|Classification and external resources|
|ICD-10||K31.5, K56.0, K56.3, K56.7, P75, P76.1|
|ICD-9||537.2, 560.1, 560.31, 777.1, 777.4|
Ileus (// or //) is a disruption of the normal propulsive ability of the gastrointestinal tract. Although ileus originally referred to any lack of digestive propulsion, including any bowel obstruction, up-to-date medical usage restricts its meaning to those disruptions caused by the failure of peristalsis, rather than by mechanical obstruction. Although certain older terms such as gallstone ileus and meconium ileus persist in usage, they are now misnomers (which doesn't mean that health care providers don't use them, but rather simply that they are known not to sound like what they are, like the "lead" in a pencil).
Decreased propulsive ability may be broadly classified as caused either by bowel obstruction or intestinal atony or paralysis. However, there are instances where there are symptoms and signs of a bowel obstruction, but with absence of a mechanical obstruction, mainly in acute colonic pseudoobstruction, also known as Ogilvie's syndrome.
Bowel obstruction is generally a mechanical obstruction of the gastrointestinal tract.
Intestinal atony or paralysis
Paralysis of the intestine is often termed paralytic ileus. To be termed "paralytic ileus", the intestinal paralysis need not be complete, but it must be sufficient to prohibit the passage of food through the intestine and lead to intestinal blockage.
Paralytic ileus is a common side effect of some types of surgery, in these cases it is commonly called postsurgical ileus. It can also result from certain drugs and from various injuries and illnesses, e.g. acute pancreatitis. Paralytic ileus causes constipation and bloating. On listening to the abdomen with a stethoscope, no bowel sounds are heard because the bowel is inactive.
A temporary paralysis of a portion of the intestines occurs typically after an abdominal surgery. Since the intestinal content of this portion is unable to move forward, food or drink should be avoided until peristaltic sound is heard from auscultation of the area where this portion lies.
Intestinal atony or paralysis may be caused by inhibitory neural reflexes, inflammation or other implication of neurohumoral peptides.
Symptoms of ileus include, but are not limited to:
- moderate, diffuse abdominal discomfort
- abdominal distension
- nausea/vomiting, especially after meals
- vomiting of biliatic fluid or Bile
- lack of bowel movement and/or flatulence
- excessive belching
- gastrointestinal surgery or other GI procedures
- electrolyte imbalance
- diabetic ketoacidosis (DKA), and other causes of metabolic acidosis
- medications (e.g. opiates or antimuscarinics)
- severe illness (Inflammation with peritonitis)
- spinal cord injury (SCI), those with injury above thoracic vertebrae 5 (T5) will have hypomotility problems within the bowel
Treatment in humans
Traditionally, nil by mouth was considered to be mandatory in all cases, but now it is recognised that gentle feeding by enteral feeding tube may help to restore motility by triggering the gut's normal feedback signals, so this is the recommended management initially. When the patient has severe, persistent signs that motility is completely disrupted, nasogastric suction and parenteral nutrition may be required until passage is restored. In such cases, continuing aggressive enteral feeding causes a risk of perforating the gut.
There are several options in the case of paralytic ileus. Most treatment is supportive. If caused by medication, the offending agent is discontinued or reduced. Bowel movements may be stimulated by prescribing lactulose, erythromycin or, in severe cases that are thought to have a neurological component (such as Ogilvie's syndrome), neostigmine. There is also evidence that 'sham (imitated) feeding', such as chewing gum, may stimulate gastrointestinal motility in the post-operative period.
If possible the underlying cause is corrected (e.g. replace electrolytes).
Treatment and complications in horses
Ileus may increase adhesion formation, because intestinal segments have more prolonged contact, allowing fibrous adhesions to form, and intestinal distention causes serosal injury and ischemia. Intestinal distention has been shown to cause adhesions in foals. Some respondents also mentioned the importance of walking horses postoperatively to stimulate motility. Repeat celiotomy to decompress chronically distended small intestine and remove fibrinous adhesions is also a useful method of treating ileus and reducing adhesions, and it has been associated with a good outcome 
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- MedlinePlus Encyclopedia Intestinal Obstruction
- Patient UK: Intestinal Obstruction and Ileus
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- Ileus at eMedicine
- Merck Manual Professional: Ileus