Nephrology Practice Questions

Q: A 29-year-old female with a history of Sjogren's syndrome presents with a 2-day episode of watery diarrhea. Physical examination is unremarkable. Considering her history, the physician checks her urine electrolytes, which show: K = 31 mEq/L, Na = 100 mEq/L, Cl = 105 mEq/L. What is her current diagnosis?

Renal tubular acidosis. ### **Explanation** The correct answer is **Renal Tubular Acidosis (RTA)**. **1. Why it is correct:** The patient has Sjogren’s syndrome, which is classically associated with **Distal (Type 1) RTA**. The key to solving this question lies in calculating the **Urine Anion Gap (UAG)**. * **Formula:** $UAG = (Na^+ + K^+) - Cl^-$ * **Calculation:** $(100 + 31) - 105 = +26\text{ mEq/L}$. A **positive UAG** indicates a failure of the kidneys to excrete ammonium ($NH_4^+$), which is characteristic of RTA [1]. In contrast, patients with diarrhea (extra-renal bicarbonate loss) typically have a negative UAG because their kidneys are functioning normally and increasing $NH_4Cl$ excretion to compensate for the acidosis. **2. Why the other options are wrong:** * **Hypochloremic metabolic alkalosis:** This usually results from vomiting or diuretic use [1]. The patient has diarrhea (which causes metabolic acidosis) and the urine chloride is high, not low. * **Malignant hypertension:** This presents with severely elevated BP (>180/120 mmHg) and end-organ damage (papilledema, encephalopathy), which are absent here. * **Respiratory alkalosis:** This is characterized by a primary decrease in $PCO_2$ (hyperventilation). The clinical context of Sjogren’s and electrolyte imbalances points toward a metabolic/renal pathology. **3. NEET-PG High-Yield Pearls:** * **Urine Anion Gap:** Positive ($>0$) = RTA; Negative ($ 5.5$) and hypokalemia [1]. * **Type 2 RTA:** Associated with Fanconi syndrome; failure to reabsorb $HCO_3^-$ in the proximal tubule. * **Type 4 RTA:** Associated with Diabetes Mellitus and **hyperkalemia**.

Q: What is the level of serum potassium at which paralysis is a possible complication of hypokalemia?

2.5 mEq/L. Explanation: Hypokalemia is defined as a serum potassium level <3.5 mEq/L. The clinical manifestations of hypokalemia correlate directly with the severity of the depletion and the rate of decline. 1. Why 2.5 mEq/L is the correct answer: Muscular manifestations typically begin when serum potassium falls below 3.0 mEq/L (causing weakness and fatigue). However, frank paralysis (ascending flaccid paralysis) and rhabdomyolysis are classic complications seen when levels drop to ≤2.5 mEq/L. At this critical level, the resting membrane potential of myocytes becomes severely hyperpolarized, impairing the ability of muscles to contract [1] and leading to profound muscle necrosis and respiratory failure. 2. Analysis of Incorrect Options: * 3.5 mEq/L: This is the lower limit of normal. Patients are usually asymptomatic. * 3.0 mEq/L: At this level (mild-to-moderate hypokalemia), patients typically experience generalized muscle weakness, myalgia, and constipation (due to ileus), but not overt paralysis [1]. * 2.0 mEq/L: While paralysis certainly occurs at this level, 2.5 mEq/L is the clinically recognized threshold where this life-threatening complication first becomes a significant risk. High-Yield Clinical Pearls for NEET-PG: * ECG Changes: Look for T-wave flattening, prominent U-waves, ST-segment depression, and prolonged QU intervals. * Muscle Involvement: Hypokalemia causes ascending paralysis (similar to GBS) but spares the cranial nerves. * Refractory Hypokalemia: If potassium levels do not rise despite supplementation, check Magnesium levels [1]. Hypomagnesemia inhibits ROMK channels, leading to continued potassium wasting in the urine. * Common Cause: In India, look for a history of chronic diarrhea or diuretic use (Thiazides/Loop diuretics).

Q: Which of the following drugs should be immediately stopped in a patient with diabetes, hypertension, and a serum creatinine level of 5.6 mg/dL?

Metformin. **Explanation:** The correct answer is **Metformin**. The primary concern in this clinical scenario is the patient’s severely impaired renal function (Serum Creatinine: 5.6 mg/dL). **1. Why Metformin must be stopped:** Metformin is primarily excreted unchanged by the kidneys. In patients with advanced Chronic Kidney Disease (CKD), the drug accumulates, leading to a shift in cellular metabolism toward anaerobic glycolysis [1]. This increases the risk of **Metformin-Associated Lactic Acidosis (MALA)**, a life-threatening condition. According to standard guidelines (FDA/KDIGO), Metformin is contraindicated when the eGFR falls below **30 mL/min/1.73 m²**. A creatinine of 5.6 mg/dL signifies Stage 5 CKD, making immediate cessation mandatory [1]. **2. Analysis of Incorrect Options:** * **Insulin:** It is the preferred agent for glycemic control in advanced renal failure. While the dose may need downward titration (as the kidneys normally degrade insulin), it is not stopped. * **Metoprolol:** This is a cardioselective beta-blocker primarily metabolized by the **liver**. It does not require dose adjustment or discontinuation in renal failure. * **Linagliptin:** This DPP-4 inhibitor is unique because it is primarily excreted via the **enterohepatic route** (bile/feces). It is the only DPP-4 inhibitor that does not require dose adjustment in renal impairment. **3. High-Yield Clinical Pearls for NEET-PG:** * **Safe Antidiabetics in CKD:** Insulin (best), Linagliptin, and Pioglitazone (though avoid if heart failure is present). * **Drugs to avoid in CKD:** Metformin, Sulfonylureas (risk of prolonged hypoglycemia), and SGLT2 inhibitors (reduced efficacy/safety concerns at very low eGFR). * **MALA Presentation:** Look for high anion gap metabolic acidosis with an increased lactate level in a patient taking Metformin with rising creatinine.

Q: Hypokalemia is not present in which of the following conditions?

Chronic renal failure. **Explanation:** The correct answer is **Chronic Renal Failure (CRF)**. In CRF, the primary electrolyte abnormality is **Hyperkalemia**, not hypokalemia. This occurs because the kidneys lose their ability to excrete potassium due to a reduced Glomerular Filtration Rate (GFR) and impaired tubular secretion. As nephrons are lost, the body cannot effectively handle potassium loads, leading to its accumulation in the blood. **Analysis of Incorrect Options:** * **Vomiting:** Causes hypokalemia through two mechanisms: direct loss of K+ in gastric juice and, more significantly, secondary hyperaldosteronism triggered by volume depletion, which increases renal K+ excretion. * **Diarrhoea:** Lower GI secretions are rich in potassium and bicarbonate. Profuse diarrhoea leads to direct fecal loss of potassium. * **Diuretics:** Loop diuretics (e.g., Furosemide) and Thiazides inhibit sodium reabsorption, increasing sodium delivery to the distal tubule. This promotes potassium secretion into the urine, leading to hypokalemia. **NEET-PG High-Yield Pearls:** * **ECG in Hyperkalemia (CRF):** Tall tented T-waves, widened QRS complex, and loss of P-waves. * **ECG in Hypokalemia:** Flattened T-waves, prominent **U-waves**, and ST-segment depression. * **Exception:** While CRF typically causes hyperkalemia, certain renal conditions like **Renal Tubular Acidosis (RTA) Types I and II** and **Fanconi Syndrome** are classic causes of hypokalemia. * **Insulin and Alkalosis:** Both cause a "transcellular shift," moving potassium from the extracellular fluid into the cells, resulting in hypokalemia.

Q: What is the most common cause of death in patients undergoing chronic dialysis?

Cardiovascular Disease. **Explanation:** **1. Why Cardiovascular Disease (CVD) is the Correct Answer:** Cardiovascular disease is the leading cause of mortality in patients with End-Stage Renal Disease (ESRD) on chronic dialysis, accounting for nearly **50% of all deaths**. The risk of cardiac death is 10 to 30 times higher in dialysis patients compared to the general population [1]. This is due to a combination of **traditional risk factors** (hypertension, diabetes, dyslipidemia) and **uremia-related factors** (chronic volume overload, hyperphosphatemia leading to vascular calcification, and left ventricular hypertrophy). Sudden cardiac death (often due to arrhythmias or hyperkalemia) and heart failure are the most frequent manifestations. **2. Why Other Options are Incorrect:** * **B. Infection:** This is the **second most common** cause of death [1]. Dialysis patients are immunocompromised and have frequent vascular access (catheters/fistulas), making them prone to sepsis and pneumonia. * **C. Malignancy:** While the risk of certain cancers (e.g., renal cell carcinoma) is slightly increased in ESRD, it is not a leading cause of acute mortality compared to CVD. * **D. Anemia:** Anemia is a classic complication of ESRD (due to erythropoietin deficiency), but with the advent of Erythropoiesis-Stimulating Agents (ESAs), it is a manageable morbidity rather than a primary cause of death. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of ESRD:** Diabetes Mellitus (followed by Hypertension) [1]. * **Most common cause of death in Renal Transplant recipients:** Cardiovascular disease (same as dialysis). * **Vascular Access:** An Arteriovenous (AV) fistula is preferred over grafts or catheters due to lower infection rates and better long-term patency [1]. * **Target Hemoglobin:** In dialysis patients, the target Hb is generally **10–11.5 g/dL**; aiming for

Q: Which one of the following is not a feature of renal artery stenosis?

Hypertension responds well to drugs. **Explanation:** Renal Artery Stenosis (RAS) is a major cause of secondary hypertension, typically resulting from either **Atherosclerosis** (common in elderly) or **Fibromuscular Dysplasia** (common in young females). **Why Option A is the Correct Answer:** Hypertension in RAS is typically **resistant** to conventional medical therapy [1]. The narrowing of the renal artery leads to decreased renal perfusion, which chronically activates the **Renin-Angiotensin-Aldosterone System (RAAS)**. This persistent activation creates a high-pressure state that is difficult to control with standard anti-hypertensive drugs, often requiring multiple agents or revascularization. **Analysis of Incorrect Options:** * **Option B (Asymmetrical Kidneys):** Chronic ischemia in the affected kidney leads to atrophy. A size difference of **>1.5 cm** between the two kidneys on ultrasound is a classic diagnostic clue for unilateral RAS [1]. * **Option C (Atherosclerotic Plaques):** This is the most common etiology of RAS (approx. 90% of cases), usually involving the ostium or proximal third of the renal artery in patients with cardiovascular risk factors. * **Option D (Creatinine increase with ACE inhibitors):** ACE inhibitors block the production of Angiotensin II. In RAS, Angiotensin II is required to constrict the **efferent arteriole** to maintain Glomerular Filtration Rate (GFR). Blocking this causes a "precipitous drop" in GFR and a rise in serum creatinine, especially in bilateral RAS or stenosis of a solitary kidney. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Renal Angiography. * **Screening Test of Choice:** Duplex Doppler Ultrasound or CT/MR Angiography [1]. * **Clinical Sign:** An abdominal bruit (systolic-diastolic) is highly specific. * **Flash Pulmonary Edema:** Recurrent unexplained pulmonary edema with preserved LV function is a strong indicator of bilateral RAS (Pickering Syndrome).

Question 1

A 29-year-old female with a history of Sjogren's syndrome presents with a 2-day episode of watery diarrhea. Physical examination is unremarkable. Considering her history, the physician checks her urine electrolytes, which show: K = 31 mEq/L, Na = 100 mEq/L, Cl = 105 mEq/L. What is her current diagnosis?

Accepted Answer

Renal tubular acidosis

Answer

Hypochloremic metabolic alkalosis

Answer

Malignant hypertension

Answer

Respiratory alkalosis

Question 2

A 25-year-old male presented with nausea, vomiting, epigastric pain, and a serum sodium level of 125 mEq/L. What is the initial treatment recommendation?

Accepted Answer

Administer hypotonic saline

Answer

Perform ultra-centrifugation

Answer

Initiate hemodialysis

Answer

Prescribe a high-protein diet

Question 3

What is the level of serum potassium at which paralysis is a possible complication of hypokalemia?

Accepted Answer

2.5 mEq/L

Answer

2.0 mEq/L

Answer

3.0 mEq/L

Answer

3.5 mEq/L

Question 4

Non-oliguric acute renal failure is typically associated with which of the following?

Accepted Answer

Aminoglycoside toxicity

Answer

Contrast-induced nephrotoxicity

Answer

Hemolytic uremic syndrome

Answer

Glomerulonephritis

Question 5

Which of the following drugs should be immediately stopped in a patient with diabetes, hypertension, and a serum creatinine level of 5.6 mg/dL?

Accepted Answer

Metformin

Answer

Insulin

Answer

Metoprolol

Answer

Linagliptin

Question 6

Which of the following statements regarding microalbuminuria is not true?

Accepted Answer

Urine protein excretion between 30-299 mg/day is defined as microalbuminuria.

Answer

It cannot be detected by routine laboratory tests.

Answer

Microalbuminuria is an independent risk factor for cardiovascular risk in diabetic patients.

Answer

Microalbuminuria is the earliest marker of diabetic nephropathy.

Question 7

Hypokalemia is not present in which of the following conditions?

Accepted Answer

Chronic renal failure

Answer

Vomiting

Answer

Diarrhoea

Answer

Patient on diuretics

Question 8

What is the most common cause of death in patients undergoing chronic dialysis?

Accepted Answer

Cardiovascular Disease

Answer

Infection

Answer

Malignancy

Answer

Anemia

Question 9

Which one of the following is not a feature of renal artery stenosis?

Accepted Answer

Hypertension responds well to drugs

Answer

Kidneys may be asymmetrical

Answer

Atherosclerotic plaques are common

Answer

Serum creatinine may increase with ACE inhibitors

Question 10

A 74-year-old woman presents with symptoms of shortness of breath on exertion and paroxysmal nocturnal dyspnea. Physical examination reveals jugular venous pressure at 8 cm, an extra third heart sound, lung crackles, and pedal edema. She is initiated on furosemide 80 mg/day for suspected heart failure while further investigations are conducted. Considering the patient's presentation and treatment, what is the most likely acid-base disorder?

Accepted Answer

Metabolic alkalosis

Answer

Metabolic acidosis

Answer

Respiratory acidosis

Answer

Respiratory alkalosis

Nephrology — MCQs

Nephrology — MCQs

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