Mechanical ileus is a type of bowel obstruction. It is a dangerous and potentially life-threatening condition that needs to be urgently solved.
The mechanical ileus itself has several subtypes according to the causative factor. One thing is common – the movement of stool and gases is blocked by an obstacle. This obstacle may be a foreign object, tumor or the intestine itself. The subtypes are follows:
In this case, the gut cavity is narrowed by a “foreign” obstacle or pathological condition of the intestine. The obstacle can be located directly in the cavity of the intestine (large gallstone from the biliary tract, badly chewed and poorly digested food, accumulated intestinal parasites, etc.) or located within the wall or even in the vicinity of the bowel (intestinal tumors, narrowing of the intestine due to an inflammation, tumors of adjacent organs, postoperative adhesions, etc). The therapy focuses on removing the obstacle. Often the surgical intervention includes removal of an entire section of the intestine.
Volvulus means a rotation of the intestine around its axis resulting in local obstruction. The stool can not pass through the rotated intestine. In addition, larger rotation may cause strangulation of local blood vessels causing disruption of local blood supply to the affected intestinal segment. The best therapeutic option is acute surgical intervention with derotation and fixation of the intestine. If the affected intestinal segment underwent necrosis due to long period of disrupted blood supply, it is necessary to remove it surgically.
Basic principle of volvulus
The strangulation means incarceration of the intestine. It is usually due to a hernia incarceration or because of so-called invagination, which is typical for children. The invagination occurs when a part of the intestine gets inserted into adjacent intestinal section. Strangulation is serious because of closure of local blood vessels similar to volvulus (see above). The therapy is surgical. The incarcerated section must be released and the surgeon evaluates its viability. When it is necrotic, it must be surgically removed.
Note: Obstruction, volvulus and strangulation affect more commonly a congenital pouch of the small intestine known as Meckel's diverticulum. It occurs in about 2% of the population.
The mechanical ileus usually manifests with an abdominal pain that has colic character. Abdominal palpation and percussion is painful. The colicky pain is due to strenuous bowel movements, which are aimed to overcome the obstacle. The acute pain slowly disappears in advanced stages of the condition as the intestinal muscles get tired and cease to move (paralytic ileus). The biggest problem is stoppage of stool and gas movement, which causes signs of constipation and vomiting. Strangulation (including invagination) manifests with a sudden severe abdominal pain accompanied with brightly red blood in stool.
The diagnosis is based on clinical symptoms and cautious physical examination of the abdomen including palpation, percussion, and listening with a stethoscope. In every case of an acute abdominal pain, digital rectal examination should be part of the examination process. An abdominal X-ray is also very important as it shows specific findings typical for intestinal obstruction (intestinal fluid levels). The cause of mechanical ileus may be further specified by ultrasound, computed tomography or by diagnostic surgical intervention (that is also therapeutic).