Adynamic Ileus · What Is It, Symptoms, Treatment, and More

Adynamic ileus, also known as paralytic ileus, is when there is a temporary loss or reduction of peristalsis, the series of waves created by the smooth muscle of the intestine which propels solids and liquids forward. In an adynamic ileus, there is no mechanical obstruction, or physical blockage, such as a mass, and therefore is considered a functional paralysis.  When this occurs, solids or liquids do not pass through the bowel properly. This can lead to build up of contents in the intestines causing various symptoms of bowel inactivity.  

The most common cause of an adynamic ileus is undergoing surgery, especially abdominal or pelvic surgery. Surgery can activate a stress response that can immobilize the digestive tract. As a result, the bowel typically takes about 24 to 72 hours after surgery to resume its normal function.  

 Other causes include severe illness, such as sepsis or trauma. Electrolyte imbalances can impair intestinal motility, such as low potassium, low sodium, and low magnesium, and are associated with causing an ileus. Additionally, medications such as opioids and anticholinergics, which slow down the GI tract, can be associated with ileus.

Most of the time when one hears the term bowel obstruction, they are thinking of a mechanical, or physical, obstruction of the intestines. However, bowel obstructions can be divided into two subcategories: mechanical or functional.  

An ileus is an interruption in the normal flow of contents through the intestine without a mechanical or physical blockage, so it falls into the category of a functional obstruction. Meanwhile, a mechanical obstruction is caused by a physical blockage in the small or large intestine. Mechanical obstructions are often complete blockages, and they are typically the result of conditions that cause sliding (i.e., intussusception) or twisting (i.e., volvulus) of the intestines onto itself, ultimately cutting off blood vessels and causing tissue death. Other physical blockages in the digestive tract can include masses, such as tumors, hernias, or gallstones, as well as adhesions that can form while healing from surgery. 

Often, individuals with an adynamic ileus present with clinical features like abdominal distension, discomfort, bloating, constipation or obstipation (i.e., no passage of stool or flatus), nausea, and vomiting. Physical examination will reveal absent or hypoactive bowel sounds on auscultation. However, in contrast to a mechanical obstruction, an ileus usually will not have high-pitched tinkling bowel sounds on auscultation. 

In some cases, when complications have occurred, there may be continuous and persistent abdominal pain and tenderness. This could be due to peritonitis, peritoneal irritation, or inflammation of the membrane covering the abdominal wall and organs.  

The treatment of an adynamic ileus is mostly conservative and supportive. It focuses on relieving the present symptoms. Most resolve within a few days when the underlying cause is addressed. 

Bowel rest, through restriction of food consumption and intravenous (IV) fluid therapy is often suggested. A severe or prolonged ileus with continuous vomiting and abdominal distension often requires insertion of a tube extending from the nose to the stomach (i.e., nasogastric tube [NG] tube) to remove gastrointestinal contents and thus relieve pressure. If the individual is at high nutritional risk, and enteral feeding attempts have been tried and failed, then total parenteral nutrition (TPN), which is a feeding method that bypasses the gastrointestinal tract, may be necessary. 

Additionally, diagnosing and treating the underlying cause can potentially minimize the duration of an ileus. This can include correcting electrolyte abnormalities, reviewing for offending medications and discontinuing them, if possible, as well as preventative measures such as early ambulation after surgery.  

If symptoms do not improve or there are complications, such as rupture of the bowel, surgery might be required.