Introduction
An intestinal obstruction (ileus) is a disturbance of the intestinal passage through a constriction or strangulation. As a result, the intestinal contents can no longer be transported further towards the anus and excreted, resulting in a congestion of faeces and the typical symptoms of an ileus, such as severe abdominal pain, vomiting, flatulence and constipation. Both the small intestine and the large intestine can be affected by intestinal obstruction. In general, intestinal obstruction is an acutely life-threatening situation that must be treated in hospital as soon as possible, otherwise parts of the intestine may die.
Overview of the causes
The causes of intestinal obstruction are manifold. Basically one must distinguish between: The two types of ileus each have different causes. In addition to the mechanical and functional intestinal obstruction, there is a third form, the mixed ileus.
This is a combination of the two types, which often represents the transition of a mechanical intestinal obstruction into an intestinal paralysis, i.e. a paralytic intestinal obstruction. – functional (paralytic) intestinal obstruction
- Mechanical ileus
- Mechanical ileus is caused by a pinching of the bowel or an obstruction that prevents further intestinal passage. – In contrast, the functional ileus has a functional rather than mechanical cause.
This means that the forward movement, the so-called peristalsis of the bowel, comes to a standstill and the intestinal contents are not transported further. The intestinal muscles no longer contract and the intestine is paralyzed. Functional causes would be, for example, the reduced supply of blood to a section of the intestine due to a vascular occlusion. A functional ileus can also be caused by the administration of various drugs, by surgical interventions or injuries.
Causes of a mechanical ileus
A mechanical intestinal obstruction can occur in various ways. The causes are strangulation, obstruction and gallstone ileus. In many cases the mechanical ileus is the result of a so-called strangulation, in which a section of the intestine is strangulated.
This happens either through adhesions, which lead to a kink in the bowel, or through internal and external hernias (hernia), which pinch off the affected section of bowel. The strangulation means that the intestinal wall can no longer be supplied with sufficient blood. As a result of the circulatory disorders, parts of the intestine die irrevocably, which is why an intestinal obstruction must be treated as an absolute emergency.
A mechanical intestinal obstruction can also occur without accompanying circulatory disturbances, in which case it is called an obstruction. In this case the inside of the intestine (intestinal lumen) is blocked by a foreign body, such as swallowed objects, tufts of hair or faeces. An obstruction can also be caused by a strongly thickened intestinal wall in the context of inflammations or tumours.
In the case of a gallstone ileus, a gallstone from the gall bladder enters the intestinal tract, where it obstructs intestinal passage. The stone enters the intestine via a non-natural connecting passage between the bile duct and the small intestine, a so-called cholecysto-duodenal fistula. Tumours that grow in the abdominal and pelvic area can cause intestinal obstruction.
This is usually a mechanical obstruction of the colon. Especially tumours that originate from the fallopian tubes or peritoneum or have metastasised there can exert strong pressure on the colon and compress it. The tumour can also grow into the wall of the intestine and thus constrict the intestinal lumen even further.
As a result, the intestine is pinched off and intestinal passage is hindered. Adhesions are the most frequent causes of the formation of a mechanical ileus. The connective tissue adhesions often form in the area of the mesenteric tissue, the vascular fatty tissue around the intestine.
The adhesions, also called bridging adhesions, cause the intestinal loops to connect with the peritoneum, sometimes causing severe pain. Especially operations in the peritoneal cavity promote the formation of the braces. Within the adhesions, a loop of small intestine can be trapped so severely that the peristalsis of the intestine comes to a complete standstill and an intestinal obstruction develops.
Crohn’s disease can be another cause of intestinal obstruction. This is an autoimmune disease in which chronic inflammation of the intestinal mucosa occurs. Due to the constant inflammation and the subsequent healing of the lesions, scars form which can lead to the formation of an ileus.
Due to the scarring of the intestinal mucosa, the intestinal wall can thicken and constrict the intestinal lumen. As a result, the intestinal contents can no longer pass through the bowel properly and an intestinal obstruction is formed. A frequent cause of mechanical intestinal obstruction is the so-called strangulation.
In the case of a strangulation, in addition to the pinching of an intestinal loop, the blood supply to the affected section of the intestinal wall is also interrupted. Causes of strangulation are twisted intestines (volvulus) or inguinal hernias (hernia). A volvulus is created when the intestine rotates around itself and swallows up in the process, resulting in a pinch-off.
In a hernia the intestines are pressed through a gap in the abdominal wall. In unfavourable cases, the hernial sac contains a complete intestinal loop, the intestinal contents of which can then no longer be transported further. Particularly in older patients, intestinal obstruction can result from diverticulitis.
Diverticulitis is the term used to describe protrusions of the intestinal wall that can become inflamed (diverticulitis). Frequently recurring inflammations of the diverticula and the associated scarring of the intestinal mucosa favour the development of an intestinal obstruction. The colon is mainly affected by this.
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