Ultrasound — MCQs

Ultrasound Indian Medical PG Practice Questions and MCQs

Question 21: Plethoric, non-collapsible IVC on echocardiography denotes?

A. Budd-Chiari syndrome
B. Hepatic venous malformation
C. Right heart failure (Correct Answer)
D. IVC thrombosis

Explanation: **Explanation:** The Inferior Vena Cava (IVC) serves as a reliable surrogate for measuring **Central Venous Pressure (CVP)** and right-sided heart function. In a healthy individual, the IVC diameter decreases by >50% during inspiration (the "sniff test") due to the negative intrathoracic pressure drawing blood into the right atrium. **Why Right Heart Failure is correct:** In **Right Heart Failure**, the heart cannot effectively pump blood forward, leading to a "backlog" of pressure in the venous system. This results in a **plethoric** (dilated, usually >2.1 cm) and **non-collapsible** IVC (collapse <50%). This lack of respiratory variation indicates high CVP and fluid overload. **Analysis of Incorrect Options:** * **Budd-Chiari Syndrome:** This involves obstruction of hepatic venous outflow. While it may cause IVC narrowing or membranes, it typically leads to hepatomegaly and ascites rather than generalized IVC plethora unless the obstruction is at the level of the suprahepatic IVC. * **Hepatic Venous Malformation:** These are localized vascular anomalies and do not typically cause systemic venous congestion or alter IVC respiratory dynamics. * **IVC Thrombosis:** While a thrombus can distend the vessel locally, it usually presents with intraluminal echoes (the clot itself) and distal venous engorgement, rather than the classic "plethoric" appearance associated with systemic heart failure. **High-Yield Clinical Pearls for NEET-PG:** * **IVC Index:** (Max diameter - Min diameter) / Max diameter. An index **<50%** suggests high CVP (>10-15 mmHg). * **Shock Assessment:** A small, hyper-collapsible IVC ("kissing walls") is a hallmark of **hypovolemic shock**. * **Point-of-Care Ultrasound (POCUS):** The IVC is best visualized in the subxiphoid long-axis view.

Question 22: The TRIANGULAR CORD Sign is seen in which condition?

A. Caroli's Disease
B. Serous Cystadenoma
C. Biliary Atresia (Correct Answer)
D. Hydatid of Liver

Explanation: **Explanation:** The **Triangular Cord Sign** is a pathognomonic ultrasonographic finding for **Biliary Atresia**. It represents a cone-shaped or triangular fibrotic mass of the cranial part of the extrahepatic biliary tree. On ultrasound, it appears as an echogenic (hyper-echoic) area located anterior to the bifurcation of the portal vein. A thickness of **>4 mm** is considered a positive sign and is highly specific for diagnosing biliary atresia in a neonate with conjugated jaundice. **Analysis of Options:** * **Biliary Atresia (Correct):** Characterized by the obliteration of the extrahepatic biliary tree. Other USG findings include a small/absent gallbladder (Ghost Gallbladder sign) and the absence of a common bile duct. * **Caroli’s Disease:** A congenital disorder characterized by multifocal segmental dilatation of large intrahepatic bile ducts. The classic radiological sign is the **"Central Dot Sign"** (portal vein branches surrounded by dilated bile ducts). * **Serous Cystadenoma:** A benign pancreatic neoplasm. On imaging, it typically shows a **"Sunburst" calcification** or a honeycomb appearance, not related to the biliary cord. * **Hydatid of Liver:** Caused by *Echinococcus granulosus*. Key USG findings include the **"Water Lily Sign"** (detached endocyst) or the presence of daughter cysts. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Intraoperative Cholangiogram (IOC). * **Surgery of Choice:** Kasai Procedure (Hepatoportoenterostomy), ideally performed before 60 days of life. * **Most Common Cause:** Biliary atresia is the most common cause of neonatal cholestasis requiring surgery. * **Associated Sign:** The "Ghost Gallbladder" sign (length <19 mm, irregular contour).

Question 23: Color Doppler study can evaluate the following EXCEPT?

A. Direction of blood flow
B. Velocity of blood flow
C. Impedance index
D. Intravascular pressure (Correct Answer)

Explanation: **Explanation:** Color Doppler ultrasound is a non-invasive imaging technique based on the **Doppler Effect**, which detects the shift in frequency of sound waves reflected off moving red blood cells. **Why Option D is the Correct Answer:** Color Doppler **cannot directly measure intravascular pressure**. While Doppler can measure the velocity of blood flow, pressure is a hemodynamic parameter that usually requires invasive catheterization (manometry) or indirect calculation using the Bernoulli equation (commonly used in Echocardiography, but not a direct measurement of the Doppler signal itself). **Analysis of Incorrect Options:** * **A. Direction of blood flow:** This is the primary function of Color Doppler. By convention, flow toward the transducer is encoded in **Red**, and flow away from the transducer is encoded in **Blue** (BART: Blue Away, Red Toward). * **B. Velocity of blood flow:** Doppler measures the frequency shift, which is directly proportional to the velocity of the moving blood cells. Spectral Doppler provides precise quantitative velocity measurements. * **C. Impedance index:** Also known as the **Resistive Index (RI)** or Pulsatility Index (PI). These are calculated ratios derived from velocity waveforms (Systolic vs. Diastolic velocities) to assess the resistance to blood flow in a vessel. **High-Yield Clinical Pearls for NEET-PG:** * **Power Doppler:** More sensitive than Color Doppler for detecting slow flow (e.g., in torsion or inflammation) but does **not** show direction or velocity. * **Duplex Scanning:** Refers to the simultaneous use of B-mode (grayscale) imaging and Doppler ultrasound. * **Aliasing Artifact:** Occurs when the blood velocity exceeds the Nyquist limit (1/2 of the Pulse Repetition Frequency), causing the color to "wrap around" and appear as the opposite direction.

Question 24: What is the recommended frequency range for transvaginal ultrasound for obstetric purposes?

A. 3 - 5 MHz
B. 5 - 7.5 MHz (Correct Answer)
C. 7.5 - 20 MHz
D. > 20 MHz

Explanation: **Explanation:** The choice of ultrasound frequency involves a fundamental trade-off between **resolution** and **penetration**. Higher frequencies provide superior image resolution but have poor depth penetration, while lower frequencies penetrate deeper at the cost of image clarity. * **Option B (5 – 7.5 MHz) is Correct:** Transvaginal ultrasound (TVS) utilizes a probe placed in close proximity to the pelvic organs (uterus and ovaries). Because the distance to the target tissue is minimal, high penetration is not required. Therefore, a higher frequency range of **5 – 7.5 MHz** is used to achieve the high-resolution images necessary for early pregnancy detection, such as identifying a gestational sac or fetal cardiac activity. **Analysis of Incorrect Options:** * **Option A (3 – 5 MHz):** This is the standard frequency for **Transabdominal Ultrasound (TAS)**. It is lower because the sound waves must penetrate through the abdominal wall and a full bladder to reach the pelvic organs. * **Option C (7.5 – 20 MHz):** These very high frequencies are reserved for **superficial structures** with minimal depth, such as the thyroid, breast, testes, or musculoskeletal imaging. * **Option D (> 20 MHz):** These frequencies are used in specialized applications like **Intravascular Ultrasound (IVUS)** or high-resolution ophthalmic imaging. **High-Yield Clinical Pearls for NEET-PG:** * **Early Pregnancy:** TVS can detect a gestational sac as early as **4.5 to 5 weeks**, whereas TAS typically requires **5.5 to 6 weeks**. * **Discriminatory Zone:** The β-hCG level at which a gestational sac should be visible is **1,500–2,000 mIU/mL** for TVS and **>6,500 mIU/mL** for TAS. * **Yolk Sac:** The first structure to appear within the gestational sac; its presence confirms an intrauterine pregnancy.

Question 25: Which of the following statements about transvaginal ultrasound is incorrect?

A. The bladder should be full. (Correct Answer)
B. The bladder should be empty.
C. Informed consent is mandatory.
D. None of the above.

Explanation: **Explanation:** In gynecological imaging, the state of the urinary bladder is a critical factor for image quality. For **Transabdominal Ultrasound (TAS)**, a **full bladder** is required because it acts as an acoustic window, pushing the gas-filled bowel loops out of the pelvis and providing a clear view of the uterus and ovaries. However, for **Transvaginal Ultrasound (TVS)**, the **bladder should be empty**. A full bladder during TVS is counterproductive as it pushes the pelvic organs away from the high-frequency vaginal probe, thereby decreasing the resolution and causing patient discomfort during probe manipulation. **Analysis of Options:** * **Option A (Correct):** This statement is **incorrect**. As established, TVS requires an empty bladder to bring the pelvic organs into the focal zone of the transducer. * **Option B:** This is a **correct** statement. Emptying the bladder improves the proximity of the probe to the target organs (uterus/adnexa). * **Option C:** This is a **correct** statement. Since TVS is an invasive procedure involving the insertion of a probe into the vaginal canal, obtaining informed consent (and often having a female chaperone present) is a mandatory medico-legal and ethical requirement. **High-Yield Clinical Pearls for NEET-PG:** * **TVS vs. TAS:** TVS uses higher frequency probes (5–9 MHz) compared to TAS (3–5 MHz), offering superior spatial resolution but less depth of penetration. * **Early Pregnancy:** TVS can detect a gestational sac as early as **4.5 to 5 weeks**, which is about 1 week earlier than TAS. * **Discriminatory Zone:** The β-hCG level at which a gestational sac should be visible on TVS is typically **1,500–2,000 mIU/mL**. * **Contraindication:** TVS is generally avoided in patients with an intact hymen (virgins) or if there is active heavy vaginal bleeding/premature rupture of membranes (relative).

Question 26: What is the characteristic radiological feature of pneumothorax on ultrasound?

A. Lung sliding sign
B. Sea shore sign
C. B lines
D. Stratosphere sign (Correct Answer)

Explanation: In ultrasound imaging of the lung, the diagnosis of pneumothorax relies on the absence of normal pleural movement. **Correct Answer: D. Stratosphere sign** In a normal lung, the visceral and parietal pleura slide against each other, creating a dynamic "shimmering" effect. In M-mode, this appears as the **Sea-shore sign** (motionless tissues above the pleura look like waves, while moving lung below looks like sand). In a **pneumothorax**, air separates the pleural layers, preventing the ultrasound beam from reaching the moving lung. This results in a series of static, horizontal parallel lines across the entire screen, resembling a barcode or the layers of the atmosphere. Hence, it is called the **Stratosphere sign** (or Barcode sign). **Explanation of Incorrect Options:** * **A. Lung sliding sign:** This is a normal finding. Its presence effectively rules out a pneumothorax at that specific location. * **B. Sea shore sign:** This is the normal M-mode appearance of a healthy, sliding lung. * **C. B lines:** Also known as "comet-tail artifacts," these are vertical hyperechoic lines originating from the pleural line. They indicate fluid in the interstitium. Their presence **rules out** pneumothorax because they require contact between the two pleural layers to form. **High-Yield Clinical Pearls for NEET-PG:** 1. **Lung Point Sign:** This is the most specific ultrasound sign for pneumothorax (100% specificity). It represents the physical transition point where the collapsed lung intermittently contacts the chest wall. 2. **E-FAST:** Ultrasound is more sensitive than a supine Chest X-ray for detecting a traumatic pneumothorax. 3. **Rule of Thumb:** If you see **Lung Sliding** or **B-lines**, you can 100% exclude a pneumothorax at that point.

Question 27: What is the investigation of choice for minimal ascites?

A. X-ray
B. Ultrasound (USG) (Correct Answer)
C. CT scan
D. MRI scan

Explanation: **Explanation:** **Ultrasound (USG)** is the investigation of choice for minimal ascites because of its high sensitivity and non-invasive nature. It can detect as little as **5–10 mL** of peritoneal fluid, typically first appearing in the **Pouch of Douglas** (in females) or the **rectovesical pouch** (in males). USG is preferred over other modalities due to its bedside availability, lack of ionizing radiation, and ability to guide diagnostic paracentesis. **Analysis of Options:** * **X-ray (A):** This is the least sensitive method. Ascites only becomes visible on a plain radiograph (as "ground-glass" opacification or bulging flanks) when the volume exceeds **500–1000 mL**. * **CT Scan (C):** While CT is highly sensitive and can detect small amounts of fluid (approx. 30 mL), it is not the *first-line* investigation due to high cost, radiation exposure, and the need for transport to a radiology suite. It is usually reserved for characterizing the cause of ascites (e.g., malignancy). * **MRI (D):** MRI is excellent for soft tissue characterization but is unnecessary, expensive, and time-consuming for the simple detection of fluid. **Clinical Pearls for NEET-PG:** * **Earliest site of fluid collection:** In a supine patient, fluid first collects in **Morison’s Pouch** (hepatorenal space). * **Physical Exam:** "Shifting dullness" requires at least **500 mL** of fluid, while "Fluid thrill" requires **1500–2000 mL**. * **FAST Scan:** Focused Assessment with Sonography for Trauma is used in emergencies to detect hemoperitoneum (blood in the peritoneal cavity).

Question 28: Match the following ultrasound probe types with their typical frequency ranges (in MHz): 1. Linear probe 2. Endoscopic probe 3. Curvilinear probe 4. Endocavitatory probe A. 7-10 MHz B. 3-5 MHz C. 10-12 MHz D. 20 MHz

A. 1-A, 2-D, 3-C, 4-B
B. 1-C, 2-A, 3-B, 4-D
C. 1-D, 2-C, 3-A, 4-B (Correct Answer)
D. 1-C, 2-B, 3-D, 4-A

Explanation: The core principle of ultrasound physics is the **inverse relationship between frequency and penetration**: High-frequency probes provide superior resolution but poor depth (used for superficial structures), while low-frequency probes provide deep penetration with lower resolution (used for deep organs). ### **Correct Match Explanation:** 1. **Linear Probe (10–12 MHz):** Used for superficial structures like the thyroid, breast, scrotum, and musculoskeletal system. High frequency is required for fine detail. 2. **Endoscopic Probe (20 MHz):** These are used during Endoscopic Ultrasound (EUS) to visualize the layers of the gut wall or adjacent small structures. They require extremely high frequency for microscopic resolution. 3. **Curvilinear Probe (3–5 MHz):** The standard probe for abdominal and obstetric scans. Low frequency is essential to penetrate deep into the peritoneal cavity. 4. **Endocavitatory Probe (7–10 MHz):** Used for Transvaginal (TVS) or Transrectal (TRUS) scans. Since the probe is physically closer to the pelvic organs than a transabdominal probe, a mid-to-high frequency is used to balance resolution and depth. ### **Why Other Options are Incorrect:** * **Option A & B:** These incorrectly assign low frequencies (3-5 MHz) to linear or endoscopic probes, which would result in poor image quality for superficial/intraluminal structures. * **Option D:** Incorrectly matches the Curvilinear probe with 20 MHz; a 20 MHz beam cannot penetrate the abdominal wall to visualize the liver or a fetus. ### **High-Yield Clinical Pearls for NEET-PG:** * **Phased Array Probe:** Uses 1–5 MHz; it has a small footprint, making it ideal for **Echocardiography** (scanning between ribs). * **Resolution vs. Penetration:** Always remember: ↑ Frequency = ↑ Resolution but ↓ Penetration. * **Piezoelectric Effect:** The fundamental principle of USG where crystals (usually Lead Zirconate Titanate - PZT) convert electrical energy into mechanical sound waves.

Question 29: Gestational sac is seen on transvaginal sonography as early as:

A. 18 days from LMP
B. 21 days from LMP
C. 35 days from LMP (Correct Answer)
D. 42 days from LMP

Explanation: **Explanation:** The visualization of pregnancy on ultrasound follows a predictable chronological sequence based on the **Last Menstrual Period (LMP)**. 1. **Why Option C is Correct:** The **Gestational Sac (GS)** is the first definitive sign of pregnancy seen on ultrasound. On **Transvaginal Sonography (TVS)**, it typically becomes visible at **4.5 to 5 weeks (32–35 days)** of gestation. At this stage, it appears as a small, eccentric fluid collection within the endometrium (the "intradecidual sign"). By 35 days, the mean sac diameter is approximately 2–5 mm. 2. **Why Other Options are Incorrect:** * **Options A & B (18 and 21 days):** These represent the 3rd week of gestation. At this point, implantation has only just occurred or is occurring. The blastocyst is microscopic and cannot be resolved by current ultrasound technology. * **Option D (42 days):** This corresponds to 6 weeks. While the GS is easily seen here, it is no longer the "earliest" finding. By 42 days, one should expect to see the **Yolk Sac** (appears at 5.5 weeks) and often the **Fetal Pole with cardiac activity** (appears by 6 weeks). **High-Yield NEET-PG Pearls:** * **TVS vs. TAS:** TVS can detect pregnancy landmarks approximately **1 week earlier** than Transabdominal Sonography (TAS). * **Discriminatory Zone:** This is the level of serum β-hCG at which a gestational sac should be visible. For TVS, it is generally **1,500–2,000 mIU/mL**. * **Order of Appearance (TVS):** 1. Gestational Sac (4.5–5 weeks) 2. Yolk Sac (5.5 weeks) – *First reliable sign of intrauterine pregnancy.* 3. Embryo/Cardiac activity (6 weeks). * **Double Decidual Sign:** Helps distinguish a true gestational sac from a pseudogestational sac (seen in ectopic pregnancy).

Question 30: Ultrasound is done in the 1st trimester for all except:

A. Multiple pregnancy
B. Fetal anomalies
C. To estimate gestational age
D. To know the position of the placenta (Correct Answer)

Explanation: ### Explanation The primary goal of a first-trimester ultrasound (performed before 13 weeks 6 days) is to confirm viability, establish accurate dating, and determine chronicity in multiple gestations. **Why Option D is the Correct Answer:** In the first trimester, the placenta is not yet fully formed; instead, we see the **decidua capsularis and basalis**. More importantly, the lower uterine segment has not yet developed. As the uterus grows, the placenta appears to "move" away from the internal os—a phenomenon known as **placental migration**. Therefore, diagnosing the definitive position of the placenta (to rule out Placenta Previa) is only clinically reliable in the **second and third trimesters** (typically after 18–20 weeks). **Analysis of Incorrect Options:** * **A. Multiple pregnancy:** The first trimester is the "Gold Standard" time to determine **chorionicity** (e.g., identifying the T-sign or Lambda sign), which is crucial for managing twin pregnancies. * **B. Fetal anomalies:** While the detailed anatomy scan occurs at 18–20 weeks, major structural anomalies (like Anencephaly) and chromosomal markers (like **Nuchal Translucency**) are assessed between 11–13.6 weeks. * **C. To estimate gestational age:** The **Crown-Rump Length (CRL)** measured in the first trimester is the most accurate parameter for dating a pregnancy (error margin of ±3–5 days). **High-Yield Clinical Pearls for NEET-PG:** * **Most accurate measurement for dating:** CRL (1st Trimester). * **First sign of pregnancy on USG:** Gestational sac (at ~4.5–5 weeks). * **First sign of intrauterine pregnancy:** Yolk sac (at ~5–5.5 weeks). * **Placental Migration:** Occurs due to the differential growth of the lower uterine segment; 90% of "low-lying" placentas identified early will resolve by term.

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Ultrasound — MCQs

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