Tubular and Interstitial Diseases — MCQs
Polyuria with low fixed specific gravity urine is seen in ?
A boy is suffering from acute pyelonephritis. The most specific investigation to confirm the diagnosis is:
The most common cause of renal scarring in a 3-year-old child is:
The most common form of acute kidney injury is:
Which part of the kidney is first affected by ischemia in the context of acute kidney injury?
Which of these conditions is classified as a nephritic syndrome?
Irregular scarred kidney with pelvic dilatation is seen with?
A 29-year-old male with HIV, on indinavir, zidovudine, and stavudine, presents with severe edema and a serum creatinine of 2.0 mg/dL. He has had bone pain for 5 years and takes large amounts of acetaminophen with codeine, aspirin, and ibuprofen. He is on prophylactic trimethoprim-sulfamethoxazole. Blood pressure is 170/110; urinalysis shows 4+ protein, 5 to 10 RBCs; 24-hour urine protein is 6.2 g. What is the most likely cause of his renal disease?
A boy is suffering from acute pyelonephritis. The most specific urinary finding will be:
Loss of foot processes seen on electron microscopy of renal biopsy is a classical feature in which of the following?
Tubular and Interstitial Diseases Indian Medical PG Practice Questions and MCQs
Question 1: Polyuria with low fixed specific gravity urine is seen in ?
- A. Diabetes mellitus
- B. Diabetes insipidus
- C. Chronic glomerulonephritis (Correct Answer)
- D. Potomania
Explanation: ***Chronic glomerulonephritis*** - Damage to the **renal tubules** in chronic glomerulonephritis impairs their ability to concentrate urine, leading to polyuria with a **low, fixed specific gravity**. [1] - This fixed specific gravity reflects the kidneys' inability to adjust urine concentration in response to hydration status, a hallmark of **chronic kidney disease**. [2] *Diabetes mellitus* - Polyuria in diabetes mellitus is caused by **osmotic diuresis** due to high glucose levels in the urine, leading to increased urinary volume. [2] - While there is polyuria, the specific gravity is not necessarily fixed and can vary, often being high due to the presence of glucose. *Diabetes insipidus* - Diabetes insipidus causes polyuria and dilute urine due to either a deficiency of **ADH (central DI)** or renal unresponsiveness to ADH **(nephrogenic DI)**. - While it causes polyuria with low specific gravity, it's typically *not* fixed; the urine specific gravity can still fluctuate to some extent depending on the patient's hydration, or in response to ADH if it's central DI. *Potomania* - Potomania, or **primary polydipsia**, is excessive water intake that leads to dilutional hyponatremia and polyuria. - The kidneys are otherwise healthy and can still concentrate urine to some extent if water intake is restricted, preventing a truly fixed low specific gravity.
Question 2: A boy is suffering from acute pyelonephritis. The most specific investigation to confirm the diagnosis is:
- A. Urine culture (Correct Answer)
- B. Leucocyte esterase test
- C. Nitrite test
- D. Bacteria in gram stain
Explanation: Urine culture - A **urine culture** is considered the gold standard for diagnosing urinary tract infections, including pyelonephritis, as it identifies the specific **pathogen** and its **antibiotic susceptibility** [1]. - It quantifies the number of bacteria present (colony-forming units/mL), confirming significant bacteriuria indicative of infection [2]. *Leucocyte esterase test* - The **leucocyte esterase test** detects enzymes produced by neutrophils, indicating the presence of **white blood cells (pyuria)** in the urine. - While suggestive of inflammation and infection, it is not specific to pyelonephritis and can be positive in other conditions like cystitis or contamination. *Nitrite test* - The **nitrite test** detects nitrites produced by some gram-negative bacteria (e.g., *E. coli*) that convert urinary nitrates to nitrites. - A positive result suggests bacteriuria but is not specific, as some pathogens do not produce nitrite, and it doesn't quantify bacterial load or identify the organism. *Bacteria in gram stain* - Direct visualization of **bacteria in a Gram stain** of uncentrifuged urine can indicate bacteriuria, especially if numerous organisms are seen [1]. - However, it provides preliminary information and cannot definitively identify the species, quantify bacterial load, or determine antibiotic sensitivity, which are crucial for confirming pyelonephilitis and guiding treatment [1].
Question 3: The most common cause of renal scarring in a 3-year-old child is:
- A. Tuberculosis
- B. Interstitial nephritis
- C. Vesicoureteral reflux-induced pyelonephritis (Correct Answer)
- D. Trauma
Explanation: ***Vesicoureteral reflux-induced pyelonephritis*** - **Vesicoureteral reflux (VUR)** allows urine to flow backward from the bladder to the kidneys, predisposing to recurrent **urinary tract infections (UTIs)** and **pyelonephritis**. - Repeated episodes of **pyelonephritis** in young children, especially those with VUR, can lead to **renal scarring** and permanent kidney damage. *Trauma* - While renal trauma can cause scarring, it is not the most common cause of **diffuse renal scarring** in a 3-year-old child. - Trauma typically causes localized injury rather than the widespread scarring seen with chronic inflammation. *Tuberculosis* - **Renal tuberculosis** can lead to scarring but is relatively rare in young children in many parts of the world. - It usually presents with symptoms beyond just scarring, such as **sterile pyuria** and constitutional symptoms. *Interstitial nephritis* - **Interstitial nephritis** is an inflammation of the spaces between renal tubules and can lead to scarring if chronic. - However, it is less common than VUR-induced pyelonephritis as the primary cause of widespread renal scarring in this age group, and often has other underlying causes like drug reactions or systemic diseases.
Question 4: The most common form of acute kidney injury is:
- A. Prerenal azotemia (Correct Answer)
- B. Acute tubular injury
- C. Acute interstitial nephritis
- D. Acute glomerular disease
Explanation: ***Prerenal azotemia*** - This is the most prevalent form of **acute kidney injury (AKI)**, accounting for approximately 50-60% of all cases [1]. - It results from **decreased renal perfusion**, leading to reduced glomerular filtration without direct damage to the kidney parenchyma [1]. *Acute tubular injury* - This is an **intrinsic form of AKI** characterized by damage to the renal tubules, often due to ischemia or nephrotoxins [1]. - While common, it is usually a consequence of prolonged or severe prerenal AKI, and thus not the *most* common initial cause [1]. *Acute interstitial nephritis* - This involves inflammation of the kidney's **interstitial tissue**, often triggered by **allergic reactions to medications** or infections [2]. - It represents a smaller percentage of AKI cases compared to prerenal causes. *Acute glomerular disease* - This form of AKI involves direct injury to the **glomeruli**, such as in glomerulonephritis [2]. - While serious, glomerular diseases are significantly less common as a cause of overall AKI compared to prerenal factors.
Question 5: Which part of the kidney is first affected by ischemia in the context of acute kidney injury?
- A. Cortex
- B. Inner medulla
- C. Outer medulla (Correct Answer)
- D. Glomerulus
Explanation: ***Outer medulla*** - The **outer medulla** is particularly vulnerable to ischemia due to its high metabolic demand and limited blood supply. - Ischemic damage typically begins here as it receives blood supply from the **vasa recta**, which are more susceptible to drops in perfusion pressure. *Glumerulus* - The **glomerulus** is primarily affected in conditions like **glomerulonephritis**, not in acute ischemic injury where tubular structures are first impacted [1]. - It is well-perfused under normal conditions, making it less likely to be the first area affected during acute kidney injury. *Cortex* - The **cortex** is indeed involved in acute kidney damage but is not the first area affected by ischemia. - The cortical region can withstand lower perfusion volumes for a shorter time compared to the outer medulla. *Inner medulla* - The **inner medulla** is the last area to suffer from ischemic damage as it is more tolerant to **hypoxic conditions**. - It primarily encounters ischemia after the outer medulla has already been compromised, thus not the first area affected. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, p. 933.
Question 6: Which of these conditions is classified as a nephritic syndrome?
- A. Minimal Change Disease
- B. Membranous Glomerulopathy
- C. Post Infectious Glomerulonephritis (Correct Answer)
- D. Focal Segmental Glomerulosclerosis
Explanation: ***Post infectious Glomerulonephritis*** - Characterized by **hematuria, hypertension, and edema**, typically following an infection, such as streptococcal pharyngitis [2]. - Immune-mediated response leads to **decreased GFR** and signs of nephritic syndrome [1][2]. *Focal segmental glomerulosclerosis* - Primarily causes **nephrotic syndrome**, characterized by proteinuria and edema rather than hematuria [2]. - Often associated with **secondary causes** like obesity or HIV, not typically post-infectious. *Membranous Glomerulopathy* - Results in significant **proteinuria** and is classified as a **nephrotic syndrome** rather than a nephritic one [2][3]. - It presents with **edema and hypoalbuminemia**, lacking the hallmark features of hematuria. *Minimal change disease* - Predominantly causes **nephrotic syndrome** with heavy proteinuria and little to no hematuria [2]. - Young children are commonly affected, and it responds well to **corticosteroid therapy** [1].
Question 7: Irregular scarred kidney with pelvic dilatation is seen with?
- A. Chronic pyelonephritis (Correct Answer)
- B. Polycystic kidney
- C. Renal artery stenosis
- D. Tuberculosis of kidney
Explanation: ***Chronic pyelonephritis*** - Characterized by irregular scarring of the kidney and often leads to **pelvic dilatation** due to recurrent infections and obstruction [1]. - The damage from inflammation results in **cortical scarring** and can affect kidney function significantly over time [1]. *Renal artery stenosis* - Typically presents with **hypertension** and may lead to ischemic atrophy, but does not cause significant **pelvic dilatation**. - The kidney appears small and often asymmetric, but not typically irregular and scarred. *Tuberculosis of kidney* - Can cause damage to the kidney, but usually leads to **caseating granulomas** and can cause abscesses, not specifically irregular scarring with pelvic dilation. - Often presents with systemic symptoms such as fever and night sweats, along with hematuria. *Polycystic kidney* - Characterized by multiple cysts in both kidneys leading to enlarged kidneys, but does not typically present as **irregularly scarred kidneys**. - Usually associated with **hemodynamic issues** and hypertension but not pelvic dilatation in the sense of scarring or fibrosis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 937-939.
Question 8: A 29-year-old male with HIV, on indinavir, zidovudine, and stavudine, presents with severe edema and a serum creatinine of 2.0 mg/dL. He has had bone pain for 5 years and takes large amounts of acetaminophen with codeine, aspirin, and ibuprofen. He is on prophylactic trimethoprim-sulfamethoxazole. Blood pressure is 170/110; urinalysis shows 4+ protein, 5 to 10 RBCs; 24-hour urine protein is 6.2 g. What is the most likely cause of his renal disease?
- A. Analgesic nephropathy
- B. Indinavir toxicity
- C. Focal sclerosis (Correct Answer)
- D. Trimethoprim-sulfamethoxazole-induced interstitial nephritis
Explanation: Focal sclerosis - The combination of **HIV infection**, severe **proteinuria** (>3.5g/day, here 6.2g/day), and **hypertension** in an African American male strongly suggests **HIV-associated nephropathy (HIVAN)**, which often manifests as focal segmental glomerulosclerosis (FSGS) on biopsy [2]. - **HIVAN** is characterized by rapidly progressive renal failure, heavy proteinuria, and is more common in individuals of African descent [2]. *Indinavir toxicity* - **Indinavir** is a protease inhibitor known to cause **nephrolithiasis** (kidney stones) and **crystal-induced nephropathy**, presenting with acute kidney injury. - It typically does not cause the severe, sustained proteinuria seen in this patient, which is characteristic of glomerular disease [1]. *Analgesic nephropathy* - This condition is caused by chronic overuse of **NSAIDs and acetaminophen**, leading to **papillary necrosis** and **chronic interstitial nephritis**. - While the patient uses these medications, his primary presentation of heavy proteinuria and rapid decline in renal function points away from typical analgesic nephropathy, which usually involves milder proteinuria and sterile pyuria [1]. *Trimethoprim-sulfamethoxazole-induced interstitial nephritis* - هذا الدواء يمكن أن يسبب **التهاب الكلى الخلالي الحاد (AIN)**، والذي يترافق عادةً مع **حمى، طفح جلدي، فرط الحمضات (Eosinophilia)**، وارتفاع في الكرياتينين [1]. - While it can cause renal dysfunction, it is less likely to cause the severe proteinuria (6.2 g) observed in this patient, which is more indicative of a glomerular lesion [1].
Question 9: A boy is suffering from acute pyelonephritis. The most specific urinary finding will be:
- A. Bacteria in gram stain
- B. W.B.C. casts (Correct Answer)
- C. Leucocyte esterase test
- D. Nitrite test
Explanation: ***W.B.C. casts*** - **WBC casts** are pathognomonic for **pyelonephritis** as they indicate inflammation and infection within the **renal tubules**. - They form when white blood cells aggregate in the **tubular lumen** and are encased in **Tamm-Horsfall protein**, reflecting their renal origin. *Leucocyte esterase test* - The **leukocyte esterase test** detects the presence of enzymes released by **neutrophils**, indicating pyuria (white blood cells in urine). - While positive in pyelonephritis, it is not specific to the kidney and can be positive in **lower urinary tract infections** as well. *Nitrite test* - A **nitrite test** detects the presence of **nitrites**, which are formed by gram-negative bacteria that convert urinary nitrates. - This test is indicative of a bacterial infection but is not specific to the **upper urinary tract** (pyelonephritis) versus a **lower urinary tract infection** (cystitis). *Bacteria in gram stain* - The presence of **bacteria** on a Gram stain of unspun urine indicates a significant bacterial presence, often associated with a urinary tract infection. - However, it does not differentiate between **upper** (pyelonephritis) and **lower** (cystitis) urinary tract infections and is therefore not specific for pyelonephritis.
Question 10: Loss of foot processes seen on electron microscopy of renal biopsy is a classical feature in which of the following?
- A. Minimal change disease (Correct Answer)
- B. Membranous nephropathy
- C. Rapidly progressive glomerulonephritis
- D. IgA nephropathy
Explanation: ***Minimal change disease*** - **Loss of foot processes** (podocyte effacement) is the hallmark ultrastructural finding in **minimal change disease** on electron microscopy [1]. - This effacement of podocyte foot processes leads to increased permeability of the **glomerular filtration barrier** to albumin, causing **nephrotic syndrome** [1], [2]. *IgA nephropathy* - Characterized by **IgA immune complex deposition** in the **mesangium** on immunofluorescence. - Electron microscopy typically shows **mesangial immune deposits**, not primarily foot process effacement. *Membranous nephropathy* - Identified by the presence of **subepithelial immune deposits** and **thickening of the glomerular basement membrane** (GBM) [3]. - On electron microscopy, these deposits are visible, often with overlying **spikes** of GBM material separating them. *Rapidly progressive glomerulonephritis* - Defined by the rapid loss of renal function and the presence of **crescents** in more than 50% of glomeruli on light microscopy [2]. - While there may be secondary podocyte changes due to severe inflammation, **foot process effacement** is not its primary diagnostic feature. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 927-928. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 527-528. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 532-533.
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