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Small Bowel

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Barium enema. Fistulogram ... Also come in enema form for colon symptoms ... Topical steroids used in colitis, as enema, without the side effects of systemic. ... – PowerPoint PPT presentation

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Title: Small Bowel


1
Small Bowel
  • Vithal Vernenkar, D.O.
  • St. Barnabas Hospital
  • Dept. Surgery

2
Structural and Functional Anatomy
  • 280cm long
  • Jejunum begins at LOT, no clear demarcation to
    ileum
  • Jejunum has long vas recta, large plicae, thick
    walls, transparent mesentery
  • Ileum has short vasa, small plicae, thin walls,
    fat in the mesentery.

3
Structural and Functional Anatomy
  • Mesentery attaches the small intestine to the
    posterior abdominal wall.
  • Contains nerves, blood vessels, lymphatics, lymph
    nodes, and fat.

4
Structural and Functional Anatomy
  • Lymph tissues known as Peyers patches are
    abundant.
  • SMA supplies the midgut structures (duodenum
    distal to the ampulla, pancreas, small intestine,
    ascending and transverse colon.)

5
Histology
  • Four layers
  • Mucosa turns over every 3-7 days
  • Submucosa contains vessels, nerves, lymph,
    Meissners plexus. This layer provides the major
    strength when suturing
  • Muscularis outer long layer, inner circ layer
  • Adventitia is a layer of visceral peritoneum

6
Physiology (CHO)
  • Daily CHO load is 350g of starch, lactose,
    sucrose
  • Initial enzyme digestion is by pancreatic and
    salivary amylase
  • CHO broken down to monosaccharides by microvilli

7
Physiology (Protein)
  • The jejunum is responsible for 80-90 of protein
    absorption
  • Proteins are converted by acid and pepsin from
    stomach to polypeptides
  • Acid is neutralized and pepsin is inactivated as
    chyme enters the duodenum

8
Physiology (Protein)
  • Trypsinogen is activated from pancreas to trypsin
    by enterokinase in the duodenum
  • Trypsin activates chymotrypsin and elastase,
    further digesting polypeps
  • Amino acids and dipeptides are absorbed

9
Physiology (Fats)
  • Emulsification begins in the stomach
  • Fat enters the duodenum, where pancreatic and
    biliary secretions mix
  • Lipase breaks down fats in to monoglycerides,
    which are absorbed by diffusion

10
Physiology (Fats)
  • In epithelial cells, triglycerides are
    resynthesized, chylomicrons are formed and enter
    the lymphatic system thru small lacteals
  • Bile salts are reabsorbed in the ileum
  • Most of the excreted fat comes from desquamated
    cells and bacteria

11
Physiology (H2O, Lytes, Minerals, Vitamins)
  • Iron is absorbed mainly in the duodenum
  • Most minerals and water soluble vitamins absorbed
    in jejunum
  • B12 is absorbed only in terminal ileum
  • Of the 5-10 liters entering the small bowel, only
    500cc enter the colon.

12
Consequences of Small Bowel Resection
  • Frequently improve with time
  • Can often be adequately treated with dietary
    changes and antiperistaltic medications

13
Consequences of Small Bowel Resection
  • Diarrhea can result from water overload in colon
  • Malabsorption (Steatorrhea)
  • Irritation of colonic mucosa by bile salts that
    haven't been reabsorbed by terminal ileum

14
Consequences of Small Bowel Resection
  • Bacterial overgrowth in the small intestine may
    occur after resection of the ileocecal valve
    (ileal brake) and can lead to deconjugation of
    bile salts in the small intestine
  • Alterations in H2O and lytes absorption lead to
    net secretion instead of absorption.
  • Fermentation of CHO leads to gas production
  • These lead to bloating, diarrhea, and steatorrhea

15
Consequences of Small Bowel Resection
  • Nutritional deficiencies- B12 supplementation
    should be provided after resection terminal ileum
  • Cholelithiasis may result from bile acid
    malabsorption after ileal resection
  • Renal stones- fat malabsorption leads to calcium
    binding of fat in the colon. This leaves oxalate
    free to form water soluble absorbable salts
    excreted in the urine.

16
Short Bowel Syndrome
  • Inadequate length of intestine
  • Generally occurs when more than 50 of the small
    intestine is resected or if less than 100cm
    remains.
  • Leads to diarrhea, steatorrhea, weight loss,
    nutritional deficiencies, hypergastrinemia
  • If the terminal ileum and valve are retained, 70
    can be resected.

17
Motility
  • Is inhibited by epinephrine
  • Is increased by acetylcholine
  • Migrating myoelectric complex (MMC) results in
    cyclic contractions occurring every three minutes
    during fasting
  • These contractions are thought to clean the
    intestine, prevent overgrowth, regulated by
    motilin

18
Motility
  • The order of recovery of bowel function after
    surgery is
  • Small bowel
  • Colon
  • Stomach

19
Crohns Disease
  • Chronic, transmural, inflammatory process
    primarily affecting young individuals
  • Also known as regional enteritis, terminal
    ileitis, and granulomatous ileocolitis
  • Incurable condition requiring ongoing medical
    management and frequent surgical interventions
  • Long term pain and disability

20
Frequency
  • 5.3 cases per 100,000, incidence increasing in
    adults and children
  • Males and females equally affected
  • Peak age of onset is between 2nd and fourth
    decades, but 5 of cases under 5y

21
Frequency
  • More common in Ashkenazi Jews, white populations
  • Positive family history in 10-15, suggesting a
    genetic predisposition
  • Relative risk of first degree relatives of these
    patients developing the disease is 10-21 times
    greater than general population

22
Etiology
  • Unknown, but many hypotheses
  • Likely multifactorial, involving an infectious
    agent, environmental exposure activating an
    immune response in a genetically susceptible host

23
Etiology
  • The first gene locus linked to Crohns was the
    IBD1 gene on Chr 16
  • Bacterial agents have long been thought to be
    involved in the pathogenesis of the disease
    although none identified as of yet.

24
Etiology
  • Environmental factors such as smoking, second
    hand smoke have been linked to the development of
    Crohns
  • HLA-DR2 and DRB1 associated with UC not Crohns

25
Pathology
  • Characteristically progresses in a discontinuous
    manner with affected bowel interspersed with
    normal bowel
  • Mouth to anus

26
Pathology
  • Most common site terminal ileum (40), colon only
    (35), small bowel only (20), perianal (5).
    Appendix often involved. Rectum frequently spared
  • Anal involvement may be characterized by fissures
    (most common), abscesses,or fistulae. Most are
    off midline, not the usual posterior midline.

27
Pathology
  • Endoscopically appears as patchy areas of
    inflammation separated by uninvolved bowel
    Skip. The earliest lesions are apthous ulcers,
    tiny erosions that typically occur over lymphoid
    follicles
  • Progress to lineal ulcers, which cross over
    transverse folds causing the cobblestone
    appearance

28
Ulcers
29
Ulcers
30
Cobblestone
31
Pathology
  • Grossly, surgical specimens are rigid, thickened
    as a result of chronic inflammation and fibrosis
    during healing periods
  • Mesentery is thickened and shortened, may
    surround the bowel creeping fat

32
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33
Pathology
  • Because of the transmural nature of the disease,
    fistulous connections can occur to other bowel or
    organs.
  • Non-caseating granulomas are found in lamina
    propria or submucosa in 50 of patients
  • Fibrosis may lead to strictures

34
Clinical Features
  • Intestinal manifestations
  • Diarrhea
  • Pain
  • Anorexia
  • Nausea, weight loss
  • Perirectal disease
  • Bleeding is uncommon in comparison to UC

35
Clinical Features
  • Extraintestinal manifestations
  • Arthritis
  • Erythema nodosum, multiforme
  • Pyoderma gangrenosum
  • Sclerosing cholangitis, cholelithiasis
  • Renal calculi
  • Endocrine disorders (growth, amenorrhea), ocular
    disease

36
Diagnosis
  • Combination of laboratory, radiological,
    pathologic examinations
  • Differential includes bacterial enteritis, viral
    enteritis, ulcerative colitis, among others.
  • Labs may show anemia, malnutrition, increased ESR
  • B12 anemia, iron deficiency, folic acid
    deficiency
  • Deficiencies in copper, selenium, zinc common

37
Work-up
  • Colonoscopy
  • UGI series with small bowel follow thru
  • CT scan
  • Barium enema
  • Fistulogram
  • Despite work-up, 10 will have indeterminate
    colitis, with features of both Crohns and UC

38
Complications of Crohns
  • Fistula (29)
  • Pelvic abscess (20)
  • Obstruction (30-50)
  • Hemorrhage (2)
  • Cancer (1)
  • Perforation (1)
  • Ureteral obstruction (1)

39
Medical Management
  • Aminosalicylates often 1st line, include
    sulfasalazine(old), mesalamine(Asacol, Pentasa),
    olsalazine, balsalazide
  • The newer meds lack the sulfapyridine carrier, so
    better tolerated. Also come in enema form for
    colon symptoms
  • 5-ASA blocks prostaglandin release, decreases
    inflammation

40
Medical Management
  • Corticosteroids for treating acuter disease, not
    long term or for achieving remission.
  • Topical steroids used in colitis, as enema,
    without the side effects of systemic.

41
Medical Management
  • Flagyl most commonly used antibiotic
  • Can heal perianal fistulas caused by Crohns to
    completion
  • Cipro is the most common alternative

42
Medical Management
  • Immunosupressants such as Azathioprine and
    6-mercaptopurine used, especially to reduce time
    on steroids, effective in maintenance therapy
  • Cyclosporine, oral treats active disease, used as
    bridge therapy until the above two start working,
    effects go on after stopping drugs for months

43
Medical Management
  • Biologic therapies against TNF-alpha
    (inflammatory cytokine)
  • FDA approved infliximab (Remicade), an antibody
    that targets TNF-alpha
  • Used for active disease, fistula

44
Surgical Therapy
  • Reserved for complications of the disease, and
    failure of medical management
  • Most patients will require surgery during their
    lifetime
  • Within 20y of the onset of their symptoms, 75
    require surgery, many multiple resections, so
    attempts to conserve bowel are a must to avoid
    SBS
  • No surgical cure

45
Surgical Therapy
  • An alternative to bowel resection is
    stricuroplasty
  • In cases of long strictures (12cm), or multiple
    strictures in close proximity, resection with
    primary anastamosis is required.
  • Anastomotic leak around 9
  • Recurrence is 2
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