1. Complete twisting of a bowel loop 2. Peritoneal wall defects permit sac protraction 3. Fibrous bands form between bowel loops 4. Intestinal segment telescopes into the immediately distal segment

1. Volvulus 2. Hernias 3. Adhesions 4. Intussusception

Path small intestine Flashcards by Tiffany Reid

Meckel Diverticulum

Rule of 2s

2 inches in length 
Within 2 feet of ileocecal valve
2% of the population
2 types of heterotropic rests
2x more common in males

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A blind pouch in the small bowel due to persistence of the proximal portion of the vitelline duct

*all 3 layers of the mucosa

Meckel diverticulum

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Congenital abnormalities of the small intestine

Meckel diverticulum

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Intestinal obstruction is most common where? Why?

Small intestine

Narrower lumen

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80% of intestinal obstructions are attributable to 4 things:

Hernias
Adhesions
Volvulus
Intussusception

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Complete twisting of a bowel loop
Peritoneal wall defects permit sac protraction
Fibrous bands form between bowel loops
Intestinal segment telescopes into the immediately distal segment

Volvulus
Hernias
Adhesions
Intussusception

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Ischemic bowel disease

Abrupt loss of blood supply

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Areas most vulnerable to ischemic bowel disease

Watershed zones between major vessel branches

-such as splenic flexure between SMA and IMA

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Which are more susceptible to ischemia, tips of villi on epithelial cells or crypt epithelial cells?

Tips of villi

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5 most important causes of ischemia are:

Atherosclerosis
Aortic aneurysm
Hypercoagulable states
Embolization
Vasculitis

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Global hypoperfusion may be associated with __

Cardiac failure
Shock
Vasoconstrictive drugs
Dehydration

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Gross morphology:

Mucosal infarction

Patchy mucosal hemorrhage

Normal serosa

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Gross morphology:

Mural infarction

Complete mucosal necrosis

Variable necrosis of submucosa and muscularis propria

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Gross morphology:

Transmural infarction

Hemorrhagic bowel segments
Serositis
Coagulative necrosis of muscularis propria within 1-4 days
Perforation

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Clinical picture of ischemic bowel disease

Late middle age-elderly
Coexisting cardiac or vascular disease
-severe ab pain and rigidity
-bloody diarrhea or melena
-nausea and vomiting

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Symptoms of malabsorption

Diarrhea
Flatus
Ab pain
Muscle wasting 
Steatorrhea

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Clinical consequences of malabsorption

Deficiencies

Vitamin K
Iron
B6, B12, or folate
Calcium
Magnesium
Vitamin D
Vitamin A

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Most common causes of malabsorption in the US

Celiac disease
Pancreatic insufficiency
Crohn disease

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Immune-mediated malabsorptive process triggered by gluten

Typically people of ___

Celiac disease

White European descent

Pathogenesis of celiac disease

Delayed-type hypersensitivity directed against alpha-gliadin polypeptide, which is resistant to digestive enzymes

*flattened villi

Celiac disease carries an increased risk of:

S.I. adenocarcinoma
Enteropathy-associated T-cell lymphoma (not true for tropical sprue)
Esophageal squamous cell carcinoma

Treatment for celiac disease vs. tropical sprue

Gluten free diet

Antibiotics

Systemic illness, mainly affects S.I. but can affect CNS, joints, lymph nodes, and other organs

Male:female is 10:1
Treat with antibiotics

Diarrhea, weight loss, lymphadenopathy, arthritis, arthralgias, fever, neurologic, cardiac, or pulmonary disease

Whipple disease

Carcinoid tumors arise from ___ cells

What predisposes to carcinoid tumors?

Neuroendocrine cells of the gut

chronic atrophic gastritis
Zollinger-Ellison

Carcinoid tumors - foregut - midgut - hindgut

- rarely metastasize and are usually cured by excision - usually multiple and aggressive - usually found incidentally and are very indolent. Excision usually cures

Morphology of carcinoids

Tan-yellow Firm Uniform, small round to oval cells Nuclei are oval

``` Cutaneous flushing Bronchospasm Increased bowel motility Sometimes projectile diarrhea Right sided cardiac valve thickening ```

Carcinoid syndrome | *rare

Kinyoun stain

Whipple disease | -shows acid fast bacteria as bright red with blue background

Worst prognosis of all small intestine lymphomas | *associated with long standing celiac disease

Enteropathy type intestinal T cell lymphoma

Most common culprits in bacterial peritonitis

``` E. coli Streptococci S. aureus Enterococci C. perfringens ```

Spontaneous bacterial peritonitis is most often seen in patients with ___ Organisms identified most often are ___

Cirrhosis and ascites E. coli and pneumococci

Morphology of peritonitis

Serosa like and peritoneal surfaces become dull and opaque - creamy suppurative material accumulates - lots of neutrophils

Carcinoid syndrome is thought to arise from excess elaboration of ___

Serotonin (5-HT)

Most of the tumors of the peritoneum are ___ Primary are ___ Secondary are ___

Malignant Uncommon Common

Primary tumors of the peritoneum arise from ___ | Associated with __

Peritoneal lining, mesotheliomas, almost always associated with asbestos exposure

Secondary tumors of the peritoneum - Direct spread to the serosal surface or metastatic seeding is called __ - The most common tumors producing diffuse serosal implants are ___ and ___ - Appendiceal mucinous carcinomas may produce ___

- Peritoneal carcinomatosis - Ovarian and pancreatic adenocarcinoma - pseudomyxoma peritonei

Hirschsprung disease

Congenital aganglionic megacolon Rectum is always involved Associated with RET gene mutation

May occur in **Chagas disease, bowel obstruction, IBD, C. diff colitis, and psychosomatic disorders

Acquired megacolon **only in Chagas disease are ganglia actually lost

Most common cause of pseudomembranous colitis

C. diff

Endoscopic findings of pseudomembranous colitis

Classic yellow-white exudates or pseudomembranes - most commonly on left colon - bleed when scraped

The pseudomembrane in pseudomembranous colitis is composed of

Fibrin Mucin Neutrophils

Diagnosis of pseudomembranous colitis

Cytotoxin A assay PCR Enzyme immunoassay (moderate sensitivity) Latex agglutination assay (lacks sensitivity and specificity)

Crohn disease vs. Ulcerative colitis

CD: patchy skip lesions, anywhere from the mouth to anus, transmural UC: continuous, colon and rectum, superficially limited to mucosa

Superficial erosions that are small, well-delineated lesions amidst normal mucosa - may coalesce into "bear claw" ulcers - can result in cobblestoned appearance and inflammatory pseudopolyps

Aphthous ulcers

Gross resection findings of Crohn disease

1. Serositis 2. Fat-wrapping/creeping 3. Fistulas 4. Thickened bowel wall 5. Strictures 6. Skip lesions 7. Aphthous lesions 8. Cobblestone appearance 9. Fissures

Microscopic morphology of Crohn disease

1. Abrupt transitions between normal and inflamed mucosa 2. Inflammation is transmural 3. Ulceration 4. Muscle hypertrophy 5. Chronic mucosal changes

Spillover of inflammation from the cecum into the terminal ileum

Backwash ileitis