Presentation, diagnosis and management of bowel

obstruction

Mr Alastair Moses

Consultant Surgeon

NHS Tayside

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.

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.

Pathophysiology: level of obstruction

• Distal small bowel / large bowel obstruction:

Can present with colicky abdominal pain and

distension. Vomiting (possibly ‘faeculent’)

can occur subsequently.

Symptoms of intestinal obstruction

• Vomiting

• Pain

• Constipation

• Large bowel obstruction

• Incomplete obstruction

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).

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.

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].

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.

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.

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.

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’.

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.

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.

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.

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)

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

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.

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).

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.

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.

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.

Mechanical causes of bowel obstruction

• Adhesions or bands: congenital or resulting from previous abdominal surgery or peritonitis.

Mechanical causes of bowel obstruction

• Incarcerated external hernias:

1. Inguinal2. Femoral3. Umbilical4. Paraumbilical5. Ventral6. incisional.

• Internal hernias.

Mechanical causes of bowel obstruction

• Volvulus of large or small bowel:

A mobile loop of bowel rotates causing

obstruction at its neck.

Mechanical causes of bowel obstruction

• Tumours

1. Gastric cancer blocking the pylorus

2. Small bowel tumours (rare)

3. Large bowel cancer

Mechanical causes of bowel obstruction

• Inflammatory strictures:

1. Crohn’s disease

2. Diverticular disease

These obstructions are usually incomplete.

Mechanical causes of bowel obstruction

• Bolus obstruction:

1. Food bolus

2. Impacted faeces

3. Impacted ‘gallstone ileus’ (rare)

4. Trichobezoar (rare)

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.

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.

Bowel strangulation

• Pain over a hernia suggests possible strangulation and is a sign requiring urgent surgical intervention.

• Can occur in external hernia or volvulus.

Adynamic bowel obstruction

• Paralytic ileus

• Pseudo-obstruction