What is an ileus?
Ileus is the medical term for a condition where the contents in the gastrointestinal tract (gut) are unable to move although there is no mechanical obstruction. It arises from a problem with the gut wall in pushing along the contents – hypomobility. The condition is therefore also known as paralytic ileus. It is a common occurrence after bowel surgery but in most cases it resolves on its own. However, the condition can become protracted and have serious consequences without prompt medical intervention.
An ileus is common after surgery. Up to 50% of patients who have major abdominal surgery will experience an ileus (postoperative ileus) which eases on its own within a few days. A gallstone ileus occurs in less than 1% of patients with gallstones and meconium ileus accounts for about 30% of intestinal obstructions in newborns.
The gut has a muscular wall which contracts in a coordinated manner to push food, fluids and wastes along its length. These coordinated movements are known as peristalsis. It allows the contents in the gut to move from one segment of the gut to the next. In order to coordinate this process, nerves within the gut wall relax the muscles as new contents enter and the contracts the muscles to push these contents into the next segment. These nerves communicate with each other in the bowel wall and through reflexes in the spinal cord. Other nerves from the brain and spinal cord and hormones in the bloodstream can help speed up or slow down this process.
Any damage to the nerves or disturbance in its function, usually with anesthesia and surgery, can affect normal gut motility. These effects are usually temporary and will wear off a short while later. It is primarily the reflexes either within the gut wall, just beyond it or as far as in the spinal cord that may be affected. This nerve damage and disruption may be intentional or accidental during the course of surgery. It can also occur with trauma to the abdomen and spinal cord.
Hormones and chemicals
Apart from the chemical effect of anesthesia which causes temporary paralysis of the gut wall muscles, other chemicals that naturally occur in the body can also have this effect. These naturally occurring chemicals play various important roles in the body but in times of the stress response, in this case induced by surgery, it hampers normal bowl motility. The levels of various hormones may also increase or decrease at these times further impacting on peristalsis.
Impairment after surgery
It is known that there may be a disturbance of normal gut motility for a period of time after surgery as follows :
- Stomach : 1 to 2 days
- Small intestine : few hours
- Large intestine : 3 to 5 days
However, some cases following surgery and various other causes can impact on gut motility for much longer periods of time.
An ileus after abdominal surgery is the most common cause. The entire alimentary tract can be affected but it is most noticeable in the stomach, small intestine and large intestine. It is is the reason that most patients experience constipation shortly after surgery. However, it resolves spontaneously and usually does not need any specific treatment. The restoration of the bowel function is gradual from the ascending to the transverse and then descending colon.
There are various other causes of an ileus :
- Trauma to the abdomen, spine or chest
- Drugs such as opioid anlgesics, antacids, anticlotting medication like warfarin, tricyclic antidepressants such as ammitriptyline and antipsychotics.
- Head injury
- Neurosurgical procedures
- Septicemia (“blood poisoning”)
- Myocardial infarction (heart attack)
- Other causes of electrolyte abnormalities – low potassium, magnesium or sodium
- Kidney stones
The terms ileus may be used in conjunction with various conditions that hamper bowel motility and various different causes. It can be broadly classified as follows :
It is the most common type of ileus and mainly arises with abdominal surgery. Ileus may also occur, but to a lesser extent, with other procedures of the brain, spinal cord and certain nerves.
This can also occur after surgery and with most of the causes mentioned above. The muscles of the gut wall are partially or completely paralyzed and peristalsis cannot occur as normal.
This type of ileus arises with gallstones. It is a mechanical obstruction of the bowel associated with one or more large gallstones. It does not arise specifically from hypomobility due to underactivity of the gut muscles.
Meconium is the first feces of a newborn baby which includes contents ingested while in the uterus. It is usually passed out within 24 hours after birth. However, sometimes it becomes very sticky and causes an obstruction of the bowels. This is known as meconium ileus.
The symptoms of an ileus are non-specific. Many other types of abdominal and gastrointestinal conditions present with the same symptoms and need to be excluded as possible causes. These symptoms include :
- Mild abdominal pain (no cramping)
- Tenderness (sometimes)
- Bloating – sensation of fullness in the abdomen
- Abdominal distention (swollen belly)
- Bowel sounds are diminished or absent
- Constipation (sometimes) with little or no gas (flatus)
The symptoms alone may not be conclusive of an ileus, particularly when the patient is still passing stool and flatus. However, the medical history is important and an ileus should be suspected after abdominal surgery. Therefore further diagnostic investigations are important.
Blood tests are helpful in establishing the cause of an ileus when it arises with dehydration or an infection. However, it cannot conclusively diagnose an ileus. Imaging studies like an x-ray are therefore needed.
A plain abdominal x-ray may reveal distension of the small intestine and colon. Radiocontrast dye inserted into the small intestine via a tube through the nose can provide better definition. This is known as enteroclysis. The dye can be seen on an x-ray and should reach the cecum of the large intestine within 4 hours.
Most cases of postoperative ileus resolves spontaneously. This means that it eases on its own often with no treatment. Therefore most doctors may initially adopt a watchful waiting approach with supportive measures instituted to prevent complications. Some of the measures that may be advised includes :
- Intravenous (IV) fluids
- Entereal feeding through a nasogastric tube.
- Medication that may be causing the ileus need to be discontinued but only with medical supervision.
- NSAIDs (non-steroidal anti-inflammatory drugs) may be used to replace opioid analgesics for post-operative pain.
- Chewing gum can stimulate gastrointestinal motility.
- Walking around after surgery (ambulation) may be helpful but this has not been clinically proven.
The treatment of an ileus depends on the cause. Most of the measures mentioned above are relevant for postoperative ileus. Other causative conditions need to be treated accordingly.