Nephrology Practice Questions

Q: A plasma urea to creatinine ratio of 20:1 may be seen in which of the following conditions?

Pre-renal failure. ### Explanation The normal plasma urea-to-creatinine ratio is typically between **10:1 and 15:1**. A ratio exceeding **20:1** is a classic biochemical marker for **Pre-renal Azotemia**. **Why Pre-renal failure is correct:** In pre-renal states (e.g., dehydration, heart failure, or hemorrhage), renal perfusion decreases [1]. This triggers the activation of the Renin-Angiotensin-Aldosterone System (RAAS). Increased proximal tubular reabsorption of sodium and water occurs, and because **urea** follows water passively, its reabsorption into the blood increases significantly [1]. In contrast, **creatinine** is not reabsorbed and is primarily excreted via filtration and minimal secretion. This disproportionate rise in blood urea relative to creatinine results in a ratio >20:1. **Analysis of Incorrect Options:** * **Rhabdomyolysis:** This causes a **low** urea-to-creatinine ratio. Massive muscle breakdown releases large amounts of endogenous creatinine into the blood, often resulting in a ratio <10:1. * **Ureteric calculi (Post-renal):** In early obstructive uropathy, both urea and creatinine are elevated proportionally, maintaining a ratio between 10:1 and 20:1. * **Chronic Glomerulonephritis (Intrinsic renal):** In intrinsic renal disease, the tubules are damaged and cannot reabsorb urea effectively. Both urea and creatinine rise in tandem as GFR falls, typically maintaining a "normal" ratio of 10:1. **High-Yield Clinical Pearls for NEET-PG:** * **Fractional Excretion of Sodium (FeNa):** 2% in Acute Tubular Necrosis (ATN). * **Urinary Osmolality:** >500 mOsm/kg in Pre-renal (concentrated urine); 20:1):** GI bleed (breakdown of blood proteins), high protein diet, and treatment with steroids (increased catabolism).

Q: Which of the following conditions is characterized by hyperchloremic acidosis with hypokalemia?

Renal tubular acidosis. **Explanation:** The hallmark of **Renal Tubular Acidosis (RTA)** is a **Normal Anion Gap Metabolic Acidosis (NAGMA)**, also known as hyperchloremic metabolic acidosis. In RTA (specifically Types 1 and 2), the kidneys fail to either reabsorb bicarbonate or excrete hydrogen ions. To maintain electroneutrality in the blood when bicarbonate is lost, chloride levels rise, leading to hyperchloremia. **Hypokalemia** occurs because the distal delivery of sodium leads to increased sodium-potassium exchange (Type 1) or because of proximal bicarbonate wasting (Type 2). **Analysis of Incorrect Options:** * **Addison’s Disease:** Characterized by mineralocorticoid deficiency, leading to hyperkalemia and metabolic acidosis (Type 4 RTA-like picture), not hypokalemia. * **Pyloric Stenosis:** Causes loss of gastric HCl, resulting in **Hypochloremic Metabolic Alkalosis** with hypokalemia (due to vomiting). * **Primary Hyperaldosteronism:** Excess aldosterone causes sodium retention and potassium/hydrogen excretion, leading to **Metabolic Alkalosis** and hypokalemia, not acidosis. **High-Yield Clinical Pearls for NEET-PG:** * **Type 1 RTA (Distal):** Inability to secrete $H^+$. Associated with urine $pH > 5.5$, hypokalemia, and nephrolithiasis. * **Type 2 RTA (Proximal):** Inability to reabsorb $HCO_3^-$. Associated with hypokalemia and Fanconi syndrome. * **Type 4 RTA (Hyperkalemic):** Associated with aldosterone deficiency or resistance (e.g., Diabetes Mellitus). It is the **only** RTA with **hyperkalemia**. * **Mnemonic:** "Hardup" or "Used Car" for NAGMA causes (Ureterosigmoidostomy, Saline, Endocrine, Diarrhea, **RTA**, Carbonic anhydrase inhibitors).

Q: Which of the following is NOT a feature of hepato-renal syndrome?

Normal GFR. Explanation: Hepatorenal Syndrome (HRS) is a form of functional renal failure that occurs in patients with advanced liver disease (cirrhosis or fulminant hepatic failure) [1]. The core pathophysiology involves intense splanchnic vasodilation, which leads to systemic hypotension and a compensatory, profound renal vasoconstriction [1]. 1. Why "Normal GFR" is the correct answer: By definition, HRS is a state of progressive renal failure. Therefore, the Glomerular Filtration Rate (GFR) is always significantly reduced (typically <40 mL/min or a doubling of serum creatinine) [1]. A "Normal GFR" is incompatible with a diagnosis of HRS. 2. Why the other options are incorrect (Features of HRS): * Normal Urinary Sediments: Since HRS is a functional failure (hemodynamic) rather than structural damage to the nephrons, the urine microscopy is characteristically "bland" or normal, without casts or hematuria [1]. * Low Na+ in Urine: Due to the activation of the Renin-Angiotensin-Aldosterone System (RAAS) in response to perceived hypovolemia, the kidneys aggressively reabsorb sodium. Urinary sodium is typically <10–15 mEq/L [1]. * Normal Renal Biopsy: Because the kidneys are histologically intact and the failure is purely functional, a biopsy would show normal architecture. Clinical Pearls for NEET-PG: * Diagnosis of Exclusion: You must first rule out shock, nephrotoxic drugs, and organic kidney disease [1]. * Key Diagnostic Criteria: No improvement in serum creatinine (to <1.5 mg/dL) after at least 2 days of diuretic withdrawal and volume expansion with Albumin (1g/kg/day) [1]. * Treatment of Choice: Vasoconstrictors (Terlipressin is preferred) plus Albumin [1]. The definitive treatment is a Liver Transplant.

Q: What is the trans-tubular potassium gradient (TTKG) in hypokalemia?

<3-4. **Explanation:** The **Transtubular Potassium Gradient (TTKG)** is a clinical tool used to estimate the conservation or secretion of potassium by the cortical collecting duct (CCD). It reflects the activity of aldosterone and the responsiveness of the distal tubule to it. **1. Why Option A is Correct:** In a patient with **hypokalemia**, a normal physiological response by the kidneys is to conserve potassium. If the kidneys are functioning correctly and the cause of hypokalemia is extra-renal (e.g., diarrhea or poor intake), the TTKG should be **low ( 6-10):** These values represent a high gradient. If a patient is hypokalemic but has a TTKG **>7**, it indicates **renal potassium wasting**. This suggests that the kidneys are inappropriately secreting potassium despite low serum levels, often due to hyperaldosteronism, diuretics, or renal tubular acidosis (RTA). **Clinical Pearls for NEET-PG:** * **Formula:** $TTKG = \frac{[K^+ \text{ urine} / (U/P \text{ osmolality})]}{[K^+ \text{ plasma}]}$ * **Prerequisites:** For TTKG to be accurate, the urine must be concentrated (Urine Osmolality > Plasma Osmolality) and urine sodium should be >25 mEq/L to ensure adequate delivery to the distal tubule. * **Hyperkalemia Context:** In a patient with hyperkalemia, a TTKG **<7** suggests mineralocorticoid deficiency (e.g., Addison’s disease) or resistance (e.g., Spironolactone).

Q: What is the most common cause of end-stage renal disease?

Diabetes. **Explanation:** **1. Why Diabetes is Correct:** Diabetes Mellitus (specifically Type 2) is globally recognized as the **leading cause of End-Stage Renal Disease (ESRD)**, accounting for approximately 40-50% of all cases [2]. The underlying pathophysiology involves chronic hyperglycemia leading to non-enzymatic glycosylation of the glomerular basement membrane, hyperfiltration injury, and eventual Kimmelstiel-Wilson (nodular) glomerulosclerosis [3]. This progression from microalbuminuria to overt nephropathy is the primary driver of the ESRD burden. **2. Why the Other Options are Incorrect:** * **Hypertension (B):** This is the **second most common cause** of ESRD [2]. It causes hypertensive nephrosclerosis. While highly prevalent, it trails behind diabetes in total incidence of renal replacement therapy (RRT) initiation. * **Chronic Glomerulonephritis (C):** This was historically a leading cause but has been overtaken by metabolic diseases. It remains a significant cause in younger populations and developing regions but is not the "most common" overall. * **Polycystic Kidney Disease (D):** Autosomal Dominant PKD is the most common **hereditary** cause of ESRD, but it accounts for only about 5% of the total ESRD population. **3. High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of ESRD:** Diabetes Mellitus [1]. * **Most common cause of Nephrotic Syndrome in adults:** Focal Segmental Glomerulosclerosis (FSGS) (Note: Membranous was previously cited, but FSGS is now more frequent in many registries). * **Earliest clinical sign of Diabetic Nephropathy:** Hyperfiltration (increased GFR) [3]. * **First laboratory sign:** Microalbuminuria (30-300 mg/day) [3]. * **Pathognomonic biopsy finding in Diabetes:** Kimmelstiel-Wilson (KW) nodules [3]. * **Drug of choice to slow progression:** ACE inhibitors or ARBs (and more recently, SGLT2 inhibitors).

Q: What is a common symptom of medullary sponge kidney disease?

Urinary tract infection. **Explanation:** **Medullary Sponge Kidney (MSK)** is a congenital malformation characterized by cystic dilatation of the collecting ducts in the renal papillae [1]. This structural abnormality leads to urinary stasis and impaired urinary acidification, creating a nidus for complications. 1. **Why Urinary Tract Infection (UTI) is correct:** The primary reason for UTIs in MSK is **urinary stasis** within the dilated pre-calyceal ducts. Additionally, MSK is frequently associated with **nephrocalcinosis** and **recurrent calcium oxalate stones** [1], [2] (due to hypercalciuria and distal renal tubular acidosis). These stones act as a focus for persistent or recurrent bacterial infections. 2. **Why other options are incorrect:** * **Nocturia:** While MSK can cause a mild concentrating defect, nocturia is not a hallmark symptom. It is more characteristic of chronic interstitial nephritis or early-stage polycystic kidney disease. * **Anemia & Azotemia:** MSK is generally a **benign, non-progressive condition**. Unlike Autosomal Dominant Polycystic Kidney Disease (ADPKD), MSK rarely leads to Chronic Kidney Disease (CKD) or renal failure [1]. Therefore, azotemia (elevated urea/creatinine) and anemia of chronic disease are typically absent. **High-Yield Clinical Pearls for NEET-PG:** * **Radiological Sign:** The classic appearance on Intravenous Urogram (IVU) is the **"Bouquet of flowers"** or **"Paintbrush"** appearance due to contrast filling the dilated collecting ducts [1]. * **Association:** MSK is associated with **Beckwith-Wiedemann syndrome** and hemihypertrophy. * **Metabolic Profile:** Patients often present with **Type 1 (Distal) RTA**, hypercalciuria, and hypocitraturia [2]. * **Management:** Focuses on preventing stone formation (increased fluid intake, thiazides) and treating UTIs.

Q: High anion gap metabolic acidosis is seen in which of the following conditions?

Diabetes mellitus. **Explanation:** Metabolic acidosis is categorized based on the **Anion Gap (AG)**, calculated as $[Na^+] - ([Cl^-] + [HCO_3^-])$. A High Anion Gap Metabolic Acidosis (HAGMA) occurs when fixed acids (unmeasured anions) are added to the blood, consuming bicarbonate. **Why Diabetes Mellitus is Correct:** In uncontrolled Diabetes Mellitus (specifically Diabetic Ketoacidosis), a lack of insulin leads to the breakdown of fatty acids into **ketoacids** ($\beta$-hydroxybutyrate and acetoacetate). These ketoacids dissociate, releasing $H^+$ ions that neutralize $HCO_3^-$, while the remaining ketoacid anions increase the unmeasured anion pool, resulting in **HAGMA**. **Analysis of Incorrect Options:** * **Diarrhea:** Causes direct loss of bicarbonate from the lower GI tract. To maintain electroneutrality, the body retains chloride, leading to **Normal Anion Gap Metabolic Acidosis (NAGMA)** or hyperchloremic acidosis. * **Adrenal Insufficiency (Addison’s Disease):** Deficiency of aldosterone leads to decreased $H^+$ secretion in the distal tubule and hyperkalemia (which inhibits ammonia production). This results in **NAGMA**. * **Renal Tubular Acidosis (RTA):** Whether due to failure to reabsorb $HCO_3^-$ (Type 2) or failure to secrete $H^+$ (Type 1), RTA is a classic cause of **NAGMA**. **NEET-PG High-Yield Pearls:** * **Mnemonic for HAGMA:** **MUDPILES** (Methanol, Uremia, DKA, Paraldehyde/Propylene glycol, INH/Iron, Lactic acidosis, Ethylene glycol, Salicylates). * **Mnemonic for NAGMA:** **HARDUP** (Hyperalimentation, Acetazolamide, Renal tubular acidosis, Diarrhea, Ureteroenteric fistula, Pancreatic fistula). * **Goldman’s Formula:** Used to calculate the expected $pCO_2$ compensation in metabolic acidosis: $pCO_2 = 1.5 \times [HCO_3^-] + 8 \pm 2$.

Q: Reversible diabetic nephropathy is characterized by which of the following?

Microalbuminuria. **Explanation:** Diabetic Nephropathy (DN) progresses through distinct stages. The hallmark of the **reversible stage** is **Microalbuminuria** (Stage III: Incipient Nephropathy) [1]. **1. Why Microalbuminuria is the Correct Answer:** Microalbuminuria is defined as the excretion of **30–300 mg/day** of albumin in the urine. At this stage, the damage is not yet structural or permanent. Strict glycemic control and the initiation of **ACE inhibitors or ARBs** can reduce intraglomerular pressure, stabilize the basement membrane, and potentially reverse the albuminuria back to normoalbuminuria [1], [2]. **2. Why the Other Options are Incorrect:** * **Macroalbuminuria (Option B):** Defined as >300 mg/day. This signifies Stage IV (Overt Nephropathy). At this point, there is a progressive decline in GFR, and the damage is generally considered irreversible, leading toward End-Stage Renal Disease (ESRD) [1]. * **Kimmelstiel-Wilson (KW) Lesion (Option C):** These are pathognomonic nodular glomerulosclerosis lesions seen on biopsy [1]. They represent advanced, irreversible structural damage [3]. * **Diffuse Glomerulosclerosis (Option D):** This is the most common histological change in DN. Like KW lesions, it represents permanent scarring and fibrosis of the glomeruli. **Clinical Pearls for NEET-PG:** * **Earliest functional change:** Hyperfiltration (Increased GFR). * **Earliest structural change:** Thickening of the Glomerular Basement Membrane (GBM) [1]. * **Most specific histological finding:** Kimmelstiel-Wilson nodules (Nodular sclerosis) [1]. * **Screening:** Patients with Type 2 DM should be screened for microalbuminuria at the time of diagnosis [2]; Type 1 DM patients should be screened 5 years after diagnosis.

Q: A 63-year-old man becomes oliguric 2 days following an open cholecystectomy. Which of the following findings would suggest that prerenal acute kidney injury is a major factor in the etiology?

Postural hypotension. ### Explanation **1. Why Postural Hypotension is Correct:** Prerenal Acute Kidney Injury (AKI) is caused by **decreased renal perfusion** without damage to the kidney parenchyma [1]. In a post-operative patient, this is often due to hypovolemia (blood loss, fluid shifts, or inadequate replacement). **Postural hypotension** (a drop in BP >20/10 mmHg upon standing) is a clinical hallmark of intravascular volume depletion. It indicates that the "pump" lacks sufficient "prime," leading to decreased glomerular filtration rate (GFR). **2. Why the Other Options are Incorrect:** * **Fractional Excretion of Sodium (FeNa) of 3%:** In prerenal AKI, the renal tubules are intact and aggressively reabsorb sodium to expand volume [2]. Therefore, **FeNa is typically 2–3% suggests Acute Tubular Necrosis (ATN), where damaged tubules cannot reabsorb sodium. * **Specific Gravity of 1.012:** In prerenal states, the kidneys secrete ADH to concentrate urine, resulting in a **high specific gravity (>1.020)**. A value of 1.012 is "isosthenuric" (similar to plasma), suggesting the kidneys have lost their concentrating ability (intrinsic AKI/ATN). * **Urine Sodium of 30 mEq/L:** To conserve volume, prerenal AKI presents with a **low urine sodium ( 20:1** (due to increased passive reabsorption of urea). * **Urine Osmolality:** High in prerenal (>500 mOsm/kg); low in ATN (<350 mOsm/kg). * **Sediment:** Prerenal AKI shows "bland" sediment or hyaline casts; ATN shows **"muddy brown" granular casts**. * **Management:** Prerenal AKI is reversible with prompt fluid resuscitation; delay can lead to ischemic ATN.

Question 1

A plasma urea to creatinine ratio of 20:1 may be seen in which of the following conditions?

Accepted Answer

Pre-renal failure

Answer

Rhabdomyolysis

Answer

Ureteric calculi

Answer

Chronic glomerulonephritis

Question 2

Which of the following conditions is characterized by hyperchloremic acidosis with hypokalemia?

Accepted Answer

Renal tubular acidosis

Answer

Addison's disease

Answer

Pyloric stenosis

Answer

Primary hyperaldosteronism

Question 3

A 47-year-old HIV-positive man presents with weakness. He has HIV nephropathy and adrenal insufficiency, and takes trimethoprim-sulfamethoxazole for PCP prophylaxis and triple-agent antiretroviral treatment. He was recently started on spironolactone for ascites due to alcoholic liver disease. Physical examination reveals normal vital signs, but his muscles are diffusely weak. Frequent extrasystoles are noted. He has mild ascites and 1+ peripheral edema. Laboratory studies show a serum creatinine of 2.5 mg/dL with a potassium value of 7.3 mEq/L. ECG shows peaking of the T-waves and QRS widening to 0.14 seconds. What is the most important immediate treatment for this patient's hyperkalemia?

Accepted Answer

IV calcium gluconate

Answer

Sodium polystyrene sulfonate (Kayexalate)

Answer

Acute hemodialysis

Answer

IV normal saline

Question 4

Which of the following is NOT a feature of hepato-renal syndrome?

Accepted Answer

Normal GFR

Answer

Normal urinary sediments

Answer

Low Na+ in urine

Answer

Normal renal biopsy

Question 5

What is the trans-tubular potassium gradient (TTKG) in hypokalemia?

Accepted Answer

<3-4

Answer

>6-7

Answer

>9-10

Answer

>10-15

Question 6

What is the most common cause of end-stage renal disease?

Accepted Answer

Diabetes

Answer

Hypertension

Answer

Chronic glomerulonephritis

Answer

Polycystic kidney disease

Question 7

What is a common symptom of medullary sponge kidney disease?

Accepted Answer

Urinary tract infection

Answer

Nocturia

Answer

Anemia

Answer

Azotemia

Question 8

High anion gap metabolic acidosis is seen in which of the following conditions?

Accepted Answer

Diabetes mellitus

Answer

Diarrhea

Answer

Adrenal insufficiency

Answer

Renal tubular acidosis

Question 9

Reversible diabetic nephropathy is characterized by which of the following?

Accepted Answer

Microalbuminuria

Answer

Macroalbuminuria

Answer

Kimmelstiel Wilson lesion

Answer

Diffuse glomerulosclerosis

Question 10

A 63-year-old man becomes oliguric 2 days following an open cholecystectomy. Which of the following findings would suggest that prerenal acute kidney injury is a major factor in the etiology?

Accepted Answer

Postural hypotension

Answer

Fractional excretion of sodium is 3%

Answer

Specific gravity is 1.012

Answer

Urine sodium is 30 mEq/L

Nephrology — MCQs

Nephrology — MCQs

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