Ultrasound Practice Questions

Q: Ultrasound diagnoses all the following except?

Down syndrome. **Explanation:** The correct answer is **Down Syndrome (Option B)** because ultrasound is a **screening tool**, not a definitive diagnostic tool, for chromosomal abnormalities. 1. **Why Down Syndrome is the correct answer:** While ultrasound can identify "soft markers" associated with Down syndrome (Trisomy 21)—such as increased **Nuchal Translucency (NT)** in the first trimester, an absent nasal bone, or cardiac defects—these findings are only suggestive. A definitive diagnosis requires **karyotyping** or chromosomal analysis via invasive procedures like Amniocentesis or Chorionic Villus Sampling (CVS). 2. **Why the other options are incorrect:** * **Anencephaly:** This is a structural neural tube defect characterized by the absence of the cranial vault and cerebral hemispheres (the "Frog-eye appearance"). It is easily diagnosed via ultrasound as early as 10–12 weeks. * **Placenta Previa:** Ultrasound is the **gold standard** for localizing the placenta. It can clearly visualize the relationship between the placental edge and the internal os of the cervix. * **Hydatidiform Mole:** Ultrasound is diagnostic for molar pregnancies, typically showing a characteristic **"Snowstorm appearance"** (a vesicular mass with multiple small cystic spaces) and the absence of a fetus in a complete mole. **High-Yield Clinical Pearls for NEET-PG:** * **Nuchal Translucency (NT):** Measured between 11 and 13+6 weeks. A value >3mm is highly suspicious for aneuploidy. * **Snowstorm Appearance:** Classic USG sign for Hydatidiform mole. * **Frog-eye/Mickey Mouse Appearance:** Classic USG sign for Anencephaly. * **Double Bubble Sign:** USG finding in Duodenal Atresia, often associated with Down Syndrome.

Q: What is the best investigation for diagnosing minimal right pleural effusion?

Ultrasound (USG). **Explanation:** The diagnosis of pleural effusion depends on the sensitivity of the imaging modality to detect small volumes of fluid. **Ultrasound (USG)** is the correct answer because it is highly sensitive and can detect as little as **5–20 mL** of pleural fluid. It is superior to conventional radiography for identifying minimal effusions, differentiating fluid from pleural thickening, and identifying loculations. **Analysis of Options:** * **A & D (Lateral Decubitus X-ray):** While more sensitive than an upright PA view (which requires ~200 mL to show costophrenic angle blunting), a lateral decubitus film still requires approximately **25–50 mL** of fluid to be visible. For a right-sided effusion, a **Right** lateral decubitus view is used (fluid layers down). * **B (CT Scan):** CT is the "gold standard" for characterizing pleural anatomy and can detect very small amounts of fluid (~10 mL). However, it is not considered the "best" initial investigation due to high radiation dose, cost, and lack of portability compared to USG. **High-Yield Pearls for NEET-PG:** 1. **Sensitivity Thresholds:** * **USG:** 5–20 mL (Most sensitive bedside tool). * **Lateral Decubitus X-ray:** 25–50 mL. * **Upright PA X-ray:** 175–200 mL (blunting of costophrenic angle). * **Lateral X-ray (Upright):** 75 mL (blunting of posterior costophrenic sulcus). 2. **USG Sign:** The "Quad sign" and "Sinusoid sign" are classic sonographic findings of pleural effusion. 3. **Clinical Utility:** USG is the investigation of choice for **guiding thoracocentesis**, significantly reducing the risk of iatrogenic pneumothorax.

Q: What is the single most sensitive marker of intrauterine growth restriction on ultrasonography?

Abdominal Circumference (AC). **Explanation:** **Abdominal Circumference (AC)** is the single most sensitive ultrasound parameter for diagnosing Intrauterine Growth Restriction (IUGR). The physiological basis lies in the fact that the fetal liver is the first organ to be affected by chronic placental insufficiency. IUGR leads to a depletion of fetal glycogen stores in the liver and a reduction in subcutaneous fat. Since the AC measurement primarily reflects the size of the liver and the thickness of the abdominal wall fat, it decreases significantly before other skeletal parameters are affected. **Analysis of Options:** * **Amniotic Fluid Index (AFI):** While oligohydramnios (low AFI) is a common association and a sign of fetal distress in IUGR, it is a non-specific marker and can occur due to various other causes (e.g., PROM, renal anomalies). * **Femur Length (FL) & Biparietal Diameter (BPD):** These are markers of skeletal growth. In "Asymmetrical IUGR" (the most common type), the fetus exhibits "brain-sparing," meaning the head and long bones continue to grow while the body remains small. Therefore, BPD and FL remain relatively preserved until the late stages of growth restriction. **Clinical Pearls for NEET-PG:** * **Most sensitive single parameter:** Abdominal Circumference (AC). * **Most sensitive ratio:** HC/AC ratio (Head Circumference/Abdominal Circumference). This ratio is elevated in asymmetrical IUGR. * **Earliest sign of IUGR on Doppler:** Increased resistance/pulsatility index in the **Umbilical Artery**. * **Gold Standard for Monitoring:** Umbilical Artery Doppler is the best tool for managing IUGR and deciding the timing of delivery.

Q: What is Doppler ultrasonography used for in twin pregnancies?

All of the above. **Explanation:** Doppler ultrasonography is a versatile tool in the management of multiple gestations, used for both diagnostic confirmation and hemodynamic monitoring. 1. **Twin-to-Twin Transfusion Syndrome (TTTS):** This is the most critical application. Doppler is used to assess the umbilical artery, ductus venosus, and middle cerebral artery (MCA) to monitor fetal distress and hemodynamic imbalance between the donor and recipient twins in monochorionic pregnancies. 2. **Conjoined Twins:** While B-mode ultrasound identifies the physical connection, Doppler is essential to evaluate shared vascular structures (e.g., shared hearts or hepatic vessels). This is crucial for surgical planning and determining viability. 3. **Diagnosis of Twins:** Color Doppler can be used early in pregnancy to identify separate fetal heartbeats and confirm the presence of multiple viable embryos, especially when B-mode imaging is ambiguous. **Why "All of the Above" is correct:** While Doppler is most famously associated with TTTS, its utility spans the entire spectrum of twin management—from initial confirmation of life to the complex anatomical assessment of conjoined twins. **High-Yield Clinical Pearls for NEET-PG:** * **TTTS Staging:** The **Quintero Staging System** uses Doppler findings (absent or reversed end-diastolic flow) to categorize the severity of TTTS. * **Twin Anemia Polycythemia Sequence (TAPS):** Diagnosed primarily using **MCA-PSV** (Peak Systolic Velocity) Doppler to detect discordant hemoglobin levels. * **TRAP Sequence:** Doppler is used to identify the "pump twin" and the retrograde flow in the "acardiac twin." * **Lambda vs. T-sign:** Remember that these are B-mode findings for chorionicity, but Doppler confirms the vascularity within the intervening membrane.

Q: Anencephaly is best diagnosed using which of the following methods?

Ultrasound (USG). **Explanation:** **Anencephaly** is a lethal neural tube defect (NTD) characterized by the absence of the cranial vault (acrania) and the cerebral hemispheres. **Why Ultrasound (USG) is the Correct Answer:** Ultrasound is the **gold standard and investigation of choice** for diagnosing anencephaly. It can reliably detect the condition as early as the late first trimester (11–14 weeks). The classic sonographic findings include the **"Frog-eye appearance"** (Mickey Mouse sign) due to prominent orbits and the absence of the calvarium above the level of the orbits. USG is preferred because it is non-invasive, provides real-time visualization, and has nearly 100% sensitivity for this condition after the first trimester. **Analysis of Incorrect Options:** * **Maternal Serum Alpha-Fetoprotein (MSAFP):** While MSAFP is a screening tool for NTDs (levels are elevated), it is not diagnostic. High levels require confirmation via ultrasound. * **Amniotic Fluid Alpha-Fetoprotein (AFAFP):** This is an invasive procedure (amniocentesis). While it shows elevated AFP and Acetylcholinesterase, it is rarely used for diagnosis today because USG provides a definitive diagnosis non-invasively. * **X-ray:** Historically used to show the absence of the skull vault, but it is now obsolete due to radiation risks to the fetus and the superior resolution of USG. **Clinical Pearls for NEET-PG:** * **Earliest Diagnosis:** Can be suspected at 10-14 weeks (Acrania-Anencephaly sequence). * **Associated Finding:** **Polyhydramnios** is common in the second trimester because the fetus lacks the swallowing reflex. * **Key Sign:** "Frog-eye" or "Mickey Mouse" appearance on coronal/axial views. * **Screening:** Elevated MSAFP (>2.5 MoM) is the first step in screening for open NTDs.

Q: What is the earliest detectable congenital malformation by ultrasound?

Anencephaly. **Explanation:** **Anencephaly** is the correct answer because it is a major neural tube defect characterized by the absence of the cranial vault and cerebral hemispheres. It can be reliably detected as early as **11 to 14 weeks** of gestation (late first trimester) during the routine nuchal translucency scan. The diagnosis is based on the **"Mickey Mouse sign"** (the appearance of prominent orbits without a surrounding calvarium) or the **"Frog-eye sign"** in the coronal view. Since the skull vault normally ossifies by 10–11 weeks, its absence is the earliest structural malformation visible on ultrasound. **Analysis of Incorrect Options:** * **Spina Bifida:** While it can sometimes be suspected in the late first trimester via indirect signs (like intracranial translucency), a definitive diagnosis usually requires a mid-trimester (18–22 weeks) anomaly scan to visualize the vertebral arch defect and secondary brain signs (Lemon/Banana signs). * **Meningocele:** Similar to spina bifida, this protrusion of meninges is typically diagnosed during the second-trimester anatomy survey when the fetal spine and skull are more developed. * **Cystic Hygroma:** Although it can be seen in the first trimester (associated with Turner syndrome), it is technically a lymphatic malformation/fluid collection rather than a primary structural "congenital malformation" of an organ system that predates the detection of anencephaly. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Sign:** Absence of the "calvarial echo." * **AFP Levels:** Anencephaly is associated with markedly **elevated Maternal Serum Alpha-Fetoprotein (MSAFP)**. * **Polyhydramnios:** Often occurs in the second/third trimester due to the fetus's inability to swallow amniotic fluid. * **Prevention:** Periconceptional **Folic Acid (400 mcg/day)** reduces the risk of neural tube defects by 70%.

Q: What is the most accurate method for estimating gestational age using ultrasonography?

Crown-rump length. **Explanation:** The **Crown-Rump Length (CRL)** is the most accurate parameter for estimating gestational age (GA) in the first trimester (specifically between 7 and 13 weeks). During this period, fetal growth is rapid and biological variation is minimal because growth is largely unaffected by external factors like placental insufficiency or genetic growth potential. The margin of error for CRL is only **±3 to 5 days**. **Analysis of Options:** * **Crown-Rump Length (CRL):** Correct. It is the gold standard for dating. Once the CRL exceeds 84 mm (approx. 14 weeks), its accuracy decreases, and second-trimester parameters must be used. * **Biparietal Diameter (BPD):** This is the most accurate parameter in the **second trimester** (up to 20 weeks), with an error margin of ±7 to 10 days. However, it is less accurate than CRL. * **Head Circumference (HC):** While a reliable predictor of GA in the second trimester and less affected by head shape (dolichocephaly/brachycephaly) than BPD, it still lacks the precision of first-trimester CRL. * **Abdominal Circumference (AC):** This is the **least accurate** parameter for dating as it is highly sensitive to fetal nutrition and growth restriction (IUGR). Its primary role is assessing fetal weight and growth rather than GA. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Sign of Pregnancy on USG:** Gestational Sac (seen at ~4.5–5 weeks). * **First Fetal Structure Visualized:** Yolk Sac (seen at ~5 weeks; confirms intrauterine pregnancy). * **Rule of Thumb:** If there is a discrepancy between LMP and USG dating, the **earliest ultrasound** (CRL) is always considered the most reliable for establishing the EDD. * **Mean Sac Diameter (MSD):** Used if the embryo is not yet visible; however, CRL is superior once the fetal pole appears.

Q: The diagnostic feature of congenital diaphragmatic hernia on prenatal ultrasonography is:

Peristalsis in the thoracic cavity. **Explanation:** Congenital Diaphragmatic Hernia (CDH) occurs due to the failure of the pleuroperitoneal membranes to fuse, most commonly on the left side (Bochdalek hernia). This allows abdominal viscera to herniate into the thoracic cavity. **Why Option C is correct:** The presence of **peristalsis in the thoracic cavity** is the most specific and pathognomonic sign of CDH on prenatal ultrasound. It directly visualizes the movement of bowel loops within the chest, confirming that abdominal contents have displaced into the thorax. **Analysis of Incorrect Options:** * **Option A:** While a fluid-filled stomach (which may look like a cyst) is often seen behind the left atrium, it is not as definitive as active peristalsis. Furthermore, the stomach is usually displaced **laterally** rather than directly behind the atrium. * **Option B:** CDH typically causes a significant **mediastinal shift** toward the contralateral side, but the **heart axis is usually abnormal** (levocardia or dextrocardia) due to compression by the herniated mass. * **Option D:** In CDH, the abdominal circumference is **abnormally small (scaphoid abdomen)** because the abdominal organs have migrated into the chest. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Left side (85%), through the **Foramen of Bochdalek** (Posterolateral). * **Key USG findings:** Herniated bowel/stomach in the chest, mediastinal shift, and **polyhydramnios** (due to esophageal compression). * **Prognostic indicator:** The **Lung-to-Head Ratio (LHR)** is used to predict pulmonary hypoplasia and postnatal survival. * **Associated Malformation:** Pulmonary hypoplasia and persistent pulmonary hypertension are the primary causes of postnatal mortality.

Question 1

Ultrasound diagnoses all the following except?

Accepted Answer

Down syndrome

Answer

Anencephaly

Answer

Placenta previa

Answer

Hydatidiform mole

Question 2

What is the best investigation for diagnosing minimal right pleural effusion?

Accepted Answer

Ultrasound (USG)

Answer

Right lateral decubitus X-ray

Answer

CT scan

Answer

Left lateral decubitus X-ray

Question 3

What is the single most sensitive marker of intrauterine growth restriction on ultrasonography?

Accepted Answer

Abdominal Circumference (AC)

Answer

Amniotic Fluid Index (AFI)

Answer

Femur Length (FL)

Answer

Biparietal Diameter (BPD)

Question 4

At what gestational week is accurate diagnosis of anencephaly typically seen on ultrasound?

Accepted Answer

14 weeks of gestation

Answer

6 weeks of gestation

Answer

8 weeks of gestation

Answer

10 weeks of gestation

Question 5

What is Doppler ultrasonography used for in twin pregnancies?

Accepted Answer

All of the above

Answer

Twin to twin transfusion

Answer

Conjoined twins

Answer

Diagnosis of twins

Question 6

Parallel shotgun appearance on Ultrasound is seen in which of the following conditions?

Accepted Answer

Obstructive jaundice

Answer

Portal hypertension

Answer

Biliary ascariasis

Answer

Sclerosing cholangitis

Question 7

Anencephaly is best diagnosed using which of the following methods?

Accepted Answer

Ultrasound (USG)

Answer

Maternal serum alpha-fetoprotein

Answer

Amniotic fluid alpha-fetoprotein

Answer

X-ray

Question 8

What is the earliest detectable congenital malformation by ultrasound?

Accepted Answer

Anencephaly

Answer

Spina bifida

Answer

Meningocele

Answer

Cystic hygroma

Question 9

What is the most accurate method for estimating gestational age using ultrasonography?

Accepted Answer

Crown-rump length

Answer

Head circumference

Answer

Abdominal circumference

Answer

Biparietal diameter

Question 10

The diagnostic feature of congenital diaphragmatic hernia on prenatal ultrasonography is:

Accepted Answer

Peristalsis in the thoracic cavity

Answer

A cyst behind the left atrium

Answer

Mediastinal shift with normal heart axis

Answer

Abnormally large abdominal circumference

Ultrasound — MCQs

Ultrasound — MCQs

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