PU Fetal Anomaly Detection 1 — Questions and Answers
Question 1: What ultrasound finding is the hallmark of anencephaly?
- Absent cranial vault above the orbits (Correct answer)
- Enlarged head
- Fluid-filled brain
- Choroid plexus cysts
Correct answer: Absent cranial vault above the orbits
Anencephaly is characterized by complete absence of the cranial vault and cerebral hemispheres above the orbits, resulting in a 'frog-eye' appearance on ultrasound.
Question 2: What is the lemon sign associated with?
- Spina bifida/open neural tube defect (Correct answer)
- Anencephaly
- Hydrocephalus
- Holoprosencephaly
Correct answer: Spina bifida/open neural tube defect
The lemon sign refers to scalloping of the frontal bones giving the skull a lemon shape and is a classic second-trimester marker for open spina bifida.
Question 3: A double bubble sign on fetal ultrasound is diagnostic of which condition?
- Duodenal atresia (Correct answer)
- Esophageal atresia
- Gastroschisis
- Omphalocele
Correct answer: Duodenal atresia
The double bubble sign represents the dilated stomach and proximal duodenum separated by the pylorus, which is pathognomonic for duodenal atresia.
Question 4: What is gastroschisis?
- A defect in the abdominal wall to the right of the umbilicus with herniated bowel (Correct answer)
- A covered midline abdominal wall defect containing liver
- A defect with a membrane covering the organs
- Herniation of organs through the umbilical cord
Correct answer: A defect in the abdominal wall to the right of the umbilicus with herniated bowel
Gastroschisis is a paraumbilical abdominal wall defect, usually to the right of the cord, through which bowel herniates freely without a covering membrane.
Question 5: Which marker on second-trimester ultrasound is associated with Down syndrome (Trisomy 21)?
- Absent or hypoplastic nasal bone (Correct answer)
- Enlarged cerebellum
- Thick corpus callosum
- Large thymus
Correct answer: Absent or hypoplastic nasal bone
An absent or hypoplastic nasal bone is one of the soft markers for Down syndrome identified on second-trimester ultrasound.
Question 6: What is the banana sign in fetal ultrasound?
- Curved shape of the cerebellum due to hindbrain herniation in spina bifida (Correct answer)
- Bent femur appearance
- Curved spine in scoliosis
- Banana-shaped kidney
Correct answer: Curved shape of the cerebellum due to hindbrain herniation in spina bifida
The banana sign describes the abnormal curved shape of the cerebellum caused by caudal displacement of the hindbrain through the foramen magnum (Chiari II malformation) in open spina bifida.
PU Fetal Anomaly Detection 1
What ultrasound finding is the hallmark of anencephaly?