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
