Etiological Factors
The development of ileus can be triggered by various factors affecting both the digestive system itself and adjacent anatomical regions. According to pathomorphological data, the primary causes of this condition include:
- Intestinal ischemia, where primary blood supply disruption leads to organ dysfunction.
- Bowel wall inflammation, where local inflammatory processes disrupt normal transit.
- Minimal surgical trauma — even minor surgical interventions can serve as a triggering mechanism.
- Traumatic injuries, particularly pelvic bone fractures and various back injuries that affect gastrointestinal function.
Mechanism of Development: Dilatation
Regardless of whether the obstruction is mechanical or paralytic in nature, the key and earliest link in the pathogenesis is dilatation — marked pathological expansion of the intestinal tube.
In the zone located immediately proximal to the obstruction site, a massive and continuous accumulation of contents begins. This space accumulates:
- Fluid.
- Ingested atmospheric air.
- Intestinal gas.
A critical characteristic of this process is its direction: pathological expansion always propagates exclusively in the oral direction (i.e., toward the oral cavity).
Morphological Changes of the Wall
As dilatation progresses, the volume of accumulated masses and gases steadily increases, leading to a sharp rise in intraluminal pressure. This pressure exerts powerful mechanical stress on all layers of the intestinal wall.
The primary consequence of this pressure is the complete occlusion of blood vessels running within the submucosal layer. A vascular block develops, initiating a cascade of morphological changes:
- Acute tissue ischemia develops due to arrested blood flow.
- Ischemia predictably transitions into necrosis (cell death). Cell death occurs strictly in a layer-by-layer fashion: the mucosa suffers first, followed by the muscular layer.
- The final stage of wall destruction is perforation — the formation of a full-thickness defect.
Systemic Consequences and Infectious Factor
Local morphological destruction is inextricably linked to severe systemic reactions.
First, a clinical consequence of impaired transit is vomiting. Along with vomitus, the patient rapidly loses water and electrolytes, leading to profound imbalance.
Second, a powerful infectious factor is incorporated into the pathogenesis. The dilated intestinal lumen becomes an ideal environment for bacteria. Rapid proliferation of gram-negative anaerobic microflora is observed here. Through their metabolic activity, these bacteria release endotoxins. Toxins penetrate the systemic circulation, causing severe endotoxemia in the patient.