Differentiating Large Bowel Obstruction from

Small Bowel Obstruction

David Birks FRACSSeptember 2010

Specialists Without BordersSeminar in Surgery

Rwanda, September 2010

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Differentiating large bowel obstruction from small bowel obstruction

Objectives• Physiology & anatomy of small/large bowel• Causes of bowel obstruction• Symptoms & signs• Investigations (plain xray)• Complications • Management – conservative & operative

Functions of intestine

• Small intestine – absorption of fluid, food, vitamins

• Large intestine – absorption of water & Na - converts 1000-2000ml into

200ml semisolid faeces

Fluid replacement - GI loss

• Type Na K Cl HCO3

Gastric 100 10 100

Bile 140 5 80 40

Pancreas 140 5 80 100

Small Bowel 90 10 90 30

Fluid replacement - GI loss

• Type Volume (litres)

Gastric 2.0

Bile 1.0

Pancreas 1.0

Small bowel 3.5

Total 7.5

Causes of small bowel obstruction

• adhesions (previous operation)• external hernia• small bowel volvulus (primary)• neoplasms• miscellaneous

Causes of large bowel obstruction

• carcinoma of colon• volvulus (sigmoid)• diverticular disease• miscellaneous

Symptoms of bowel obstruction

• abdominal pain• vomiting• distension• constipation (no flatus)

High small bowel obstruction

• frequent, profuse vomiting• central abdo pain • minimal distension

Lower small bowel obstruction

• colic pain • moderate vomiting ( may be faeculent)• moderate distension

Large bowel obstruction

• abdominal distension• constipation• lower abdo pain ( may be minimal)• minimal vomiting

Physical Examination

• abdo scars• external hernia• signs strangulation (tenderness, fever, mass)

Investigations

• Plain Xray – supine - erect - chest

• Hb, WCC, Urea & Electrolytes

Further investigations

• CT abdomen• contrast study (via NG )

Plain x ray SBO

• dilated loops with gas• centrally placed• transverse lines (circular folds)

Plain x ray LBO

• dilated bowel with gas (caecum)• peripheral • haustra (not lines across bowel)• may have cut-off point

http://www.learningradiology.com/images/giimages1/abdomensbo.JPG

SBO

LBO

Supine

Carcinoma of Sigmoid – LBO – Decompressed into SB

Prone

http://www.learningradiology.com/caseofweek/caseoftheweekpix2008-2/cow338lg.jpg

Complications of bowel obstruction

• fluid & electrolyte loss - small bowel• aspiration – small bowel• respiratory restriction– large bowel• strangulation – small bowel• caecal perforation – large bowel (competent

Ileo-caecal valve)

Management of bowel obstruction

• nil orally• IV fluid & electrolyte replacement• NasoGastric drainage (small bowel)

Operation for bowel obstruction

• external hernia (SBO) – emergency• signs of strangulation – emergency• SBO not settling – within 24-48 hr• LBO due to carcinoma - soon

Non-operative treatment of bowel obstruction

• sigmoid volvulus – decompress via sigmoidoscope

• post-operative SBO• intussusception in infants (2/12 – 2 yr)• previous operations for SBO• radiation• abdominal carcinomatosis

Operation - SBO

• midline incisionlook for ileo-caecal valve

• treat cause• external hernia – incision over hernia

- if gangrene convert to midline

Operation - LBO

• midline and resect bowel pathology +/- anastomosis+/- stoma

• if left sided obstruction – transverse colostomy through right upper trans incision

Summary of bowel obstruction

• Physiology & anatomy of small/large bowel• Causes of bowel obstruction• Symptoms & signs• Investigations (plain xray)• Complications • Management – conservative & operative

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