Nephrology Practice Questions

Q: All of the following are true regarding Bartter syndrome except?

Hypomagnesuria. Bartter syndrome is a group of autosomal recessive disorders characterized by a defect in the thick ascending limb (TAL) of the loop of Henle, mimicking the effect of loop diuretics (Furosemide). **Why Option B is the Correct Answer (The False Statement):** In Bartter syndrome, there is typically **Hypermagnesuria** (increased magnesium in urine), not hypomagnesuria. The defect in the TAL disrupts the positive transepithelial potential difference normally required for the paracellular reabsorption of magnesium and calcium. This leads to increased urinary excretion of magnesium, which can result in **hypomagnesemia** (low serum magnesium). **Analysis of Incorrect Options:** * **Option A (Hypokalemic alkalosis):** This is a hallmark of Bartter syndrome. Failure of NaCl reabsorption in the TAL leads to increased distal delivery of sodium, which stimulates the Renin-Angiotensin-Aldosterone System (RAAS), causing potassium and hydrogen ion secretion in the collecting duct [1]. * **Option C & D (Hearing defect & Barttin mutation):** **Type IV Bartter syndrome** (Neonatal Bartter with sensorineural deafness) is caused by a mutation in the **BSND gene**, which encodes **Barttin**, a subunit of the ClC-Ka and ClC-Kb chloride channels. These channels are essential for both renal salt reabsorption and the maintenance of endolymph in the inner ear. **NEET-PG Clinical Pearls:** * **Bartter vs. Gitelman:** Bartter syndrome presents early (infancy/childhood) with **hypercalciuria** (loop diuretic-like), whereas Gitelman syndrome presents later (adolescence) with **hypocalciuria** (thiazide-like). * **Key Feature:** Patients often present with polyhydramnios in utero and severe salt wasting postnatally. * **Mnemonic:** **B**artter acts like a **B**ig loop (Loop diuretics), **G**itelman acts like a **G**entle thiazide.

Q: A 57-year-old male is admitted to the hospital for a suspected kidney infection (likely pyelonephritis). The patient is placed on intravenous antibiotic therapy but continues to have a temperature of 103°F after 3 days of therapy. The urine culture grows lactose-fermenting Gram-negative bacilli which are pan drug-sensitive. On examination, he appears ill and has marked left flank tenderness. Ultrasound depicts a specific finding. What is the most likely diagnosis?

Perinephric abscess. ***Perinephric abscess*** - **Persistent high fever** despite 3 days of appropriate antibiotic therapy in pyelonephritis strongly suggests **abscess formation**, as antibiotics cannot penetrate well into enclosed collections. - Ultrasound would show a **hypoechoic fluid collection** in the **perinephric space** surrounding the kidney, which is the key diagnostic finding. *Hydronephrosis* - Would present with **obstructive symptoms** and **dilated renal pelvis** on ultrasound, not persistent fever after antibiotic treatment. - Usually associated with **decreased urine output** and **relief of pain** with positioning, unlike this case. *Nephrolithiasis* - Typically presents with **colicky pain** that radiates to the groin, not constant flank tenderness. - Ultrasound would show **echogenic stones** with **acoustic shadowing**, and fever would resolve with antibiotics if infection was present. *Emphysematous pyelonephritis* - Occurs primarily in **diabetic patients** and involves **gas-forming bacteria** creating emphysema in renal parenchyma. - Ultrasound would show **hyperechoic foci** with **dirty shadowing** from gas, and the organism is typically **Klebsiella** or **E. coli**, not just any lactose-fermenter.

Q: What is the most common cause of renal papillary necrosis?

Diabetes mellitus. **Explanation:** Renal Papillary Necrosis (RPN) is an ischemic infarct of the renal papillae, which are particularly vulnerable due to their relatively low blood supply and high osmolality. **Why Diabetes Mellitus is the Correct Answer:** While multiple conditions cause RPN, **Diabetes Mellitus** is statistically the **most common cause** (associated with over 50% of cases). The pathogenesis involves a combination of diabetic microangiopathy (ischemia) and a predisposition to recurrent urinary tract infections (pyelonephritis), which synergistically lead to papillary infarction. **Analysis of Incorrect Options:** * **Analgesic Nephropathy:** Historically a major cause due to phenacetin use, it is now less common. It occurs because NSAIDs inhibit prostaglandins, leading to medullary vasoconstriction and ischemia. * **Sickle Cell Disease/Trait:** A common cause in younger populations. Sickling of RBCs in the hypertonic, hypoxic environment of the renal medulla leads to micro-thrombosis and infarction. * **Chronic Pyelonephritis:** While severe infection can cause RPN, it is usually a secondary factor or occurs in the presence of obstruction or diabetes. **NEET-PG High-Yield Pearls:** * **Mnemonic for Causes (POSTCARDS):** **P**yelonephritis, **O**bstruction, **S**ickle cell, **T**uberculosis, **C**irrhosis, **A**nalgesics, **R**enal vein thrombosis, **D**iabetes mellitus, **S**ystemic vasculitis. * **Clinical Presentation:** Gross hematuria, flank pain (mimicking renal colic due to sloughed papillae obstructing the ureter), and "ring sign" on IVP (contrast surrounding a sloughed papilla). * **Key Distinction:** In Diabetes, RPN is often bilateral; in Sickle Cell, it can occur even in asymptomatic carriers (Sickle Cell Trait).

Q: Normal anion gap metabolic acidosis can occur in which of the following conditions?

Renal failure. **Explanation:** Metabolic acidosis is categorized based on the **Anion Gap (AG)**, calculated as $[Na^+] - ([Cl^-] + [HCO_3^-])$. **1. Why Renal Failure is Correct:** Renal failure is a unique cause that can present with both types of acidosis depending on the stage: * **Early Renal Failure (CKD Stages 1-4):** Often presents as **Normal Anion Gap Metabolic Acidosis (NAGMA)**. This occurs because the kidneys lose the ability to excrete ammonium ($NH_4^+$) and reabsorb bicarbonate, but the glomerular filtration rate (GFR) is still high enough to filter titratable acids (phosphates/sulfates). * **Advanced Renal Failure (ESRD/Stage 5):** As GFR drops significantly (<15-20 mL/min), the kidney can no longer filter unmeasured anions like phosphates, sulfates, and organic acids. These accumulate, leading to a **High Anion Gap Metabolic Acidosis (HAGMA)**. **2. Why Incorrect Options are Wrong:** * **Liver Failure, Severe Anemia, and Malignancy:** These conditions are classically associated with **Type A or Type B Lactic Acidosis** [1]. Lactic acid dissociates into lactate (an unmeasured anion), which increases the anion gap, resulting in **HAGMA**, not NAGMA. **3. NEET-PG High-Yield Pearls:** * **NAGMA Mnemonic (USED CARP):** **U**reterosigmoidostomy, **S**aline (Normal Saline infusion), **E**ndocrine (Addison’s), **D**iarrhea (most common cause), **C**arbonic anhydrase inhibitors (Acetazolamide), **A**mmonium chloride, **R**enal tubular acidosis (RTA), **P**ancreatic fistula [1]. * **HAGMA Mnemonic (MUDPILES):** **M**ethanol, **U**remia (Advanced Renal Failure), **D**KA, **P**ropylene glycol, **I**soniazid/Iron, **L**actic acidosis, **E**thylene glycol, **S**alicylates [1]. * **Key Distinction:** In NAGMA, the drop in $HCO_3^-$ is compensated by a rise in $Cl^-$, which is why it is also called **Hyperchloremic Metabolic Acidosis** [1].

Q: Which of the following statements about kidney injury molecule-1 (KIM-1) is false?

KIM-1 is abundantly expressed in distal tubular cells.. Kidney Injury Molecule-1 (KIM-1) is a type I transmembrane glycoprotein that has emerged as a highly specific and sensitive **biomarker for proximal tubular injury**. **1. Why Option B is the correct (False) statement:** KIM-1 is **not** expressed in distal tubular cells. In a healthy kidney, KIM-1 is virtually undetectable. However, following an ischemic or nephrotoxic insult, it is **markedly upregulated specifically in the proximal tubular epithelial cells**. It plays a role in tubular regeneration and acts as a phosphatidylserine receptor, transforming epithelial cells into "semi-professional" phagocytes to clear apoptotic debris. **2. Analysis of other options:** * **Option A:** KIM-1 is indeed a **novel biomarker** of AKI [1]. Unlike Serum Creatinine, which is a marker of function and rises late, KIM-1 is a marker of structural damage. * **Option C:** KIM-1 is highly stable and its ectodomain is shed into the lumen, allowing it to be **detected in the urine shortly after injury** (within hours), long before a rise in creatinine occurs. **High-Yield Clinical Pearls for NEET-PG:** * **Localization:** Proximal Tubule (High-yield: Contrast this with **NGAL**, which is expressed in both proximal and distal tubules). * **FDA Status:** KIM-1 is one of the few biomarkers qualified by the FDA for use in drug development to monitor nephrotoxicity. * **Predictive Value:** Higher urinary KIM-1 levels are associated with an increased risk of progressing to Chronic Kidney Disease (CKD). * **Other AKI Biomarkers:** NGAL (earliest), IL-18, L-FABP, and IGFBP-7 × TIMP-2 (Cell cycle arrest markers).

Q: Which of the following is seen in nephrotic syndrome?

Hypercoagulability. **Explanation:** Nephrotic syndrome is characterized by a triad of massive proteinuria, hypoalbuminemia, and generalized edema [1]. The correct answer is **Hypercoagulability**, which is a significant complication of this condition [1]. **1. Why Hypercoagulability is correct:** The loss of plasma proteins through the damaged glomerular basement membrane [2] includes natural anticoagulants, most notably **Antithrombin III (AT-III)**, Protein C, and Protein S. Simultaneously, the liver increases the synthesis of pro-coagulant factors (like Fibrinogen) and there is increased platelet aggregation. This imbalance shifts the hemostatic system toward a pro-thrombotic state, increasing the risk of deep vein thrombosis (DVT) and **Renal Vein Thrombosis (RVT)**, especially in Membranous Nephropathy [1]. **2. Why other options are incorrect:** * **A. Proteinuria less than 3.5 gm/day:** By definition, nephrotic-range proteinuria must be **>3.5 gm/24 hours** (in adults). Values below this are considered sub-nephrotic or characteristic of nephritic syndrome [2]. * **B. Hyperalbuminemia:** Nephrotic syndrome causes **Hypoalbuminemia** (<3 g/dL) due to massive urinary loss and catabolism of albumin in the proximal tubule [1]. * **C. Hypertension:** While hypertension can occur in some types of nephrotic syndrome (like FSGS), it is a classic hallmark of **Nephritic Syndrome** [2]. Nephrotic syndrome is primarily defined by metabolic and protein disturbances rather than inflammatory hematuria and hypertension. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of RVT:** Membranous Nephropathy. * **Hyperlipidemia:** Seen in nephrotic syndrome due to compensatory hepatic synthesis of lipoproteins (LDL/VLDL) in response to low oncotic pressure [1]. * **Infection Risk:** Patients are prone to infections (e.g., *S. pneumoniae*) due to the loss of **Immunoglobulins (IgG)** and Complement factors in urine.

Question 1

A 47-year-old HIV-positive man presents with weakness, HIV nephropathy, and adrenal insufficiency. He is taking 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. Once the patient is stabilized and the T-waves have normalized, it is important to review the potential causes of his hyperkalemia and to take steps to prevent this from happening again. As you consider the pathophysiology of each factor, which of the following statements is true?

Accepted Answer

Spironolactone, a diuretic for ascites in cirrhosis, acts as a competitive aldosterone inhibitor at the collecting duct, decreasing potassium excretion and causing hyperkalemia.

Answer

Trimethoprim-sulfamethoxazole, used for Pneumocystis infection prophylaxis, causes hypokalemia and therefore would have prevented this patient's presentation.

Answer

The patient likely had pseudo-hyperkalemia due to hemolysis caused by using a small needle and rough specimen handling, leading to potassium release into the serum.

Answer

Once hospitalized, the patient may receive heparin for DVT prophylaxis, which would help ameliorate hyperkalemia in the ensuing days.

Question 2

A patient being treated for leukemia develops unilateral flank pain. Radiologic studies demonstrate a dilated renal pelvis and dilation of the upper one-third of the corresponding ureter. A stone with which of the following compositions is most likely causing this patient's problems?

Accepted Answer

Uric acid

Answer

Calcium salts

Answer

Cholesterol

Answer

Cystine

Question 3

All of the following are true regarding Bartter syndrome except?

Accepted Answer

Hypomagnesuria

Answer

Hypokalemic alkalosis

Answer

Congenital sensorineural hearing defect

Answer

Associated with Barttin mutation

Question 4

All of the following are true about Bartter syndrome except?

Accepted Answer

Mineralocorticoid antagonists can be used.

Answer

Urinary calcium is increased.

Answer

Hypokalemic alkalosis is present.

Answer

Blood pressure is normal.

Question 5

A 57-year-old male is admitted to the hospital for a suspected kidney infection (likely pyelonephritis). The patient is placed on intravenous antibiotic therapy but continues to have a temperature of 103°F after 3 days of therapy. The urine culture grows lactose-fermenting Gram-negative bacilli which are pan drug-sensitive. On examination, he appears ill and has marked left flank tenderness. Ultrasound depicts a specific finding. What is the most likely diagnosis?

Accepted Answer

Perinephric abscess

Answer

Hydronephrosis

Answer

Nephrolithiasis

Answer

Emphysematous pyelonephritis

Question 6

A 24-year-old man has a urine analysis that is positive for blood. The microscopic examination of the urine is negative for casts or red blood cells. Which of the following is the most likely diagnosis?

Accepted Answer

Myoglobinuria

Answer

Hematuria

Answer

Nephritic syndrome

Answer

Renal cell carcinoma

Question 7

What is the most common cause of renal papillary necrosis?

Accepted Answer

Diabetes mellitus

Answer

Analgesic nephropathy

Answer

Sickle cell disease

Answer

Chronic pyelonephritis

Question 8

Normal anion gap metabolic acidosis can occur in which of the following conditions?

Accepted Answer

Renal failure

Answer

Liver failure

Answer

Severe anemia

Answer

Malignancy

Question 9

Which of the following statements about kidney injury molecule-1 (KIM-1) is false?

Accepted Answer

KIM-1 is abundantly expressed in distal tubular cells.

Answer

KIM-1 is a novel biomarker of acute kidney injury (AKI).

Answer

KIM-1 can be detected shortly after ischemic injury in the urine.

Answer

All the above statements are false.

Question 10

Which of the following is seen in nephrotic syndrome?

Accepted Answer

Hypercoagulability

Answer

Proteinuria less than 3.5 gm/day

Answer

Hyperalbuminemia

Answer

Hypertension

Nephrology — MCQs

Nephrology — MCQs

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