Intestinal Obstruction and Ileus

The term ileus has changed in meaning over the years. It is now most frequently used to imply non-mechanical intestinal obstruction.¹ The term paralytic ileus is sometimes used when the problem is inactivity of the bowel.

N.B. Obstruction to free passage of contents can occur at any level of the gut but only obstruction of beyond the duodenum will be considered here. For conditions causing obstruction at a higher level, see the articles on Oesophageal Strictures, Webs and Rings, Carcinoma of the Oesophagus, Gastric Carcinoma, and Pyloric Stenosis.

Small intestinal obstruction accounts for about 5% of acute surgical admissions.² A significant number of colo-rectal malignancies present with obstruction. One large study found an incidence of 16%.³

Risk factors

• Small intestinal obstruction is caused by adhesions in 60%, strangulated hernia in 20%, malignancy in 5% and volvulus in 5%. Malignancy usually means a tumour of the caecum as small bowel malignancies are very rare.²
• Large intestinal obstruction is most often the result of colo-rectal malignancies. Patients are often over 70 years old. The risk of obstruction increases the further down the bowel the lesion is sited, as the contents become more solid. Tumours are often advanced with 25% having distant metastases. Perforation can occur at the site of the tumour or in a dilated caecum.⁴
• Sigmoid and caecal volvulus describes rotation of the gut on its mesenteric axis. The sigmoid colon is the commonest site of volvulus and accounts for 5% of large bowel obstruction. It is usually seen in the elderly or those with psychiatric illness. It is the commonest cause of intestinal obstruction in Africa and Asia where the incidence is 10 times higher than in Europe or North America.⁵
• Paralytic ileus describes the condition in which the bowel ceases to function and there is no peristalsis. Intestinal pseudo-obstruction is also called Ogilvie's syndrome. It results from massive dilatation of the colon but possibly small intestine too. It may occur in association with a number of medical conditions including:⁶
  • Chest infection
  • Acute myocardial infarction
  • Stroke
  • Acute renal failure
  • Puerperium
  • Trauma
  • Severe hypothyroidism
  • Electrolyte disturbance
  • Diabetic ketoacidosis
• Post operative ileus is a significant problem. Reduced handling of the bowel at operation is recommended.⁷
• Congenital gastrointestinal malformations can cause neonatal intestinal obstruction. Another cause is meconium ileus in cystic fibrosis. Volvulus and midgut malrotations affect children and are uncommon.⁸
• Hirschsprung's disease can cause blockage of the bowel. It may present early or late in childhood. Intussusception in children blocks the bowel. Intussusception in adults is much less common and does not tend to obstruct.⁹
• Miscellaneous causes in adults include gallstone ileus (which occurs when a large gall stone is passed into the gut and blocks it), severe constipation causing faecal impaction, and Crohn's disease.^10,11 Malignancy may cause obstruction from outside the gut. An example is gynaecological tumours.¹²
• Body packers can develop intestinal obstruction when packets of illicit drugs packed in condoms are swallowed and trapped in the bowel. The packages may be visible on x-ray. If they leak intoxication will occur.¹³

The relationship between psychiatric or neurological illness and colonic disease is interesting. Volvulus, impaction of the intestine, constipation and megacolon are all more common in patients with presenile dementia and Alzheimer's disease, Parkinson's disease, multiple sclerosis, and quadriplegia. Schizophrenia has an increased risk for megacolon and constipation whilst major depression is associated only with constipation, but with none of the other colonic diseases.¹⁴

History

There is considerable overlap with the presentation of the various conditions although some features may be more prominent or occur earlier in one cause than another. Differentiation on clinical grounds alone is often not possible.

• Diffuse, central abdominal pain of a colicky nature. Pain is less or absent in paralytic ileus but there may be a history to suggest causes.
• Vomiting tends to be early in high level obstruction. Faeculent vomiting is extremely unpleasant and is limited to low obstruction. Retrograde peristalsis results in faecal material being brought back.
• The progress of the condition tends to be faster in small bowel obstruction and slower with lower levels of lesions.
• Abdominal distension: the lower the level of obstruction, the more marked this will be.
• Absolute constipation is early in low obstruction and late in high level obstruction. In low level obstruction there may be a history of progressive constipation or change in bowel habit. In paralytic ileus there is no bowel movement and no flatus.
• In sigmoid volvulus the picture is rather like large bowel obstruction with pain, constipation, late vomiting and a very marked degree of abdominal distension. Half of such patients will have had a previous episode.⁵
• Pseudo-obstruction presents like a large bowel obstruction but the other medical history may indicate the true nature.⁶
• Severe pain and tenderness suggests ischaemia or perforation.

Examination

• Look for signs of dehydration such as poor peripheral perfusion, tachycardia and hypotension. Dehydration is caused by water remaining unabsorbed in the bowel and losses from vomiting without the ability to replace orally. Pyrexia may suggest perforation or infarction of the bowel.
• Examination of the abdomen starts with observation. Abdominal distension will be apparent. It may be worth measuring abdominal girth to monitor progress. Massive peristalsis may even by visible.
• Distended bowel is very resonant on percussion. Abdominal masses may possibly be felt but even a large mass may be missed in a grossly distended abdomen.
• If strangulation or perforation occurs there will be features of an acute abdomen with peritonism.
• Check hernial orifices. Femoral hernia is at high risk of obstruction. Inguinal hernia is a lower risk factor but it is much more common.
• Place a stethoscope on the abdomen to listen for bowel sounds. In obstruction they are very active and tinkling bowel sounds are characteristic. In ileus the bowel is silent or nearly so. Bowel sound are very irregular and so auscultation must not be rushed if a true picture is to be achieved.
• The patient may be generally toxic and unwell because ischaemia of the bowel allows bacteria and toxins to enter the circulation.

• Fluid charts are required to monitor intake and output, especially as an intravenous infusion is almost certainly required, a naso-gastric tube may be passed and oliguria is an important sign of early dehydration.
• Plain abdominal x-ray is a very important investigation. Films are taken supine and erect. A systematic approach is required. Obstruction of the small bowel shows ladder-like series of small bowel loops but this also occurs with an obstruction of the proximal colon. Fluid levels in the bowel can be seen in upright views. Distended loops may be absent if obstruction is at the upper jejunum. The colon is in the more peripheral part of the film and distension may be very marked. Fluid levels will also be seen in paralytic ileus and the small bowel is distended throughout its length. In an erect film a fluid level in the stomach is normal as may be a level in the caecum. Multiple fluid levels and distension of the bowel is abnormal. Gas under the diaphragm suggests perforation.
• Blood should be taken for FBC, urea and electrolytes and creatinine and group and cross-match as major surgery may be required. Glucose may be slightly elevated by stress but very high levels are a cause for concern.
• If there is doubt about a low level obstruction, a water soluble contrast enema x-ray may be helpful. Water-soluble contrast may also be helpful in small bowel obstruction due to adhesions.¹⁶
• CT scanning has been used to good effect to predict the need for surgery in small bowel obstruction.¹⁷

• Abdominal pain and vomiting can occur with gastroenteritis but if the abdomen is bloated and there is little or no bowel movement, obstruction must be considered. Diarrhoea and vomiting will also cause very active bowel sounds that may be confused with the tinkling of obstruction
• Ischaemia of the gut can cause pain and distension but there is usually bloody diarrhoea.
• The pain of acute pancreatitis tends to radiate to the back. There may be an associated paralytic ileus. Amylase is often raised in obstruction but levels are very high in pancreatitis.
• Perforation of the gut can produce an acute abdomen with pyrexia and vomiting. Peptic ulcer disease, perforated diverticular disease and a perforated carcinoma are all possible causes.
• Intussusception should be considered in children.
• Tuberculosis can present as gastrointestinal disease.
• Non-gastrointestinal conditions to bear in mind include myocardial infarction (small bowel) ovarian cancer (large bowel).

• Resuscitation is very important. Correction of fluid and electrolytes considerably reduces the operative risk before surgery for obstruction. In pseudo-obstruction, correction of such abnormalities with facilitate the return of normal bowel function. Note urine output as a sign of adequate replacement. In paralytic ileus a nasogastric tube will reduce vomiting.
• Laparotomy may be required without a clear diagnosis. Resection of the bowel may be required and so blood must be cross-matched and available. Informed consent before operation should include the fact that a stoma may be required.
• Check the drug chart and stop all anticholinergic medication or drugs with codeine or similar properties.
• If possible, it is worth awaiting full resuscitation and fluid replacement before surgery but if the patient is toxic with possible perforation or infarction of bowel, early intervention is required.
• Early surgery is required if there is local or generalised peritonitis, evidence of perforation or an irreducible hernia. A palpable mass and failure to improve are relative indications to intervene surgically.
• A more conservative approach is acceptable if there is incomplete obstruction, previous surgery suggesting adhesions, advanced malignancy or suggestion that it is pseudo-obstruction.
• In view of the risk of perforation and absorption of toxins from ischaemic bowel, prophylactic antibiotics for gut surgery are advised.
• If operation is required a full laparotomy is usually performed with search for the cause of obstruction and management of it. This is often carcinoma of colon and the liver should be checked for metastases. Hemicolectomy, or the appropriate operation is performed for any malignancy. Ischaemic bowel needs to be resected. Even in the absence of malignancy, dilated bowel needs to be rested by formation of a stoma. A Cochrane review has suggested greater standardisation in the surgical management of large bowel obstruction so that comparisons can be made.¹⁸
• In recent years, laparoscopic management of small bowel obstruction has been attempted, with significant success.¹⁹
• Endoscopic stenting is a further advance in the management of small and large bowel obstruction, and may be particularly useful in the palliative care of cancer patients, and in the elderly.^20,21
• If adhesions are thought to be the cause of obstruction then conservative measures will suffice in 65%. History and investigations give no indication as to who will settle and who will needs operation.²²
• Sigmoid volvulus can be treated conservatively in 80% of cases. Sigmoidoscopy and passage of a flatus tube may be successful. Minimally invasive techniques offer much promise but failure of decompression or evidence of perforation requires operation.²³
• Around 25% of colonic volvulus is of the caecum. It involves the terminal ileum and ascending colon. Decompression via the colonoscope may work but usually surgery is required. Ischaemic bowel may require resection. Fixation prevents recurrence. Caecal volvulus is an uncommon and poorly recognised condition.²⁴ There may be a history of previous, intermittent, self limiting abdominal pain.
• In intestinal pseudo-obstruction the cautious use of neostigmine may aid recovery but most important is the correction of fluid and electrolyte imbalance.²⁵ Colonoscopy may need to be used for decompression.. Early recognition and management is vital if perforation is to be avoided.²⁶
• The management of patients with obstruction due to malignancy who are unfit for surgery provides considerable problems.²⁷ Steroids may be of benefit.²⁸

• Any carcinoma that causes obstruction is already advanced and may be metastatic.
• Perforation and ischaemia of the bowel may cause peritonitis and septicaemia.
• Fluid and electrolyte imbalance, hypovolaemia and septicaemia may all contribute to circulatory collapse and acute renal failure.
• In acute colonic pseudo-obstruction, if perforation or ischaemia occurs the mortality is 40%.²⁶

• The prognosis of advanced carcinoma of the colon remains poor. A high proportion of patients who present with obstruction have distant metastases.³⁰
• 50% of sigmoid volvulus will recur in the next 2 years.³¹
• 60% of stomas are never reversed.³²
• Older patients are less able to withstand the rigours of serious illness and major surgery.