following stains is not used to identify organisms?

A. Masson Fontana
B. PAS (Periodic acid-Schiff) stain
C. Congo red (Correct Answer)
D. Gomori methenamine silver

Explanation: ***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.

Question 528: All the following are features of Polycystic disease of kidneys EXCEPT:

A. Erythrocytosis (Correct Answer)
B. Renal failure
C. Haematuria
D. Hypertension

Explanation: ***Erythrocytosis*** - While other renal conditions like **renal cell carcinoma** can cause erythrocytosis due to increased **erythropoietin** production, it is generally **not a typical feature** of Polycystic Kidney Disease (PKD). - Patients with PKD usually have **normal or even low erythropoietin levels** despite compromised kidney function, and anemia is more common, particularly as **renal failure progresses**. *Renal failure* - **Progressive cyst growth** leads to replacement of normal kidney parenchyma, inevitably culminating in **end-stage renal disease** [1] in the majority of patients. - This is a hallmark feature, often necessitating **dialysis or transplant** later in life for individuals with autosomal dominant polycystic kidney disease (ADPKD) [2]. *Haematuria* - **Gross or microscopic hematuria** is a common symptom in PKD, often resulting from **cyst rupture** [1], bleeding into a cyst, or the passage of a calculus due to urinary stasis. - It can be a presenting symptom and can cause significant pain and anxiety for patients. *Hypertension* - **Hypertension** is an early and frequent complication of PKD, often preceding any significant decline in glomerular filtration rate. - It is primarily caused by activation of the **renin-angiotensin-aldosterone system (RAAS)** [3] due to arterial compression and ischemia from expanding cysts. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 951-955. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 544-545. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 520-521.

Question 529: A renal biopsy shows 'bamboo spine' pattern in arterioles. Which immunofluorescence finding would best support thrombotic microangiopathy?

A. Mesangial IgA deposits
B. Linear IgG deposits
C. Granular C3 deposits
D. Minimal/negative immunofluorescence staining (Correct Answer)

Explanation: ***Minimal/negative immunofluorescence staining*** - Thrombotic microangiopathy (TMA) is characterized by **thrombi** in arterioles and capillaries, leading to **ischemic injury** and **fibrin deposition**, but typically lacks significant immune complex deposition [3]. - Therefore, immunofluorescence in TMA often shows **negative** or only very subtle, non-specific staining for immunoglobulins and complement components, which helps differentiate it from immune-mediated glomerular diseases [3]. *Mesangial IgA deposits* - This finding is characteristic of **IgA nephropathy**, a primary glomerular disease, not typically associated with the 'bamboo spine' pattern of arteriolar thrombi seen in TMA. - IgA nephropathy involves immune complex deposition in the **mesangium**, leading to hematuria and proteinuria. *Linear IgG deposits* - **Linear IgG deposits** on the glomerular basement membrane are the hallmark of **Goodpasture syndrome** (anti-GBM disease), an autoimmune condition causing rapidly progressive glomerulonephritis [1]. - This is distinct from TMA, which involves microvascular thrombosis, not anti-GBM antibodies [3]. *Granular C3 deposits* - **Granular C3 deposits**, often with IgG or IgM, are classic findings in various forms of **immune complex-mediated glomerulonephritis** (e.g., post-infectious glomerulonephritis, lupus nephritis) [1]. - While complement activation can occur in some TMAs, prominent granular C3 deposition is more suggestive of immune complex disease rather than the primary thrombotic process of TMA [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 526-527. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 534-535. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 540-541.

Question 530: A kidney biopsy shows 'tram-track' appearance on silver stain. Which immunofluorescence pattern would best support membranoproliferative glomerulonephritis?

A. Granular C3 deposits
B. Mesangial IgA deposits
C. Fibrillar deposits
D. Granular C3 and IgG deposits (Correct Answer)

Explanation: ***Granular C3 and IgG deposits*** - **Membranoproliferative glomerulonephritis (MPGN) Type I** is an immune complex-mediated disease characterized by deposition of **both complement (C3) and immunoglobulins (IgG, IgM)** in the glomeruli [1]. - The **"tram-track" appearance** on silver stain represents basement membrane splitting due to mesangial and endothelial cell proliferation with subendothelial immune complex deposition [1], [3]. - **Immunofluorescence shows granular deposits of C3 along with IgG**, reflecting the immune complex nature of the disease, making this the best pattern to support the diagnosis of classic MPGN [1]. *Granular C3 deposits* - **Isolated or predominant C3 deposits** without significant immunoglobulin deposition are characteristic of **C3 glomerulopathy** (including Dense Deposit Disease, formerly MPGN Type II) [2]. - While C3 glomerulopathy can show membranoproliferative patterns, it represents a distinct complement-mediated pathophysiology rather than classic immune complex-mediated MPGN [2]. - The absence of immunoglobulins distinguishes this from classic MPGN Type I [1]. *Mesangial IgA deposits* - **Mesangial IgA deposits** are the defining feature of **IgA nephropathy**, which typically presents with episodic hematuria following upper respiratory infections [3]. - IgA nephropathy does not characteristically show the "tram-track" appearance and has a different pathologic pattern with predominant mesangial involvement [3]. *Fibrillar deposits* - **Fibrillar deposits** are characteristic of **fibrillary glomerulonephritis**, a rare condition with organized non-amyloid fibrils (12-20 nm diameter) visible on electron microscopy. - This entity does not typically produce the "tram-track" appearance and represents a distinct glomerular disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 925-926. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 926-927. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, p. 911.

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