Expansion
Sympathetic overactivity, inflammation and opioids inhibit coordinated motility
Expansion
Mechanisms
- Sympathetic hyperactivity from surgical stress, inhibiting the enteric nervous system
- Inflammatory response in the bowel wall after handling, with macrophage activation and nitric oxide release
- Opioids, acting on mu receptors in the gut
- Electrolyte disturbance, particularly hypokalaemia, and hypomagnesaemia
- Immobility
Recovery order
- Small bowel: within 4 to 8 hours
- Stomach: 24 to 48 hours
- Colon: 48 to 120 hours, and therefore the rate-limiting step, which is why passage of flatus is the marker of resolution
Enhanced recovery strategies all target these mechanisms: minimally invasive surgery, opioid-sparing analgesia including epidurals and regional blocks, early enteral feeding, chewing gum (sham feeding to stimulate vagal activity), early mobilisation, avoiding fluid overload, and correcting electrolytes.
Distinguishing ileus from mechanical obstruction matters: ileus gives a silent abdomen with diffuse gas including in the colon, whereas obstruction gives active tinkling bowel sounds and a transition point.