Nephrology Practice Questions

Q: Which is not a feature of classic distal renal tubular acidosis?

Hyperkalemia. ### Explanation **Distal Renal Tubular Acidosis (Type 1 RTA)** is characterized by a defect in the alpha-intercalated cells of the distal tubule, leading to an inability to secrete hydrogen ions ($H^+$) [1]. **1. Why Hyperkalemia is the correct answer:** In classic Type 1 RTA, the primary defect is the failure of the $H^+$-ATPase pump. To maintain electrical neutrality, the kidney excretes potassium ($K^+$) instead of hydrogen ions. This results in **hypokalemia**, not hyperkalemia. Hyperkalemia is a hallmark of **Type 4 RTA** (Hypoaldosteronism), making it the "odd one out" for distal RTA. **2. Analysis of Incorrect Options:** * **Urine pH > 5.5:** This is the most characteristic feature [1]. Because the distal tubule cannot secrete $H^+$, the urine cannot be acidified below a pH of 5.5, even in the presence of systemic acidemia [1]. * **Positive Urine Anion Gap (UAG):** UAG ($Na + K - Cl$) is a surrogate marker for urinary ammonium ($NH_4^+$) excretion. In Type 1 RTA, $NH_4^+$ production is impaired due to the distal defect, leading to a low chloride concentration and a **positive** UAG. * **Nephrocalcinosis:** Chronic acidemia leads to bone resorption (releasing calcium) and inhibits citrate reabsorption. The combination of hypercalciuria and hypocitraturia in alkaline urine causes calcium phosphate stones and medullary nephrocalcinosis. **Clinical Pearls for NEET-PG:** * **Type 1 (Distal):** Hypokalemia, Urine pH > 5.5, Stones (Nephrocalcinosis). * **Type 2 (Proximal):** Hypokalemia, Urine pH < 5.5 (eventually), associated with **Fanconi Syndrome**. * **Type 4 (Hyperkalemic):** Only RTA with **Hyperkalemia**; associated with Diabetes Mellitus and Addison’s disease. * **Mnemonic:** "Distal is **D**istant from 7 (pH is high/alkaline)" and "Type **4** adds **K** (Hyperkalemia)."

Q: Which of the following is characteristic of CRF?

Chronic Renal Failure (CRF). **Explanation:** The hallmark of **Chronic Renal Failure (CRF)**, now more commonly referred to as Chronic Kidney Disease (CKD), is the irreversible and progressive loss of nephron function over a period of at least three months. The characteristic features that distinguish CRF from acute conditions include **bilateral small, shrunken kidneys** (on ultrasound), **secondary hyperparathyroidism**, and **renal osteodystrophy**. The presence of broad waxy casts in urinary sediment is also a specific indicator of the dilated, hypertrophied nephrons seen in end-stage renal disease. **Analysis of Options:** * **Acute Glomerulonephritis (Ac GN):** This is characterized by the sudden onset of hematuria (coca-cola colored urine), hypertension, and edema. It is an inflammatory process, not a failure state, and is typically reversible. * **Acute Renal Failure (ARF/AKI):** ARF involves a rapid decline in GFR (hours to days). Key differentiators from CRF include **normal-sized kidneys** and the potential for full recovery of renal function once the underlying insult is removed. * **Renal Tuberculosis:** This typically presents with "sterile pyuria" (pus cells in urine without bacterial growth on routine culture) and characteristic imaging findings like infundibular stenosis or "putty kidney," rather than generalized renal failure. **NEET-PG High-Yield Pearls:** * **Kidney Size Exception:** While small kidneys are characteristic of CRF, certain conditions cause **CRF with large/normal kidneys**: Diabetes Mellitus (most common), Amyloidosis, Polycystic Kidney Disease (PCKD), and HIV-associated nephropathy. * **Anemia:** Normocytic normochromic anemia due to Erythropoietin deficiency is a classic sign of CRF. * **Electrolytes:** CRF typically presents with hypocalcemia, hyperphosphatemia, and hyperkalemia.

Q: What is the most common cause of hypovolemic hyponatremia in a hospitalized patient?

Diuretic-induced. ### Explanation **Correct Option: B. Diuretic-induced** Hypovolemic hyponatremia occurs when there is a loss of both water and sodium, but the sodium loss is disproportionately greater [1]. In hospitalized patients, **diuretics (especially Thiazides)** are the most common cause [1]. * **Mechanism:** Diuretics inhibit sodium reabsorption (Thiazides at the distal convoluted tubule; Loop diuretics at the Thick Ascending Limb). This leads to volume depletion, which triggers the non-osmotic release of **Antidiuretic Hormone (ADH)**. ADH causes water retention in the collecting ducts via V2 receptors and aquaporin channels, further diluting the serum sodium and resulting in hyponatremia [2]. **Analysis of Incorrect Options:** * **A. Intravenous fluids:** While common in hospitals, IV fluids (like 5% Dextrose) typically cause **euvolemic** hyponatremia due to the administration of free water, rather than hypovolemic hyponatremia [1]. * **C. Severe pain:** Pain, stress, and nausea are potent stimulators of ADH secretion (SIADH physiology). This leads to **euvolemic** hyponatremia, as there is no primary fluid volume deficit [1]. * **D. Congestive heart failure (CHF):** CHF is a classic cause of **hypervolemic** hyponatremia [1]. Despite low effective arterial blood volume, the total body water and sodium are increased (edematous state). **NEET-PG High-Yield Pearls:** * **Thiazides vs. Loop Diuretics:** Thiazides cause hyponatremia more frequently than Loop diuretics because they do not interfere with the medullary osmotic gradient, allowing ADH to work more effectively. * **Urinary Sodium Check:** In hypovolemic hyponatremia, if $U_{Na} 40$ mEq/L, the loss is renal (e.g., diuretics or Addison’s disease) [1]. * **Management:** The mainstay of treatment for hypovolemic hyponatremia is **Isotonic (0.9%) Saline** to restore volume and shut off the ADH stimulus [3].

Q: Which of the following tests is most sensitive for detecting early diabetic nephropathy?

Microalbuminuria. **Explanation:** **Microalbuminuria** (Option C) is the earliest clinical marker of diabetic nephropathy [1]. It refers to the excretion of small amounts of albumin (30–300 mg/day or an albumin-to-creatinine ratio of 30–300 mg/g) that are not detectable by standard urine dipstick tests [1]. In diabetes, chronic hyperglycemia leads to glomerular hyperfiltration and basement membrane thickening, causing this "leakage" [2]. Detecting it early is crucial because this stage is **potentially reversible** with strict glycemic control and ACE inhibitors/ARBs. **Why other options are incorrect:** * **Serum Creatinine (Option A):** This is a late marker. Creatinine levels often remain within the normal range until more than 50% of kidney function (GFR) is lost [3]. * **Creatinine Clearance (Option B):** While it measures GFR, it is not the most sensitive for *early* detection. In the very early stages of diabetes, GFR may actually be **increased** (hyperfiltration) rather than decreased. * **Ultrasonography (Option D):** USG is used to assess kidney size and rule out obstruction. In diabetic nephropathy, kidneys are typically **enlarged or normal-sized** even in advanced stages (unlike most chronic kidney diseases where kidneys shrink), but it cannot detect early functional damage. **High-Yield Clinical Pearls for NEET-PG:** * **Screening:** Type 1 DM patients should be screened 5 years after diagnosis; Type 2 DM patients should be screened **at the time of diagnosis** [2]. * **Gold Standard:** The most accurate method is a 24-hour urine collection, but the **Spot Urine Albumin-to-Creatinine Ratio (ACR)** is the preferred screening method due to convenience [3]. * **Progression:** Microalbuminuria (Stage III) → Macroalbuminuria/Overt Nephropathy (Stage IV) → ESRD (Stage V).

Q: What is the cause of hypercoagulation in nephrotic syndrome?

Loss of antithrombin III (AT III). ### Explanation **Nephrotic syndrome** is characterized by a hypercoagulable state, leading to an increased risk of venous and arterial thromboembolism (most classically **Renal Vein Thrombosis**) [2]. **1. Why Option A is Correct:** The primary mechanism for hypercoagulability is the **urinary loss of low-molecular-weight proteins** due to increased glomerular permeability. **Antithrombin III (AT III)**, a natural anticoagulant that inhibits thrombin and Factor Xa, has a molecular weight similar to albumin. Its massive loss in the urine leads to a deficiency in the plasma, shifting the balance toward a pro-thrombotic state. **2. Why the Other Options are Incorrect:** * **Option B:** Fibrinogen levels are actually **increased**, not decreased [1]. The liver increases the synthesis of fibrinogen (and other clotting factors like V and VIII) as a compensatory response to low oncotic pressure. [1] * **Option C:** Vitamin K metabolism is not significantly altered in nephrotic syndrome. Hypercoagulability is driven by protein loss and hepatic overproduction, not vitamin K levels. * **Option D:** While Protein C and S levels can be variable, they are often **decreased** due to urinary loss. An increase in Protein C would be anticoagulant, which contradicts the hypercoagulable state. **Clinical Pearls for NEET-PG:** * **Most common complication:** Renal Vein Thrombosis (RVT), especially in **Membranous Nephropathy**. * **Triad of RVT:** Flank pain, hematuria, and a sudden increase in proteinuria/creatinine. * **Other factors:** Increased platelet aggregation and hyperlipidemia also contribute to the pro-thrombotic environment.

Question 1

Which is not a feature of classic distal renal tubular acidosis?

Accepted Answer

Hyperkalemia

Answer

Urine pH >5.5

Answer

Positive urine anion gap

Answer

Nephrocalcinosis

Question 2

Which of the following is characteristic of CRF?

Accepted Answer

Chronic Renal Failure (CRF)

Answer

Acute Glomerulonephritis (Ac GN)

Answer

Acute Renal Failure (ARF)

Answer

Renal Tuberculosis (Renal TB)

Question 3

An 80-year-old female presented with diffuse muscle pain in the back, buttocks, and right thigh. On examination, the patient was obtunded, responsive only to simple commands, and had paralysis of the left half of her body. Neighbors found her after she did not respond to multiple calls. CT brain was performed. Lab findings revealed increased serum creatinine out of proportion to BUN. Which of the following ECG findings corresponds with the most common electrolyte abnormality found in this condition?

Accepted Answer

All of the above

Answer

ECG showing peaked T waves

Answer

ECG showing flattened T waves

Answer

ECG showing prolonged QT interval

Question 4

A 20-year-old female presents with a blood pressure of 160/110 mm Hg. Clinical examination reveals a bruit in both flanks. Which of the following statements about this patient is not true?

Accepted Answer

The condition is nearly always bilateral.

Answer

Enalapril may deteriorate renal function.

Answer

The most definitive diagnostic procedure is contrast-enhanced angiography.

Answer

Surgical intervention may be used.

Question 5

A 64-year-old man with a history of good health is admitted following a head injury and ruptured spleen sustained in a motor vehicle accident. He underwent laparotomy and splenectomy and received 5% dextrose in 0.5% normal saline at 125 mL/h for the first 4 days. His daily fluid outputs were 450-600 mL of nasogastric drainage and 700-1000 mL of urine. The patient was somnolent but easily arousable until the morning of the 5th hospital day, when he became deeply comatose and began having seizures by the afternoon. His laboratory data are as follows: Serum electrolytes (mEq/L): Na+ 130, K+ 1.9, Cl- 96, HCO3- 19. Serum osmolality: 260 mOsm/L. Urine electrolytes (mEq/L): Na+ 61, K+ 18. Which of the following statements about the diagnosis or treatment of this patient's condition is TRUE?

Accepted Answer

A small quantity of hypertonic saline should be administered.

Answer

Emergency carotid arteriogram is indicated.

Answer

Hypokalemia is secondary to metabolic acidosis.

Answer

IV infusion of 20 mL of 50% MgSO4 should be given over 4 hours.

Question 6

A 72-year-old female presents with periorbital edema, a maculopapular rash on her chest, and a fever of 38.3°C. Laboratory findings include a blood urea of 77 mg/dL and a serum creatinine of 3.1 mg/dL. Urinalysis shows mild proteinuria and eosinophils, but is negative for glucose and ketones. Her past medical history is significant for hypertension, diabetes, and osteoarthritis. Which of the following medications is most likely responsible for her signs and symptoms?

Accepted Answer

Ibuprofen

Answer

Acarbose

Answer

Clonidine

Answer

Metformin

Question 7

A 30-year-old male presents with hemoptysis, facial puffiness, microscopic hematuria, and increased serum creatinine. Which of the following investigations should be included?

Accepted Answer

Antinuclear antibody (ANA)

Answer

Chest X-ray

Answer

Antineutrophil cytoplasmic antibody (ANCA)

Answer

CT scan of the chest

Question 8

What is the most common cause of hypovolemic hyponatremia in a hospitalized patient?

Accepted Answer

Diuretic-induced

Answer

Intravenous fluids

Answer

Severe pain

Answer

Congestive heart failure

Question 9

Which of the following tests is most sensitive for detecting early diabetic nephropathy?

Accepted Answer

Microalbuminuria

Answer

Serum Creatinine

Answer

Creatinine clearance

Answer

Ultra sonography

Question 10

What is the cause of hypercoagulation in nephrotic syndrome?

Accepted Answer

Loss of antithrombin III (AT III)

Answer

Decreased fibrinogen

Answer

Decreased metabolism of vitamin K

Answer

Increase in Protein C

Nephrology — MCQs

Nephrology — MCQs

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