Nelson: Small Intestine and Colon Pathology Flashcards
Ileus
loss of normal propulsive function of the bowel in the absence of mechanical obstruction
o Can be associated with surgery complications, trauma, peritonitis, ischemia, meds (narcotics) infection.
abdominal pain, distension, vomiting lack of flatus and constipation
ileus
Hernia
defect in peritoneal wall allowing protrusion of serosal lined pouch of peritoneum.
o Most common in inguinal or femoral canals, umbilicus or surgical scars.
Visceral protrusion of bowel can lead to venous obstruction → stasis, edema, entrapment and infarct.
Hernia
Bowel adhesions
fibrous bands of scar tissue between bowel segments, abdominal wall or operative sites.
usually secondary to insult
Bowel adhesions can lead to…
obstruction and formation of loops through which bowel can herniate (internal hernia) and become trapped.
Volvulus
complete twisting of a loop of bowel about its mesenteric base>
leads to obstruction, vascular compromise and infarct
*can be caused by developmental abnormalities
What part of the intestine does volvulus usually occur in?
sigmoid then cecum
intussusception
segment of the bowel telescopes into the immediately distal segment>
obstruction, mesenteric blood flow compromise, infarct
Intussuception usually occurs in the…and is usually associated w/ ……
in the young
usually associated with anatomical defect in older children/adults think intraluminal tumor.
What is stenosis?
form of atresia
lumen is markedly decreased in caliber, usually associated w/ fibrous thickening of hte wall
What are common sites for stenosis?
esophagus
small bowel
anus (imperforate)
What is atresia?
incomplete development, can occur in any portion of the GI tract
What is an omphalocele?
incomplete closure of abdominal musculature, viscera herniate into ventral peritoneal sac
What is gastroschisis?
similar to omphalocele but involves all layers of abdominal wall
Define meckel’s diverticulum
true diverticulum of the small bowel composed of all three layers (mucosa, submucosa and muscularis propria)
Occurs as a result of failed involution of the VITELLINE DUCT, which connects the developing gut to the YOLK SAC.
What are complications associated with meckel’s diverticulum?
o Ulceration (ectopic gastric mucosa → acid production & peptic ulcers in adjacent ileum) o Perforation o Hemorrhage o Fistula formation to the bladder o Intussusception
failure to pass meconium (neonates) infants OR an older adult with obstructive constipation, abdominal distension and vomiting
Hirchsprung’s Disease
What pathological abnormality causes Hirchsprung’s Disease?
Normal neural crest cell migration from cecum to rectum is arrested prematurely or ganglion die> Coordinated peristalsis absent and proximal dilation occurs.
What are hte MC sites for Hirchsprung’s disease?
distal sigmoid colon and rectum
both the submucosal and myenteric plexus lacking
What is ischemic bowel disease?
mucosal ischemic injury → atrophy/loss of surface epithelium, a hemorrhagic and hyalinized lamina propria, and crypt atrophy.
Severe ischemia → transmural necrosis
Ischemic bowel disease tends to occur in what population?
Tends to occur in older individuals with coexisting cardiac or vascular disease
What are causes of ischemic bowel disease?
- Acute arterial obstruction/thrombosis- atherosclerosis, aortic aneurysm, hypercoagulability, thromboembolism. Typically results in transmural infarct
- Mesenteric venous thrombosis- hypercoagulability, portal hypertension due to cirrhosis, trauma, neoplasm and masses.
- Hypoperfusion- cardiac failure, shock, dehydration, vasoconstrictive drugs, vasculitis. –> Can cause ischemic damage in watershed zones.
What bowel segments are most susceptible to ischemia?
Intestinal segments at the end of an arterial supply
- Splenic flexure (SMA/IMA watershed zone)
- Sigmoid colon & rectum (IMA/pudendal/iliac watershed)
