Abnormalities Arising From Abnormal Embryological Development ✅ Flashcards
What abnormalities of the GI tract can result from abnormal embryological development?
- Duodenal atresia or stenosis
- Exomphalos
- Gastroschisis
- Meckel’s diverticulum
- Midgut malrotation
- Meconium ileus
- Duplication cysts
- Hirschsprung’s disease
- Anorectal abnormalities
- Intussusception
Where in the GI tract can atresia occur?
At any point
Are GI atresias single or multiple?
Can be either
Are atresias complete or incomplete?
Can be either
What is the most common site of GI atresia?
The duodenum
What is the incidence of duodenal atresia?
1 in 10,000-30,000 live births
Where do most duodenal atresias occur?
At the ampulla of Vater
What can cause a duodenal atresia?
Either a complete mucosal membrane or a blind-ending proximal loop, probably due to failure of canalisation of the duodenum after the 7th week
What causes failure of canalisation of the duodenum after the 7th week?
Ischaemia
What % of cases of duodenal atresia have associated abnormalities?
50%
Give 2 abnormalities that may be associated with duodenal atresia?
- Down’s syndrome
- Prader-Willi syndrome
How might duodenal atresia present?
- Antenatal presentation with polyhydraminos or ‘double bubble’ on ultrasound scan
- Bilious vomiting, usually immediately after first feed
What is the incidence of exomphalos?
1 in 3000
What is exomphalos?
A midline defect of the anterior abdominal wall, where some of the organs line outside of the abdominal cavity
What are the organs encased in in exomphalos?
A membranous sac derived from the amniotic membrane
What organs are contained within the sac in exomphalos?
Vary, but can include stomach, intestine, liver, and spleen
What is the defect classified based on in exomphalos?
Size
What are the classifications of exomphalos?
- Major (>4cm)
- Minor (<4cm)
What is exomphalos frequently associated with?
- Other congenital abnormalities, such as trisomy 13, 18, and 21
- Associated structural problems such as cardiac abnormalities
What % of cases of exomphalos are associated with other structural problems?
75%
When is exomphalos usually identified?
Antenatal scanning
What is the management of exomphalos?
Surgical correction
Do babies born with exomphalos need emergency surgery?
Generally not an emergency providing the intra-abdominal structures are well perfused (but depends on size of defect and if sac remains in tact)
What is the incidence of gastroschisis?
4 per 10,000
What are the risk factors for gastroschisis?
- Low maternal age
- Drug misuse
- Low socioeconomic status
- Smoking
- Ethnic origin
What happens in gastroschisis?
The abdominal muscles are normal, but the stomach and intestines herniate through the anterior abdominal wall on the right-hand side of the umbilicus
What is often associated with gastroschisis?
Atresia
In what % of cases are there atresias associated with gastroschisis?
Up to 10%
What causes atresias in gastroschisis?
Ischaemia
Are other congenital anomalies usually present with gastroschisis?
No
What causes gastroschisis?
Spontaneous herniation of the intra-abdominal wall in utero, or from incomplete reduction of the abdominal contents during rotation during the first weeks of life
What is the site of herniation through intra-abdominal wall in gastroschisis?
Possibly at the site of the right omphalomesenteric artery
What is the difference between gastroschisis and exomphalos?
In gastroschisis, the abdominal contents are not exposed to amniotic fluid
What is the result of the organs not being exposed to amniotic fluid in gastroschisis?
Causes serositis with matting together of the intestines
What might be required if there is matting together of the intestines with gastroschisis?
May need resection after birth
What is the risk of intrauterine death with gastroschisis?
15%
Why is the risk of intrauterine death high in gastroschisis?
Due to ischaemia
What is the result of the high risk of intrauterine death in gastroschisis?
Serial antenatal ultrasound scans are recommended
How are babies with gastroschisis delivered?
Can be vaginal or operative, but should take place in a specialist paediatric surgical centre
What is done after birth in gastroschisis?
A protective membrane is placed over the eviscerated abdominal contents to prevent them from drying out, and urgent surgery is usually required to close the defect
Is primary or secondary closure used in gastroschisis?
Can be either
When will secondary closure of gastroschisis be done?
If the defect is too large to replace all the contents in one stage without causing respiratory compromise from splinting of the diaphragm
What may be used to preserve the intestinal contents when complete closure of gastroschisis is awaited?
A silo
Why does it often take time for feeding to be established in gastroschisis?
Due to poor intestinal mobility
What may be required due to difficulties in establishing feeding in gastroschisis?
A prolonged course of parenteral nutrition
What is the overall survival of gastroschisis?
90%
How common is Meckel’s diverticulum?
2-4% of newborn infants
What causes Meckel’s diverticulum?
The remnant of the omphalomesenteric duct does not fully regress and remains attached to the ileal mucosa
What kind of mucosa is present in a Meckel’s diverticulum?
Gastric
What is the result of a Meckel’s diverticulum containing gastric mucosa?
It produces acid
How can Meckel’s diverticulum be detected?
Using a technetium-99m scan
What is the sensitivity of a technetium-99m scan at detecting Meckel’s diverticulum?
85%
What is the specificity of a technetium-99m scan at detecting Meckel’s diverticulum?
95%
How can Meckel’s diverticulum present?
- Lower GI bleeding
- Intussusception
- Small bowel volvulus
Is Meckel’s diverticulum always symptomatic?
No, it may never cause problems, depending on the size of the sac
How is symptomatic Meckel’s diverticulum managed?
Surgical resection
What can failure of the omphalomesenteric duct to regress rarely result in?
An intestinal fistula
How might an intestinal fistula present?
Umbilical discharge
What does an intestinal fistula appear similar to?
An umbilical granuloma
How can an intestinal fistula be differentiated from an umbilical granuloma?
In an intestinal fistula, it is possible for a catheter to be inserted
How is an intestinal fistula managed?
Surgical resection
What is midgut malrotation?
When the intestine lies in an abnormal position within the peritoneal cavity
What is the risk with midgut malrotation?
There is a risk of torsion (volvulus) around the superior mesenteric artery axis
What causes malrotation?
Incomplete rotation of the gut contents during the first 11 weeks of embryogenesis
What is the most common defect in midgut malrotation?
The duodenum lies to the right of the vertebral column instead of the left, with the caecum lying in the upper abdomen to the left of the duodenum.
What forms in the most common defect in midgut malrotation?
Bands of peritoneum (Ladd’s bands)
Where do Ladd’s bands form?
They pass from the caecum, across the duodenum, to the posterior abdominal wall
What might Ladd’s bands cause?
Extrinsic obstruction of the duodenum
What can obstruction of the duodenum caused by Ladd’s bands in midgut malrotation cause?
Bilious vomiting, usually in infancy
What complication might arise in midgut malrotation?
Midgut volvulus and ischaemia
Why is there an increased risk of midgut volvulus and ischaemia in midgut malrotation?
As a result of the malrotation, the midgut has a short attachment to the base of the superior mesenteric artery, and so may twist clockwise around this pedicel, resulting in ischaemia
When should midgut volvulus be suspected?
In any child with bilious vomiting
Why is it important to consider midgut volvulus in any child with bilious vomiting?
As the ischaemia could potentially be reversed if the Ladd’s bands are divided and the pressure from the arterial supply to the midgut is relieved
How might children with midgut malrotation present?
Subacute symptoms of intermittent abdominal pain and vomiting
What is the investigation of choice in midgut malrotation?
Barium meal
Why is a barium meal the investigation of choice in midgut malrotation?
As it can show the position of the duodenal-jejunal flexible
Why is the true incidence of midgut malrotation unknown?
Because there are probably individuals with undiagnosed malrotation who have never had any problems
When will children with midgut malrotation not have any problems?
If the pedicle is long enough
What causes meconium ileus?
Pancreatic insufficiency
How does pancreatic insufficiency cause meconium ileus?
It causes the distal ileum to become impacted with thick, viscous meconium
What is meconium ileus associated with in most cases?
Cystic fibrosis
What % of newly diagnosed children with CF develop meconium ileus?
20%
What are duplication cysts?
Congenital cysts attached to the gastrointestinal tract
Where do gastrointestinal cysts occur?
Can occur anywhere in the GI tract between mouth and anus, but are most commonly found in ileocaecal region
What is the histological nature of a duplication cyst related to?
The adjoining structure
How might duplication cysts present?
As abdominal mass or obstruction
How are duplication cysts managed?
When problems occur, surgical excision is required
What is the problem in Hirschsprung’s disease?
There is an absence of ganglion cells in a variable segment of the bowel (aganglionosis)
What is the incidence of Hirschsprung’s disease?
1 in 5000 live births
What gender is Hirschsprung’s disease more common in?
Boys
What site is affected in Hirschsprung’s disease?
The sigmoid and rectum are the most commonly affected sites, although the whole colon and, very rarely, the entire large and small bowel can be affected
What does the lack of ganglion cells cause in Hirschsprung’s disease?
Inability of the bowel to relax, resulting in functional bowel obstruction
When should Hirschsprung’s disease be suspected?
In infants who have not passed meconium in the first 48 hours of life, or in infants who present with bowel obstruction
What examination feature is suspicious of Hirschsprung’s disease?
Dramatic decompression on DRE (‘explosive diarrhoea’)
What measures should be taken in DRE in infants?
Should be performed by a senior doctor, and limited to only one examination when possible
How is a diagnosis of Hirschsprung disease confirmed?
Rectal biopsy to confirm absence of ganglion cells
What kind of biopsy is used to confirm Hirschsprung disease in younger children?
Suction rectal biopsy
What kind of biopsy is used to confirm Hirschsprung’s disease in older children?
Strip rectal biopsy
How is Hirschsprung’s disease managed?
Surgery to remove aganglionic section of bowel
What is one of the major complications of Hirschsprung’s disease surgery?
Enterocolitis
How does enterocolitis following Hirschsprung’s disease surgery present?
- Malaise
- Fever
- Diarrhoea
- Generalised sepsis
What causes enterocolitis after Hirschsprung’s disease surgery?
The pathophysiology is incompletely understood, but thought to be due to gastrointestinal stasis, altered gut flora, and impaired mucosal immunity
What is the incidence of anorectal anomalies?
1 in 2500 births
What is the pathophysiological of anorectal anomalies?
Poorly understood, but thought to be due to failure of the breakdown of tissue at the caudal end of the GI tract in week 3 of gestation
When are anorectal anomalies most commonly identified?
On routine postnatal check
What % of infants with anorectal anomalies have other congenital abnormalities of the GI or GU tract?
60%
What congenital abnormalities might accompany anorectal anomalies in boys?
Fistula to urethra
What congenital abnormality may accompany anorectal anomalies in girls?
Vestibule adjacent to vagina
What should be considered in infants presenting with anorectal anomalies?
Other anomalies, such as VACTERL
Is Intussusception considered an embryological abnormality?
Not classically
Can intussusception occur in the presence of a structurally normal gut?
Yes
Why is intussusception associated with congenital abnormalities of the GI tract?
Even minor gut abnormalities, such as a polyp or Meckel’s diverticulum, may predispose a child to this condition
What is intussusception?
When one section of the intestine invaginate into another section
What complication can intussusception result in?
Obstruction
Where in the bowel does intussusception occur?
Most common site is ileo-caecal junction, but can occur at other sites if there is a lead point (e.g. polyp or Meckel’s diverticulum)
How do patients with intussusception usually present?
- Acute onset abdominal pain
- Drawing up of legs
- Pallor
- Redcurrant jelly stool
What is the limitation of redcurrant jelly stool as a sign of intussusception?
It is a late sign
How is intussusception diagnosed?
Ultrasound
What is found on US in intussusception?
Target-shaped mass
How is intussusception managed?
Aim to reduce with air enema, but surgical reduction may be required
