Presentation, diagnosis and management of bowel obstruction

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: • Inguinal • Femoral • Umbilical • Paraumbilical • Ventral • 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 • Gastric cancer blocking the pylorus • Small bowel tumours (rare) • Large bowel cancer

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

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

Presentation, diagnosis and management of bowel obstruction