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Small Bowel Obstruction
Liane S. Feldman, MD, FRCSCOctober 25, 2000
Bowel Obstruction
Small Bowel Obstruction
One of the most common problems we face
Partial or complete blockage of lumenOur Goal = intervene before gangrenous
bowel develops
Bowel Obstruction
Classification of SBO
Paralytic (ileus)
Mechanical
Partial Complete
SBO
Bowel Obstruction
Causes of Mechanical SBO
ExtrinsicIntrinsic
Intraluminal Intramural
Bowel Obstruction
SBO: Extrinsic Causes
Adhesions postop, congenital, postinflammatory
Hernias external, internal
VolvulusMass effect
abscess, carcinomatosis, endometriosis, pseudocyst
Bowel Obstruction
SBO: Intraluminal Causes
GallstoneIntussusceptionPolypoid lesionBezoarEnteroliths
Foreign bodyMeconium ileusParasitesInspissated fecesInspissated barium
Bowel Obstruction
SBO: Intramural Causes
Congenital atresia, stricture, web, duplication, Meckels
Inflammatory Crohn’s, radiation, diverticulitis, postischemic
stricture, meds (NSAID, KCl)
Neoplasm primary, secondary
Traumatic
Bowel Obstruction
Etiology of SBO
Adhesions……..60%Malignancy…….20%Hernia…………….10%IBD………………….5%Volvulus…………..3%Miscellaneous…2%
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Approach to SBO
How can we recognize SBO?Is it partial or complete?Is it simple or strangulated?
Bowel Obstruction
Recognition of SBO: History
Previous surgery, esp. pelvicAbdominal pain
Colicky early on Vomiting: the more distal, the later the
onsetObstipation
Bowel Obstruction
Recognition of SBO: Exam
Distention: Varies with levelBowel sounds: may be hypoactive if
lateR/o incarcerated groin, femoral,
obturator (on rectal) hernia !!!Rectal exam: masses, blood
Bowel Obstruction
Radiology: plain films
Supine and uprightDistended loops of SB, air-fluid
levels, paucity of colonic airBut diagnostic only 50-80% of the
time Remember gasless abdomen with
closed loop obstruction (air can’t accumulate in loop)
Bowel Obstruction
Radiology: CT Scan
Discriminates mechanical vs ileus Fluid or air-filled loops proximally Transition zone Collapsed bowel distally
Can look for extrinsic causesNote that obstructing ileocecal lesion can
look like ileus
Bowel Obstruction
New modalities
Ultrasound SB loop dilated > 3 cm Dilated loop > 10 cm Peristalsis of dilated loop Collapsed colon
MRI
Bowel Obstruction
Partial or Complete Obstruction?
Can be diagnostic challenge Important because risk of strangulation
and thus initial management differs Partial: negligible risk of strangulation
(except Richter’s), so nonoperative first Complete: 20-40% risk of strangulation,
so early operation required
Bowel Obstruction
Partial or Complete Obstruction?
Partial suggested by: Flatus 6-12 hrs after onset Colonic air 6-12 hrs after onset
Patients with complete obstruction may still pass gas early on due to distal peristalsis
Bowel Obstruction
Partial or Complete Obstruction?
Barium test: 50 ml of barium via NG Clamp tube x 1 hour (unclamp if vomits, etc) Repeat x-rays over next 12-24 hrs
See if get to colon Contraindicated if suspect LBO: inspissates
CT scan can also be useful Degree of distention, amount of distal air
Bowel Obstruction
Simple vs Strangulated SBO
Presence of strangulation increases mortality to 20% and morbidity to 40%
So why not just operate on the ones with strangulation?
Problem: we can’t diagnose strangulation on clinical grounds!!!
Bowel Obstruction
“Classic” signs of strangulation?
...Continuous pain...Fever
...Tachycardia...Peritoneal signs
...Leukocytosis...Elevated K, amylase, alk phos, LDH, CK
PREDICT NECROSIS, NOT ISCHEMIA
Bowel Obstruction
Predicting Reversible Ischemia
Unfortunately, reversible ischemia is not discernable clinically
CT: thickened bowel wall, pneumatosis, PV air, bowel wall nonenhancement Most are signs of necrosis not ischemia
Bowel Obstruction
Management
ResuscitationTube decompressionTiming of surgeryOperative strategySpecific examples
Bowel Obstruction
Resuscitation
All patients have intravascular depletion: Decreased po intake Vomiting Fluid sequestration
Aggressive resuscitation with IV isotonic solution required Urine output, pulse guide resuscitation CVP line in some cases
Bowel Obstruction
Tube decompression
NG tube: removes swallowed air and gastric fluid Symptomatic relief: vomiting, pain Can give barium down tube Prevent aspiration during induction
Longer tubes not better than NG tubes
Bowel Obstruction
Timing of surgery: Partial SBO
Usually patients suspected of adhesions from previous surgery
Initial nonoperative treatment for few days 60-85% will resolve without operation
Repeat physical exam and AXR q12 hours Reassess decision to operate or not q12
hours Worsening status or failure to improve are
indications for OR
Bowel Obstruction
Timing of surgery: Complete SBO
The issue20-40% incidence of strangulationCannot predict reversible ischemia
clinically
The StrategyOperation after initial 12 - 24 hours of
resuscitation
Bowel Obstruction
Operative Strategy
May involve: Lysis of adhesions Resection of obstructing lesion with
anastomosis Intestinal bypass Rarely, stoma placement
Bowel Obstruction
Operative Technique
1. Clear adhesions to anterior abdominal wall Avoid blind finger dissection and excessive
countertraction; careful, sharp dissection best
2. Inspect region of cecum If distended, is this really a LBO?
3. Work back from collapsed bowel to point of obstruction Don’t need to free adhesions proximal to point of
obstruction
Bowel Obstruction
Assessing viability of intestine
Place back in abdomen with warm towelConventional clinical criteria: normal color,
peristalsis, marginal arterial pulsations Doppler probe does not improve this impression
IV fluorescein dye (1 amp) with Wood lamp more reliable than clinical judgement alone for borderline bowel (Bulkley, Ann Surg, 1981)
Rarely, second look in 24 hours
Bowel Obstruction
Adhesions
Pathophysiology Transudated fibrinogen activated by tissue
factor Forms fibrin clot which initiates adhesion
formation
Peritoneal trauma and ischemia promote adhesion formation by release of tissue factor
Bowel Obstruction
Prevention of Adhesions
Avoid serosal traumaAvoid lysis of nonobstructing adhesionsAvoid spillage in peritoneal cavity Aggressive irrigation of debrisAdjuvent agent: bioresorbable membrane
of hyaluronic acid and carboxymethylcellulose Reduced adhesions to anterior abdominal wall
in RCT (Becker, JACS, 1996)
Bowel Obstruction
Incarcerated hernia
Acutely incarcerated nonreducible hernia = early operative management Site of incarceration is external ring -
make sure bowel does not reduce prior to direct examination
If suspect strangulation, consider midline incision
Bowel Obstruction
Intraabdominal abscess
Severe localized ileus near abscess mimics SBO
Drainage of abscess often sufficient to relieve SBO May be amenable to CT-guided drainage
Bowel Obstruction
Malignant tumor
Primary or secondary neoplasm with SBO - in general, treat like any other obstruction
History of cancer or suspected carcinomatosis- may be challenge Don’t assume the worst: up to 40% due to
benign causes (adhesions, radiation, stricture) Individualize treatment
Bowel Obstruction
Radiation enteritis
Acute enteritis (within few wks of radiation): Try tube decompression, steroids
Chronic Laparotomy usually required
Bowel looks fibrotic, gray-white, thick adhesions
Local resection or bypass if resection difficultTo ascending colon - outside of pelvic radiation field
Avoid anastomosis of radiated bowel
Bowel Obstruction
Acute postoperative obstruction
Risk of obstruction 1% within 4 weeks Causes: adhesions (90%); internal hernia,
abscess, volvulus, intussusception (10%)
Challenge is to differentiate ileus and SBOCT with oral contrast very useful
R/o abscess Delineate degree, site of obstruction
Bowel Obstruction
Acute postoperative obstruction
Management: like late obstructions Partial: initially nonoperative, NG
decompression Complete: early surgery
Laparotomy required in up to 50%As interval from first operation approaches
2-3 weeks, character of adhesions worsens and operation is much harder
Bowel Obstruction
Recurrent Obstruction
Risk of SBO after surgery is about 5% Recurrence rates vary from 5-30%
Initial nonoperative trial usually safe Bowel less mobile and apt to twist due to
dense adhesions
Evaluate each patient to formulate planBowel fixation procedures largely
abandoned
Bowel Obstruction
Role of laparoscopy in SBO
Key is careful selection:(1) mild distention(2) proximal obstruction(3) partial obstruction(4) “single band” anticipated
Best chance of cure: recurrent abdominal pain in localized area with adhesions at same site
Bowel Obstruction
Take Home Messages
How to diagnose SBO History, physical, radiology
Classify it as partial or completeOperate early in complete SBO (12-
24 hrs) because we cannot diagnose strangulation clinically
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Proximal or Distal?
Symptom Proximal(open loop)
Distal(open loop)
Closed loop
Pain I ntermitt ent,colicky, relieved
by vomiting
I ntermitt entto constant
Progressive,rapidlyworsens
Vomiting Large volumes,bilious
Low volume,feculent over
time
May beprominent(refl ex)
Tenderness Epigastric, mildunless
strangulated
Diff use andprogressive
Diff use,progressive
Distention Absent Moderate tomarked
Of ten absent
Obstipation May not bepresent
Present May not bepresent