Ultrasound — MCQs

Ultrasound Indian Medical PG Practice Questions and MCQs

Question 121: What does 'pseudo kidney' refer to on ultrasound?

A. Thickened bowel loop (Correct Answer)
B. Hydronephrosis
C. Unascended kidney
D. Undescended testes

Explanation: **Explanation:** The **'Pseudo-kidney' sign** is a classic sonographic appearance where a segment of bowel mimics the morphology of a kidney. This occurs when there is significant **mural thickening of a bowel loop** (the "cortex") surrounding a central echogenic area representing trapped air, mucus, or collapsed mucosa (the "medullary/sinus" equivalent). **Why Option A is correct:** In conditions like **Intussusception**, inflammatory bowel disease (Crohn’s), or bowel malignancies (Lymphoma/Adenocarcinoma), the bowel wall becomes edematous and thickened. On ultrasound, the hypoechoic thickened wall resembles the renal cortex, while the central echogenic lumen resembles the renal sinus, creating the "pseudo-kidney" appearance. **Why other options are incorrect:** * **B. Hydronephrosis:** This refers to the dilatation of the renal pelvis and calyces, typically appearing as an interconnected fluid-filled (anechoic) collection within the kidney, not a bowel mimic. * **C. Unascended kidney (Pelvic Kidney):** This is a true kidney located in an ectopic position. It possesses actual renal architecture (pyramids, vessels) rather than just mimicking the shape. * **D. Undescended testes:** These appear as oval, homogeneous structures in the inguinal canal or abdomen, often associated with a "mediastinum testis" (linear echogenic band), but do not resemble a kidney. **High-Yield Clinical Pearls for NEET-PG:** * **Intussusception:** The most common cause of the pseudo-kidney sign in children. Other associated signs include the **Target sign** or **Donut sign** (transverse view). * **Doughnut Sign:** Also refers to bowel wall thickening where the hypoechoic rim is prominent. * **Clinical Correlation:** If you see a pseudo-kidney sign in an elderly patient with weight loss, suspect **Gastrointestinal Malignancy**.

Question 122: The 'Filaria dance' sign is observed in which imaging modality?

A. Radiography
B. Ultrasonography (Correct Answer)
C. HRCT
D. Nuclear scan

Explanation: **Explanation:** The **'Filaria Dance' sign** is a classic pathognomonic finding on **Ultrasonography (USG)**. It refers to the characteristic undulating, high-velocity, twirling movement of live adult filarial worms (typically *Wuchereria bancrofti*) within dilated lymphatic vessels. **1. Why Ultrasonography is correct:** High-frequency ultrasonography (usually 7.5–10 MHz) allows for real-time visualization of the lymphatic channels. In patients with lymphatic filariasis, the adult worms reside in the scrotal lymphatics (most common site) or the breast. Their continuous, irregular thrashing motion appears as curvilinear echogenic structures moving rapidly within an anechoic (fluid-filled) dilated space. This "dance" is a definitive sign of active infection. **2. Why other options are incorrect:** * **Radiography (X-ray):** Cannot visualize soft tissue parasites or lymphatics in real-time. It may only show calcified dead worms (Rice-grain calcifications), but not the "dance." * **HRCT:** While excellent for lung parenchyma, it lacks the real-time temporal resolution required to observe the rapid movement of parasites. * **Nuclear Scan:** Lymphoscintigraphy is used to assess lymphatic flow and obstruction (showing "hot spots" or delayed clearance), but it cannot visualize individual worm movement. **Clinical Pearls for NEET-PG:** * **Most common site:** Scrotal lymphatics (filarial scrotal dance). * **Doppler finding:** On Color Doppler, the movement produces a characteristic **optical flow artifact** (random color signals) due to the high velocity of the worms, not blood flow. * **Treatment:** Diethylcarbamazine (DEC) is the drug of choice; the "dance" typically disappears after successful treatment as the worms die. * **Associated finding:** Tropical Pulmonary Eosinophilia (TPE) is a systemic manifestation often tested alongside filariasis.

Question 123: What is the commonly used frequency range in obstetrical ultrasonography?

A. 3.5-5 KHz
B. 20-25 KHz
C. 3.5-5 MHz (Correct Answer)
D. 20-25 MHz

Explanation: **Explanation:** In obstetrical ultrasonography, the choice of frequency is a balance between **penetration depth** and **axial resolution**. 1. **Why 3.5–5 MHz is correct:** Standard transabdominal ultrasound (TAS) for pregnancy requires the sound waves to travel through the maternal abdominal wall, subcutaneous fat, and uterine wall to reach the fetus. Frequencies in the **3.5–5 MHz** range provide the optimal penetration depth (up to 20 cm) necessary to visualize deep pelvic structures while maintaining sufficient resolution to assess fetal anatomy and growth. 2. **Why the other options are incorrect:** * **A & B (KHz range):** These are audible sound frequencies (20 Hz to 20 KHz). Diagnostic ultrasound operates in the **Megahertz (MHz)** range (millions of cycles per second), which is well above the human hearing threshold. * **D (20–25 MHz):** High-frequency waves provide excellent resolution but have very poor penetration. These frequencies are used for superficial structures (e.g., ophthalmology or intravascular USG) and cannot reach the depth required for obstetrics. **High-Yield Clinical Pearls for NEET-PG:** * **Transvaginal Sonography (TVS):** Uses higher frequencies (**5–10 MHz**) because the probe is closer to the target organs. This offers superior resolution for early pregnancy (first trimester) and cervical assessment. * **The Inverse Relationship:** Frequency is inversely proportional to penetration but directly proportional to resolution. (↑ Frequency = ↑ Resolution but ↓ Penetration). * **Safety:** Ultrasound is the preferred modality in pregnancy because it uses non-ionizing radiation, following the **ALARA** (As Low As Reasonably Achievable) principle.

Question 124: Paradoxical embolism is detected by?

A. MRI Chest
B. Bubble contrast Echocardiography (Correct Answer)
C. CT scan Chest
D. Impedance plethysmography

Explanation: **Explanation:** **Paradoxical embolism** occurs when a thrombus originating in the systemic venous circulation (e.g., DVT) bypasses the lungs and enters the systemic arterial circulation through a **Right-to-Left shunt**, most commonly a **Patent Foramen Ovale (PFO)** or an Atrial Septal Defect (ASD). **Why Bubble Contrast Echocardiography is correct:** Agitated saline (bubble contrast) is the gold standard bedside screening tool for detecting these shunts. During the procedure, saline is agitated to create microbubbles and injected into a peripheral vein. In a normal heart, these bubbles are filtered out by the pulmonary capillary bed. However, in the presence of a right-to-left shunt, the bubbles appear in the **left atrium/ventricle** within 3 to 6 cardiac cycles. Performing a **Valsalva maneuver** increases right atrial pressure, further enhancing the sensitivity of the test by forcing the shunt open. **Analysis of Incorrect Options:** * **MRI and CT Chest:** While useful for diagnosing pulmonary emboli or structural lung disease, they are not dynamic enough to visualize the real-time transit of microbubbles across a septal defect. * **Impedance Plethysmography:** This is an older, non-invasive method used to detect Deep Vein Thrombosis (DVT) by measuring changes in electrical resistance related to blood flow in the leg. It cannot detect intracardiac shunts. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for PFO:** Transesophageal Echocardiography (TEE) with bubble contrast is more sensitive than Transthoracic Echocardiography (TTE). * **Platypnea-Orthodeoxia Syndrome:** A rare condition where a patient experiences dyspnea and deoxygenation when upright, often associated with a PFO. * **Cryptogenic Stroke:** Paradoxical embolism should be suspected in young patients presenting with a stroke and no identifiable arterial risk factors.

Question 125: A gas shadow in the heart and great vessels appears in which condition?

A. Intrauterine device (IUD) (Correct Answer)
B. Abortion
C. Stillbirth
D. None of the above

Explanation: **Explanation:** The presence of gas shadows within the fetal heart and great vessels on an X-ray or ultrasound is known as **Robert’s Sign**. This is a classic radiological indicator of **Intrauterine Fetal Death (IUFD)**. 1. **Why Option A is Correct:** In the context of this question, "Intrauterine device" (IUD) is often used interchangeably with **Intrauterine Death** in older or specific exam terminologies (though "IUFD" is the standard clinical term). When a fetus dies in utero, anaerobic autolysis of fetal blood occurs, leading to the release of gas (primarily nitrogen) into the circulatory system. Robert’s Sign is one of the earliest radiological signs of fetal death, appearing as early as 12 hours after the event. 2. **Why Other Options are Incorrect:** * **Abortion:** While fetal death occurs in a missed abortion, the term "abortion" refers to the termination of pregnancy before viability. Robert’s Sign is specifically associated with the radiological evaluation of a more advanced fetus (IUFD). * **Stillbirth:** This is a clinical outcome (a baby born dead after 24 weeks). While a stillborn fetus may have shown Robert’s Sign in utero, the sign itself is a diagnostic tool used to confirm death *before* delivery. **High-Yield Clinical Pearls for NEET-PG:** * **Robert’s Sign:** Gas in fetal heart/vessels (earliest sign, ~12 hours). * **Spalding’s Sign:** Overlapping of fetal skull bones due to loss of liquor and brain liquefaction (appears after 2–7 days). * **Deuel’s Halo Sign:** Edema of fetal scalp causing elevation of the subcutaneous fat layer (indicates fetal distress/death). * **Ball’s Sign:** Abnormal acute angulation of the fetal spine.

Question 126: Endoscopic ultrasound is extremely useful in staging which tumour?

A. Carcinoma of the Colon
B. Carcinoma of the Esophagus (Correct Answer)
C. Carcinoma of the Stomach
D. Carcinoma of the Head of the Pancreas

Explanation: **Explanation:** **Endoscopic Ultrasound (EUS)** is considered the "gold standard" for the **locoregional staging (T and N staging)** of esophageal carcinoma. Its high-frequency transducer allows for detailed visualization of the individual layers of the esophageal wall, making it superior to CT and MRI for determining the depth of tumor invasion (T-stage) and identifying periesophageal lymphadenopathy (N-stage). * **Why Esophagus is the Correct Answer:** In **Carcinoma of the Esophagus**, EUS is the most accurate modality to differentiate between T1, T2, and T3 lesions. This is critical for clinical decision-making, specifically in determining whether a patient is a candidate for primary surgery or requires neoadjuvant chemoradiotherapy. * **Why other options are incorrect:** * **Carcinoma of the Colon:** Conventional colonoscopy and CT/MRI are preferred. EUS is technically difficult in the proximal colon and is primarily reserved for **Rectal Cancer** (Endorectal US). * **Carcinoma of the Stomach:** While EUS is used, CT is often the initial staging tool for distant metastasis. EUS is less accurate here than in the esophagus due to the larger lumen and gastric folds. * **Carcinoma of the Head of Pancreas:** EUS is excellent for biopsy (EUS-FNA) and detecting small tumors, but **Contrast-Enhanced CT (CECT) - Pancreatic Protocol** is the primary modality for staging and assessing vascular resectability. **High-Yield NEET-PG Pearls:** * **T-Staging:** EUS is the most sensitive tool for T-staging in esophageal and rectal cancers. * **M-Staging:** EUS is **not** used for distant metastasis (M-stage); PET-CT or CECT is required. * **EUS-FNA:** It is the investigation of choice for tissue diagnosis of pancreatic masses and mediastinal lymph nodes.

Question 127: Ultrasonogram is not useful in which of the following conditions?

A. Distal common bile duct stones (Correct Answer)
B. Breast cyst
C. Ascites
D. Full bladder

Explanation: **Explanation:** The correct answer is **Distal common bile duct (CBD) stones**. **1. Why Distal CBD stones?** Ultrasound (USG) is the initial investigation of choice for the biliary tree; however, its sensitivity significantly decreases in the **distal (intrapancreatic) portion of the CBD**. This is primarily due to **overlying bowel gas** from the duodenum and stomach, which reflects sound waves and creates acoustic shadowing, obscuring the view. While USG is excellent at detecting proximal ductal dilation, it often misses the specific causative stone in the distal segment. For this reason, **Endoscopic Ultrasound (EUS)** or **MRCP** are the gold standards for visualizing distal CBD pathology. **2. Analysis of Incorrect Options:** * **Breast Cyst:** USG is the definitive tool to differentiate between solid and cystic breast masses. Cysts appear as well-defined, anechoic (black) structures with posterior acoustic enhancement. * **Ascites:** USG is highly sensitive and can detect as little as **5–10 mL** of peritoneal fluid. It is the standard procedure for identifying and marking fluid for paracentesis. * **Full Bladder:** A distended bladder acts as an **"acoustic window,"** displacing gas-filled bowel loops and allowing the ultrasound beam to travel through fluid to visualize pelvic organs like the uterus, ovaries, and prostate. **Clinical Pearls for NEET-PG:** * **IOC (Investigation of Choice)** for Gallstones/Cholelithiasis: Ultrasound. * **Gold Standard** for CBD stones: ERCP (Therapeutic) or MRCP (Diagnostic). * **Acoustic Shadowing:** Seen behind dense structures (stones/calcification). * **Acoustic Enhancement:** Seen behind fluid-filled structures (cysts/bladder).

Question 128: Transesophageal echocardiography is useful in which of the following conditions?

A. Sinus venosus type of atrial septal defect
B. Dissection of the arch of aorta
C. Prosthetic valve endocarditis
D. All of the above (Correct Answer)

Explanation: **Explanation:** Transesophageal Echocardiography (TEE) provides superior resolution compared to Transthoracic Echocardiography (TTE) because the transducer is positioned in the esophagus, directly behind the heart, eliminating interference from the chest wall, ribs, and lungs. * **Sinus Venosus ASD:** This defect is located high in the atrial septum near the entry of the Superior Vena Cava. Due to its posterior location, it is often missed or poorly visualized on TTE. TEE is the gold standard for diagnosing sinus venosus defects and associated anomalous pulmonary venous drainage. * **Dissection of the Arch of Aorta:** TEE is highly sensitive and specific for aortic dissections, particularly in the ascending aorta and the arch. It is often preferred in hemodynamically unstable patients as it can be performed at the bedside. * **Prosthetic Valve Endocarditis:** Prosthetic valves create "acoustic shadowing" on TTE, making it difficult to see small vegetations or perivalvular abscesses. TEE allows a clear view from the posterior aspect, making it the investigation of choice for suspected prosthetic valve complications. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** TEE is the most sensitive test for detecting **Left Atrial Appendage (LAA) thrombi** before cardioversion. * **Best for Posterior Structures:** TEE is superior for evaluating the left atrium, mitral valve, and thoracic aorta. * **Contraindications:** The main contraindications are esophageal pathologies (e.g., strictures, varices, or perforation). * **Intraoperative Use:** TEE is routinely used during cardiac surgeries to monitor real-time valve function and ventricular wall motion.

Question 129: Which study of the fetus in the first trimester carries the least radiation hazard?

A. X-ray abdomen
B. Pelvimetry
C. CT scan
D. Ultrasound (Correct Answer)

Explanation: **Explanation:** The correct answer is **Ultrasound**. **Why Ultrasound is correct:** Ultrasound is the imaging modality of choice in pregnancy because it is **non-ionizing**. It utilizes high-frequency sound waves to produce images, which does not cause DNA damage or cell ionization. Therefore, it carries **zero radiation hazard** to the developing fetus, making it safe for routine screening in the first trimester (e.g., for dating, viability, and Nuchal Translucency scans). **Why the other options are incorrect:** * **X-ray Abdomen & Pelvimetry:** Both involve **ionizing radiation**. The first trimester is the period of organogenesis, where the fetus is most sensitive to radiation. Exposure can lead to teratogenesis, growth retardation, or increased risk of childhood leukemia. Pelvimetry, specifically, involves high-dose pelvic X-rays and is now largely obsolete due to radiation concerns. * **CT Scan:** This involves the **highest dose** of ionizing radiation among the options. A CT of the abdomen/pelvis can deliver a significant radiation dose (often >10 mGy) to the fetus, which is avoided in the first trimester unless there is a life-threatening maternal indication. **NEET-PG High-Yield Pearls:** * **Safe Modalities in Pregnancy:** Ultrasound and MRI (MRI is generally avoided in the 1st trimester unless essential, but it is non-ionizing). * **Threshold for Teratogenicity:** Radiation doses **<50 mGy** (5 rad) are generally not associated with an increased risk of fetal anomalies or pregnancy loss. * **Most Sensitive Period:** The fetus is most sensitive to CNS effects (microcephaly, intellectual disability) between **8–15 weeks** of gestation. * **ALARA Principle:** Always follow "As Low As Reasonably Achievable" when using radiation in clinical practice.

Question 130: What is the best marker for gestational age in the second trimester?

A. Biparietal diameter (Correct Answer)
B. Head circumference
C. Crown-rump length (CRL)
D. Femur length

Explanation: **Explanation:** The determination of gestational age (GA) via ultrasound relies on different parameters depending on the trimester. In the **second trimester (13–26 weeks)**, the **Biparietal Diameter (BPD)** is considered the most classic and reliable single marker for dating, with an accuracy of ±7–10 days. It is measured at the level of the thalami and cavum septum pellucidum. While Head Circumference (HC) is also highly accurate, BPD remains the traditional gold standard for this specific period in most standardized examinations. **Analysis of Options:** * **B. Head Circumference (HC):** While HC is less affected by head shape (like dolichocephaly or brachycephaly) than BPD, BPD is historically the preferred answer for "best marker" in the second trimester for exam purposes. * **C. Crown-Rump Length (CRL):** This is the **most accurate** method for dating a pregnancy overall, but it is only used in the **first trimester** (up to 13 weeks 6 days). After this, the fetus begins to curl, making CRL measurements inaccurate. * **D. Femur Length (FL):** This is a reliable marker used in the second and third trimesters, but it is generally considered slightly less accurate than head measurements for dating unless there is cranial pathology. **High-Yield Clinical Pearls for NEET-PG:** * **Best overall predictor of GA:** Crown-Rump Length (CRL) in the 1st Trimester (Accuracy: ±3–5 days). * **Best marker in 3rd Trimester:** Femur Length (FL) is often preferred as BPD accuracy falls to ±3 weeks due to biological variation. * **Composite GA:** Using a combination of BPD, HC, AC (Abdominal Circumference), and FL is more accurate than any single parameter. * **Abdominal Circumference:** The best predictor of **fetal weight** and growth (IUGR/Macrosomia), but the poorest predictor of gestational age.

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Small Parts Ultrasonography

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Musculoskeletal Ultrasonography

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Vascular Ultrasonography

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Ultrasound — MCQs

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