[Perforation in Crohn's ileitis and its impact on the natural history of the disease. Note 1. Pathogenic process of the event, its relationship with intestinal obstruction, and its immediate consequences].

The pathogenesis and consequences of perforation in Crohn's disease were studied in 175 patients submitted to surgery. Perforation occurred in 40 (23%) patients with ileitis or ileocolitis, always in the terminal ileum; so-called "free" perforation occurred in 1 patient, "limited" perforation in all the others. Perforation is always a consequence of a chronic intestinal obstruction caused by the stricture of the terminal ileum, which becomes absolute because of the blocking by solid intestinal content. It occurs in the borderline between the stricture and proximal dilated loop, where the fissures (typical of Crohn's ileitis) are stretched to the utmost and dilated by the hyperpressure and distension of the wall following ileal stenosis. Perforation in the peritoneal cavity is always free; its consequence is usually not a diffuse septic peritonitis but an abscess, because only a small amount of intestinal content leaks out. This happens because in the proximal occluded bowel, pressure decreases abruptly following the spilling of intestinal content, particularly of gas. The abscess fed by intestinal content enlarges and finally opens into a hollow organ or onto the skin, causing a fistula (internal or external). The rational therapeutic approach to perforation and its consequences (the infrequent diffuse septic peritonitis, or the more common abscesses and fistulas) is always and only ileal stenosis removal.