CONGENITAL ABNORMALITIES OF THE INTESTINE Flashcards
What are the congenital abnormalities of the intestine?
Meckels diverticulum
Hirschsprung’s disease
Acquired megacolon
Intestinal malrotation
Gastroschisis and exomphalos
Imperforate anus
Omphalocele
Intestinal atresia
What is gastroschisis?
A congenital herniation of the bowel through the abdominal wall, usually just to the right of the umbilical cord.
What are risk factors for gastroschisis?
Young maternal age - <20 years old (16 fold higher incidence than women 25-29)
Maternal exposure to cigarette smoke
Maternal cocaine use
Mstrtnal COX inhibitor use e.g. aspirin
Environment exposure e.g. nitrosamines
Whats the proposed pathophysiology for gastroschisis?
The exact mechanism of gastroschisis is currently unknown.
It’s thought to be because of reduced blood supply to the abdominal wall
Genetic and environmental factors play a role
During embryonic folding, the lateral folds dont close all the way, leaving an opening in the abdominal wall
When does gastroschisis first present?
either visible at birth or detected early on prenatal ultrasound scans at 20 weeks
What are the clinical features of gastroschisis?
Abdominal organs are herniated outside the abdominal cavity through a full-thickness opening often found to the right of the umbilical cord. - commonly small intestine, large intestine, liver and stomach
No membrane covers abdominal contents
Intestines appear swollen, inflamed thickened and short
A thick fibrous peel can be seen over the contents
Neonatal abdominal cavity appears smaller than expected
Malabsorption and hypomotility = delayed bowel function
Why does gastroschisis have a thick fibrous peel over the herniated organs?
Direct intestinal exposure to amniotic fluid in utero leads to chemical reactions, creating a thick inflammatory film or peel over the bowel
What is gastroschisis associated with?
Intestinal malroattion
Intestinal atresia
How is gastroschisis diagnosed?
Prenatal ultrasound in second trimester. Ultrasonography may show dilated loops of bowel freely floating in the amniotic cavity
From birth…
Alpha fetoprotein is elevated in abdominal wall defects (may be due to direct protein loss from intestine into surrounding amniotic fluid) - if positive then need ultrasound
How is gastroschisis managed immediately ?
Immediate fluid resuscitation and maintaining adequate temperature.
A sterile, clear covering over the herniated contents protects the bowel, preventing evaporation, heat loss, and infection.
The infant is placed on his right side to prevent kinking of mesenteric vessels
How is gastroschisis managed definitively?
Surgery aims to reduce the protruding organs and close the abdominal wall defect.
Larger defects may need a staged surgical approach to return the contents into the abdominal cavity gradually; this will involve placing the bowel in a clear sac called a silo, which is tightened until there is enough space to reduce the bowel completely. This prevents further damage to the gut due to tight space within the abdomen.
Following surgery, a nasogastric tube is inserted to decompress the bowel, and parenteral feeding is commenced while the inflammatory peel recovers and the bowel starts functioning.
What are complications of gastroschisis?
Abdominal Compartmental Syndrome
Persistent bowel dysfunction
Wound infection
Necrotizing Enterocolitis
Short gut syndrome
Whats the prognosis of gastroschisis?
Overall mortality is 25-50%
What is short gut syndrome?
a condition in which your body is unable to absorb enough nutrients from the foods you eat because you don’t have enough small intestine (may be physical loss or loss of function)
What is abdominal compartment syndrome?
organ dysfunction caused by intra-abdominal hypertension
It occurs when the pressure in the abdominal cavity elevates beyond 20 mmHg
Often caused by excessive fluid resuscitation or massive blood trasnfusions
Whats the difference between gastroschisis and omphalocele?
Gastroschisis is when the intestines are exposed to air due to no peritoneal layer
Omphalocele is when the intestine protrudes into the umbilical cord, sealed by the peritoneal layer so not exposed to amniotic fluid/air
What is omphalocele?
When some of the bowels herniate out into the umbilical cord
a congenital, abdominal wall defect at the insertion of the umbilical cord. Abdominal contents herniates outside the abdomen within a membranous sac consisting of the peritoneum and amnion
Whats the pathophysiology of omphalocele
During normal development of the intestines, the midgut begins to elongate at around 6 weeks gestation. However, at this time the liver and stomach are also growing, meaning there is not enough room in the abdomen to accommodate the midgut. In order to continue developing, the midgut herniates through the umbilical ring out of the abdomen into the umbilical cord (called physiological umbilical herniation). During the 10th week, the abdomen has enlarged enough for the midgut to return
The exact cause of omphalocele is unknown, however the main theory is failure of this normal intestinal migration back into the abdominal cavity, and persistence of the physiological umbilical herniation
What are the complications of omphalocele?
Abdominal cavity doesnt grow normally
Pinched blood vessels - loss of blood flow to organs
Abdominal compartmental syndrome
Ruptured omphalocele
Whats the cause of omphalocele?
Unknown but thought to be genetic and environmental factors
Linked to some disorders - trisomy 13, 18, 21, Turner syndrome, klinefelter syndrome, triploidy, penological of Cantrell, OEIS complex and Beckwith-widemann syndrome
What are risk factors for omphalocele?
Consumption of alcohol and tobacco during pregnancy
Obesity
Certain meds e.g. SSRI
Maternal age >40
How is omphalocele diagnosed?
Before birth via ultrasound or raised maternal serum alpha-fetoprotein levels
After birth it is visible
How is omphalocele treated?
Surgery to place organs back in and repair defect
If organs are large this surgery may need to be done slowly over a period of time
Why do abdominal wall defects cause a raised alpha-fetoprotein?
direct protein loss from intestine into surrounding amniotic fluid
What is an imperforate anus?
A congenital lower GI malformation
Narrowed anal opening or complete atresia - the anal canal may end blindly at the anal membrane or a fistula may form between the rectum and perineum. Or the rectum may empty into the vagina or urethra forming a rectovaginal or ureorectal fistula
What are the signs and symptms of an imperforate anus?
Constipation
Obstipation
Vomiting and abdominal distension
How is imperforate anus managed?
Anoplasty if possible
Colostomy if not
What is meckels diverticulum?
An abnormal pouch on the ileum
The remnant of the vitelline duct present in embryonic life.
Whats the prevalence of meckels diverticulum?
2% - most common congenital abnormality of the GIT
Twice as common in males
How large is meckels diverticulum and where is it found
2 inches
Found about 2 feet from the caecum
When does meckels diverticulum present symptomatically?
Before the age of 2
Why can meckels diverticulum cause ulcers?
Heterotrophic gastric epithelium may sometimes be found - including HCL secreting oxyntic cells = peptic ulceration
What are the complications of meckels diverticulum?
Diverticulitis
Ulcers
Perforation of diverticulum
Food impacyion
Lothian is
Peritonitis
Peritoneal adhesions
Intussusception
Volvulus
Neoplasms
What are the signs and symptoms of meckel’s diverticulum?
Usually asymptomatic
Abdominal pain and distension - tenderness is near the navel
Melena
Vomiting
Constipation
How is meckels diverticulum diagnosed?
Abdominal ultrasound/CT - usually incidental finding
Angiography
Surgery - incidenctal finding
How is meckels diverticulum treated?
Resection of diverticulum
What causes meckels diverticulum?
Incomplete obliteration of the vitelling duct leading to the formation of a true diverticulum of the small intestine
Why is meckels diverticulum also known as a true diverticulum?
Because it contains all 3 layers of the bowel wall
Whats the blood supply to meckels divertuiculum?
The vitelline artery (branch if superior mesenteric)
What ectopic tissue may a meckels diverticulum have?
Ectopic pancreatic (amylase release) or gastric tissue (HCL release)
What is intestinal atresia?
Malformation during foetal development results in an absent portion of the small or large intestine
Whats the difference between intestinal atresia and stenosis?
Atresia is the failure of canalisation so results in complete obstruction
Stenosis is the narrowing of the lumen and can cause a partial obstruction
Where are intestinal atresia and stenosis most likely to happen?
In the duodenum
What disease is duodenal atresia and stenosis related to?
Trisomy 21 - Down syndrome
Outline the normal stages of vacuolation?
The guts a hollow tube
6 weeks - epithelium proliferates plugging up lumen
Cells undergo apoptosis and by 9 weeks the tube is hollow again (recanalazistaion)
Whats the pathophysiology of duodenal atresia?
Failure in duodenal vacuolization during foetal development
What does duodenal atresia look like on x-ray/ultrasound?
Baby swallows amniotic fluid but atresia means the fluid has no where to go so stomach and duodenum fills up / distension = double bubble appearance on x-ray separated by the muscular pyloric valve
Why does intestinal atresia cause polyhydramnios?
Because less amniotic fluid is swallowed and more stays in the amniotic sac
How does intestinal atresia present?
Bilious vomiting for first few days after birth (bile can’t be excreted)
Abdominal pain
Malnutrition
What are the 2 types of intestinal atresia?
Duodenal and non-duodenal intestinal atresia
Whats the pathophysiology of non-duodenal intestinal atresia>
Intrauterine ischaemic injury - supplied by superior mesenteric artery
What are the complications of intestinal atresia?
Distension of stomach and duodenum
Polyhydramnios
Intestinal perforation and pneumoperitoneum
How is intestinal atresia diagnosed?
Prenatal ultrasound (dilated fluid-filled stomach/duodenum or bowel loops depending on type)
Postnatal X-ray
Apple peel shape of intestines upon visual examination during surgery
Amniocentesis to determine possible trisomy 21
How is intestinal atresia treated?
Gastric decompression
IV fluid compensation
Surgical reattachment of functional portions of intestines
What is hirschsprung disease?
Congenital aganglionic megacolon
Absence of ganglion cells in Auerbachs and Meissners plexus in the distal bowel as a result of a failure of neuroblasts to migrate during weeks 5-12 of gestation
The circular muscle layer of the intestine goes into spasm (no peristalsis so muscles can’t relax and stay contracted), resulting in intestinal obstruction and dilation if the intestine occurs proximal to the area in spasm
What area of the bowel does hirschsprung disease affect?
Rectum and distal colon
In severe cases it may also affect the small intestine
Whats the prevalence of hirschsprung disease?
1 in 5000 live births
4 times more likely to occur in males
How does hirschsprung disease present?
Less severe cases - chronic constipation
Severe vases - sympotms of obstruction
Babies will often not pass their mechanism within the first 2 days. They might have a swollen abdomen and vomit green bile
Why is hirschsprung disease 10 times more likely to occur in children with Down syndrome?
RET and EDNRB mutations can lead to an absence of the migration and development of nerve fibres
RET gene mutations have also been linked to down syndrome
What is megacolon?
an abnormal dilation of the colon that is not caused by mechanical obstruction
Diameters:
Caecum >12cm
Ascending colon >8cm
Transverse colon >6cm
How is hirschsprung disease diagnosed?
Abdominal x-ray with radiocontrast shows megacolon full of stool
Definitive diagnosis - rectal suction biopsy in narrow area of colon where submucosa and mucosa are extracted - check for submucosal plexus
How is hirschsprung disease treated?
Surgical resection of area lacking nerve fibres and healthy end is connected to the anus ‘pull through operation’
How can megacolon be acquired?
Bowel obstruction
IBD
Chagas’ disease/Trypanosoma cruzi
Medication
Megacolon secondary to infection
Clostridium difficile
Pheochromocytoma, possibly secondary to its presenting constipation
Whats the leading cause of toxic megacolon in HIV/AIDS patients?
CMV
What are the complications of megacolon?
colonic perforation, peritonitis, sepsis, bleeding/blood loss
What is volvulus?
An obstruction caused by a loop in the intestines that twists around itself and surrounding mesentery
What are the 3 most common type of volvulus?
Sigmoid volvulus - most common
Cecal volvulus
Midgut volvulus
When do sigmoid volvulus develop?
Pregnancy - foetus scan cause displacement and twisting of the colon
Middle aged and elderly due to chronic constipation - big stool acts like a pivot point that the colon twists around
Hirschsprung disease
Abdominal adhesions - serves as a pivot point
When do cecal volvulus tend to occur?
In young adults
In those with abnormal development of abdominal mesentery - colon can flap freely so large objects (e.g. baby or large stool) can act as a pivot point and cause colon to twist
When does midgut volvulus tend to occur?
In babies and small children - due to abnormal intestinal development in foetuses causing malrotatuin which puts them at risk of volvulus
Whats the pathophysiology of volvulus?
Portion of intestines becomes twisted and pinches the lumen shut, resulting in bowel obstruction. This prevents the normal passage of digested food and water
Sometimes the mesentery can be so twisted that blood flow is cut off and this causes infarction - risk of intestinal wall break down which releases bacteria and can cause spsesis and cardiovascular collapse
What are the symptoms of volvulus?
Bloating
Constipation
Severe pain
Bloody stool
How is volvulus diagnosed?
Abdominal X-ray - shows bent inner tube/coffee bean shape
Barium enema would show a bird beak shape (enlarged at one end and tapered at the other
How is a volvulus treated?
Sigmoid volvulus - Sigmoidoscopy
Cecal volvulus - colonoscopy
Surgery immediately or within 2 days of treated - this untwists the intestine if necessary, and attaching it to the abdominal wall to prevent it repeating again
If infarction then a resection may be necessary
Sigmoid volvulus - rigid sigmoidoscopy with flatus tube insertion to decompress and untwist the loop. Otherwise resection of the redundant sigmoid colon.
Caecal volvulus - surgery e,.g. Right hemicolectomy
What is intestinal malrotation?
Improper rotation of the midgut during embryogenesis
Due to error, several organs move into the incorrect anatomical position:
Small intestine on right side
Caecum in epigastrium
Appendix follows caecum
Ladd’s bands (bands of peritoneum) span over vertical duodenum, compressing from outside
What are the complications of intestinal malrotation?
Omphalocele
Volvulus
Ileus
Ischaemic bowel
Malnutrition
Hernias
What are the signs and symptoms of intestinal malrotation?
May be asymptomatic
Colic, bilious regurgitation and abdominal distension
What diagnostic imaging is done for intestinal malrotation?
MRI/CT/ barium assisted radiography to detect improper organ position
How is intestinal malrotation treated?
Surgical repositioning of intestines
Resection of ladd’s bands to remove duodenal obstruction
Preventative appendectomy
What is total colonic aganglionosis?
When the entire colon is affected by hirschsprung disease - no innveration in entire colon
What syndromes is Hirschsprung’s disease associated with?
Downs syndrome
Neurofibromatosis
Waardenburg syndrome (a genetic condition causing pale blue eyes, hearing loss and patches of white skin and hair)
Multiple endocrine neoplasia type II
