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%

Bowel Obstruction

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

Bowel Obstruction

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