1. Presentation, diagnosis and management of bowel obstruction
Mr Alastair Moses
Consultant Surgeon
NHS Tayside

2. Pathophysiology
Any part of the GI tract may become obstructed and present as an acute abdomen.
Dilatation of bowel proximal to obstruction with air and fluid.
Peristalsis is disrupted.
The manner of presentation depends on the level of obstruction.

3. Pathophysiology: level of obstruction
Upper small bowel obstruction:
Can present acutely within hours of onset with large volumes of gastric, pancreatic and biliary secretions regurgitated into the stomach and vomited.

4. Pathophysiology: level of obstruction
Distal small bowel / large bowel obstruction:
Can present with colicky abdominal pain and
distension. Vomiting (possibly ‘faeculent’)
can occur subsequently.

5. Symptoms of intestinal obstruction
Vomiting
Pain
Constipation
Large bowel obstruction
Incomplete obstruction

6. Symptoms of intestinal obstruction: vomiting
The more proximal the obstruction, the earlier vomiting develops.
Can occur even if nothing is taken by mouth: GI secretions continue to be produced –
Saliva, gastric , pancreatic, bile, small intestine (up to several litres per day).

7. Symptoms of intestinal obstruction: vomiting
Nature of vomitus gives clues to the level of obstruction:
- Semi-digested food eaten a day or two previously (no bile) suggests gastric outlet obstruction.
- Copious bile-stained fluid suggests upper small bowel obstruction.

8. Symptoms of intestinal obstruction: vomiting
Nature of vomitus gives clues to the level of obstruction:
- Thicker, brown, foul-smelling vomitus (‘faeculent’) suggests a more distal obstruction.
[Faeculent vomitus contains altered small bowel contents, not faeces].

9. Symptoms of intestinal obstruction: pain
Distension of the bowel caused by swallowed air and intestinal fluid secreted proximal to an obstruction causes pain.
Intermittent episodes of colicky pain occur as peristalsis attempts to overcome the obstruction.

10. Symptoms of intestinal obstruction: constipation
Propulsion of bowel contents is arrested.
Bowel gas is absorbed distal to the obstruction.
‘Absolute constipation’ (neither faeces or flatus passed rectally) is pathognomonic of bowel obstruction.

11. Symptoms of intestinal obstruction: large bowel obstruction
Symptoms tend to develop more gradually in large bowel obstruction due to the large capacity of the colon and caecum and their absorptive activity.

12. Symptoms of intestinal obstruction: large bowel obstruction
If the ileo-caecal valve remains competent (50% cases) backward flow of accumulated bowel contents is prevented .
The thin walled caecum progressively distends with swallowed air and eventually may rupture: ‘closed loop obstruction’.

13. Symptoms of intestinal obstruction: large bowel obstruction
If the ileo-caecal valve becomes incompetent (50% cases) the small bowel distends, delaying the onset of symptoms.

14. Symptoms of intestinal obstruction: incomplete obstruction
If the bowel is only partially obstructed, the clinical features may be less clearly defined.
Vomiting may be intermittent and bowel habit erratic.

15. Symptoms of intestinal obstruction: incomplete obstruction
Chronic incomplete obstruction leads to gradual hypertrophy of the muscle of the bowel wall proximally.
Peristaltic activity in this hypertrophic muscle is responsible for bouts of colicky pain which can be more prominent than in complete obstruction.

16. Physical signs of intestinal obstruction
Dehydration (dry mouth, loss of skin turgor and elasticity)
Abdominal distension
Visible peristalsis
Relative lack of abdominal tenderness (obstruction with tenderness may indicate bowel strangulation)

17. Physical signs of intestinal obstruction
Obstructing abdominal mass may be palpable
On percussion the centre of the abdomen tends to be resonant due to gaseous distension
Groins must be examined for an obstructing hernia

18. Physical signs of intestinal obstruction
Bowel sounds are traditionally described as high-pitched and tinkling. In practice they may be absent at the time of auscultation, echoing (cavernous quality), or may sound like water lapping against a boat.

19. Investigation of suspected bowel obstruction
Most useful initial investigation is a supine abdominal X-ray:
Bowel proximal to the obstruction is distended with gas.
Erect abdominal films are no longer part of routine clinical practice (multiple air fluid levels).

20. Investigation of suspected bowel obstruction
Distended small bowel loops tend to lie in a central position and have valvulae coniventes.
Distended large bowel tends to lie in its anatomical position and has haustra coli.

21. Investigation of suspected bowel obstruction
Initial plain abdominal X-ray is often followed by CT scan of abdomen to look for the cause of obstruction.
A ‘cut off’ will be observed between dilated proximal and collapsed distal bowel at the site of obstruction.

22. Principles of management of intestinal obstruction
Initial management is ‘drip and suck’.
Nil by mouth.
Insert IV cannula and send blood for: urea & electrolytes.
Resuscitate with IV fluids, replacing electrolyte losses.
Pass a nasogastric tube to decompress the stomach.

23. Mechanical causes of bowel obstruction
Adhesions or bands: congenital or resulting from previous abdominal surgery or peritonitis.

24. Mechanical causes of bowel obstruction
Incarcerated external hernias:
Inguinal
Femoral
Umbilical
Paraumbilical
Ventral
incisional.
Internal hernias.

25. Mechanical causes of bowel obstruction
Volvulus of large or small bowel:
A mobile loop of bowel rotates causing
obstruction at its neck.

26. Mechanical causes of bowel obstruction
Tumours
Gastric cancer blocking the pylorus
Small bowel tumours (rare)
Large bowel cancer

27. Mechanical causes of bowel obstruction
Inflammatory strictures:
Crohn’s disease
Diverticular disease
These obstructions are usually incomplete.

28. Mechanical causes of bowel obstruction
Bolus obstruction:
Food bolus
Impacted faeces
Impacted ‘gallstone ileus’ (rare)
Trichobezoar (rare)

29. Mechanical causes of bowel obstruction
Intussusception: a segment of bowel wall becomes telescoped into the segment distal to it.
Usually initiated by a mass in the bowel wall: enlargement of lymphatic tissue or tumour.
Common in children.

30. Bowel strangulation
Strangulation occurs when a segment of bowel becomes trapped so that its lumen becomes obstructed (incarcerated) and its blood supply compromised (strangulated).
If strangulation is not relieved this will progress to infarction and perforation.

31. Bowel strangulation
Pain over a hernia suggests possible strangulation and is a sign requiring urgent surgical intervention.
Can occur in external hernia or volvulus.

32. Adynamic bowel obstruction
Paralytic ileus
Pseudo-obstruction