Ileus overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Akshun Kalia M.B.B.S.[2]
Overview
Ileus is a disruption of the normal propulsive gastrointestinal motor activity from non-mechanical mechanisms.[1][2] Motility disorders that result from structural abnormalities are termed mechanical bowel obstruction. Some mechanical obstructions are misnomers, such as gallstone ileus and meconium ileus, and are not true examples of ileus by the classic definition. [3]
Historical Perspective
The word ileus has been derived from the Greek word "είλειν" which means to twist. In 1958, Robertson, Eddy, and Vosseler were the first to describe a case of adynamic ileus associated with cecal perforation.
Classification
There is no specific system for classification of postoperative ileus. However, based on etiology, postoperative ileus may be classified into drug induced ileus, metabolic and electrolyte abnormalities induced ileum, and systemic disorder induced ileus.
Pathophysiology
Ileus is defined as temporary cessation of intestinal peristalsis in the absence of mechanical obstruction. The pathogenesis of ileus is multifactorial. Ileus is most commonly seen in the postoperative period. When a patient undergoes a surgical procedure, it often puts the body under significant stress. It is thought that, ileus is the result of surgical stress induced inflammatory process, that leads to release of inflammatory and neuroendocrine mediators (such as nitric oxide, VIP and substance P). Additionally, manipulation of intestine leads to activation of afferent pathways that travel to the brainstem. In turn, the brainstem sends increased autonomic output to the sympathetic neurons resulting in increased secretion of adrenergic output and decreased intestinal motility. Commonly used pain medications such as opiates and intraoperative anesthesia may also aggravate the development of ileus. Commonly associated conditions with ileus include diabetes mellitus, hypothyroidism, and hypoparathyroidism. On gross pathology findings of ileus include bowel contortion with distended small and large intestine. On microscopic histopathological analysis, findings of ileus include inflammatory cells predominantly macrophage and mast cells.
Causes
Common causes of ileus include surgery (major abdominal & non-abdominal operations), metabolic and electrolyte disturbances (hyponatremia, hypokalemia, hypocalcemia and hypomagnesemia), endocrinological disorders (such as diabetes, hypoparathyroidism, hypothyroidism, and adrenal insufficiency), systemic disorders (such as myocardial infarction, pneumonia, renal failure) trauma, sepsis, drugs (such as opiates, anticholinergic agents, autonomic blockers, tricyclic antidepressants and general anesthesia).
Differentiating Ileus overview from Other Diseases
Ileus must be differentiated from other diseases that cause abdominal pain, constipation, nausea and vomiting such as small bowel obstruction, gastric outlet obstruction, gastroparesis, gastrointestinal perforation, acute cholecystitis, acute pancreatitis, chronic pancreatitis, liver abscess and spontaneous bacterial peritonitis.
Epidemiology and Demographics
Ileus is most commonly seen in patients undergoing surgical treatment. The incidence and prevalence of ileus varies with the type of surgery performed. Patients with large incisions are relatively at a higher risk of developing ileus as compared to patients undergoing minor surgical procedures with small incisions. The incidence of ileus in patients undergoing laparotomy is approximately 9000 per 100,000 cases worldwide. The prevalence of ileus is not precisely known. However, it is estimated that that around 10 percent of the people undergoing surgical procedures develop ileus lasting more than three days. Patients of all age groups may develop ileus but more commonly seen in elderly due to underlying comorbidities. There is no racial predilection for ileus and both men and women are affected equally.
Risk Factors
Common risk factors in the development of ileus include increasing age, electrolyte abnormalities , previous history of abdominal surgery, prolonged abdominal or pelvic surgery (laparotomy of lower GI procedures), delayed enteral nutrition, use of preoperative albumin, postoperative deep venous thrombosis, and hypothyroidism. Less common risk factors include spinal cord injury (thoracic cord), obesity, and peripheral vascular disease.
Screening
There is insufficient evidence to recommend routine screening for ileus.
Natural History, Complications, and Prognosis
If left untreated, patients with ileus may progress to develop abdominal pain, abdominal distention, nausea and vomiting with postprandial discomfort. Common complication of ileus include electrolyte imbalance, malabsorption, dehydration, intestinal perforation, ascites, sepsis, jaundice, and pulmonary complications. Depending on the duration of the postoperative ileus at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good. Most cases of postoperative ileus resolve spontaneously and do not require any further treatment.
Diagnosis
Diagnostic Study of Choice
The diagnosis of ileus is made in the presence of positive history and physical exam findings with signs of intestinal aperistalsis on an x-ray. In patients where findings of x ray are equivocal, CT scan of the abdomen should be done to rule out underlying mechanical obstruction as a cause of delayed intestinal motility.
History and Symptoms
Obtaining a history gives important information in making a diagnosis of ileus. The areas of focus should be on onset, duration, and progression of symptoms with special focus on past medical history and current medications. Previous history of hypothyroidism, diabetes and renal failure may hasten the onset of ileus. Common symptoms of ileus include postprandial abdominal discomfort, abdominal distension, nausea and vomiting, feeding intolerance, constipation, flatulence, and belching. Less common symptoms include wound dehiscence and impaired wound healing.
Physical Examination
Physical examination of patients with ileus is usually remarkable for abdominal distension, abdominal tenderness, and minimal or absent bowel sounds. Patients with prolonged ileus may progress to develop peritoneal signs such as rigidity, guarding and rebound tenderness.
Laboratory Findings
There are no diagnostic laboratory findings associated with ileus. However, laboratory evaluations must be done to identify the severity and presence of other complications of ileus such as electrolyte abnormalities and hypovolemia. Common laboratory test include complete blood count, liver function test, renal function test, serum electrolytes, serum lipase and amylase, serum albumin, and measurement of inflammatory markers.
X-ray
An abdominal x-ray with barium meal (small bowel series) may be helpful in the diagnosis of ileus. Findings on an x-ray suggestive of ileus include multiple air–fluid levels throughout the abdomen, elevated diaphragm with dilatation of both large and small intestine, slow movement of barium with a patent intestinal lumen. Serial x rays may also differentiate paralytic ileus from mechanical small intestinal obstruction.
CT
An abdominal and pelvic CT scan is used to confirm the diagnosis of postoperative ileus only in cases when x ray is not diagnostic. Abdomen and pelvis CT scan (with intravenous contrast and oral water soluble contrast) can also distinguish early postoperative ileus from mechanical obstruction. Findings on CT scan diagnostic of postoperative ileus include multiple air–fluid levels throughout the abdomen, elevated diaphragm, dilatation of both large and small intestine with no evidence of mechanical obstruction.
MRI
There are no MRI findings associated with ileus.
Ultrasound
There are no specific ultrasound findings associated with ileus. However, patients with ileus for more than seven days (prolonged ileus) may be evaluated with an abdomen and pelvic ultrasound to determine the underlying cause. Prolonged ileus is generally due to mechanical obstruction and an ultrasound can be done to determine the etiology.
Other Imaging Findings
There are no other imaging findings associated with ileus.
Other Diagnostic Studies
Other diagnostic studies for ileus include enteroclysis. An enteroclysis is done when abdominal x ray and CT scan are inconclusive but patient is still suspected of underlying ileus. In enteroclysis, water-soluble radio-opaque contrast material such as Gastrografin is used to observe the movements of intestine. Enteroclysis can also help in differentiating ileus from small bowel obstruction.
Treatment
Medical Therapy
The majority of cases of ileus are resolved with correction of underlying electrolyte disorder and only require supportive care. Intravenous hydration is advised with appropriate rapid supplementation for electrolyte abnormalities. NSAID are used as baseline analgesic medications and opiates are used in case of severe intractable pain. Patients are put on NPO and nasogastric tube is advised to relieve recurrent vomiting or abdominal distention associated with pain. Prokinetic agents such as erythromycin are not routinely recommended.
Surgery
Surgical intervention is not routinely recommended for the management of ileus. However, patients of prolonged ileus (> 7 days) or signs of intestinal perforation (peritoneal signs) may require urgent surgical intervention to identify and alleviate complications of ileus.
Primary Prevention
Effective measures for the primary prevention of ileus include early mobilization, avoidance of Ryle's tube (nasogastric tube), prior oral feeding with high carbohydrate solid or liquid solution (preferably 6 hours prior to surgery), limited parenteral fluids, avoidance of pain medications such as opiates, and use of epidural anesthesia for postoperative analgesia.
Secondary Prevention
Effective measures for the secondary prevention of ileus include use of local spinal anesthesia via epidural approach and IV ketorolac as a baseline analgesic for postoperative pain seen in patients of ileus. Ileus associated nausea and vomiting should be treated with serotonin receptor antagonist. Other measures include Early mobilization and ambulation with removal of urinary within 24 to 48 hours of surgery with avoidance of nasogastric tubes and abdominal drains.
References
- ↑ Townsend CM, Beauchamp RD, Evers BM, Mattox KL. Sabiston Textbook of Surgery. The biological basis of modern surgical practice. 17/e. Elsevier Saunders, 2004.
- ↑ Livingston EH, Passaro EP. Postoperative ileus. Dig Dis Sci 1990;35:121.
- ↑ Feldman M, Friedman LS, Brandt LJ, Sleisenger MH. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. Intestinal Obstruction and Ileus. 8/e. Elsevier Saunders, 2006.