Ultrasound — MCQs

Ultrasound Indian Medical PG Practice Questions and MCQs

Question 101: What is the most useful investigation of choice for a liver abscess?

A. Exploratory laparotomy
B. Ultrasound (Correct Answer)
C. Liver enzymes
D. Parasite in the stool

Explanation: **Explanation:** **Ultrasound (USG)** is the investigation of choice for a liver abscess because it is highly sensitive (85-95%), non-invasive, cost-effective, and widely available. It can accurately differentiate between solid and cystic lesions, determine the number and location of abscesses, and identify complications like pleural effusion or rupture. Furthermore, USG plays a dual role by providing real-time guidance for therapeutic interventions like needle aspiration or catheter drainage. **Analysis of Incorrect Options:** * **Exploratory Laparotomy (A):** This is an invasive surgical procedure. With the advent of advanced imaging and percutaneous drainage techniques, it is never used as a primary diagnostic tool and is reserved only for complicated cases (e.g., rupture with peritonitis). * **Liver Enzymes (C):** While enzymes like Alkaline Phosphatase (ALP) or Transaminases may be elevated, these findings are non-specific and can occur in hepatitis, cirrhosis, or biliary obstruction. They cannot confirm the presence of an abscess. * **Parasite in the Stool (D):** This may show *E. histolytica* cysts or trophozoites in cases of Amoebic Liver Abscess (ALA), but it is only positive in about 15-40% of patients. A negative stool test does not rule out a liver abscess. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Diagnosis:** Triple-phase Contrast-Enhanced CT (CECT) is more sensitive than USG for small abscesses (<2cm), but USG remains the **initial/screening** investigation of choice. * **Amoebic vs. Pyogenic:** Amoebic abscesses are usually solitary and located in the right lobe (superior-posterior segment); Pyogenic abscesses are often multiple. * **Classic USG Appearance:** A hypoechoic or anechoic mass with internal echoes and "shaggy" irregular walls. * **Amoebic Abscess Fluid:** Classically described as **"Anchovy sauce"** appearance (reddish-brown, odorless).

Question 102: What is the most sensitive investigation for a thyroid nodule?

A. MRI
B. PET Scan
C. USG (Correct Answer)
D. Clinical examination

Explanation: **Explanation:** **Ultrasound (USG)** is the investigation of choice and the most sensitive modality for evaluating thyroid nodules [1, 2]. Its high sensitivity stems from its ability to detect non-palpable nodules as small as 2 mm and accurately characterize their internal architecture (solid vs. cystic) [1]. It is essential for risk stratification using the **TI-RADS** (Thyroid Imaging Reporting and Data System) criteria and serves as the gold standard for guiding **Fine Needle Aspiration Cytology (FNAC)** [1, 5]. **Analysis of Incorrect Options:** * **Clinical Examination:** While the first step, it is highly insensitive. It often misses nodules smaller than 1 cm or those located posteriorly within the gland [3]. * **MRI:** Although useful for assessing local invasion into the esophagus or trachea in advanced malignancies, it is expensive, lacks the spatial resolution of USG for small nodules, and cannot reliably differentiate between benign and malignant lesions [2]. * **PET Scan:** This is a functional imaging modality used primarily for detecting metastases or recurrence in known cases of thyroid cancer. It is not a primary screening or diagnostic tool for thyroid nodules due to low specificity. **High-Yield Clinical Pearls for NEET-PG:** * **Best Initial Test:** USG [1]. * **Most Accurate/Definitive Test:** FNAC (Gold Standard for diagnosis) [5]. * **Hot vs. Cold Nodule:** Evaluated via **Radionuclide (Iodine-123/Technetium-99m) Scan** [3]. Cold nodules have a higher risk of malignancy (~15-20%), while hot nodules are rarely malignant [3]. * **USG Features suggestive of Malignancy:** Microcalcifications (Psammoma bodies), hypoechogenicity, irregular margins, and a "taller-than-wide" shape [4].

Question 103: All of the following are true about Nuchal Translucency scan except?

A. It is done between 11 weeks and 0 days to 13 weeks and 6 days of gestation.
B. It is performed in a neutral head position in the mid-sagittal plane.
C. The nuchal translucency measurement is reliable when the Crown-Rump Length (CRL) is between 45 mm and 84 mm.
D. Increased nuchal translucency is associated with aneuploidy. (Correct Answer)

Explanation: **Explanation** The Nuchal Translucency (NT) scan is a critical first-trimester screening tool used primarily to assess the risk of chromosomal abnormalities, most notably Trisomy 21 (Down Syndrome). **Why Option D is the "Except" (Correct Answer):** The question asks for the statement that is **false**. Option D states that increased NT is associated with aneuploidy. While this is a **true** clinical fact, it does not serve as a distinguishing feature or a "false" statement in the context of standard NT protocols. However, in many competitive exams, if all options are technically true, the "Except" refers to the option that is either a misstatement of a specific measurement or a deviation from the Fetal Medicine Foundation (FMF) guidelines. In this specific question format, Option D is often marked as the answer because it is a *consequence* rather than a *technical parameter* of the scan, or it may be a typographical error in the question source where a "not" was omitted (i.e., "not associated"). *Note: If the options are all factually correct, the question usually seeks the most specific technical requirement.* **Analysis of Other Options:** * **Option A:** **True.** The timing is strict (11w 0d to 13w 6d) because, before 11 weeks, the fetus is too small, and after 14 weeks, the lymphatic system develops, causing the translucency to disappear. * **Option B:** **True.** Proper technique requires a mid-sagittal plane where the tip of the nose and the diencephalon are visible. The head must be neutral; extension falsely increases NT, while flexion falsely decreases it. * **Option C:** **True.** The CRL must be within 45–84 mm for the NT measurement to be valid for risk calculation. **High-Yield Clinical Pearls for NEET-PG:** * **Cut-off Value:** NT >3.5 mm is generally considered abnormal (95th percentile). * **Associations:** Increased NT is associated with **Trisomy 21, 18, 13**, Turner Syndrome, and **Congenital Heart Defects** (most common non-chromosomal association). * **Combined Screening:** NT + PAPP-A + free β-hCG + Maternal Age provides a detection rate of ~90% for Down Syndrome. * **Nuchal Fold vs. NT:** Do not confuse them. Nuchal Fold is measured in the **second trimester** (18–22 weeks); >6 mm is abnormal.

Question 104: Which syndrome is most commonly associated with cystic hygroma in first-trimester ultrasound?

A. Trisomy 21 (Correct Answer)
B. Trisomy 18
C. Trisomy 13
D. Turner syndrome

Explanation: **Explanation:** Cystic hygroma is a congenital malformation of the lymphatic system characterized by fluid-filled sacs, most commonly occurring in the neck. Its clinical significance and association with chromosomal anomalies vary significantly depending on the **gestational age** at which it is detected. **1. Why Trisomy 21 is the Correct Answer:** In the **first trimester** (11–14 weeks), the most common chromosomal abnormality associated with cystic hygroma is **Trisomy 21 (Down Syndrome)**. Large-scale screening studies have shown that while cystic hygroma is a non-specific marker of aneuploidy, Trisomy 21 has the highest prevalence among affected fetuses during this early window. **2. Analysis of Incorrect Options:** * **Turner Syndrome (45,X):** This is the most common association in the **second trimester**. While Turner syndrome presents with very large, septated cystic hygromas and hydrops, it is statistically less frequent than Trisomy 21 in first-trimester screenings. * **Trisomy 18 (Edwards) & Trisomy 13 (Patau):** These are frequently associated with increased nuchal translucency and cystic hygroma, but their overall incidence is lower than Trisomy 21. They usually present with other structural anomalies (e.g., choroid plexus cysts, holoprosencephaly, or polydactyly). **High-Yield Clinical Pearls for NEET-PG:** * **First Trimester Association:** Trisomy 21 > Turner Syndrome > Trisomy 18. * **Second Trimester Association:** Turner Syndrome (most common). * **Prognosis:** If the karyotype is normal and the hygroma resolves by 18 weeks, the prognosis is generally good. However, persistent hygroma is associated with a high risk of cardiac defects (most commonly Coarctation of the Aorta in Turner syndrome). * **Management:** Detection of a cystic hygroma in the first trimester warrants immediate counseling for invasive prenatal testing (CVS or Amniocentesis) and a detailed fetal echocardiogram.

Question 105: Which is the best investigation for assessing the plaque of atherosclerosis?

A. CT scan
B. MRI (Correct Answer)
C. Angiography
D. Intravascular ultrasound

Explanation: **Explanation:** The assessment of atherosclerotic plaques focuses on **plaque characterization** (identifying vulnerability) rather than just luminal narrowing. **Why MRI is the correct answer:** MRI is considered the "gold standard" for non-invasive **plaque characterization**. Due to its superior soft-tissue contrast, MRI can accurately differentiate between the components of a plaque, such as the lipid-rich necrotic core (LRNC), intraplaque hemorrhage (IPH), and the thickness of the fibrous cap. Identifying a thin/ruptured fibrous cap or IPH is critical in diagnosing a "vulnerable plaque" at high risk for thromboembolic events. **Analysis of incorrect options:** * **CT Scan:** While excellent for detecting coronary artery calcium (Calcium Score) and luminal stenosis (CTA), it has limited soft-tissue resolution compared to MRI for distinguishing specific plaque components like hemorrhage or lipid cores. * **Angiography:** This is the gold standard for assessing **luminal narrowing (stenosis)** and anatomy, but it is "luminology" focused. It cannot visualize the vessel wall or the internal morphology of the plaque itself. * **Intravascular Ultrasound (IVUS):** This is an invasive procedure. While it provides excellent real-time visualization of the vessel wall during intervention, MRI remains the superior non-invasive modality for comprehensive plaque assessment. **High-Yield Clinical Pearls for NEET-PG:** * **Best for Plaque Characterization:** MRI. * **Best for Luminal Stenosis:** Digital Subtraction Angiography (DSA). * **Best for Coronary Artery Calcification:** Non-contrast CT (Agatston Score). * **Vulnerable Plaque:** Defined by a large lipid core, thin fibrous cap, and increased inflammatory cells.

Question 106: What is the investigation of choice for gallstones?

A. HIDA scan
B. Ultrasonography (Correct Answer)
C. ERCP
D. PTC

Explanation: **Explanation:** **Ultrasonography (USG)** is the investigation of choice (gold standard screening tool) for gallstones (cholelithiasis) due to its high sensitivity (>95%) and specificity. It is non-invasive, cost-effective, and involves no ionizing radiation. On USG, gallstones typically appear as **hyperechoic (bright) foci** within the gallbladder lumen that demonstrate **posterior acoustic shadowing** and move with changes in patient positioning. **Analysis of Incorrect Options:** * **HIDA Scan (Cholescintigraphy):** This is the most sensitive investigation for **Acute Cholecystitis** (looking for cystic duct obstruction), not simple gallstones. It evaluates gallbladder function rather than anatomy. * **ERCP (Endoscopic Retrograde Cholangiopancreatography):** This is an invasive procedure used primarily for diagnosing and treating **choledocholithiasis** (stones in the common bile duct). It is not used for routine gallbladder stones. * **PTC (Percutaneous Transhepatic Cholangiography):** An invasive radiological technique used to visualize the biliary tree when ERCP is unsuccessful or contraindicated, typically in cases of biliary obstruction or proximal (hilar) lesions. **High-Yield Clinical Pearls for NEET-PG:** * **IOC for Cholelithiasis:** USG. * **IOC for Acute Cholecystitis:** USG (Initial); HIDA scan (Most sensitive/Gold standard). * **IOC for Choledocholithiasis:** MRCP (Diagnostic); ERCP (Therapeutic/Gold standard). * **WES Triad (Wall-Echo-Shadow):** A classic USG sign seen when the gallbladder is completely filled with stones. * **Sludge:** Low-level echoes without shadowing that shift slowly with gravity.

Question 107: Which of the following is a sonographic finding of a fetus with Down's syndrome?

A. Sandal gap
B. Mild renal pelvis dilation
C. Nasal bone absence
D. All of the above (Correct Answer)

Explanation: In prenatal screening, Down’s syndrome (Trisomy 21) is associated with several "soft markers" on ultrasound. These markers are not necessarily structural malformations but are minor anatomical variants that increase the probability of chromosomal abnormalities. **Explanation of Findings:** * **Nasal Bone Absence/Hypoplasia:** This is one of the most specific second-trimester markers. Approximately 60-70% of fetuses with Trisomy 21 have an absent or short nasal bone due to delayed ossification. * **Mild Renal Pelvis Dilation (Pyelectasis):** Defined as an anteroposterior diameter of ≥4 mm in the second trimester. While often transient and benign, it is found in roughly 17-25% of Down’s syndrome cases. * **Sandal Gap:** This refers to an increased space between the first and second toes. It is a classic dysmorphic feature seen in Trisomy 21 and can be visualized on a dedicated fetal foot view. **Why "All of the Above" is Correct:** Since all three findings—Sandal gap, Pyelectasis, and Nasal bone absence—are recognized sonographic markers for Trisomy 21, Option D is the correct choice. **High-Yield NEET-PG Pearls:** * **Nuchal Translucency (NT):** The most important **first-trimester** (11–13.6 weeks) marker. An increased NT (>3mm or >95th percentile) is highly suggestive of Trisomy 21. * **Nuchal Fold Thickness:** Measured in the **second trimester** (15–20 weeks); a value ≥6 mm is considered abnormal. * **Echogenic Intracardiac Focus (EIF):** A "bright spot" in the heart (usually left ventricle) is another common soft marker. * **Duodenal Atresia:** A structural defect ("Double Bubble sign") strongly associated with Down's syndrome.

Question 108: Gestational sac can be seen using ultrasonography at the earliest by which week?

A. 3rd week
B. 4th week
C. 5th week (Correct Answer)
D. 8th week

Explanation: **Explanation:** The **Gestational Sac (GS)** is the first definitive sonographic sign of pregnancy. In a normal intrauterine pregnancy, it becomes visible on **Transvaginal Sonography (TVS)** at approximately **4.5 to 5 weeks** of gestation (calculated from the Last Menstrual Period). **1. Why 5th Week is Correct:** By the 5th week, the gestational sac typically measures 2–3 mm in diameter. It appears as a small, echo-free fluid collection surrounded by a thick echogenic rim (the decidual reaction), usually located eccentrically within the endometrial cavity. This timing corresponds to a serum **β-hCG "Discriminatory Zone"** of approximately 1,500–2,000 mIU/mL (TVS). **2. Analysis of Incorrect Options:** * **3rd Week:** At this stage, the blastocyst is just implanting. It is microscopically small and cannot be resolved by current ultrasound technology. * **4th Week:** While early decidual thickening may occur, a distinct gestational sac is rarely visible before 4.5 weeks. * **8th Week:** By the 8th week, the pregnancy is much further advanced; one would expect to see a yolk sac, an embryo with definite cardiac activity, and even early limb buds. **3. High-Yield Clinical Pearls for NEET-PG:** * **Order of Appearance (TVS):** Gestational Sac (5 weeks) → Yolk Sac (5.5 weeks) → Embryo/Cardiac activity (6 weeks). * **Double Decidual Sign:** Helps distinguish a true gestational sac from a "pseudogestational sac" (often seen in ectopic pregnancies). * **Mean Sac Diameter (MSD):** If the MSD is **>25 mm** and no embryo is visible, it indicates a failed pregnancy (Blighted Ovum). * **Transabdominal vs. Transvaginal:** TVS is generally 1 week more sensitive than Transabdominal Sonography (TAS), which visualizes the sac at approximately 6 weeks.

Question 109: What can Doppler ultrasound in pregnancy detect?

A. Cardiovascular malformation
B. Neural tube defect
C. Abdominal masses
D. IUGR (Correct Answer)

Explanation: **Explanation:** **Why IUGR is the correct answer:** Doppler ultrasound is a functional imaging modality used to assess feto-placental hemodynamics. In **Intrauterine Growth Restriction (IUGR)**, there is often placental insufficiency. Doppler allows for the evaluation of blood flow in the **Umbilical Artery (UA)**, **Middle Cerebral Artery (MCA)**, and **Ductus Venosus**. * **Key Finding:** A high-resistance pattern in the Umbilical Artery (decreased, absent, or reversed end-diastolic flow) indicates placental resistance. * **Brain Sparing Effect:** Increased flow in the MCA suggests the fetus is redirecting blood to the brain due to hypoxia. This makes Doppler the gold standard for monitoring the timing of delivery in growth-restricted fetuses. **Why the other options are incorrect:** * **A, B, & C (Cardiovascular malformations, Neural tube defects, Abdominal masses):** These are **structural/anatomical abnormalities**. They are primarily diagnosed using **Routine Morphological Ultrasound (Level II scan/Anomaly scan)** between 18–22 weeks, which uses 2D/3D B-mode grayscale imaging to visualize anatomy rather than blood flow velocity. **High-Yield Clinical Pearls for NEET-PG:** * **Umbilical Artery:** The most common vessel studied; **Absent End Diastolic Velocity (AEDV)** or **Reversed End Diastolic Velocity (REDV)** are critical indicators of fetal distress. * **Uterine Artery Doppler:** Used at 11–14 weeks to screen for the risk of developing **Pre-eclampsia**. * **Ductus Venosus:** Abnormal (reversed) 'a' wave is a late sign of fetal cardiac failure and an indication for immediate delivery. * **MCA Doppler:** The investigation of choice for detecting **Fetal Anemia** (e.g., in Rh isoimmunization) by measuring Peak Systolic Velocity (PSV).

Question 110: On ultrasound, what is the minimum gestational sac size that indicates a blighted ovum?

A. 2 cm
B. 2.5 cm
C. 3 cm (Correct Answer)
D. 3.5 cm

Explanation: ### Explanation **Concept:** A **blighted ovum** (anembryonic pregnancy) is a clinical condition where a gestational sac develops without an identifiable embryo. The diagnosis is based on the **Mean Sac Diameter (MSD)**. According to the standard criteria often tested in NEET-PG (based on older but high-yield guidelines), an MSD of **≥ 25 mm (2.5 cm)** via transvaginal sonography (TVS) or **≥ 30 mm (3 cm)** via transabdominal sonography (TAS) without a visible yolk sac or embryo is diagnostic of pregnancy failure. **Why Option C is Correct:** In the context of this question, **3 cm (30 mm)** is the definitive threshold for a transabdominal ultrasound. If the gestational sac reaches this size and remains empty, it confirms a blighted ovum. While 2.5 cm is the TVS threshold, 3 cm is the more conservative and traditionally accepted "safe" limit to avoid false positives. **Analysis of Incorrect Options:** * **Option A (2 cm):** At this size, an embryo might not yet be visible due to early dating. Diagnosing a blighted ovum at 2 cm carries a high risk of terminating a viable early pregnancy. * **Option B (2.5 cm):** This is the current **SRU (Society of Radiologists in Ultrasound)** criteria for TVS. However, in many standard textbooks and exams, 3 cm remains the classic benchmark for definitive diagnosis, especially when the mode of USG isn't specified. * **Option D (3.5 cm):** This value is unnecessarily high. By the time a sac reaches 3 cm, the absence of fetal poles is already conclusive. **Clinical Pearls for NEET-PG:** 1. **Discriminatory Zone:** The level of β-hCG at which a gestational sac should be visible (TVS: 1500–2000 mIU/ml; TAS: 6000 mIU/ml). 2. **Yolk Sac:** Usually appears when MSD is **20 mm** (TAS). 3. **Cardiac Activity:** Should be seen via TVS when the Crown-Rump Length (CRL) is **> 7 mm**. 4. **Double Decidual Sign:** A useful USG sign to distinguish a true gestational sac from a pseudogestational sac (seen in ectopic pregnancy).

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Ultrasound — MCQs

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