Nephrology Practice Questions

Q: Chronic laxative abuse can result in the formation of which type of renal stone?

Ammonium urate. **Explanation:** The correct answer is **Ammonium urate**. **Pathophysiology:** Chronic laxative abuse leads to chronic diarrhea, resulting in significant loss of water, bicarbonate, and potassium from the gastrointestinal tract. This triggers a specific metabolic environment conducive to ammonium urate stone formation: 1. **Dehydration:** Leads to low urine volume and concentrated urine. 2. **Metabolic Acidosis:** Loss of bicarbonate causes the kidneys to increase **ammoniagenesis** (production of $NH_4^+$) to buffer the acid. 3. **Hypokalemia:** Intracellular potassium depletion further stimulates renal ammonia production. 4. **Hyperuricosuria:** The resulting acidic, concentrated urine with high ammonium concentrations promotes the precipitation of ammonium acid urate. **Analysis of Incorrect Options:** * **A. Xanthine:** These are rare stones typically associated with hereditary xanthine oxidase deficiency or the use of Allopurinol. * **B. Cysteine:** These occur due to an autosomal recessive defect in the transport of dibasic amino acids (COLA: Cysteine, Ornithine, Lysine, Arginine) in the proximal tubule. * **D. Struvite (Triple Phosphate):** These are "infection stones" (Magnesium Ammonium Phosphate) associated with urease-producing bacteria like *Proteus* or *Klebsiella*, which make the urine alkaline [1]. **Clinical Pearls for NEET-PG:** * **Ammonium urate stones** are radiolucent (like pure uric acid stones) but may appear faintly radiopaque if they co-precipitate with calcium [2]. * They are also commonly seen in patients with **inflammatory bowel disease (IBD)** due to similar chronic malabsorption/diarrhea mechanisms. * **Key Triad for Laxative Abuse:** Hypokalemia, metabolic alkalosis (if vomiting) or acidosis (if diarrhea), and ammonium urate stones.

Q: A 68-year-old man weighing 60 kg has a plasma creatinine of 3 mg/dL. What is his estimated creatinine clearance?

20 mL/min. To calculate the estimated Creatinine Clearance (eCrCl) in a clinical setting, the **Cockcroft-Gault formula** is the gold standard for exam purposes. ### **Calculation using Cockcroft-Gault Formula:** The formula is: $\text{CrCl (mL/min)} = \frac{(140 - \text{Age}) \times \text{Weight (kg)}}{72 \times \text{Plasma Creatinine (mg/dL)}}$ *Note: For females, multiply the result by 0.85.* **Plugging in the values:** $\text{CrCl} = \frac{(140 - 68) \times 60}{72 \times 3}$ $\text{CrCl} = \frac{72 \times 60}{72 \times 3}$ $\text{CrCl} = \frac{60}{3} = \mathbf{20 \text{ mL/min}}$ ### **Analysis of Options:** * **Option B (20 mL/min):** This is the correct value derived from the standard formula. * **Options A, C, and D:** These are incorrect as they do not align with the mathematical calculation. A common error is forgetting to include the "72" constant or miscalculating the age factor (140 - 68 = 72). ### **NEET-PG High-Yield Pearls:** 1. **Formula Variables:** Remember that CrCl is **directly proportional** to body weight and **inversely proportional** to age and serum creatinine. 2. **Gender Adjustment:** Always check the gender in the clinical vignette. If this patient were female, the answer would be $20 \times 0.85 = 17 \text{ mL/min}$. 3. **Limitations:** The Cockcroft-Gault formula overestimates GFR because creatinine is not only filtered by the glomerulus but also secreted by the proximal tubules [1]. 4. **CKD Staging:** A CrCl of 20 mL/min places this patient in **Stage 4 Chronic Kidney Disease** (Severely decreased GFR: 15–29 mL/min).

Q: Which of the following is NOT typically seen in cystitis?

Fever. **Explanation:** The clinical differentiation between **Lower Urinary Tract Infection (Cystitis)** and **Upper Urinary Tract Infection (Pyelonephritis)** is a high-yield concept for NEET-PG. **1. Why Fever is the Correct Answer:** Cystitis is a localized mucosal inflammation of the bladder. It is typically **afebrile** because the infection is confined to the bladder surface and does not involve the renal parenchyma or systemic circulation. The presence of high-grade fever, chills, and rigors strongly suggests that the infection has ascended to the kidneys (Acute Pyelonephritis) or has resulted in bacteremia [1]. [2] **2. Analysis of Incorrect Options:** * **Dysuria (Option C):** This is the hallmark symptom of cystitis, caused by the irritation of the urethral and bladder mucosal lining during micturition. * **Nocturia (Option D) and Frequency:** Inflammation of the bladder wall (detrusor muscle) leads to decreased bladder capacity and increased irritability, resulting in the frequent urge to void during the day and night. * **Hematuria (Option B):** Gross or microscopic hematuria occurs due to the friability of the inflamed bladder mucosa [3]. When present with dysuria, it is often termed "hemorrhagic cystitis." **Clinical Pearls for NEET-PG:** * **The "Triad" of Cystitis:** Dysuria, Frequency, and Urgency. * **Pyelonephritis Indicators:** Fever, flank pain (CVA tenderness), and nausea/vomiting [2]. * **Most Common Pathogen:** *E. coli* remains the leading cause of both cystitis and pyelonephritis [2]. * **Sterile Pyuria:** If a patient has symptoms of cystitis but negative routine cultures, consider *Chlamydia trachomatis* or *Neisseria gonorrhoeae* [1].

Q: Which of the following is NOT a part of "Triple therapy" immunosuppression for a post-renal transplant patient?

Belatacept. The "Triple Therapy" regimen is the gold standard for maintenance immunosuppression in post-renal transplant patients. It is designed to target different pathways of the immune response to maximize graft survival while minimizing the toxicity of any single drug. ### **Explanation of the Correct Answer** **D. Belatacept:** This is a selective T-cell costimulation blocker (binds to CD80 and CD86). While it is FDA-approved for prophylaxis of organ rejection, it is **not** part of the classic "Triple Therapy" regimen. It is typically used as an alternative to Calcineurin Inhibitors (CNIs) to avoid nephrotoxicity, but it is administered via intravenous infusion rather than the standard oral triple-drug protocol. ### **Analysis of Incorrect Options** The classic Triple Therapy consists of one drug from each of the following three categories: * **A. Prednisone (Corticosteroids):** Provides broad anti-inflammatory and immunosuppressive effects by inhibiting cytokine gene expression. * **B. Cyclosporine (Calcineurin Inhibitors):** Inhibits IL-2 production. In modern practice, **Tacrolimus** has largely replaced Cyclosporine due to better efficacy, but both are considered the "backbone" of triple therapy. * **C. Azathioprine (Antimetabolites):** Inhibits purine synthesis to prevent T-cell proliferation. In contemporary regimens, **Mycophenolate Mofetil (MMF)** is more commonly used than Azathioprine. ### **NEET-PG High-Yield Pearls** * **Standard Modern Triple Therapy:** Tacrolimus + Mycophenolate Mofetil (MMF) + Prednisolone. * **Side Effect Profile:** * **Cyclosporine:** Nephrotoxicity, Gingival hyperplasia, Hirsutism. * **Tacrolimus:** Nephrotoxicity, Neurotoxicity, Post-transplant Diabetes Mellitus (PTDM). * **MMF:** GI upset and Bone marrow suppression. * **Sirolimus (mTOR inhibitor):** Often used if CNIs must be withdrawn due to nephrotoxicity, but it impairs wound healing.

Q: What does the delta gap compare?

Change in anion gap with bicarbonate. **Explanation:** The **Delta Gap** (also known as the Delta-Delta) is a clinical calculation used to assess complex acid-base disorders, specifically when a High Anion Gap Metabolic Acidosis (HAGMA) is present. **Why the correct answer is right:** The fundamental principle of HAGMA is that for every unit increase in the Anion Gap (due to unmeasured anions like lactate or ketones), there should be a corresponding molar decrease in bicarbonate ($HCO_3^-$) as it buffers the added acid. The Delta Gap compares the **change in Anion Gap ($\Delta AG$)** to the **change in Bicarbonate ($\Delta HCO_3^-$)**. * **Formula:** $\Delta \text{Gap} = (\text{Measured AG} - 12) / (24 - \text{Measured } HCO_3^-)$ * A ratio of **1 to 2** suggests a pure HAGMA. * A ratio **> 2** suggests a concurrent Metabolic Alkalosis. * A ratio **< 1** suggests a concurrent Normal Anion Gap Metabolic Acidosis (NAGMA). **Why incorrect options are wrong:** * **Options A, B, and D:** While Sodium ($Na^+$), Potassium ($K^+$), and Chloride ($Cl^-$) are components used to calculate the initial Anion Gap ($AG = Na^+ - [Cl^- + HCO_3^-]$), the Delta Gap specifically evaluates the *relationship* between the excess anions and the buffering capacity of bicarbonate. It does not compare the AG change to cations ($Na, K$) or chloride in isolation. **High-Yield Clinical Pearls for NEET-PG:** * **Normal Anion Gap:** 8–12 mEq/L. * **Winter’s Formula:** Used to calculate expected $pCO_2$ compensation in metabolic acidosis ($1.5 \times HCO_3^- + 8 \pm 2$). * **MUDPILES:** Mnemonic for HAGMA causes (Methanol, Uremia, DKA, Propylene glycol, Iron/INH, Lactate, Ethylene glycol, Salicylates). * **Key Rule:** If the Delta Gap is significantly elevated (>2), always look for a hidden metabolic alkalosis (e.g., vomiting or diuretic use).

Q: A patient with chronic renal failure on intermittent hemodialysis presents with anemia refractory to iron therapy. Which of the following additional drugs is indicated?

Erythropoietin. The primary cause of anemia in Chronic Kidney Disease (CKD) is the **deficiency of Erythropoietin (EPO)**. [1] EPO is a glycoprotein hormone produced by the peritubular interstitial cells of the renal cortex. [1] In patients with chronic renal failure, the loss of functional renal parenchyma leads to inadequate EPO production, resulting in normocytic, normochromic anemia. **Why Erythropoietin is the correct answer:** In clinical practice, anemia of CKD is managed by first ensuring adequate iron stores (Transferrin saturation >30% and Ferritin >500 ng/mL). If the anemia remains **refractory to iron therapy**, the next step is the administration of **Erythropoiesis-Stimulating Agents (ESAs)** like Recombinant Human Erythropoietin or Darbepoetin alfa to stimulate red blood cell production in the bone marrow. [1] It is also important to note that anemia of chronic inflammation can be refractory to iron due to hepcidin upregulation. [2] **Analysis of Incorrect Options:** * **Cyanocobalamin (B12) & Folic Acid:** While water-soluble vitamins are lost during hemodialysis, they are rarely the primary cause of refractory anemia in CKD unless a specific nutritional deficiency is documented (megaloblastic anemia). * **Pyridoxine (B6):** Supplementation is often required in dialysis patients to prevent neuropathy or if they are on drugs like Isoniazid, but it is not the standard treatment for the primary anemia of renal failure. **High-Yield Clinical Pearls for NEET-PG:** * **Target Hemoglobin:** In CKD patients on EPO, the target Hb should be **10–11.5 g/dL**. Exceeding 13 g/dL increases the risk of stroke, venous thromboembolism, and hypertension. * **Most common cause of EPO resistance:** Iron deficiency. Always check iron status before escalating EPO dosage. * **Side Effect:** The most common side effect of EPO therapy is the **exacerbation of hypertension**.

Question 1

Chronic laxative abuse can result in the formation of which type of renal stone?

Accepted Answer

Ammonium urate

Answer

Xanthine

Answer

Cysteine

Answer

Struvite

Question 2

A patient has Insulin-Dependent Diabetes Mellitus diagnosed at age 15 years. What is the most reliable indicator for diabetic nephropathy?

Accepted Answer

Urinary protein greater than 550 mg per day for 3 consecutive samples

Answer

Urine albumin less than 50 mg per day in 3 consecutive samples

Answer

Development of diabetic retinopathy

Answer

Hematuria

Question 3

A patient presents with acute renal failure (ARF) and complete anuria. An ultrasound shows normal findings. What is the next appropriate investigation?

Accepted Answer

Radio renogram

Answer

Intravenous pyelography (IVP)

Answer

Antegrade pyelography

Answer

Retrograde pyelography

Question 4

A 68-year-old man weighing 60 kg has a plasma creatinine of 3 mg/dL. What is his estimated creatinine clearance?

Accepted Answer

20 mL/min

Answer

10 mL/min

Answer

30 mL/min

Answer

40 mL/min

Question 5

Which of the following is NOT typically seen in cystitis?

Accepted Answer

Fever

Answer

Hematuria

Answer

Dysuria

Answer

Nocturia

Question 6

All of the following factors are associated with adverse prognosis and high risk of renal progression in Lupus Nephritis, EXCEPT:

Accepted Answer

Anti-LA (SSB)

Answer

High levels of Anti-ds DNA

Answer

Persistent proteinuria (nephrotic range > 3 gm/day)

Answer

Hypocomplementenemia

Question 7

Which of the following is NOT a part of "Triple therapy" immunosuppression for a post-renal transplant patient?

Accepted Answer

Belatacept

Answer

Prednisone

Answer

Cyclosporine

Answer

Azathioprine

Question 8

What does the delta gap compare?

Accepted Answer

Change in anion gap with bicarbonate

Answer

Change in anion gap with chloride only

Answer

Change in anion gap with sodium and potassium

Answer

Change in anion gap with sodium only

Question 9

Hypophosphatemia is seen in which of the following conditions?

Accepted Answer

Rickets

Answer

Pseudohypoparathyroidism

Answer

Chronic renal failure

Answer

Respiratory acidosis

Question 10

A patient with chronic renal failure on intermittent hemodialysis presents with anemia refractory to iron therapy. Which of the following additional drugs is indicated?

Accepted Answer

Erythropoietin

Answer

Cyanocobalamin

Answer

Folic acid

Answer

Pyridoxine

Nephrology — MCQs

Nephrology — MCQs

On this page

Practice by Chapter

Want unlimited practice?