Small Intestine and Colon Pathology Flashcards
Ileus
Loss of normal propulsive function of bowel in absence of mechanical obstruction
Hernia
Defect in wall of peritoneal cavity, leading to protrusion of hernia sac.
Complication from hernia
Infarction or entrapment
Bowel adhesions
Fibrous bands of scar tissue between bowel segments, abdominal wall, or operative sites.
When do bowel adhesions usually occur?
After surgery, infection, other causes of peritoneal injury/inflammation. Rarely congenital.
Complications from bowel adhesions
Obstruction or formation of closed loops.
Volvulus
- -Twisting loop of bowel about mesenteric base, leads to bowel infarction.
- -Commonly in sigmoid colon
- -Caused by embryologic malrotation
- -See dilated colon and absence of air in rectum on X-ray
Intussusception
- -Segment of bowel telescopes into immediately distal segment
- -Peristalsis further propels down and causes obstruction
Intussusception association in infants/children
Anatomic defects
Intussusception association in older children/adults
Intraluminal tumor or mass
Stenosis
Form of atresia. Lumen decreased in size. Commonly have fibrous thickening of the wall.
–Esophagus, small bowel, anus common locations
Atresia
Incomplete development. Ex. esophageal atresia and TE fistula
Omphalocele
Incomplete closure of ventral abdominal musculature. Abdominal viscera herniates into peritoneal sac
Gastroschisis
Incomplete closure of all layers of abdominal wall with abdominal viscera herniating
Meckel’s diverticulum
- -True diverticulum of small bowel
- -Failed involution of vitelline duct
Complications of Meckel’s diverticulum
- -Ulceration
- -Perforation
- -Hemorrhage
- -Fistula formation to bladder
- -Intussusception
Meckel’s Diverticulum Rule of 2’s
- -Located on antimesenteric side of ileum in 2% of population
- -Present within 2 feet of ileocecal valve
- -2 inches long
- -2x more common in males
- -Symptoms occur by age 2 (if present)
Hirschsprung’s disease (congenital aganlionic mesocolon) pathologic abnormality
Loss of ganglion cells of affected segment in submucosal (Meissner’s) and myenteric (Auerbach’s) plexuses
What mutation often present with Hirschsprung’s disease?
Heterozygous for loss-of-function mutation for receptor tyrosine kinase RET
Hirschsprung’s disease clinical presentation
- -Failure to pass meconium
- -Infants and older children present with obstructive constipation, abdominal distention, vomiting
- -4x more common in males
- -10% of cases occur in patients with Down syndrome
Malabsorption
Impaired absorption of nutrients. Involves at least one phase of nutrient absorption
Diarrhea
Excessive increase in stool mass, frequency, fluidity.
>3 loose stools/day. Acute 4 weeks
> 200 g stool day.
4 types of diarrhea
- -Secretory
- -Osmotic
- -Malabsorptive
- -Exudative
Secretory diarrhea
Isotonic stool
Osmotic diarrhea
Excessive osmotic forces from unabsorbed luminal solutes
Malabsorptive diarrhea
Failure of global nutrient absorption w/steatorrhea
Exudative diarrhea
Inflammatory processes, w/bloody stools, increased stool neutrophils
Celiac disease pathologic findings
Immune-mediated enteropathy triggered by gluten ingestion–>damage to surface of epithelium of small bowel
Histologic findings of celiac disease
- -Intraepithelial lymphocytes
- -Villous atrophy
Lab tests for celiac disease
HLA-DQ2 and HLA-DQ8
Tropical sprue
- -Mimics celiac disease
- -Occurs in tropics
- -Thought to be secondary to some infectious agent causing overgrowth of aerobic enteric bacteria
Tropical sprue location and histologic changes
- -Location: usually distal small bowel
- -Inflammatory small bowel changes with milder degree of villous atrophy than celiac disease
Complication of tropical sprue?
Vit B12 deficiency
Treatment of tropical sprue
Broad spectrum antibiotics
Abetalipoproteinemia inheritance type and mutation
- -Autosomal recessive
- -Mutation in microsomal triglyceride protein (responsible for assembling glycerides into chylomicrons
Abetalipoproteinemia is an example of what?
Disorder in transepithelial transport
What happens to in abetalipoproteinema?
Accumulate in cytoplasm because they are not moved by chylomicrons
Presentation of abetalipoproteinemia
- -Infants
- -FTT
- -Diarrhea
- -Steatorrhea
- -Absent ApoB
- -Deficiency in fat soluble vitamins
Lab findings in abetalipoproteinemia
Lipid membrane defects in RBCs produces Burr cells (acanthocytes)
Whipple disease cause
Infection by G+ actinomycete (Tropheryma whippelli)
Diagnosis of Whipple disease
H and E stain
–Effacement of normal lamina propria by sheet of swollen macrophages
Symptoms of whipple disease?
- -Diarrhea
- -Weight loss
- -Malabsorption
- -Abdominal pain
- -Arthritis
- -Arthralgia
- -Fever
- -Lymphadenopathy
- -Neurologic
- -Endocarditis
- -Pulmonary disease
Pathology of Whipple disease
Macrophages filled with organism accumulate in lamina propria of small bowel and mesenteric lymph nodes–> lymphatic obstruction
Where can macrophages accumulate in Whipple disease?
Lamina propria of small bowel, mesenteric lymph nodes, synovial membranes, cardiac valves, brain and other organs
Most common type of disaccharidase deficiency
Adult onset lactase deficiency
Pancreatic insufficiency common causes (in adults and in children)
Often due to EtOH induced chronic pancreatitis in adults and CF in children
Pancreatic insufficiency pathology
Decreased luminal lipase and trypsin–> undigested fats and protein. Carbohydrate absorption not affected.
