Chapter 13: GI Small Intestine Vascular Flashcards
An infant presents with intestinal pain and shock. Autopsy reveals the following findings.
Volvulus has occluded the most commonly occluded artery that causes this condition.
Small bowel ischemia/infarct.
The vessel occluded is the superior mesenteric artery.
Can also be caused by intrinsic vascular lesion, vasculitis, embolic or thrombotic occlusion, volvulus, intussusception, incarceration of the intestine in a hernial sac.
What are other causes of intestinal ischemia?
Nonocclusive - shock, hypoxia.
Mesenteric vein thrombosis: Hypercoagulable state, stasis, inflammation (pylephlebitis).
What are signs of ischemic bowel?
Edematous, diffusely purple.
Adynamic ileus: Bowel proximal to lesion dilated and filled with fluid. Intestinal organisms pass through damaged wall, peritonitis or septicemia.
Nonocclusive: Restricted injury initially to mucosa. Heal with granulation tissue and fibrosis with stricture formation.
A patient presents with chronic abdominal pain that starts within a half hour of eating and lasts a few hours.
Atherosclerotic narrowing of major splanchnic arteries.
Celiac compression syndrome: Pressure on celiac axis from surrounding structures can cause poor blood flow.
Can lead to fibrosis and stricture formation. Submucosa thickened, fibrotic with granulation tissue, strictures. Hemosiderin deposition.
What two substances are preferentially absorbed by the distal small intestine?
Bile salts and vitamin B12.
What is the most common cause of luminal-phase malabsorption?
What causes that?
Insufficient bile acids.
- Interruption of normal continuity of distal stomach and duodenum
- Pancreatic dysfunction
- Deficient or ineffective bole salts. Impaired excretion, bacterial overgrowth, and deficient bile salts due to absence or bypass of distal ileum.
What are some causes of intestinal-phase malabsorption?
- Microvilli: Disaccharidase deficiencies. Celiac disease damage to villi.
- Absorptive area: 1. Small bowel resection (short bowel syndrome). 2. Gastrocolic fistula. 3. Mucosal damage (celiac, tropical sprue, Whipple)
- Metabolic function of absorptive cells: Abetalipoproteinemia - can’t make chylomicrons. Erythrocyte acanthocytosis. Celiac disease, tropical sprue, Whipple disease
- Transport: Whipple disease, intestinal lymphoma, congenital lymphangiectasia.
What are some forms of specific or isolated malabsorption?
One nutrient.
Disaccharidase deficiency (notably lactase)
Lack of intrinsic factor (B12 insuffieicney/pernicious anemia).
Bleeding diathesis: Vitamin K deficiency
Tetany, osteomalacia, or rickets: Malabsorption of vitamin D or calcium.
What are some forms of generalized malabsorption?
Absorption of several or all nutrient classes is impaired.
Weight loss, cachexia, failure to thrive, poor growth/weight gain. Diarrhea may be a secondary effect of nonabsorbed or partially absorbed substances.
The hallmark sign of generalized malabsorption is…
Steatorrhea (fat in stools).
How does the D-Xylose absorption test work?
A five-carbon sugar, absorption does not require any component of the luminal phase. Blood levels and urinary excretion of this compount after ingestion useful to test intestinal phase of absorption.
How does the 14CO2-cholyl-glycine breath test work?
Measure 14-CO2 in exhaled air after oral administration.
Tests bile salt absorption by the ileum. Used in diagnosis of blind or stagnant-loop syndrome (bacterial overgrowth) and of ileal absorptive function.
What is the Schilling test?
Initially for pernicious anemia (Give isotopically labeled B12, measure blood level).
Now also can detect ileal absorption, bacterial overgrowth, and pancreatic function.
A young girl presents with growth retardation, fatty stool and small intestinal mucosal lesions.
A biopsy is taken and shows blunting of the villi, damaged mucosal surface epithelial cells with numerous intraepithelial lymphocytes and plasma cells in the lamina propria.
Picture: Top left - normal. Top right: Normal, lymphocyte in epithelium and curved intact brush border.
Bottom left: Patient, loss of villi with infiltration of lamina propria with lymphocytes and plasma cells. Crypts increased in height.
Bottom right: Epithelium damaged, loss of brush border, intraepithelial lymphocytes.
Celiac Disease/Celiac sprue, gluten-sensitive enteropathy.
HLA-B8 and HLA-DR8 and DQ2.
Serotype 12 adenovirus infection. Homology to alpha-gliadin.
Serum antigliadin and antiendomysial antibodies present in patients.
Dermatitis herpetiformis sometimes present: Extensor surfaces and extended parts of the body. Basement membrane IgA deposits detected.
Late complications: Ulcerative jejunitis and small bowel T-cell lymphoma. Adenocarcinoma of the small bowel and squamous cancers of the oropharynx and esophagus. Increased risk colorectal cancer. Follicular keratosis, peripheral neuropathy, infertility.
A patient presents with malabsorption. A biopsy shows deposition of collagen in the lamina propria of the small bowel. The patient does not respond to a gluten-free diet.
Collagenous sprue.
Prognosis is grave.
A 35 year-old man presents with fatty stools and fever.
A biopsy is taken. By microscopy…
Top picture: Section of jejunal mucosa, villi are distorted and lamina propria packed with large, pale-staining macrophages.
Bottom left: Periodic acid-Schiff reaction shows macrophages filled with cytoplasmic granular material
Bottom right: Electron micrograph shows small bacilli in a macrophage.
Whipple disease. Macrophages are packed with Tropheryma whippelii, a gram-positive actinomycetes. Defective T-cell function may predispose to disease. Macrophages impaired ability to degrade intracellular microorganisms. CD11b levels reduced (activate macrophages).
Associated with: Increased skin pigmentation, anemia, lymphadenopathy, arthritis, pericarditis, pleurisy, endocarditis, and CNS involvement.
