Ileus

Obstipation and intolerance of diet due to non-mechanical factors

Aetiology

• Post-op (especially laparotomy)
  • About 15% of colectomy
  • 3% of hysterectomy
  • 10% of radical cystectomy
  • 10% of open AAA
• Metabolic and electrolyte derangements (hypokalaemia, hyponatraemia, hypomagnesaemia, uraemia, diabetic coma, hypoparathyroidism)
• Drugs
  • Opioids
  • Antihypertensive agents (calcium channel blockers including verapamil, clonidine)
  • Antidiarrhoeal/spasmodic agents (loperamide, hyoscyamine)
  • Phenothiazine antiemetics (prochlorperazine, promethazine)
  • Oral iron preparations
  • Zoledronic acid
  • Anticholinergics (SSRIs, TCAs, antipsychotics, Parkinson disease medications, first-generation antihistamines, muscle relaxants, overactive bladder medications, atropine)
• Intra-abdominal inflammation
  • Gastroenteritis
• Retroperitoneal haemorrhage or inflammation
  • Pancreatitis
• Intestinal ischaemia
• Systemic sepsis (pneumonia)
• Multi-trauma (spinal injury, rib or pelvic fractures, severe burns)
• Systemic illness (renal failure, heart failure, critical illness, MI, stroke)
• Diabetes and ketoacidosis
• Acute intermittent porphyria
• Botulism
• Parkinson disease
• Epilepsy

High-risk factors

• Particularly seen in prolonged abdominal or pelvic surgery, and lower GIT surgery
• Open procedures
• Delaying enteral nutrition
• Peri-operative complications including abscess, bleeding, transfusion, peritonitis/sepsis
• Hypoalbuminaemia and aggressive IV fluids
• Opioids

Pathophysiology

• Inflammation
  • Degree of manipulation is directly related to both the degree of leucocyte infiltration into muscularis, and the amount of intestinal dysmotility
  • This effect is not limited to the manipulated segment - inflammation can even occur in non-abdominal surgery
• Neural reflexes
  • Inhibitory neural reflexes appear to impede return of normal function
  • Blockade of spinal afferents with epidural can improve post-op ileus
• Neurohumeral peptides
  • Nitric oxide, VIP, and possibly substance P all slow gut motility
  • Opioids increase resting tone while decreasing gastric motility and emptying, and decrease propulsive colonic movements

Diagnosis of prolonged post-op ileus - two or more of the following on day 4 or after, with differential diagnoses excluded by imaging

• Nausea or vomiting
• Inability to tolerate an oral diet over the preceding 24 hours
• Absence of flatus over the preceding 24 hours
• Abdominal distension
• Radiologic confirmation

Differential diagnosis

• Physiologic ileus
• Mechanical SBO
  • SBO typically has return of bowel function and oral intake, followed by new onset of symptoms; whereas ileus never comes back
  • Early post-operative adhesions are typically soft and likely to resolve spontaneously
  • Consider likelihood of internal hernia, masses, peritoneal disease

Sign or symptom	Ileus	SBO
Abdominal distention	May be present	May be present
Bowel sounds	Usually quiet or absent	May be high pitched, may be absent
Obstipation	May be present	May be present
Pain	Mild and diffuse	Moderate to severe, colicky
Peritoneal signs	Absent	May be present
Radiography	Dilated loops of bowel, paucity of colonic gas	Dilated loops of bowel, differential air-fluid levels, paucity or absence of colonic gas
Fever, tachycardia	Absent	Should raise suspicion
Vomiting	May be present	May be present, may be bilious or feculent

• Colonic pseudo-obstruction

Investigation

• CT
  • With oral contrast, has a sensitivity and specificity >90% for differentiating ileus from complete SBO
  • Can also identify secondary causes of ileus (abscess, bleeding)
  • Diffuse dilation of the entire small bowel without a transition point
• Bloods
  • Identify reversible factors that may be contributing
  • Seek evidence of alternative diagnosis
• A post-op ileus after laparoscopic surgery should raise suspicion for occult injury (bowel, bladder, ureteral)

Treatment

• Correct underlying abnormality
• NGT indications
  • Moderate/severe vomiting
  • Significant abdominal distension
• IVF and bowel rest
  • Sips of clear fluids
  • Once distension resolves and bowel sounds return, start free fluids
  • When the patient is able to take in adequate oral fluids, restart normal diet
• Analgaesia - minimise opioids, regular paracetamol, regular NSAIDs if possible
• Nutritional support
• CT with oral contrast on day 5 post-op if persisting symptoms
• No resolution by two weeks is an indication for re-operation, although likely to be tough due to adhesions

Unproven treatments

• Gastrografin - may decrease time to stool, but not tolerance of oral diet or resolution of nausea/vomiting