Congenital Anatomical Anomalies
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Direct answer
A newborn who chokes and coughs on the first feed, drooling excessively, with a coiled nasogastric tube on the chest film and a history of polyhydramnios, has oesophageal atresia with distal tracheo-oesophageal fistula — the commonest variant, Gross type C, of the anomaly the examination reaches for first. The whole congenital anatomy syllabus is a set of such recognisable stem-plus-signature pictures: the double bubble of duodenal atresia in a Down syndrome infant, the scaphoid abdomen and bowel sounds in the chest of Bochdalek hernia, the midline cyst that moves on tongue protrusion of thyroglossal origin, and the bilious vomiting of midgut volvulus that is a surgical emergency within hours. Behind each sits a named embryological failure — non-closure, non-recanalisation, non-descent or non-fusion — and matching the picture to the failure is the skill tested.
What you must remember
- Neural tube defects: failure of closure by about day 26 to 28 — anencephaly with elevated maternal alpha-fetoprotein and polyhydramnios; spina bifida spectrum from occulta through meningocele to myelomeningocele, the last associated with Chiari II and hydrocephalus; periconceptional folic acid (400 micrograms, 4 mg after an affected pregnancy) is preventive.
- Head and neck: cleft lip from failure of fusion of the medial nasal and maxillary processes; cleft palate from failure of palatine shelf fusion by week 12; thyroglossal cyst moves on tongue protrusion (Sistrunk's operation); branchial cyst of second-cleft origin along sternocleidomastoid's anterior border.
- Tracheo-oesophageal fistula: type C — proximal oesophageal atresia with distal fistula — is the commonest; polyhydramnios antenatally, frothy saliva, choking on first feed, coil of the tube at T3–T4; associated with VACTERL.
- Congenital diaphragmatic hernia: left posterolateral Bochdalek defect commonest — respiratory distress at birth, scaphoid abdomen, mediastinal shift, and pulmonary hypoplasia that determines survival; Morgagni defects are small, anterior and right-sided.
- Gut anomalies: duodenal atresia (failure of recanalisation, double bubble, strong Down association); annular pancreas encircling D2; malrotation with volvulus — bilious vomiting in a neonate, the Ladd procedure; Meckel's diverticulum by the rule of twos — about 2 per cent prevalence, 2 feet from the ileocaecal valve, 2 inches long, ectopic gastric or pancreatic tissue in a minority; Hirschsprung disease — aganglionosis from failed neural crest migration, delayed meconium passage, diagnosed by suction rectal biopsy.
- Genitourinary: bilateral renal agenesis — Potter sequence of oligohydramnios, limb deformities and pulmonary hypoplasia; horseshoe kidney trapped below the inferior mesenteric artery during ascent; hypospadias — foreskin is preserved for repair, so no circumcision; undescended testis — orchiopexy within the first year or two to preserve fertility and allow examination.
- Cardiac anchoring: ventricular septal defect is the commonest congenital heart defect; tetralogy of Fallot is the commonest cyanotic defect after the neonatal period; transposition presents with cyanosis in the first day and is duct-dependent.
A newborn who chokes on the first feed
Walk the type C scenario from antenatal clinic to theatre. The obstetric scan shows polyhydramnios because the fetus cannot swallow and absorb amniotic fluid through a blocked oesophagus. At birth the baby drools frothy saliva; the first feed produces coughing, choking and cyanosis as milk floods the fistula-connected airway. A 10 Fr catheter passed through the nose arrests at about 10 to 12 cm, and the radiograph shows the coil at the upper mediastinum with gas in the stomach and bowel — the distal fistula lets swallowed air down. Management follows the anatomy: suction of the upper pouch, head-up nursing, nothing by mouth, and referral for repair — ligation of the fistula and primary anastomosis of the oesophageal ends. Contrast the mimics: an H-type fistula presents later with recurrent pneumonias and choking on feeds, and pure atresia without fistula gives a gasless abdomen. The same pattern-reading orders the region: bilious vomiting means malrotation until excluded; projectile non-bilious vomiting at three weeks is hypertrophic pyloric stenosis.
Association questions
The screening paper pairs anomaly with association rather than asking for definitions. The Down syndrome stem expects duodenal atresia or endocardial cushion defects; the VACTERL acronym is offered against a TEF with vertebral and renal anomalies; the oligohydramnios stem expects Potter sequence; the polyhydramnios list expects TEF or anencephaly. Two traps recur: offering circumcision in hypospadias, where the foreskin is the repair material, and mislabelling the midline cyst that moves on tongue protrusion.
Frequently asked questions
Which is the commonest type of tracheo-oesophageal fistula?
Gross type C — oesophageal atresia with a distal tracheo-oesophageal fistula — comprising the large majority of cases.
What is the double bubble sign?
Dilation of the stomach and proximal duodenum on a neonatal radiograph, indicating duodenal atresia, which is strongly associated with Down syndrome.
Why does a thyroglossal cyst move on tongue protrusion?
Because it remains attached to the foramen caecum by the persisting thyroglossal tract, so protrusion of the tongue elevates the cyst — the sign that distinguishes it from a dermoid or branchial cyst.
How do gastroschisis and omphalocele differ?
Gastroschisis is a right paraumbilical wall defect with free, uncovered bowel and few associated anomalies, whereas omphalocele is a midline defect covered by a sac and linked to chromosomal and cardiac defects.
Why is circumcision avoided in hypospadias?
The foreskin is used to reconstruct the urethra during repair, so it must be preserved until the definitive operation.