Fiser Chapter 35 SMALL BOWEL Flashcards
Duodenum blood supply
Superior and inferior pancreaticoduodenal arteries
Superior off gastroduodenal
Inferior off SMA
Maximum site of all absorption
-Jejunum: most nutrients, and 95% of NaCl, and 90% of H2O
- Duodenum: iron
- Ileum: non-conjugated bile acids
- Terminal ileum: B12, conjugated bile acids, folate?
Jejunum blood supply
SMA
Ileum blood supply
SMA
Intestinal brush border enzymes
Maltase
Sucrase
Limit dextrinase
Lactase
Normal diameters for small bowel, colon, and cecum
3 / 6 / 9 cm
Gut cell types
Absorptive cells
Goblet cells (mucin secretion)
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 ileum)
M cells: Antigen presenting cells
Ab released into gut
IgA (also in breast milk)
Heme and iron transport
small bowel
Migrating motor complex phases
Gut motility:
Phase I - rest
Phase II - acceleration and GB contraction
Phase III - peristalsis (motilin)
Phase IV - deceleration
Most important hormone for migrating motor complex
motilin
Bile salt reabsorption
95% is reabsorbed
50% passive absorption (non-conjugated) in ileum and a little bit colon
50% active resorption (conjugated) in terminal ileum ONLY (Na/K ATPase)
Why do gallstones form after terminal ileum resection?
It’s the only place where conjugated bile salts are reabsorbed
Diarrhea, steatorrhea, weight loss, nutritional deficiency after bowel resection
Short gut syndrome: generally need at least 75cm to survive off TPN; 50 cm with competent ICV
Dx: -Sudan red stain: fecal fat
-Schilling test: checks for B12 abruption (radiolabeled B12 in urine)
Tx: Restrict fat, PPI to reduce acid, Lomotil (diphenoxylate and atropine)
Steatorrhea causes
- Gastric hypersecretion of acid (decreased intestinal motility in acidic env’t)
- Interruption of bile salt resorption (TI resection, interferes with micelle formation and fat absorption)
Tx: Lomotil (diphenoxylate and atropine), decrease oral intake especially fats, pancrease, PPI
Causes of nonhealing fistula
FRIENDS
- Foreign body
- Radiation
- Infection or IBD
- Epithelialization
- Neoplasm
- Distal obstruction
- Sepsis/steroids
Other: high output, small bowel less likely to close than colonic
Patient with nonhealing fistula presents with fever
Check for abscess: fistulogram, CT, UGI with SBFT
Fistula treatment
-NPO, TPN, stoma appliance, octreotide
Most close without surgery
Surgery: resect small bowel segment containing fistula and perform primary anastomosis
Most common causes of obstruction
Small bowel: hernia, if prior surgery adhesions
Large bowel: cancer
Patient with nausea, emesis, crampy abdominal pain, failure to pass gass or stool, AXR shows air-fluid level, distended loops of small bowel, distal decompression
Bowel obstruction
SBO tx
Aggressive fluid resuscitation, bowel rest, NG tube
Cures 80% of partial SBO, 40% of complete SBO
Surgical indications for SBO
Progressing pain, peritoneal signs, fever, increasing WBCs (signs of strangulation or perforation), or failure to resolve
Patient with SBO and air in the biliary tree
Gallstone ileus, gallstone usually in TI
Caused by fistula between gallbladder and second portion of duodenum
Tx:
- Remove stone from TI (if any signs of ischemia at cecum then resect)
- If NOT too sick, also perform cholecystectomy and close duodenum
1yo child with painless lower GI bleed
Meckel’s (true) diverticulum, caused by failure of closure of omphalomesenteric duct
Rule of 2’s: 2 ft from ICV, 2% of population, presents with bleeding in first 2 years of life
Most common tissue found in Meckel’s
Pancreas, can cause diverticulitis
Most likely type of meckel’s to be symptomatic
Gastric mucosa (bleeding)
Meckel’s presentation
Either bleeding <2yo, or obstruction in adults
What do you do if you encounter an incidental Meckel’s?
Usually not removed unless gastric mucosa suspected (diverticulum feels thick) or has a very narrow neck
Meckel’s dx and tx
-Meckel’s 99Tc scan if trouble localizing (mucosa lights up)
- Diverticulectomy for uncomplicated diverticulitis or bleeding
- Indications for resection: complicated diverticulitis (perforation), neck > 1/3 diameter of normal bowel lumen, or diverticulitis involves the base
Small bowel diverticula
Duodenal > jejunal > ileal
Need to rule out gallbladder-duodenal fistula
Observe unless perforated, bleeding, obstructed, or symptomatic:
- Surgery: segmental resection (avoid Whipple!)
- Biliary symptoms: juxta-ampullary needs choledochojejunostomy
- Pancreatitis: ERCP with stent
25yo Jew with intermittent abdominal pain, diarrhea, weight loss, fistulas, anal skin tags
Crohn’s, anywhere from mouth to anus, though usually spares rectum
Most commonly involved segment is TI
Crohn’s extraintestinal manifestations
- Arthritis, arthralgias
- Pyoderma gangrenosum
- Erythema nodosum
- Ocular disease
- Growth failure
- Megaloblastic anemia from folate and B12 malabsorption
Crohn’s dx
Colonoscopy with biopsies and enteroclysis can help
Path: transmural involvement, segmental disease (skin lesions), cobblestoning, narrow deep ulcers, creeping fat, fistulas
Crohn’s pancolitis: same colon CA risk as UC
Crohn’s tx
- 5-ASA, loperamide
- Acute flares: steroids
- Steroid-resistance or fistulas: Infliximab (TNF-alpha inhibitor)
- TPN may induce remission and fistula closure with small bowel disease
NO agents affect natural course of disease
90% eventually need an operation
Crohn’s surgical indications
Just need 3cm away from gross disease, do not need clear path margins.
Unlike in UC, surgery NOT curative
- Obstruction (if fails nonop mgt)
- Abscess (drainage)
- Megacolon
- Hemorrhage (unusual)
- Blind loop obstruction
- Fissures (NO lateral internal sphincteroplasty in Crohn’s)
- EC fistula (usually nonop)
- Perineal fistula (unroof to check for abscess, then let heal)
- Anorectovaginal fistulas (may need rectal advancement flap or colostomy)
Crohn’s with diffuse colon disease, what is tx
Proctocolectomy and ileostomy (no pouches or ileoanal anastomosis)
What do you do if you are attempting an appy and find IBD with normal appy?
Appendectomy if cecum not involved (avoids future confounding diagnosis)
Patient with Crohn’s and multiple bowel strictures and past operations
Stricturoplasty: longitudinal incision through stricture, close transversely, consider if has multiple bowel strictures to save small bowel length, not good 1st operation as leaves disease behind
10% leakage/abscess/fistula rate
Incidence of Crohn’s recurrence requiring more surgery after resection?
50%
Terminal ileum removal, complications?
- Megaloblastic anemia (decreased B12 uptake)
- Osmotic diarrhea and steatorrhea (decreased bile salt uptake)
- Gallstones from above too
- Ca oxalate kidney stones (decreased oxalate binding to calcium d/t increased intraluminal fat) -> oxalate absorption in colon and released in urine -> hyperoxaluria and stones
Intermittent flushing and diarrhea, asthma symptoms, CT negative but octreotide scan localizes liver mass
Carcinoid syndrome:
Kulchitsky cells (enterochromaffin or argentaffin cell) produce SEROTONIN, part of APUD (amine precursor uptake decarboxylase system) -> 5-HIAA is a breakdown product of serotonin measured in urine (also false elevation with eating fruits) -> bulky liver mets -> diarrhea (serotonin) and flushing (kallikrein)
Bradykinin also released -> asthma symptoms
Right heart valve lesions
Tx: liver mets resection, cholecystectomy in case of future embolization
Most common sites for carcinoid
- Appendix
- Ileum
- Rectum
If small bowel: increased risk for multiple primaries and second unrelated malignancy
Carcinoid tx
- Appendectomy (< 2 cm)
- Right hemicolectomy if 2 cm or greater or involving base
- Segmental resection with lymphadenectomy if anywhere else in GI tract
- Streptozocin and 5FU for unresectable disease
- Octreotide for syndrome palliation
- Aprotinin for bronchospasm
- Alpha-blockers (phenothiazine) for flushing
Intusussception tx
Adult: presents as obstruction, can be from tumor, often a malignant lead point (small bowel or cecal)
Tx: RESECTION
Small bowel tumors
Adenomas (benign)
Peutz-Jeghers syndrome (benign)
Adenocarcinoma (malignant)
Leiomyosarcoma (malignant)
Lymphoma (malignant)
Small bowel adenomas
Most often in duodenum
Present with bleeding or obstruction
Need resection (endoscopic) if identified
Peutz-Jeghers syndrome
Autosomal dominant
Hamartomas throughout GI tract
Mucocutaneous melanotic skin pigmentation
Patients have increased extraintestinal malignancies (breast cancer most commonly) and small risk of GI malignancies; NO prophylactic colectomy
Small bowel adenocarcinoma
Rare, though most common malignant SB tumor
Most in duodenum
Tx: resection and adenectomy; if in 2nd portion of duodenum, Whipple
Duodenal adenoCa risk factors
- FAP
- Gardner’s
- Polyps
- Adenomas
- Von Recklinghausen’s (neurofibromatosis 1)
Leiomyosarcoma
Usually in jejunum and ileum, most extraluminal
Hard to differentiate from leiomyoma (> 5 mitoses/HPF, atypia, necrosis)
Make sure not a GIST: check C-kit
Tx: Resection, NO adenectomy required
Lymphoma
Usually in ileum, and NHL B cell type, 40% 5-year survival
Associated with:
- Wegener’s
- SLE
- AIDS
- Crohn’s
- Celiac sprue
In post-transplant patient: increased risk of bleeding and perforation
Dx: CT, node sampling
Tx: Wide en bloc resection (include nodes) unless 1st or 2nd portion of the duodenum (chemorad, NO Whipple)
Parastomal hernias
Highest incidence with colostomies, generally well tolerated and do not need repair unless symptomatic
Most common stomal infection
Candida
Diversion colitis (Hartmann’s pouch) is due to what
Lack of short-chain fatty acids
Tx: short chain fatty acid enemas
Stomal complications
Parastomal hernias (colostomies)
Infection (candida)
Diversion colitis (lack of short chain fatty acids)
Stenosis (d/t ischemia - dilate)
Fistula (Crohn’s)
Abscess (irrigation device causes it)
Gallstones and uric acid kidney stones (ileostomies)
25yo with anorexia followed by periumbilically abdominal pain, then vomiting, then RLQ pain. Normal WBC.
Appendicitis: luminal obstruction -> appy distension -> venous congestion and thrombosis -> ischemia -> gangrene necrosis -> rupture
CT findings in appendicitis
- diameter > 7 mm
- wall thickness > 2 mm
- fat stranding
- no contrast in in appendiceal lumen, try to give rectal contrast
Appendiceal area most likely to perforate
Midpoint of anti-mesenteric border
MCC of appendicitis in children and adults
Infants: rare
Children: hyperplasia, can follow a viral illness
Adults: fecalith
Appy tx
Walled-off perforation (elderly): perc drainage, interval appy when symptoms improving; consider follow-up barium enema or colonoscopy to rule out perforated cecal colon CA
Difference in presentation between kids, adults, elderly in appy
- Children and eldery higher rupture rate d/t delayed diagnosis
- Children higher fever, more vomiting and diarrhea
- Elderly signs/symptoms can be minimal, may need R hemicolectomy if cancer suspected
Most common cause of acute abdominal pain in 1st trimester of pregnancy
- Appendicitis. Make incision where pain is. Displaced superiorly.
- Although more likely to occur in 2nd trimester, and more likely to perforate in 3rd trimester (RUQ pain)
- 35% fetal mortality with rupture
Appendix mucocele
- Can be benign or malignant mucous papillary tumor
- Needs OPEN resection (don’t spill tumor contents), and Right hemicolectomy if malignant
- Rupture can cause pseudomyxoma peritonei
- MCC death is small bowel obstruction from peritoneal tumor spread
Regional ileitis
Can mimic appendicitis, and 10% go on to Crohn’s
What do you do if you attempt appendectomy but find ruptured ovarian cyst, thrombosed ovarian vein, or regional enteritis not involving cecum?
Still perform appy (prevents future confounding diagnosis)
Most common cause of ileus
Surgery
Also hypokalemia, peritonitis, ischemia, trauma, drugs
Ileus versus obstruction
Ileus: dilatation uniform through stomach, small bowel, colon, rectum, NO decompression
Obstruction: bowel decompression distal to obstruction
Child with RLQ pain, diarrhea, fever, headaches, maculopapular rash, leukopenia, rarely bleeding or perforation
Typhioid enteritis: caused by salmonella
Tx: Bactrim
