The small and large intestines are in constant motion to move digested food in waves toward the rectum. This movement, typical of the gastrointestinal tract, is called peristalsis. How strong the peristalsis can be can be seen particularly well in diarrhea. However, intestinal obstruction can also trigger violent intestinal movements.
The result is severe abdominal pain, which, depending on the cause, can be sharp, dull or crampy (colicky). At first, the pain can be fairly well assigned to a specific region, but over time the discomfort expands to the entire upper and lower abdomen. Intestinal obstruction in which obstructions in the intestine interfere with or prevent the intestinal contents from moving on is called mechanical intestinal obstruction (ileus).
What causes mechanical ileus?
Overall, the passenger obstruction is more often localized in the small intestine than in the large intestine (small bowel ileus in 80 percent, large bowel ileus in 20 percent of cases). Mechanical ileus is also referred to as obturation ileus because the intestinal clearing is constricted (obturated) from the inside or outside.
Causes of mechanical ileus may include:
- Adhesions and brides (adhesions); a very common cause, especially after previous surgery.
- Constricting tumors (often in the colon as colon carcinoma).
- Foreign bodies (for example, gallstones, fecal stones).
- Obstructions / constrictions
- Scarring in healing (for example, in diverticulitis, Crohn’s disease, ulcerative colitis).
- Hernias (connective tissue sacs), in which the intestine is wedged together with its contents; especially inguinal and testicular hernias.
After any operation in the abdominal cavity, adhesions (= adhesions) can develop between the intestinal loops or form scarred strands (= brides), narrowing the diameter of the intestine. Adhesion or bridenileus after surgery can occur as early as a few days after abdominal surgery, but can also occur months or years later. If the affected person has already undergone several abdominal preoperations, the likelihood of developing adhesion or bridenileus later increases significantly.
Mechanical ileus: Other causes
Abdominal scarring can also occur after severe injury, extensive inflammatory bowel disease, or peritonitis that has healed. In the case of peritonitis (for example, appendicitis with intestinal perforation), the risk of subsequent development of ileus is much higher than after appendectomy without perforation.
In strangulated ileus, intestinal wall perfusion is impaired because the intestinal vessels are twisted or strangulated. In a volvulus, there is a twisting of a loop of intestine around its own axis, and in an intussusception, a section of intestine bulges over the next adjacent section of intestine in the form of a fold.
In inflammatory bowel diseases or malignant tumors, the diameter of the bowel may be reduced to such an extent that only a thread-like passage is possible. The violent intestinal movements (peristalsis) that seek to move the stool through this thread-like passage toward the rectum can even cause so-called overflow diarrhea (watery diarrhea). Large gallstones breaking through from the gallbladder directly into the colon and fecal stones or foreign bodies are among the less common causes of mechanical ileus.
