CHAPTER 35- SMALL BOWEL.txt

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CHAPTER 35- SMALL BOWEL.txt
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  1. Function of the small intestine:
    nutritient and water absorption
  2. Function of large intestine:
    water absorption
  3. Name the parts of the duodenum:
    Bulb (1st)- 90% of ulcers are here

    Descending (2nd)- contains ampulla of Vater (duct of wirsung) and duct of santorini

    • Transverse (3rd)
    • Ascending (4th)
  4. Which parts of the duodenum are retroperitoneal?
    descending and transverse portions of the duodenum are retroperitoneal
  5. How do you know where the transition point is between the 3rd and 4th portions of the duodenum?
    transition point is at the acute angle between the aorta (posterior) and the SMA (anterior)
  6. Whats the vascular supply of the duodenum?
    • Vascular supply is superior (off gastroduodenal artery) and inferior (off SMA) pancreaticoduodenal arteries.
    • - both have anterior and posterior branches
    • - many communications between these arteries
  7. Jejunum
    1) 100 cm long, long vasa recta, circular muscle folds

    • 2) maximum site of all absorption, except:
    • 1- B12 (terminal ileum)
    • 2- bile acids (ileum, nonconjugated; terminal ileum-conjugated)
    • 3- iron (duodenum)
    • 4- folate (terminal ileum)

    3) 95% NaCl absorbed, 95% water absorbed in jejunum

    4) Vascular supply- SMA
  8. Ileum
    1) 150cm long; short vasa recta, flat

    Vascular supply- SMA
  9. Intestinal brush border
    • 1- maltase
    • 2- sucrase
    • 3- limit dextrinase
    • 4- lactase
  10. Normal sizes of

    Small Bowel
    transverse colon
    cecum
    small bowel- 3cm

    transverse colon- 6cm

    cecum- 9cm
  11. What does the SMA ultimately branch off
    SMA eventually branches off ileocolic artery
  12. Cell Types:
    • 1) absorptive cells
    • 2) goblet cells- mucin secretion
    • 3) paneth cells- secretory granules, enzymes
    • 4) Enterochromaffin cells- APUD, 5-hydroxytryptamine release, carcinoid precursor
    • 5) Brunner's glands- alkaline solution
    • 6) Peyer's patches- lymphoid tissue; increased in the ileum
    • 7) M cells- antigen presenting cells in intestinal wall
  13. Where is IgA released?
    Into the gut and also in mother's milk
  14. Fe
    both heme and Fe transporters
  15. Migrating motor complex (gut motility)
    Phase I - rest

    Phase II - acceleration and gallbladder contraction

    Phase III - peristalsis

    Phase IV - deceleration

    Motilin is the most important hormone in migrating motor complex
  16. Fat and cholesterol:
    • 1) broken down by:
    • 1- cholesterol esterase
    • 2- phospholipase A2
    • 3- lipase
    • 4- colipase in combination with bile salts

    2) converted to free fatty acids and monacylglycerides--> form micelles

    3) TAGs are reformed in the intestinal cells and released as chylomicrons into the lymphatics via terminal villous lacteals

    • 4) Chylomicrons- released into lymphatics
    • 1- 90% TAGs
    • 2- 10% phospholipid
    • 3- cholesterol
    • 4- protein

    5) Long-chain fatty acids- released into lymphatics

    • 6) Short and medium chan fatty acids- released into portal vein
  17. Bile salts:
    • 1) 95% of bile salts are reabsorbed
    • - 50% passive absorption- 45% ileum and 5% colon
    • - 50% active resorption in terminal ileum (Na/K ATPase)

    2) Conjugated bile is absorbed only in the terminal ileum

    3) bile is conjugated to taurine and glycine

    4) can also be deconjugated in the colon by bacteria and absorbed there (small amount)

    • 5)
    • primary bile acids- cholic and chenodeoxycholic
    • secondary bile acids- deoxycholic and lithocolic (from bacterial action on primary bile acids in the gut)

    6) gallstones can form after terminal ileum resection from malabsorption of bile acids
  18. Short gut syndrome
    1) diagnosis is made on symptoms, not length of bowel

    • 2) Symptoms:
    • 1- diarrhea
    • 2- steatorrhea
    • 3- weight loss
    • 4- nutritional deficiency

    • 3) Lose:
    • 1- fat
    • 2- B12
    • 3- electrolytes
    • 4- water

    4) Sudan red stain- checks for fecal fat

    5) Schilling test- checks for B12 absorption (radiolabeled B12 in urine)

    6) Probably need at least 75cm to survive off TPN; 50 cm with competent ileocecal valve

    • 7) Treatment-
    • 1- try to restrict fat with diet resumption
    • 2- H2 blockers to reduce acid
    • 3- lomotil
  19. Causes of steatorrhea
    1) gastric hypersecretion of acid--> decreased pH --> increased intestinal motility; interferes with fat absorption

    2) Interruption of bile salt resorption interferes with micelle formation (i.e. terminal ileum resection)

    • 3) Treatment:
    • 1- control diarrhea (codeine, lomotil)
    • 2- decrease oral intake, especially fats
    • 3- pancrease
    • 4- H2 blocker
  20. Nonhealing fistulas
    • 1) "FRIENDS" pneumonic for causes of nonhealing fistulas:
    • Foreign body
    • Radiation
    • Inflammatory bowel disease
    • Epithelialization
    • Neoplasm
    • Distal obstruction
    • Sepsis/infection

    2) High-output fistulas are most likely with proximal bowel (duodenum or proximal portion of jejunum) and are less likely to close with conservative management

    3) Colonic fistulas are more likely to close than those in small bowel

    4) Patients with persistent fever- need to check for abscesses (fistulogram, abdominal CT, upper GI with small bowel follow-through series)

    5) Most fistulas are iatrogenic and treated conservatively 1st --> TPN, skin protection, NG tube, stoma appliance, octreotide

    6) 40% close spontaneously

    • 7) surgical options:
    • 1- resect bowel segment containing fistula and perform primary anastomosis
  21. Obstruction
    • Without previous surgery (most common)
    • -small bowel- hernia
    • -large bowel- cancer

    • With previous surgery (most common)
    • -small bowel- adhesions
    • -large bowel-cancer

    • Symptoms:
    • nausea and vomiting
    • crampy abdominal pain
    • failure to pass gas or stool

    • Abdominal x-ray:
    • air-fluid level
    • distended loops of small bowel
    • distal decompression

    Get bacterial overgrowth; 3rd spacing of fluid into bowel lumen

    Air with bowel obstruction- from swallowed nitrogen

    • Treatment:
    • 1- NG tube
    • 2- IV fluids
    • 3- bowel rest
    • - cures 80% of partial SBO and 20-40% of complete SBO

    • Surgical Indications:
    • 1- progressing pain
    • 2- peritoneal signs
    • 3- fever
    • 4- increasing WBCs
    • -signs of strangulation or perforation, failure to resolve
  22. Gallstone Ileus
    • 1- small bowel obstruction from gallstone in terminal ileum
    • 2- classically see air in biliary tree in a patient with small bowel obstruction
    • 3- caused by a fistula between gallbladder and second portion of the duodenum
    • 4- Tx: remove stone from terminal ileum
    • - can leave gallbladder and fistula if patient is too sick
    • -if not too sick, peform cholecystectomy and close duodenum
  23. Meckel's Divertuculum (a true diverticulum)
    • 1)
    • 2ft from ileocecal valve
    • 2% of population
    • usually presents in 1st 2 years of life with bleeding

    2) caused by failure of closure of the omphalomesenteric duct

    3) accounts for 50% of all painless lower GI bleeds in children <2 years old

    4) pancreas tissue- most common tissue found in Meckel's

    5) gastric mucosa- most likely to be symptomatic

    6) obstruction- most common presentation in adults

    7) incidental --> usually not removed unless gastric mucosa suspected (diverticulum feels thick) or has very narrow neck

    8) Dx: can get a Meckel's scan (99Tc) if having trouble localizing (mucosa lights up)

    • 8) Treatment: diverticulectomy for uncomplicated diverticulitis
    • -need segmental resection for complicated diverticulitis or neck >1/2 the diameter of the normal bowel lumen or if the diverticulitis involves the base
  24. Duodenal Diverticula
    • 1) need to rule out gallbladder disease (chronic cholecystitis) origin
    • 2) Observe unless perforated, bleeding, causing obstruction, or highly symptomatic
    • 3) Frequency of diverticula: duodenal> jejunal>ileal
    • 4) Treatment: segmental resection; may need temporary gastrojejunosomy for duodenal perforation
  25. Crohn's Disease
    1) intermitent abdominal pain, diarrhea, and weight loss; low grade fever

    2) 15-35 years old at 1st presentation

    3) increased in ashkenazi jews

    4) can have extraintestinal manifestations (arthritis, arthralgias, pyoderma gangrenosum, erythema nodosum, ocular disease, growth failure, megaloblastic anemia from folate and vitamin B12 malabsorption)

    5) can occur anywhere from mouth to anus

    6) Terminal ileum- most commonly involved bowel segment

    • 7) anal/perianal disease- 1st presentation in 10%
    • Tx: flagyl

    8) anal disease most common symptom- large skin tags

    • 9) most common sites for initial presentation:
    • 1- terminal ileum and cecum -40%
    • 2- colon only 35%
    • 3- small bowel only 20%
    • 4- perianal 5%

    10) Diagnosis: colonoscopy with biopsies and enteroclysis can help make the diagnosis
  26. Whats the pathology of Crohn's disease:
    • 1- transmural involvement
    • 2- segmental disease (skip lesions)
    • 3- cobblestoning
    • 4- narrow deep ulcers
    • 5- creeping fat
    • 6- fistulas
    • 7- small bowel may be involved
    • 8- perianal disease common
  27. Medical treatment:
    • 1) 5-ASA/sulfasalazine (essentially provides topical antiinflammatory relief inside intestine)
    • 2) steroids
    • 3) azathioprine (DNA synthase inhibitor)
    • 4) methotrexate (inhibits metabolism of folic acid)
    • 5) remicade monoclonal antibody against TNF-alpha (infliximab, TNF-alpha inhibitor, usually used for absess or fistula)
    • 6) loperamide (anti-diarrheal, llarge intestine specific mu opiod receptor agonist)

    NO AGENTS affect the natural course of disease

    TPN- may induce remission and fistula closure with small bowel crohn's disease

    90% of patients with Crohn's disease will eventually need an operation
  28. Surgical indications
    • 1) unlike ulcerative colitis, surgery is not curative
    • 2) obstruction- usually just partial and can be initially treated conservatively
    • 3) abscess- can usually be treated with percutaneous drainage
    • 4) megacolon- perforation occurs in 15%, usually contaminated
    • 5) hemorrhage- unusual in Crohn's but can occur
    • 6) blind loop obstruction
    • 7) fissures- no lateral internal sphincteroplasy in patients with Crohn's disease
    • 8) enterocutaneous fistula- can usually be treated conservatively
    • 9) perineal fistulas- unroof and rule out abscess; let heal on its own
    • 10) anorectovaginal fistulas- may need rectal advancement flap; usually need colostomy
    • - do not need clear margins; just get 2cm away from gross disease

    • - perirectal disease may respond to resection of small bowel
    • - patients with diffuse disease of colon and rectum- proctocolectomy and ileostomy are the procedures of choice
    • -incidental finding of inflammatory bowel disease in patient with presumed appendicitis who has normal appendix- remove appendix if cecum not involved

    • Stricturoplasty:
    • 1- consider if patient has mutiple strictures to save small bowel length
    • 2- probably not good for patient's 1st operation as it leaves disease behind
    • 3- 10% leakage/abscess/fistula rate with stricturoplasty

    -50% recurrence rate requiring surgery for Crohn's disease after resection
  29. Complications from removal of terminal ileum:
    • 1) decreased B12 uptake can result in megaloblastic anemia
    • 2) decreased bile salt uptake causes osmotic diarrhea (bile salts) and steatorrhea (fat) in the colon
    • 3) decreased oxalate binding secondary to increased intraluminal fat that binds calcium--> oxalate then gets absorbed in the colon--> released in the urine--> Ca oxalate kidney stones (hyperoxaluria)
    • 4) gallstones can form after terminal ileum resection from malabsorption of bile acids
  30. Carcinoid
    • 1) serotonin is produced by Kulchitsky cells (enterochromaffin cell or argentaffin cell)
    • - part of amine precursor uptake decarboxylase system (APUD)
    • - 5-HIAA is a breakdown product of serotonin- can meausure this in urine
    • - tryptophan is the precursor to serotonin
    • - increased use of tryptophan can lead to niacin deficiency and pellagra (diarrhea, dermatitis, dementia)

    2) Bradykinin- also released by carcinoid tumors

    • 3) Carinoid syndrome- caused by bulky liver metastases
    • 1- intermittent flushing and diarrhea- hallmark symptoms
    • 2- can also get asthma-type symptoms and right heart valve lesions
    • 3- if patient has carcinoid syndrome with small bowel carcinoid primary, it indicates metastasis to liver (liver usually clears serotonin)
    • 4- all patients with carcinoid syndrome need abdominal exploration unless unresectable
    • 5- if resection of liver metastases is performed, perform cholecystectomy in case of future embolization
    • 6- GI symptoms from vasoconstriction and fibrosis (desmoplastic reaction)
    • 7- octreotide scan- good for localizing tumor not seen on CT scan
  31. where are carcinoid tumors most common?
    appendix carcinoid is the most common site for carcinoid tumor (50% of carcinoids arise here; ileum and rectum next most common)
  32. Small bowel carcinoid-
    1) patients at high risk for multiple primaries and second unrelated malignancies

    • 2) cardinoid in appendix:
    • <2cm--> appendectomy
    • >2cm or involving base --> right hemicolectomy

    3) Carcinoid anywhere else in GI tract --> treat like cancer (segmental resection with lymphadenectomy)

    • 4) Chemotherapy-
    • 1- streptozocin (alkylating agent; causes damage to DNA)
    • 2- 5FU (works in S phase, pyrimidine analogue works through noncompetitive inhibition of thymidylate synthase);
    • usually just for patients with unresectable disease and carcinoid syndrome

    5) octreotide- useful for patients with carcinoid syndrome

    6) bronchospasm- Tx: Aprotinin

    7) Flushing- Tx alpha blockers (phenothiazine)

    8) Pentagastrin- can exacerbate symptoms

    7) Flushing- Tx: alpha blockers (phenothiazine)
  33. What will give you a false 5-HIAA?
    fruits
  34. Intussusception in adults
    • 1) can occur from small bowel or cecal tumors
    • 2) most common presentation is bleeding or obstruction
    • 3) worrisome in adults it often has a malignant lead point (i.e. cecal Ca)
    • 4) Treatment: resection
  35. Benign Small Bowel tumors
    • 1) rare
    • 2) benign small bowel tumors are more common than malignant
    • 3) Leiomyomas- most common benign small bowel tumor; usually extraluminal
    • 4) Adenomas- most found in the ileum; present with bleeding, obstruction
    • - need resection when identified
  36. Benign Small Bowel tumors:
    Peutz-Jeghers Syndrome (Autosomal dominant)
    • 1) jejunal and ileal hamartomas
    • 2) mucocutaneous melanotic skin pigmentation
    • 3) patients have increased extraintestinal malignancies
    • -slight increased risk of colon Ca in patients who have these polyps
    • -lipomas, neurogenic tumors, and hemangiomas can occur in these patients as well
  37. Conditions associated with increased risk of neoplasia:
    (Preexisting condition --> Potential malignancy)

    • Adenomatous polyps --> adenocarcinoma
    • Familial adenomatous polyposis --> adenocarcinoma
    • Peutz-Jeghers Syndrome/Hamartomatous polyps --> adenocarcinoma
    • Leiomyomas --> possible leiomyosarcoma
    • Neurofibromatosis --> leiomyosarcoma, carcinoid, adenocarcinoma
    • Crohn's disease --> adenocarcinoma
    • Celiac sprue --> lymphoma, adenocarcinoma
    • Immunosuppression --> lymphoma
    • HIV invection -->lymphoma, kaposi sarcoma
    • H. pylori infection --> low-grade lymphoma (mucosal associated lymphoid tissue)
    • EBV infection --> lymphoma
  38. Malignant Small Bowel Tumors:
    Adenocarcinoma
    • 1) rare, but the most common malignant small bowel tumor
    • 2) high proportion is in the duodenum
    • 3) treatment: resection and adenectomy; whipple if in duodenum
  39. Malignant Small Bowel tumors:
    Duodenal Ca
    • Risk factors:
    • 1- FAP
    • 2- Gardner's
    • 3- polyps
    • 4- adenomas
    • 5- von Recklinghausen's
  40. Malignant Small Bowel Tumors:
    Leiomyosarcoma:
    • 1) usually in jejunum and ileum; most extraluminal
    • 2) hard to differentiate compared with leiomyoma (>5 mitosis/HPF, atypia, necrosis)
    • 3) Treatment: resection; no adenectomy required
  41. Malignant Small Bowel Tumors:
    Lymphoma:
    • 1) usually in ileum; increased incidence in patients with:
    • 1- Wegener's disease
    • 2- SLE
    • 3- AIDS
    • 4- Crohn's
    • 5- Celiac sprue

    2) posttrasplanation- increases risk of bleeding and perforation

    3) Diagnosis: abdominal CT, UGI, node sampling

    4) Treatment: XRT, chemotherapy, wide en-bloc resection may be needed; include nodes

    5) 40% 5 year survival rate

    6) usually NHL B cell type

    7) Mediterranean variant occurs in young males and they get clubbing
  42. Stomas
    1) loop ileostomies- 1-2% obstruction rate

    2) parastomal hernias- increased with loop colostomies- relocation is the best treatment

    3) candida is the most common stomal infection

    • 4) Diversion colitis (hartmann's pouch) secondary to decreased short-chain fatty acids
    • -treatment- short-chain fatty acid enemas

    • 5) Ischemia- most common cause of stenosis of stoma
    • Treatment- dilation if mild

    6) Crohn's disease- most common cause of fistula near stoma site

    7) Abscesses- underneath stoma site often caused by irrigation device

    8) gallstones and uric acid kidney stones- increased in patients with ileostomy
  43. Appendix:
    Appendicitis-
    • 1) Appendicitis:
    • 1st- anorexia
    • 2nd- abdominal pain (periumbilical)
    • 3rd- vomiting

    2) pain gradually migates to the RLQ as peritonitis sets in

    3) most commonly occurs to patients 20-35 years old

    4) patients can have a normal WBC

    • 5) CT scan-
    • 1- diameter >7mm or wall thickness >2mm (looks like a bulls eye)
    • 2- fat stranding
    • 3- no contrast in appendiceal lumen; try to give rectal contrast

    6) midpoint of antimesenteric border- most likely to perforate

    7) hyperplasia- most common cause in children- can follow a viral illness

    8) Fecalith- most common cause in adults

    • 9) Nonoperative situation- CT scan shows a walled off perforated appendix
    • 1- treatment- percutaneous drainage and interval appendectomy at a later date as long as symptoms are improving
    • 2- consider follow-up barium enema or colonoscopy to rule out perforated colon ca

    • 10) Children and elderly- have higher propensity to rupture secondary to delayed diagnosis
    • 1- children often have higher fever and more vomiting and diarrhea
    • 2- elderly- signs and symptoms can be minimal; may need right hemicolectomy if cancer suspected

    11) appendicitis is infrequent in infants

    12) Perforation- patient generally more ill; can have evidence of sepsis
  44. Appendicitis during pregnancy
    • 1) most common cause of acute abdominal pain in the 1st trimester
    • 2) more likely to occur in the 2nd trimester but is not the most common cause of abdominal pain
    • 3) more likely to perforate in the 3rd trimester- confused with contractions
    • 4) need to make the incision where the patient is having pain- the appendix is displaced superiorly
    • 5) may have symptoms of RUQ pain in the 3rd trimester
    • 6) 35% fetal mortality with rupture
    • 7) women with suspected appendicitis need beta-hcg drawn +/- abdominal ultrasound to rule out Ob/Gyn causes of abdominal pain
  45. Mucocele-
    • 1) can be benign or malignant mucous papillary adenocarcinoma; needs resection
    • 2) need right hemicolectomy if malignant
    • 3) can get pseudomyxoma peritonei with rupture
    • 4) most common cause of death- SBO from tumor spread
  46. Regional ileitis
    • 1) can mimic appendicitis
    • 2) 10% go on to Crohn's disease
  47. Gastroentertis
    • 1- nausea
    • 2- vomiting
    • 3- diarrhea
  48. Presumed appendicitis- but find ruptured ovarian cyst, or thrombosed ovarian vein, or region enteritis not involving cecum, what do you do?
    still perform appendectomy
  49. Ileus
    • 1) causes include:
    • 1- surgery (most common)
    • 2- electrolyte abnormalities (decreased K)
    • 3- peritonitis
    • 4- ischemia
    • 5- trauma
    • 6- drugs

    2) Ileus- dilation is uniform throughout the stomach, small bowel, colon, and rectum without decompression

    3) Obstruction- there is bowel decompression distal to the obstruction
  50. Typhoid enteritis (salmonella)
    • 1) rare bleeding/perforation; fever, headaches, maculopapular rash, leukopenia, abdominal pain.
    • 2) Treatment: bactrim (TMP-SMX)-

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