|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 is commonly defined simply as bowel obstruction. However, authoritative sources define it as decreased motor activity of the GI tract due to non-mechanical causes. In such sense, this does not include motility disorders that result from structural abnormalities, and, therefore, some mechanical obstructions are misnomers, such as gallstone ileus and meconium ileus, and are not true examples of ileus.
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 
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
- lack of bowel movement and/or flatulence
- excessive belching
Risk factors 
- 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).
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 
See also 
- thefreedictionary.com > Ileus Citing:
- Dorland's Medical Dictionary for Health Consumers. 2007
- The American Heritage Medical Dictionary Copyright 2007
- Mosby's Medical Dictionary, 8th edition. 2009
- Saunders Comprehensive Veterinary Dictionary, 3 ed. 2007
- Merriam-Webster's medical dictionary. Retrieved Nov, 9, 2010
- Townsend CM, Beauchamp RD, Evers BM, Mattox KL (2004). "The biological basis of modern surgical practice". Sabiston Textbook of Surgery (17th ed.). Elsevier Saunders.
- Livingston EH, Passaro EP (January 1990). "Postoperative ileus". Dig. Dis. Sci. 35 (1): 121–32. PMID 2403907.
- Feldman M, Friedman LS, Brandt LJ, Sleisenger MH (2006). "Intestinal Obstruction and Ileus". Sleisenger & Fordtran's Gastrointestinal and Liver Disease (8th ed.). Elsevier Saunders.
- Kitabchi AE, Umpierrez GE, Murphy MB, et al. (January 2001). "Management of hyperglycemic crises in patients with diabetes". Diabetes Care 24 (1): 131–53. PMID 11194218.
- McClave SA, Martindale RG, Vanek VW, et al. (2009). "Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.)". JPEN J Parenter Enteral Nutr 33 (3): 277–316. doi:10.1177/0148607109335234. PMID 19398613.
- Fitzgerald JE, Ahmed I (December 2009). "Systematic review and meta-analysis of chewing-gum therapy in the reduction of postoperative paralytic ileus following gastrointestinal surgery". World J Surg 33 (12): 2557–66. doi:10.1007/s00268-009-0104-5. PMID 19763686.
- Lundin C, Sullins KE, White NA, Clem MF, Debowes RM, Pfeiffer CA (November 1989). "Induction of peritoneal adhesions with small intestinal ischaemia and distention in the foal". Equine Vet. J. 21 (6): 451–8. PMID 2591362.
- Vachon AM, Fischer AT (September 1995). "Small intestinal herniation through the epiploic foramen: 53 cases (1987–1993)". Equine Vet. J. 27 (5): 373–80. PMID 8654353.
- Southwood LL, Baxter GM (August 1997). "Current concepts in management of abdominal adhesions". Vet. Clin. North Am. Equine Pract. 13 (2): 415–35. PMID 9290192.
- MedlinePlus Encyclopedia Intestinal Obstruction
- Patient UK: Intestinal Obstruction and Ileus
- PubMed Health: Intestinal obstruction
- Ileus at eMedicine
- Merck Manual Professional: Ileus