Nephrology Practice Questions

Q: What is the most common cause of death in Autosomal Dominant Polycystic Kidney Disease (ADPKD)?

Cardiovascular disease. **Explanation:** **1. Why Cardiovascular Disease is Correct:** While ADPKD is primarily a renal disorder, the most common cause of mortality is **Cardiovascular Disease (CVD)**, accounting for nearly 50% of deaths. The underlying mechanism is multifactorial: chronic hypertension (the most common complication of ADPKD), left ventricular hypertrophy (LVH), and accelerated atherosclerosis. Hypertension in ADPKD occurs early—often before any decline in GFR—due to intrarenal ischemia caused by expanding cysts, which triggers the **Renin-Angiotensin-Aldosterone System (RAAS)**. **2. Analysis of Incorrect Options:** * **Renal Failure (Option A):** Although ADPKD is a leading cause of End-Stage Renal Disease (ESRD), patients on dialysis or post-transplant are more likely to die from cardiovascular complications than from uremia itself. Mutations in the PKD1 gene account for 85% of cases and PKD2 for about 15%; ESRD occurs in approximately 50% of patients with PKD1 [1]. * **Ruptured Berry Aneurysm (Option B):** This is a high-yield association (occurring in ~10% of patients), but it is **not** the most common cause of death. It is a significant cause of sudden neurological death, but its overall incidence is much lower than CVD. * **Sepsis (Option C):** While cyst infections and urinary tract infections are common morbidities, they are rarely the primary cause of death in the modern antibiotic era. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common extra-renal manifestation:** Hepatic cysts (usually asymptomatic). * **Most common initial symptom:** Flank pain or hematuria [1]. * **Genetics:** PKD1 (Chromosome 16) is more common and severe; PKD2 (Chromosome 4) has a slower progression [1]. * **Treatment Tip:** **Tolvaptan** (V2 receptor antagonist) is used to slow cyst growth and disease progression. * **Screening:** Ultrasound is the initial screening modality of choice for family members.

Q: An 80-year-old person has developed a posterior circulation (PCA) territory stroke. On ambulatory Holter, he is found to be having atrial fibrillation. What calculation should be used to evaluate for renal insufficiency of the patient?

Cockcroft-Gault formula. ### Explanation **Correct Answer: D. Cockcroft-Gault formula** The patient has suffered an embolic stroke due to **Atrial Fibrillation (AF)**. In clinical practice, the management of AF requires anticoagulation (e.g., Warfarin or Direct Oral Anticoagulants like Dabigatran, Rivaroxaban). Most **Direct Oral Anticoagulants (DOACs)** require precise dose adjustments or are contraindicated based on renal function. The **Cockcroft-Gault formula** is the gold-standard method specifically used in clinical trials for DOACs to estimate **Creatinine Clearance (CrCl)** and determine appropriate dosing. **Analysis of Incorrect Options:** * **A. NIHSS score:** This is a tool used to quantify the neurological deficit and severity of an acute stroke. It does not assess renal function. * **B. ABCD2 score:** This is used to predict the risk of a stroke in the days following a Transient Ischemic Attack (TIA). * **C. CHA₂DS₂-VASc score:** This is a clinical prediction rule for estimating the **risk of stroke** in patients with non-valvular atrial fibrillation to determine if anticoagulation is necessary. It does not measure renal insufficiency. **Clinical Pearls for NEET-PG:** * **Cockcroft-Gault Formula:** $CrCl = \frac{(140 - \text{age}) \times \text{weight (kg)}}{72 \times \text{Serum Creatinine (mg/dL)}} \times (0.85 \text{ if female})$. * **High-Yield:** While MDRD and CKD-EPI are preferred for staging Chronic Kidney Disease (CKD), **Cockcroft-Gault** remains the standard for **drug dosing** (especially DOACs and Aminoglycosides) [1]. Serum creatinine is the most widely used compound for indirectly assessing GFR in clinical practice [1]. * **PCA Stroke Presentation:** Look for "The 3 Ds": Diplopia, Dizziness, and Dysarthria, or contralateral homonymous hemianopia with macular sparing.

Q: A 44-year-old woman presents with symptoms of muscle weakness and fatigue. Her laboratory findings include serum potassium of 2.5 mEq/L, bicarbonate of 18 mEq/L, and a normal anion gap. Urine potassium is 40 mEq/L. What is the most likely diagnosis for this patient's hypokalemia?

Renal tubular acidosis (RTA). ### Explanation The patient presents with a triad of **hypokalemia**, **metabolic acidosis** (low bicarbonate), and a **normal anion gap**. The key to differentiating the cause lies in the urinary potassium excretion. **1. Why Renal Tubular Acidosis (RTA) is Correct:** In a patient with metabolic acidosis, the kidneys should ideally conserve potassium. However, in RTA (specifically Type 1 and Type 2), there is significant **renal potassium wasting**. A urine potassium level >20 mEq/L in the presence of hypokalemia indicates a renal cause of loss. The combination of a normal anion gap metabolic acidosis (NAGMA) and high urinary potassium (40 mEq/L) is classic for RTA. **2. Why the other options are incorrect:** * **Lower GI losses (e.g., Diarrhea):** While diarrhea causes NAGMA and hypokalemia [1], the kidneys would respond by conserving potassium. Therefore, urine potassium would typically be **<20 mEq/L** [1]. * **Prior use of diuretics:** While diuretics cause hypokalemia, they typically result in metabolic **alkalosis** (contraction alkalosis), not acidosis. * **Current use of diuretics:** Similar to prior use, this would present with metabolic alkalosis. Additionally, while urine potassium would be high, the acid-base status does not fit the NAGMA seen in this patient. **Clinical Pearls for NEET-PG:** * **NAGMA + Hypokalemia:** Think RTA or Diarrhea. Check Urine Potassium [1]. * **Urine Anion Gap (UAG):** In RTA, the UAG is usually **positive** (reflecting decreased NH4+ excretion), whereas in diarrhea, it is **negative**. * **Type 1 RTA (Distal):** Associated with high urine pH (>5.5) and hypokalemia. * **Type 2 RTA (Proximal):** Associated with Fanconi syndrome and hypokalemia. * **Type 4 RTA:** The only RTA associated with **hyperkalemia**.

Q: Which of the following genes is not associated with Autosomal Dominant Tubulointerstitial Kidney Disease?

NPHS2. **Autosomal Dominant Tubulointerstitial Kidney Disease (ADTKD)** is a group of rare genetic disorders characterized by progressive interstitial fibrosis, tubular atrophy, and eventual end-stage renal disease (ESRD), typically with a bland urinary sediment and minimal proteinuria. **Why NPHS2 is the correct answer:** **NPHS2** encodes **Podocin**, a critical protein located in the slit diaphragm of the glomerular podocyte. Mutations in *NPHS2* are associated with **Autosomal Recessive Steroid-Resistant Nephrotic Syndrome (SRNS)** and Focal Segmental Glomerulosclerosis (FSGS) [1]. Unlike ADTKD, which is a primary tubulointerstitial pathology, *NPHS2* mutations cause a primary glomerular pathology. **Analysis of Incorrect Options:** * **MUC1 (ADTKD-MUC1):** Caused by a frameshift mutation in the *MUC1* gene. It is a classic cause of ADTKD, often presenting with slowly progressive renal failure. * **HNF1B (ADTKD-HNF1B):** Mutations in *Hepatocyte Nuclear Factor-1β* lead to a multi-system syndrome. It is unique among ADTKD types as it often presents with **renal cysts**, maturity-onset diabetes of the young (**MODY5**), and genitourinary malformations. * **UMOD (ADTKD-UMOD):** The most common cause of ADTKD. It involves mutations in the *Uromodulin* gene (encoding Tamm-Horsfall protein). A key clinical hallmark is **early-onset hyperuricemia and gout**, often preceding the decline in GFR. **High-Yield Clinical Pearls for NEET-PG:** * **ADTKD Hallmark:** Positive family history + Bland urine sediment (no casts/blood) + Normal-sized kidneys on ultrasound (except in HNF1B). * **UMOD Mutation:** Think "Gout in a teenager or young adult with CKD." * **HNF1B Mutation:** Think "Renal cysts + Diabetes (MODY5)." * **REN Mutation:** Another cause of ADTKD, often associated with anemia and mild hyperkalemia in childhood.

Q: What is the gold standard investigation for renovascular hypertension in a patient showing asymmetrical kidneys on ultrasound?

Angiography. **Explanation:** Renovascular hypertension (RVH) is most commonly caused by atherosclerosis or fibromuscular dysplasia, leading to renal artery stenosis (RAS). When a patient presents with asymmetrical kidneys on ultrasound, it suggests chronic ischemia and necessitates a definitive diagnosis. **1. Why Angiography is the Correct Answer:** **Digital Subtraction Angiography (DSA)** remains the **Gold Standard** for diagnosing renal artery stenosis. It provides the highest spatial resolution to visualize the anatomy of the renal vasculature. Its primary advantage is that it is both **diagnostic and therapeutic**, allowing for immediate intervention via percutaneous transluminal renal angioplasty (PTRA) or stenting if a significant lesion is identified. **2. Why Other Options are Incorrect:** * **Captopril Radionuclide Scan:** This is a functional screening test, not an anatomical one. While it helps determine if a known stenosis is hemodynamically significant, it has high false-negative rates in patients with bilateral disease or renal failure. * **Spiral CT (CTA) and MRI (MRA):** These are excellent **non-invasive screening tools** with high sensitivity and specificity. However, they can overestimate the degree of stenosis and cannot be used for concurrent intervention. MRA is also contraindicated in patients with metallic implants or severe renal insufficiency (risk of NSF). **Clinical Pearls for NEET-PG:** * **Best Initial Screening Test:** Duplex Doppler Ultrasound (non-invasive and cheap). * **Gold Standard:** Digital Subtraction Angiography (DSA). * **Classic Presentation:** Sudden onset hypertension in young females (Fibromuscular dysplasia) or elderly males (Atherosclerosis), or hypertension refractory to ≥3 drugs. * **Key Sign:** Presence of an abdominal bruit or a >1.5 cm difference in kidney size on ultrasound.

Q: What is the bacterial count in a midstream urine specimen that defines a urinary tract infection?

10^5 or over. ### Explanation The diagnosis of a Urinary Tract Infection (UTI) is traditionally based on the concept of **significant bacteriuria**, a term introduced by Edward Kass. **Why 10⁵ or over is correct:** The threshold of **≥10⁵ colony-forming units (CFU) per mL** in a clean-catch midstream urine (MSU) sample was established to distinguish true infection from urethral or vaginal contamination. In asymptomatic individuals, this count has a high specificity (approx. 95%) for identifying actual bacterial multiplication in the bladder rather than transient flora introduced during voiding. **Why other options are incorrect:** * **A, B, and C (100, 1000, 10⁴):** While these counts can represent infection in specific clinical contexts (e.g., symptomatic women, catheterized patients, or suprapubic aspirates), they do not meet the standard diagnostic criteria for "significant bacteriuria" in a routine midstream specimen. Lower counts are often considered indicative of contamination in an asymptomatic patient. **High-Yield Clinical Pearls for NEET-PG:** * **Kass Criteria:** Originally defined as ≥10⁵ CFU/mL of a single uropathogen in two consecutive midstream urine samples in asymptomatic women. * **Symptomatic Patients:** In women with classic symptoms of cystitis (dysuria, frequency), a lower threshold of **≥10² to 10³ CFU/mL** is often considered clinically significant. * **Catheterized Patients:** A count of **≥10² CFU/mL** is sufficient to diagnose infection. * **Suprapubic Aspiration:** **Any** bacterial growth (even <10² CFU/mL) is considered significant because the bladder is normally sterile. * **Sterile Pyuria:** Presence of WBCs in urine with no growth on standard media; consider *Chlamydia*, *Ureaplasma*, or Renal Tuberculosis.

Question 1

Gross hematuria, 3 days following an upper respiratory tract infection in a young female is likely due to?

Accepted Answer

IgA nephropathy

Answer

Post-streptococcal glomerulonephritis

Answer

Minimal change disease

Answer

Membranous glomerulonephritis

Question 2

What is the most common cause of death in Autosomal Dominant Polycystic Kidney Disease (ADPKD)?

Accepted Answer

Cardiovascular disease

Answer

Renal failure

Answer

Ruptured berry aneurysm

Answer

Sepsis

Question 3

An 80-year-old person has developed a posterior circulation (PCA) territory stroke. On ambulatory Holter, he is found to be having atrial fibrillation. What calculation should be used to evaluate for renal insufficiency of the patient?

Accepted Answer

Cockcroft-Gault formula

Answer

NIHSS score

Answer

ABCD2 score

Answer

CHADS2-Vasc score

Question 4

A 44-year-old woman presents with symptoms of muscle weakness and fatigue. Her laboratory findings include serum potassium of 2.5 mEq/L, bicarbonate of 18 mEq/L, and a normal anion gap. Urine potassium is 40 mEq/L. What is the most likely diagnosis for this patient's hypokalemia?

Accepted Answer

Renal tubular acidosis (RTA)

Answer

Lower gastrointestinal losses

Answer

Prior use of diuretics

Answer

Current use of diuretics

Question 5

Which of the following genes is not associated with Autosomal Dominant Tubulointerstitial Kidney Disease?

Accepted Answer

NPHS2

Answer

MUC1

Answer

HNF1b

Answer

UMOD

Question 6

Which of the following is an absolute indication for hemodialysis in chronic kidney disease?

Accepted Answer

Uremic pericarditis

Answer

Metabolic acidosis

Answer

Uremic lung

Answer

Hyperkalemia

Question 7

All of the following are associated with low complement levels except?

Accepted Answer

Diarrhea associated hemolytic uremic syndrome

Answer

Lupus nephritis

Answer

Mesangiocapillary glomerulonephritis

Answer

Glomerulonephritis related to bacterial endocarditis

Question 8

What is the preferred method for determining microalbuminuria?

Accepted Answer

Urinary albumin-to-creatinine ratio (ACR) in a spot voided sample

Answer

Urinary dipsticks

Answer

24-hour urinary protein collection

Answer

Urinary albumin-to-creatinine ratio (ACR) in a 24-hour collection

Question 9

What is the gold standard investigation for renovascular hypertension in a patient showing asymmetrical kidneys on ultrasound?

Accepted Answer

Angiography

Answer

Captopril radionuclide scan

Answer

Spiral CT

Answer

MRI

Question 10

What is the bacterial count in a midstream urine specimen that defines a urinary tract infection?

Accepted Answer

10^5 or over

Answer

100

Answer

1000

Answer

10^4

Nephrology — MCQs

Nephrology — MCQs

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