Renal Nuclear Medicine — MCQs
In the context of bilateral renal artery stenosis, which antihypertensive drug is considered contraindicated?
Tc-labeled RBCs are used for all except:
In a child, non-functioning kidney is best diagnosed by:
A dense nephrogram is obtained by
The T1/2 of Iodine-131 is:
Which of the following agents is used to measure Glomerular Filtration Rate (GFR)?
In a child, non-functioning kidney is best diagnosed by
Which artificial radioisotopes are used in nuclear medicine?
Which radiopharmaceutical is used for a liver scan?
What is the investigation of choice for whole-body imaging in metastasis?
Renal Nuclear Medicine Indian Medical PG Practice Questions and MCQs
Question 1: In the context of bilateral renal artery stenosis, which antihypertensive drug is considered contraindicated?
- A. Beta-blockers
- B. Calcium channel blockers
- C. ACE inhibitors (Correct Answer)
- D. Diuretics
Explanation: ***ACE inhibitors*** - In bilateral renal artery stenosis, ACE inhibitors can precipitate **acute kidney injury** by severely reducing **glomerular filtration pressure**, as both kidneys rely on **angiotensin II** for maintaining this pressure [1]. - They inhibit the production of **angiotensin II**, leading to **efferent arteriolar dilation** and a drop in glomerular hydrostatic pressure, which is critical for filtration in stenosed kidneys [2]. *Beta-blockers* - Beta-blockers are generally considered safe and effective in treating hypertension associated with renal artery stenosis, as they do not directly interfere with **renal autoregulation** in the same critical way as ACE inhibitors. - They lower blood pressure by reducing **cardiac output** and inhibiting renin release but do not acutely compromise **glomerular filtration** in the presence of stenosis. *Calcium channel blockers* - Calcium channel blockers are safe to use in bilateral renal artery stenosis and are often effective in controlling blood pressure. - They dilate **afferent arterioles**, which can actually help maintain or improve **glomerular filtration rate** by increasing blood flow to the glomerulus. *Diuretics* - Diuretics can be used cautiously in renal artery stenosis to manage blood pressure and fluid overload. - However, aggressive diuresis can lead to intravascular volume depletion, which might exacerbate **renal hypoperfusion** in already stenosed kidneys.
Question 2: Tc-labeled RBCs are used for all except:
- A. Liver adenoma (Correct Answer)
- B. LV function
- C. GI bleeding
- D. Liver hemangioma
Explanation: ***Liver adenoma*** - Tc-labeled RBCs are primarily used to highlight a specific type of tissue or process. **Liver adenomas** do not typically show an affinity for **Tc-labeled RBCs**, as they are benign epithelial tumors with a different vascular composition. - While adenomas can be vascular, they do not inherently contain the **vascular pooling** or blood volume characteristics that would be specifically targeted by **Tc-labeled RBCs** for diagnostic imaging. *LV function* - **Tc-labeled RBCs** (or Tc-99m-pertechnetate) are commonly used in **gated blood pool imaging** (MUGA scan) to assess **left ventricular (LV) function**, including **ejection fraction** and wall motion abnormalities. - This technique directly visualizes the blood pool within the cardiac chambers, making it suitable for assessing functional parameters of the heart. *GI bleeding* - **Tc-labeled RBCs** are a standard imaging agent for detecting and localizing **active gastrointestinal (GI) bleeding**, especially when the bleeding rate is intermittent or slow. - The labeled RBCs extravasate at the site of hemorrhage, creating a 'hot spot' that can be identified over time. *Liver hemangioma* - **Tc-labeled RBCs** are highly effective in diagnosing **liver hemangiomas**, which are benign vascular tumors composed of large, dilated blood vessels. - These lesions show characteristic uptake and retention of **labeled RBCs** due to their slow blood flow and large intravascular space, appearing as early peripheral enhancement with subsequent centripetal filling.
Question 3: In a child, non-functioning kidney is best diagnosed by:
- A. Ultrasonography
- B. IVU
- C. Creatinine clearance
- D. DTPA renogram (Correct Answer)
Explanation: ***DTPA renogram*** - A **DTPA (diethylenetriamine pentaacetic acid) renogram** is a nuclear medicine study that assesses **renal blood flow**, **glomerular filtration**, and urinary drainage. It directly measures the function of each kidney by quantifying tracer uptake and excretion, making it ideal for diagnosing a non-functioning kidney in a child. - The test provides information on the **relative function** of each kidney and outflow obstruction, which is crucial for determining if a kidney is truly non-functioning rather than just poorly visualized. *Ultrasonography* - While ultrasound can visualize the **anatomy** of the kidney (size, shape, presence of hydronephrosis), it does not directly assess renal function. - It may show a small, atrophic, or poorly developed kidney, but cannot definitively determine if it is non-functioning without functional studies. *IVU (Intravenous Urogram)* - An **IVU** relies on the kidneys' ability to excrete contrast material, which is visualized by X-ray. If a kidney is non-functioning, it will not excrete the contrast, leading to non-visualization. - However, IVU exposes the child to **radiation** and **iodinated contrast**, and newer, safer, and more precise functional studies like renograms are preferred, especially in pediatric cases where radiation exposure should be minimized. *Creatinine clearance* - **Creatinine clearance** is a measure of overall **glomerular filtration rate (GFR)** for both kidneys combined. - It does not provide information on the individual function of each kidney, so it cannot diagnose a non-functioning unilateral kidney.
Question 4: A dense nephrogram is obtained by
- A. Dehydrating the patient
- B. Rapid (Bolus) injection of dye (Correct Answer)
- C. Using non ionic media
- D. Increasing the dose of contrast media
Explanation: ***Rapid (Bolus) injection of dye*** - A **rapid bolus injection** of contrast material ensures a high concentration reaches the kidneys simultaneously, leading to optimal opacification and a **dense nephrogram**. - This method allows for the collection of a **large bolus of undiluted contrast** in the renal vessels and parenchyma, improving visualization of the renal parenchyma during the nephrographic phase. - The dense nephrogram phase occurs when contrast is within the renal tubules and interstitium, producing uniform opacification. *Dehydrating the patient* - **Dehydration** would concentrate the urine in the collecting system, but it does not directly contribute to the **dense nephrogram** appearance of the renal parenchyma. - While dehydration may improve visualization of the pelvicalyceal system on delayed images, it can increase the risk of **contrast-induced nephropathy**. *Using non ionic media* - **Non-ionic contrast media** are associated with fewer adverse reactions and greater patient safety compared to ionic media due to their lower osmolality. - However, the type of contrast media (ionic vs. non-ionic) does not primarily determine the **density of the nephrogram** itself, but rather patient tolerability and safety profile. *Increasing the dose of contrast media* - While increasing the dose might provide more contrast overall, it does not guarantee a **dense nephrogram**, which requires a high concentration of contrast to be present acutely in the renal parenchyma. - A dense nephrogram is better achieved by **rapid bolus injection technique** rather than simply increasing the total dose. - Excessive contrast increases the risk of **adverse reactions** and contrast-induced nephropathy without necessarily improving nephrographic density proportionally.
Question 5: The T1/2 of Iodine-131 is:
- A. 8 days (Correct Answer)
- B. 12 hours
- C. 13 days
- D. 2 days
Explanation: ***8 days*** - Iodine-131 (¹³¹I) has a relatively short half-life of **8.02 days**, making it suitable for diagnostic and therapeutic uses with a controlled radiation exposure window. - This **half-life** allows for effective patient monitoring and targeted treatment while minimizing long-term radiation risks. *12 hours* - This is an incorrect value; 12 hours is a significantly shorter half-life than that of **Iodine-131**. - Other isotopes, such as **Iodine-123**, have a half-life of 13.2 hours, which is closer to this value but still distinct from **Iodine-131**. *13 days* - This value is close but incorrect; the correct half-life for **Iodine-131** is approximately **8 days**. - A 13-day half-life would imply a longer period of radioactivity, altering its clinical applications. *2 days* - This is an incorrect half-life for **Iodine-131**, which has a significantly longer half-life of approximately 8 days. - A 2-day half-life would mean the isotope decays much faster than it actually does.
Question 6: Which of the following agents is used to measure Glomerular Filtration Rate (GFR)?
- A. Iodohippurate
- B. Tc99m-DTPA (Correct Answer)
- C. Tc99m-MAG3
- D. Tc99m-DMSA
Explanation: ***Tc99m-DTPA*** - Technetium-99m-Diethylenetriaminepentaacetic acid (**Tc99m-DTPA**) is a radiopharmaceutical that is cleared almost exclusively by **glomerular filtration** (~98%), making it the ideal agent for measuring GFR. - Its **renal clearance rate** directly correlates with the GFR, providing an accurate, non-invasive assessment of kidney function. - Used for dynamic renal scintigraphy to calculate GFR quantitatively. *Iodohippurate* - **Iodohippurate (OIH)** is primarily cleared by **tubular secretion** (~80%), similar to Para-aminohippuric acid (PAH). - It is used to measure **renal plasma flow (RPF)** or **effective renal plasma flow (ERPF)**, not GFR. - Not suitable for GFR measurement due to its tubular handling mechanism. *Tc99m-MAG3* - Technetium-99m-Mercaptoacetyltriglycine (**Tc99m-MAG3**) is predominantly handled by **tubular secretion** (~90%). - Used to assess **effective renal plasma flow (ERPF)** and is preferred in patients with impaired renal function due to its high extraction efficiency. - Has largely replaced OIH in clinical practice but does not measure GFR. *Tc99m-DMSA* - Technetium-99m-Dimercaptosuccinic acid (**Tc99m-DMSA**) binds to the **proximal tubular cells** in the renal cortex (~40-50% accumulation). - Used for **static renal cortical scintigraphy** to evaluate renal morphology, differential renal function, and detect cortical scarring. - Not cleared by glomerular filtration and unsuitable for GFR measurement.
Question 7: In a child, non-functioning kidney is best diagnosed by
- A. Creatinine clearance
- B. Ultrasonography
- C. IVU
- D. DTPA renogram (Correct Answer)
Explanation: ***DTPA renogram*** - A **DTPA renogram** (diethylene triamine pentaacetic acid scan) is a nuclear medicine study that assesses **renal blood flow** and **glomerular filtration rate (GFR)**. - It is highly effective in determining if a kidney is non-functioning because it directly measures the **uptake and excretion of a radiotracer** by the kidney, providing quantitative data on its functional capacity. *Creatinine clearance* - **Creatinine clearance** is a measure of overall kidney function, reflecting the GFR of **both kidneys combined**. - It cannot specifically identify a non-functioning individual kidney, as the other kidney might compensate for the non-functioning one, leading to a near-normal overall creatinine clearance. *Ultrasonography* - **Ultrasonography** is excellent for evaluating **renal anatomy**, such as size, shape, and presence of cysts, hydronephrosis, or stones. - While it can show structural abnormalities, it provides limited direct information about the **functional status** of the kidney, and a structurally normal kidney can still be non-functional. *IVU (Intravenous Urography)* - **Intravenous Urography (IVU)** uses contrast dye injected intravenously to visualize the kidneys, ureters, and bladder, assessing both anatomy and some aspects of function. - If a kidney is non-functioning, it would show **no uptake or excretion of the contrast dye**, but IVU involves radiation exposure and nephrotoxic contrast, making DTPA renogram often preferred in children for functional assessment.
Question 8: Which artificial radioisotopes are used in nuclear medicine?
- A. Radium
- B. Uranium
- C. Plutonium (Correct Answer)
- D. Iridium
Explanation: ### Explanation **Correct Answer: C. Plutonium** In nuclear medicine, radioisotopes are categorized as either **natural** (found in nature) or **artificial** (man-made via nuclear reactors or cyclotrons). **Plutonium (specifically Pu-238)** is an artificial radioisotope produced in nuclear reactors. While not used as a diagnostic tracer or therapeutic agent for internal administration, it has a significant historical and niche clinical application as a power source for **Radioisotope Thermoelectric Generators (RTGs)** in long-lived **cardiac pacemakers**. Its high energy density and long half-life made it ideal for devices requiring decades of operation without battery replacement. **Analysis of Incorrect Options:** * **A. Radium:** This is a **naturally occurring** radioactive metal found in uranium ores. While Radium-223 is used in treating bone metastases (Xofigo), the element itself is classified as natural. * **B. Uranium:** This is a **naturally occurring** heavy metal. It is the raw material used to produce artificial isotopes but is not used directly in clinical nuclear medicine. * **C. Iridium:** While Iridium-192 is used in Brachytherapy, it is generally classified as a transition metal used in "sealed sources" for radiotherapy rather than being the classic example of an "artificial radioisotope" in the context of general nuclear medicine tracers (like Technetium-99m). However, in the context of this specific question, Plutonium is the most distinct "artificial/man-made" element. **High-Yield Clinical Pearls for NEET-PG:** * **Technetium-99m (Tc-99m):** The most commonly used artificial radioisotope in diagnostic nuclear medicine (produced in a Mo-99/Tc-99m generator). * **Cyclotron-produced isotopes:** Include F-18 (used in PET scans), I-123, and Thallium-201. * **Reactor-produced isotopes:** Include I-131, Mo-99, and Xenon-133. * **Therapeutic Alpha Emitter:** Radium-223 is the first alpha-emitting radiopharmaceutical approved to improve survival in castration-resistant prostate cancer with bone metastases.
Question 9: Which radiopharmaceutical is used for a liver scan?
- A. Tc-99m sulphur colloid (Correct Answer)
- B. Tc-99m mebrofenin
- C. Tc-99m MIBI
- D. Tc-99m DTPA
Explanation: **Explanation:** The correct answer is **Tc-99m sulphur colloid**. The underlying principle for a liver-spleen scan is the **phagocytic activity of the Reticuloendothelial System (RES)**. When Tc-99m sulphur colloid is injected intravenously, the particles (sized 0.1–1.0 μm) are cleared from the blood by Kupffer cells in the liver (80–90%), splenic macrophages (5–10%), and bone marrow. This scan is primarily used to evaluate functional liver anatomy and detect "cold nodules" (e.g., abscesses or tumors) or "hot spots" (e.g., Focal Nodular Hyperplasia). **Analysis of Incorrect Options:** * **Tc-99m Mebrofenin:** This is an IDA (Iminodiacetic acid) derivative used for **HIDA scans**. It evaluates the **hepatobiliary system** (hepatocyte uptake and biliary excretion) and is the gold standard for diagnosing Acute Cholecystitis. * **Tc-99m MIBI:** Primarily used for **Myocardial Perfusion Imaging** and Parathyroid imaging. It is taken up by mitochondria. * **Tc-99m DTPA:** A chelating agent cleared by glomerular filtration, used for **Renal Dynamic Scans** to assess GFR and obstructive uropathy. **High-Yield Clinical Pearls for NEET-PG:** 1. **Colloid Shift:** In portal hypertension or cirrhosis, there is decreased liver uptake and increased uptake in the spleen and bone marrow. 2. **Focal Nodular Hyperplasia (FNH):** This is the only liver lesion that typically appears "hot" or "isointense" on a sulphur colloid scan due to the presence of Kupffer cells. 3. **Hot Spot on Liver Scan:** Classically seen in **Superior Vena Cava (SVC) Obstruction** (due to collateral flow via the vein of Sappey).
Question 10: What is the investigation of choice for whole-body imaging in metastasis?
- A. Magnetic Resonance Imaging
- B. Radiography
- C. Bone scan (Correct Answer)
- D. CT Scan
Explanation: **Explanation:** **Bone Scan (Technetium-99m MDP)** is the investigation of choice for screening whole-body skeletal metastases because of its high sensitivity and ability to image the entire skeleton in a single session. It works on the principle of detecting increased osteoblastic activity (bone remodeling) at sites of tumor infiltration. Its primary advantage is the ability to detect "hot spots" weeks or months before structural changes become visible on conventional X-rays. **Why other options are incorrect:** * **Radiography (X-ray):** It has low sensitivity for early metastasis. A bone lesion only becomes visible on an X-ray after **30-50% of bone mineral density is lost**. It is, however, the best modality to confirm a finding seen on a bone scan. * **CT Scan:** While excellent for evaluating cortical bone and detailed anatomy, it is not practical for whole-body screening due to high radiation doses and lower sensitivity for early marrow-based lesions compared to nuclear imaging. * **MRI:** MRI is the most sensitive modality for detecting **bone marrow infiltration**. However, it is not typically the first-line "investigation of choice" for whole-body screening due to high costs, long scan times, and limited availability of whole-body MRI protocols. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Tc-99m MDP (Methylene Diphosphonate) adsorbs onto the **hydroxyapatite crystals** of the bone. * **The "Cold Scan" Exception:** Highly aggressive or purely osteolytic tumors (e.g., Multiple Myeloma, Renal Cell Carcinoma, or Thyroid Cancer) may show as "cold" or false-negative on a bone scan because they do not trigger an osteoblastic response. * **Flare Phenomenon:** An apparent increase in tracer uptake seen shortly after starting chemotherapy, which actually represents healing bone rather than disease progression. * **Superscan:** A bone scan showing intense, uniform skeletal uptake with **absent renal/bladder activity**, typically seen in diffuse metastatic prostate cancer or hyperparathyroidism.
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