Congenital malformations of the gut
How the embryonic gut tube is divided, hollowed out, rotated, given its nerves and opened at its lower end, and how a failure at each step causes oesophageal atresia, duodenal atresia, malrotation, Meckel and Hirschsprung disease or an anorectal malformation.
By the end, you can
- Describe how the primitive gut forms and is shaped by septation, recanalisation, rotation, neural crest migration and division of the cloaca.
- Relate oesophageal atresia, duodenal atresia, malrotation, Meckel diverticulum, Hirschsprung disease and anorectal malformations each to the developmental step that failed.
- Explain why pyloric stenosis appears weeks after birth and how its vomiting causes a hypochloraemic, hypokalaemic metabolic alkalosis.
- Explain how the level of an obstruction decides polyhydramnios, the timing and colour of vomiting, distension and the passage of meconium.
- Recognise the classic signs, imaging and biopsy findings of each malformation, and explain how surgical correction restores the mechanism that failed.
What it is
Congenital malformations of the gut are structural defects of the digestive tube present at or soon after birth. Most are errors of one developmental process: separation of the trachea from the oesophagus, recanalisation of the duodenum, rotation of the midgut, closure of the vitelline duct, migration of neural crest cells into the gut wall, or division of the cloaca. Most present as obstruction in the newborn; some (malrotation, Meckel diverticulum, short-segment Hirschsprung disease) can stay silent for years.
5 types to tell apart
- Atresia, stenosis and web
- A segment is interrupted, narrowed or crossed by a membrane: oesophageal, duodenal, jejunal or ileal atresia, and anal atresia.
- Fistula
- An abnormal channel between two tubes that should be separate: trachea and oesophagus, or rectum and urinary or genital tract.
- Malposition and remnants
- The midgut fails to rotate and fix normally (malrotation), or an embryonic structure persists (Meckel diverticulum).
- Innervation defect
- Neural crest cells fail to reach the end of the bowel, leaving an aganglionic segment that cannot relax (Hirschsprung disease).
- Muscle hypertrophy after birth
- Pyloric stenosis: the pyloric muscle thickens in the first weeks of life in a predisposed infant, rather than forming abnormally in the embryo.
US spelling: oesophagus → esophagus, coeliac → celiac.
Normal function
Building the gut tube
In the fourth week the flat embryonic disc folds, and the lining the yolk sac is drawn inside to form the primitive gut, a tube from the mouth to the cloaca. Its lining and glands come from endoderm; its muscle and connective tissue come from the wrapped round it. Its blood supply, from branches of the (later one aorta), divides it into the foregut (to the middle of the duodenum: coeliac trunk), the midgut (to two-thirds of the way along the transverse colon: superior mesenteric artery) and the hindgut (to the upper anal canal: inferior mesenteric artery).
The tube is then shaped by the processes that build every organ. A bud grows from the foregut and is split off as the trachea (septation). The lining of the duodenum proliferates until it plugs the lumen, then hollows out again (recanalisation). The midgut grows so fast that it loops out into the umbilical cord, rotates round the superior mesenteric artery and returns. The vitelline duct linking the midgut to the yolk sac closes, and the cloaca at the tail end is divided into the rectum and the urinary tract.
Meanwhile cells, which arise beside the closing neural tube, migrate into the gut wall from the top downwards and become the neurons of the myenteric and submucosal plexuses. Each process has its own window, mostly between weeks 4 and 12, and each can fail in its own way.
Underlying change · Step 1 of 6
Oesophageal atresia and tracheo-oesophageal fistula
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 6
Blocked outlet: pyloric stenosis and duodenal atresia
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 3 of 6
Midgut rotation, malrotation and Meckel diverticulum
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 4 of 6
Hirschsprung disease: nerve cells that never arrive
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 5 of 6
Anorectal malformations: dividing the cloaca
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 6 of 6
How the level of the block shapes the picture
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 6 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .