Mechanical, dynamic, or adynamic obstruction of the bowel; may be accompanied by severe colicky pain, abdominal distention, vomiting, absence of passage of stool, and often fever and dehydration.
Ileus is non-mechanical obstruction.
Terminology related to ileus:
There are two types of intestinal obstructions, mechanical and non-mechanical. Mechanical obstructions occur because the bowel is physically blocked and its contents can not pass the point of the obstruction. This happens when the bowel twists on itself (volvulus) or as the result of hernias, impacted feces, abnormal tissue growth, or the presence of foreign bodies in the intestines. Unlike mechanical obstruction, non-mechanical obstruction, called or paralytic it, occurs because peristalsis stops. Peristalsis is the rhythmic contraction that moves material through the bowel. Ileus is most often associated with an infection of the peritoneum (the membrane lining the abdomen). It is one of the major causes of bowel obstruction in infants and children. Another common cause of ileus is a disruption or reduction of the blood supply to the abdomen. Handling the bowel during abdominal surgery can also cause peristalsis to stop, so people who have had abdominal surgery are more likely to experience ileus. When ileus results from abdominal surgery the condition is often temporary and usually lasts only 48-72 hours.
Ileus is a partial or complete non-mechanical blockage of the small and/or large intestine. It is a functional rather than mechanical obstruction of the bowel. It is a lack of propulsive peristalsis (wave-like movement) of the bowel. It stops the movement of bowel contents downward. There is abdominal distention and an absence of bowel sounds. Ileus may be the result of anesthesia, interruption of nerve supply to the bowel, intestinal ischemia (obstruction of circulation), abdominal wound infections, electrolyte imbalance (loss of potassium leads to lack of intestinal peristalsis) or metabolic diseases. The result of ileus is the distention of the bowel with gas and fluid. The process is similar to obstruction.
Symptoms and signs include abdominal distention
, vomiting, and vague discomfort. Pain rarely has the classic colicky pattern present in mechanical obstruction. There may be obstipation or passage of slight amounts of watery stool. Auscultation reveals a silent abdomen or minimal peristalsi
s. The abdomen is not tender unless the underlying cause is inflammatory.
Causes and Risk factors:
Ileus is most often associated with an infection of the peritoneum (the membrane lining the abdomen) or other intra-abdominal infections such as appendicitis. It is one of the major causes of bowel obstruction in infants and children. Another common cause of it is a disruption or reduction of the blood supply to the abdomen. Handling the bowel during abdominal surgery can also cause peristalsis to stop, so people who have had abdominal surgery are more likely to experience it.
Ileus can also be caused by kidney diseases, especially when potassium levels are decreased (a condition called hypokalemia). Narcotics and certain chemotherapy drugs, such as vinblastine (Velban, Velsar) and vincristine (Oncovin, Vincasar PES, Vincrex) can also cause ileus. Infants with cystic fibrosis are more likely to experience meconium ileus (obstruction of a dark green material in the intestine in newborns).
When the bowel stops functioning, the following symptoms occur:
- Abdominal distention (pain often increases as distention increases).
- Nausea, vomiting, and/or diarrhea.
- Failure to pass gas or stool.
Gastrointestinal surgery or other GI procedures.
- Electrolyte imbalance.
- Medications (e.g. opiates).
Clinical diagnosis is based on the history and physical examination. The goals of further diagnostic evaluation are to identify any reversible conditions and to differentiate between ileus and mechanical bowel obstruction. Mechanical obstruction can be excluded with:
Abdominal x-rays: typically a patient will have a non-specific gas pattern showing uniform distention of the small bowel on x-ray. The colon may or may not be distended, without mechanical obstruction.
- CT scan of the abdomen and pelvis
- Water-soluble small bowel series and/or contrast enema.
Physical examination: The abdominal examination reveals distention but without significant tenderness to palpation. The abdomen should be examined for any evidence of mechanical obstruction such as hernias, and for any evidence of peritoneal inflammation.
Vital signs should be evaluated as the patient may be hypovolemic or hemodynamically unstable due to underlying conditions. A hypovolemic patient may be expected to present with mild tachycardia or hypotension, though severe abnormalities could indicate a different diagnosis. Hypovolemia may also manifest as low urine output (normal urine output for an adult is above 0.5 mL/kg/hour).
Initial Tests: Electrolytes, FBC and abdominal x-rays (both upright and supine) are the initial tests to perform in anyone with a clinical diagnosis of ileus.
Ileus and obstruction may be accompanied by hypokalemia and hypochloremia. Hypermagnesemia may be present. Alkalosis may be present in dehydrated states, and acidosis may be present in intestinal ischaemia. Alkalosis and/or acidosis can be inferred from the carbon dioxide level that is found on a standard chemistry panel. A significantly elevated WBC level is an unexpected finding in a patient with ileus, and another cause should be considered.
Upright and supine abdominal x-rays typically show air-fluid levels and distended small bowel loops throughout the abdomen. Air may or may not be present in the colon, and is a non-specific finding.
Liver enzymes tests as well as amylase and lipase are useful when causes for ileus other than post-surgery, such as cholecystitis or pancreatitis are suspected. Albumin and pre-albumin levels evaluate the nutritional state of the patient.
In post-operative patients, a CT scan should be performed if the presumed ileus has not resolved in 5 to 7 days, or the clinical condition of the patient worsens. CT scan of the abdomen may be performed with intravenous contrast and oral water-soluble contrast. In the immediate post-operative period, CT scan with oral contrast is the method of choice in differentiating prolonged ileus and mechanical obstruction. This may help to identify a transition zone in a mechanical obstruction, and exclude any intra-abdominal fluid collections or anastomotic complications.
In patients with renal insufficiency, caution should be exercised prior to administering intravenous contrast, which can be avoided if necessary. Water-soluble contrast should be used in place of barium as this is contra-indicated if there is a possible perforation. Barium peritonitis is associated with a high mortality. Also, barium may become inspissated in the bowel if it remains there for a significant amount of time, as may happen in an ileus or obstruction. In addition, water-soluble contrast has a cathartic effect, which may be helpful in patients with ileus. This is due to its hypertonicity and hydrophilic properties, which have been shown to be beneficial in treating meconium ileus in babies with cystic fibrosis. 
In cases of prolonged ileus (lasting longer than 3 days or prolonging the normal post-operative course), a small bowel series may be done to evaluate for any evidence of mechanical obstruction that may have been missed on a CT scan.
Rarely, in patients with other risk factors for gastroparesis or gastric outlet obstruction, a gastric emptying study may be considered. For those on parenteral nutrition, electrolytes should be checked daily to identify electrolyte abnormalities associated with post-operative intravenous feeding and the NPO state.
Most cases of postoperative ileus resolve with watchful waiting and supportive treatment. Patients should receive intravenous hydration. For patients with vomiting and distension, use of a nasogastric tube provides symptomatic relief; however, no studies in the literature support the use of nasogastric tubes to facilitate resolution of ileus. Long intestinal tubes have no benefit over nasogastric tubes.
The use of postoperative narcotics can be diminished by supplementation with nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDS may improve ileus by improving local inflammation and by decreasing the amount of narcotics used. Myoelectric activities recorded from electrodes placed on the colon have revealed faster resolution from ileus in patients given ketorolac versus those given morphine14; however, the drawbacks of NSAID use include platelet dysfunction and gastric mucosal ulceration. Consider the use of cyclooxygenase-2 agents, which negate these adverse effects.
No single objective variable accurately predicts the resolution of ileus. A clinician must assess the overall status of the patient and evaluate for adequate oral intake and good bowel function. A patient's report of flatus, bowel sounds, or stool passage may prove misleading; therefore, clinicians must not rely solely on self-reporting.
Other treatments may be used to help ease symptoms. These may include:
Diet Limitation: Patients who suffer from ileus should not be fed until the ileus has resolved.
Medicine and medications:
- Nasogastric Suction (NG Tube): A tube is inserted through the nose and into the stomach to remove digestive fluids. This will help relieve pain and bloating.
- Intravenous Fluids and Electrolytes: Fluids are given by vein to avoid dehydration. Electrolytes are given by vein to help the ileus resolve.
- Medications: There are medications that increase peristalsis (ie, neostigmine, tegaserod) that can be used in selected patients to help ileus resolve.
- Colonoscopic Decompression: A flexible tube may be inserted into the colon to relieve pressure.
Rectal cisapride (Propulsid), a serotonin agonist, has reportedly been successful in treating ileus, but the US Food and Drug Administration (FDA) has withdrawn this agent because of the possibility it causes cardiac dysrhythmias.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
- Studies have shown that combinations of thoracic epidurals containing bupivacaine alone or in combination with opioids improve postoperative ileus.
- Alvimopan is indicated to help prevent postoperative ileus following bowel resection.