Small Bowel

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Small Bowel
2011-01-15 13:05:10
Small Bowel Absite Review

Small Bowel Absite Review
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  1. Small Bowel Anatomy and Physiology
    • Small intestine: nutrient and water absorption
    • Large intestine: water absorption
  2. Duodenum
    • Bulb (1st): 90% ulcers here
    • Descending (2nd): ampulla of Vater (duct of Wirsung) and duct of Santorini
    • Transverse (3rd)
    • Ascending (4th)

    • Descending and transverse: retroperitoneal
    • 3rd and 4th: transition point at the angle between the aorta and SMA
  3. Duodenal vascular supply
    • Superior (off the gastroduodenal artery) and inferior (off SMA) pancreaticoduodenal arteries
    • Both have anterior and posterior branches
    • Many communications
  4. Jejunum
    • 100cm
    • Long vasa recta
    • Circular muscle folds
    • Vascular supply from the SMA
    • Maximum site of most absorption...
    • Terminal ileum: B12, conjugated bile acids, folate
    • Ileum: nonconjugated bile acids
    • Duodenum: iron
  5. Ileum
    • 150cm
    • Short vasa recta
    • Flat
    • Vascular supply from the SMA
  6. Intestinal brush border
    • Maltase
    • Sucrase
    • Limit dextrinase
    • Lactase
  7. Cell types
    • Absorptive cells
    • Goblet cells: mucin
    • Paneth cells: secretory granules, enzymes
    • Enterochromaffin cells: APUD, 5-hydroxytryptamine release, carcinoid precursor
    • Brunner's glands: alkaline solution
    • Peyer's patches: lymphoid tissue, increased in the ileum
    • M cells: antigen presenting cells in intestinal wall

    • IgA: released into gut, mother's milk
    • Fe: heme and Fe transporters
  8. Migrating motor complex
    • Phase I: rest
    • PhaseII: acceleration and gallbladder contraction
    • Phase III: peristalsis
    • PhaseIV: deceleration
    • Motilin: regulating hormone
  9. Fat and Cholesterol
    • Broken down b cholesterol esterase, phospholipase A2, lipase, colipase in combination with bile salts
    • Converted to FFA and monacylglycerides: micelles
    • TAGs are reformed in intestinal cells and released as chylomicrons into the lymphatics via terminal vilious lacteals
    • Chylomicrons: 90% TAGs, 10% phospholipid, cholesterol, protein; released into lymphatics
    • Long-chain fatty acids: released into lymphatics
    • Short and medium chain fatty acids: released into portal vein
  10. Bile salts
    • 95% of bile salts are reabsorbed
    • 50% of passive absorption (45% ileum, 5% colon)
    • 50% active resorption in terminal ileum
    • Conjugated bile absorbed only in terminal ileum
    • Bile is conjugated to taurine and glycine
    • Deconjugated in colon by bacteria
    • Primary bile acids: cholic and chenodeoxycholic
    • Secondary bile acids: deoxycholic and lithocholic
    • Gallstones can form after terminal ileum resection from malabsorption of bile acids
  11. Short-gut syndrome
    • Dx made on symptoms and not length of bowel
    • Sx: diarrhea, steatorrhea, wt loss, nutritional deficiency
    • Lose fat, B12, electrolytes, water
    • Sudan stain red: check for fecal fat
    • Schilling test: checks for B12 absorption
    • Need 75cm to survive off TPN, 50cm with competent ileocecal valve
    • Tx: restrict fat with diet resumption, H2 blockers to reduce acid, Lomotil
  12. Steatorrhea
    • Causes: gastric hypersecretion of acid, decreased pH, increased intestinal motility, interferes with fat absorption
    • Interruption of bile salt resorption: interferes with micelle formation
    • Tx: Lomotil, decrease oral (fat) intake, Pancrease, H2 blocker
  13. Nonhealing fistulas
    • Foreign body
    • Radiation
    • Inflammatory bowel disease
    • Epithiealization
    • Neoplasm
    • Distal obstruction
    • Sepsis
    • High output: likely with proximal bowel (duodenum or prox jejunum)
    • Colonic: more likely to close
    • Persistent fever: check for abscess (fistulogram, abdominal CT, UGI with SBFT)
    • Cause: iatrogenic
    • Tx: TPN, skin protection, NG, stoma appliance, octreotide
    • 40% close spontaneously
    • Surgery: resect bowel segment with fistula and perform primary anastomosis
  14. Obstruction
    • H/O surgery
    • Small bowel: adhesions, hernia
    • Large bowel: cancer
    • Sx: n/v, crampy abdominal pain, obstipation
    • ABXR: air fluids levels, distended small bowel, distal decompression
    • Bacterial overgrowth from 3rd spacing of fluid in bowel lumen
    • Tx: bowel rest, NG tube, IVF
    • Surgery: progressive pain, peritoneal signs, fever, increasing WBCs, strangulation, perforation, failure to resolve
  15. Gallstone ileus
    • SBO due to gallstone in terminal ileum
    • Air in biliary tree
    • Fistula between gallbladder and 2nd portion of duodenum
    • Tx: remove stone, can leave fistula if pt sick, if not, cholecystectomy and close duodenum
  16. Meckel's Diverticulum
    • True diverticulum
    • 2 ft fom ileocecal valve
    • 2% of population
    • Presents in 1st 2 yrs of life: with bleeding
    • 50% of painless lower GI bleeds in kiddos <2 yo
    • Pancreas tissue: most common
    • Gastric mucosa: most likely to be sx
    • Obstruction: most common presentation in adults
    • Incidental: remove if gastric mucosa suspected, diverticulum feels thick or has narrow neck
    • Dx: Technetium scan
    • Tx: Diverticulectomy; segmental resection for complicated diverticulits or neck >1/3 diameter of the normal bowel lumen or if diverticulitis involves the base
  17. Duodenal diverticula
    • R/O gallbladder disease
    • Observe unless perforated, bleeding, obstructing or sx
    • Frequency: dudodenal>jejunal>ileal
    • Tx: segmental resection, temporary gastroj for perf
  18. Crohn's
    • Intermittent abdominal pain, diarrhea, wt loss, low grade fever
    • 15-35 yrs at first presentation
    • Ashkenazi Jews
    • Extraintestinal manifestations: arthritis, arthralgia, pyoderma gangrenosum, erythema nodosum, ocular diseases, growth failure, megaloblastic anemia from folate and B12 deficiency
    • Mouth-anus
    • Terminal ileum: most commonly involved segment
    • Anal/perianal disease: 1st presentation in 10%
    • Tx: Flagyl
    • Anal disease most common sx with large skin tags
    • Common sites for initial presentation: terminal ileum and cecum (40%), colon (35%), small bowel (20%), perianal (5%)
    • Dx: colonoscopyy with biopsies and enteroclysis
  19. Crohn's pathology
    Pathology: transmural involvement, skip lesions, cobblestoning, narrow deep ulcers, creeping fat
  20. Crohn's tx
    • 5-ASA, sulfasalazine, steroids, azathioprine, methotrexate, Remicade (infliximab: TNF alpha inhibitor used for abscesses or fistula), loperamide
    • No agents affect natural course of the disease
    • TPN: may induce remission and fistula closure in small bowel disease
    • 90% will need operation
  21. Crohn's surgical indications:
    • Obstruction (if partial, treat conservatievely)
    • Abscess (may be able to perc drain)
    • Megacolon
    • Hemorrhage
    • Blind loop obstruction
    • Fissures (do not do a lateral internal spincteroplasty)
    • EC fistula: can tx conservatively first
    • Perineal fistula: unroof and rule out abscess, let heal on its own
    • Anorectovaginal fistula: rectal advancement flap with colostomy
    • Do not need clear margins: 2cm from gross disease
    • Perirectal disease: may respond to resection of small bowel
    • Diffuse disease of colon and rectum: proctocolectomy and ileostomy
    • Incidental finding of IBD in pt with presumed appendicitis: remove appendix if cecum not involved
    • Stricturoplasty: if pt has multiple strictures to save small bowel length, not good for pt's 1st operation b/c leaves disease behind, 10% risk of abscess/fistula/leak
    • 50% recurrence rate after resection
  22. Crohn's complications after removal of terminal ileum
    • Megaloblastic anemia: B12 deficiency
    • Diarrhea and steatrorrhea: decreased bile salt uptake
    • Ca oxalate kidney stones: decreased oxalate binding secondary to increased intraluminal fat that binds Ca, oxalate gets absorbed in colon and released in urine
    • Gallstones: malabsorption of bile acids
  23. Carcinoid
    • Serotonin: produced by Kulchitsky cells (enterochromaffin cell or argentaffin cell)
    • Part of amine precursor uptake decarboylase system (APUD)
    • 5-HIAA is a breakdown product of serotonin: measure in urine
    • Tryptophan: precursor to serotonin
    • Increased use can lead to niacin deficiency and pellagra: diarrhea, dermatitis, dementia
    • Bradykinin also released by carcinoid tumors
  24. Carcinoid Syndrome
    • Caused by bulky liver mets
    • Intermittent flushing and diarrhea
    • Asthma type symptoms
    • GI symptoms from vasoconstriction and fibrosis (desmoplastic reaction)
    • Right heart valve lesions
    • If present with small bowel primary, it indicates liver mets
    • Octreotide scan can localize tumors not seen on CT
    • All pts need abdominal exploration unless unresectable
  25. Appendix carcinoid
    • Most common site for carcinoid
    • 50% of carcinoids arise here
    • Next most common: ileum and rectum
  26. Small bowel carcinoid
    Pts at risk for multiple primaries and second unrelated malignancies
  27. Carcinoid tx
    • Appendix: <2cm appendectomy, >2cm or involved base right hemicolectomy
    • Anywhere else in GI tract: tx like cancer with segmental resection and lymphadenectomy
    • Chemo (streptozocin, 5FU): for unresectable disease and carcinoid syndrome
    • Octreotide
    • Bronchospasm: treat with aprotinin
    • Flushing: treat with alpha blockers (phenothiazide)
    • False 5-HIAA: fruits
    • Pentagastrin can exacerbate symptoms
  28. Intussusception in adults
    • Small bowel or cecal tumors
    • Presentation: bleeding or obstruction
    • Often has malignant lead point
    • Tx: resection
  29. Benign small bowel tumors
    • Rare
    • More common than malignancies
    • Leiomyomas: most common, usually extraluminal
    • Adenomas: most in the ileum, bleeding obstruction (need resection when identified)
  30. Benign small bowel tumors: Peutz Jeghers
    • Autosomal dominant
    • Jejunal and ileal harmatomas
    • Mucocutaneous melanotic skin pigmentation
    • Increased extraintestinal malignancies
    • Slight increased risk of colon CA in pt with polyps
    • Lipomas, neurogenic tumors, and hemangiomas
  31. Malignant small bowel tumors: conditions with increased risk of neoplasia
    • Adenomatous polyps
    • Familial adenomatous polyposis
    • Peutz-Jeghers syndrome
    • Leiomyomas
    • Neurofibromatosis
    • Crohn's
    • Celiac sprue
    • Immunosupression
    • HIV infection
    • H. pylori
    • EBV
  32. Adenocarcinoma
    • Rare
    • Most common malignant small bowel tumor
    • Most in duodenum
    • Sx: obstruction, jaundice
    • Tx: resection and adenectomy, Whipple if in duodenum
  33. Duodenal CA
    Risks: FAP, Gardner's, polyps, adenomas, von Recklinghausen's
  34. Leiomyosarcoma
    • Usually in jejunum and ileum
    • Most extraluminal
    • Hard to differentiate compared with leiomyoma (>5mitoses/HPF, atypia, necrosis)
    • Tx: resection, no adenectomy
  35. Lymphoma
    • Usually in ileum
    • Increased incidence with Wegener's, SLE, AIDS, Crohn's, celiac sprue
    • Posttransplantation: increased risk of bleeding and perforation
    • Dx: abdominal CT, UGI, node sampling
    • Tx: XRT, chemo, wide en bloc resection, include nodes
    • 40% 5 yr survival rate
    • Usually NHL B cell type
    • Mediterranean variant: young males with clubbing
  36. Stomas
    • Loop ileostomies: 1-2% obstruction rate
    • Parastomal hernias: increased with loop colostomies, relocation is the best tx
    • Candida: most common infection
    • Diversion colitis (Hartmann's pouch): secondary to decreased short chain fatty acids - treat with short chain fatty acid enemas
    • Ischemia: most common cause of stenosis of stoma - tx: dilation if mild
    • Crohn's disease: most common cause of fistula near stoma site
    • Abscesses: underneath stoma site often caused by irrigation device
    • Gallstones and uric acid kidney stones: increased in pt with ileostomy
  37. Appendix
    • Anorexia
    • Abdominal pain (periumbilical that radiates to RLQ as peritonitis sets in)
    • Vomiting
    • 20-35 yrs
    • Nl WBC possible
    • CT: diameter >7mm or wall thickness>2mm (looks like a bull's eye), fat stranding, no contrast in appendiceal lumen (give rectal contrast)
    • Midpoint of antimesenteric border: likely to perforate
    • Hyperplasia: most common in children
    • Fecalith: most common in adults (luminal obstruction>appendiceal distention>venous congestion>thrombosis>ischemia>gangrene necrosis>finally rupture
    • Nonoperative: walled off perforated appendix, treat with perc drain and interval appendectomy, consider f/u barium enema or colonoscopy
    • Children and elderly: higher risk of rupture due to delayed diagnosis
    • Children have more vomiting and diarrhea
  38. Appendicitis in pregnancy
    • Most common cause of acute abdominal pain in the first trimester
    • Most likely to occur in 2nd trimester
    • Most likely to perforate in 3rd trimester
    • Make incision where pt is having pain (appendix displaced superiorly)
    • Sx of RUQ pain in 3rd trimester
    • 35% fetal mortality with rupture
    • Women with suspected appendicitis need beta-HCG drawn +/- abdominal US to r/o OBGYN causes
  39. Mucocele
    • Can be benign or malignant mucous papillary adenocarcinoma, needs resection
    • Right hemicolectomy if malignant
    • Pseudomyxoma peritonei with rupture
    • MCC of death: SBO from tumor spread
  40. Regional ileitis
    • Can mimic appendicitis
    • 10% will have Crohn's
  41. Gastroenteritis
  42. Presumed appendicitis
    • Ruptured ovarian cyst
    • Thrombosed ovarian vein
    • Regional enteritis not involving cecum
    • Still do appendectomy
  43. Ileus
    • Causes: surgery, electrolyte abnormalities, peritonitis, ischemia, trauma
    • Dilation is uniform throughout the stomach, small bowel, colon, and rectum without decrompression
    • Obstruction with distal bowel decompression
  44. Typhoid enteritis
    • Rare bleeding/perforation
    • Fever
    • HA
    • Maculopapular rash
    • Leukopenia
    • Abdominal pain
    • Tx: Bactrim