Small Bowel, SBO, IBD Outline Small bowel physiology SBO physiology Absorption Barrier SBO physiology Hyperperistalsis Decreased absorption Increased secretion Clinical aspects

Small Bowel, SBO, IBD Outline (cont’d) Crohn’s disease Epidemiology Pathology Indications for operation Ulcerative colitis

Small Bowel Physiology Small Bowel, SBO, IBD Small Bowel Physiology Absorbs water, electrolytes, nutrients Varies between jejunum and ileum Compromised in certain disease states Requires glutamine as energy source Barrier function Requires enteral nutrition for maintenance Compromised by lack of feeding ?Leads to nosocomial infection

Layers of the small intestine Layers of the small intestine. A large surface is provided by villi for the absorption of required nutriments. The solitary lymph follicles in the lamina propria of the mucous membrane are not labeled. In the stroma of both sectioned villi are shown the central chyle (lacteal) vessels or the villous capillaries. (From Sobotta J, Figge FHJ, Hild WJ: Atlas of Human Anatomy. New York, Hafner, 1974, with permission.)

Digestion and absorption of proteins.

Absorption of water and electrolytes in the small bowel and colon Absorption of water and electrolytes in the small bowel and colon. (Adapted from Westergaard H: Short bowel syndrome. In Feldman M, Scharschmidt BF, Sleisenger MH [eds]: Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management. Philadelphia, WB Saunders, 1998, p 1549.)

The mucosal barrier of the gut The mucosal barrier of the gut. Antigens contact specialized microfold (M) cells overlying Peyer’s patches, which then process and present the antigen to the immune system. When B lymphocytes are stimulated by antigenic material, the cells develop into antibody-forming cells that secrete various types of immunoglobulins (Igs), the most important of which is IgA. (Adapted from Duerr RH, Shanahan F: Food allergy. In Targan SR, Shanahan F [eds]: Immunology and Immunopathology of the Liver and Gastrointestinal Tract. New York, Igaku-Shoin, 1990, p 510.)

Small Bowel, SBO, IBD SBO Physiology Global hyperperistalsis Decreased absorption of H2O & lytes Increased secretion of protein rich fluid Hypoperistalsis in late stages

Small Bowel, SBO, IBD SBO Physiology Pain and tenderness doesn’t differentiate type Simple SBO Usually partial Differentiation by plain X-ray or CT May resolve Strangulated SBO Usually complete Often “closed loop” Requires urgent operation

Common causes of small bowel obstruction in industrialized countries.

FIGURE 46-13A. Plain abdominal radiographs of a patient with a complete small bowel obstruction. A, Supine film shows dilated loops of small bowel in an orderly arrangement, without evidence of colonic gas. B, Upright film shows multiple, short, air-fluid levels arranged in a stepwise pattern. (Courtesy of Melvyn H. Schreiber, M.D., The University of Texas Medical Branch.)

CT scan through the mid abdomen shows dilated small bowel loops filled with fluid and decompressed ascending and descending colon. These are typical CT findings in small bowel obstruction. (Courtesy of Eric Walser, M.D., The University of Texas Medical Branch.)

Crohn’s Disease Epidemiology Disease of young adults Peak incidence in late teens and 20’s Smaller peak in 50’s & 60’s Incidence varies amongst ethnic groups Cause unknown ?Autoimmune ?Infectious ?Genetic

Crohn’s Disease Pathology Full-thickness involvement Thickened bowel wall and mesentery 50% with non-caseating granulomas May involve any portion of GI tract

Gross pathologic features of Crohn’s disease Gross pathologic features of Crohn’s disease. A, Serosal surface demonstrates extensive “fat wrapping” and inflammation. B, Resected specimen demonstrates marked fibrosis of the intestinal wall, stricture, and segmental mucosal inflammation. (Courtesy of Mary R. Schwartz, M.D., Baylor College of Medicine.)

Crohn’s colitis with noncaseating granuloma.

Crohn’s Disease Pathology (cont’d) Ileal involvement most common Colon-only involvement seen Peri-rectal disease common Extra-intestinal manifestations Surgery not curative Malignancy uncommon

Crohn’s colitis. This barium enema demonstrates segmental inflammation of the left colon, characteristic of Crohn’s disease. The rectum is spared, a clinical finding that is useful in distinguishing Crohn’s colitis from ulcerative colitis. The rectal mucosa is virtually always affected in patients with ulcerative colitis, whereas the pattern of colonic inflammation is variable in Crohn’s colitis.

Small bowel contrast study demonstrating “string sign” caused by inflammation and narrowing of the terminal ileum.

Crohn’s colitis. Linear ulceration of the mucosa, giving appearance of “railroad track” or “bear claw ulcers.”

Indications for Operation Crohn’s Disease Indications for Operation Abscess Certain fistulae Obstruction Intractability

Elective operations for Crohn’s colitis.

Surgical Considerations Crohn’s Disease Surgical Considerations Important aspect of overall care Bowel conservation important Limited resection Resect, don’t bypass Long-term risk of short-gut is low J-pouch not an option in colonic disease

Ulcerative Colitis Epidemiology Similar to Crohn’s disease Early and late incidence peaks Variable incidence among ethnic groups

Ulcerative Colitis Pathology Involves only mucosa and submucosa Involves only colon and rectum Serosa normal Normal bowel wall thickness Normal mesentery

Ulcerative colitis, macroscopic appearance of pancolitis Ulcerative colitis, macroscopic appearance of pancolitis. Because the entire colon is involved with inflammatory changes, this specimen represents a case of universal colitis or pancolitis. The distal colon shows a large longitudinal ulcer with heaped-up adjacent mucosa. In the midportion of the colon, the mucosa is relatively flat and featureless. In the right side of the colon, there are multiple projections, or pseudopolyps, creating a cobblestone appearance. The ileocecal valve is edematous and irregular, whereas the terminal ileum is spared. (Courtesy of M. Markowitz Haber, M.D., Hahnemann University Hospital.)

Ulcerative colitis, macroscopic appearance of left-sided colitis Ulcerative colitis, macroscopic appearance of left-sided colitis. The left side of the colon displays continuous disease manifested as erythema and granularity of the mucosal surface, whereas the right colon appears normal. (Courtesy of M. Markowitz Haber, M.D., Hahnemann University Hospital.)

Active ulcerative colitis Active ulcerative colitis. The glands are irregular with branching, and, focally, the long axis of the gland is horizontal rather than perpendicular. A central crypt abscess is present. There are increased numbers of chronic inflammatory cells throughout the lamina propria. (Courtesy of M. Markowitz Haber, M.D., Hahnemann University Hospital.)

Barium enema demonstrating stricture in transverse colon of patient with ulcerative colitis of 15 years’ duration.

Photograph of resected colon from patient in Figure 48-28, revealing the stricture (arrow) to be invasive cancer. The patient had liver metastases

Ulcerative Colitis Pathology (cont’d) Extraintestinal manifestations Malignancy Duration of disease Extent of disease

Ulcerative Colitis Presentation Diarrhea, often bloody Abdominal pain Constitutional symptoms Weight loss Fulminant colitis Toxic megacolon

Indications for Operation Ulcerative Colitis Indications for Operation Bleeding (uncommon) Unresponsive fulminant colitis Toxic megacolon Intractability Inability to wean steroids Cancer prevention

Elective operations for ulcerative colitis Elective operations for ulcerative colitis. IPAA, ileal pouch-anal anastomosis

Ulcerative Colitis Surgical Aspects Colectomy curative Total proctocolectomy with ileostomy Ileo-anal pouch pull-through

Creation of an ileal J pouch using a cutting linear stapler Creation of an ileal J pouch using a cutting linear stapler. For replacement of the rectum, a reservoir is created from the distal ileum. The stapler joins two limbs of intestine with staples while dividing the intervening wall. The diameter of the pouch so created is twice as large as the original diameter of the ileum.

Hand-sewn ileal pouch anal anastomosis following anorectal mucosectomy.