Introduction: It is unanimously acknowledged that the aetiopathogenesis of Crohn's disease (CD) is still a mystery despite the fact that almost 70 years have elapsed since it nosological identification. Another mystery and major problem of CD of the bowel is its histopathology, which has yet to be clarified; consequently, we do not know what kind of disease it is, that is to say, which process, among the ones known to us, it actually corresponds to.
Material and methods: The present paper presents the results of a new histopathological interpretation of the disease on the basis of 100 surgical cases of Crohn's ileitis and ileocolitis.
Results and conclusions: The disease is not a form of enteritis, but a lymphoedema of the intestinal wall, caused by a congenital lack of patency of the mesenteric lymphatic collectors, giving rise to stasis of lymph in the lymphatic network of the corresponding bowel segment and consequently to hypertension which dilates the lymph vessels in the intestinal wall. The lymph, which cannot be reabsorbed by the veins, because the venous wall denies entry to protein macromolecules, accumulates in the interstitial space with the result that the intestinal wall thickens considerably. Since the process takes place in the intestine perfused by a continuous flow of septic matter, the process is complicated by the development of lymphocytic lymphangitis, which occurs throughout almost the entire lymphatic network, obstructing the dilated lumen, limiting the dispersion of lymph and preventing gross spread of the intestinal contents into the dilated lymphatic vessels. The lymphocytic lymphangitis causes "transparietal phlogosis", which is rightly regarded as a characteristic of the disease, but is wrongly interpreted by those who have studied it. This transparietal phlogosis is neither excessive nor disproportionate to its task of obstructing the intestinal contents; it is transparietal because the lymphatic network where it takes places is itself transparietal. The reactive lymphocytic lymphangitis prevents the gross spread of the intestinal contents into the dilated lymphatic network, as stated above, but cannot prevent the limited uptake of dissolvable toxic bacterial substances (FMLP, PG-PS, LPS) conjugated in immuno-complexes. The immuno-complexes developing in the lymphatic network undergo lymph- and blood-borne spread, causing; obstructive lymphangitis in branches of the mesenteric lymphatic collectors which are still patent, increasing the degree of lymphatic obstruction and thus the extent of the intestinal lesions; general complications of so-called "metastatic Crohn's disease", which were once interpreted as autoimmune processes, but actually correspond to forms of vasculitis which may be localised in any of the organs or apparatuses of the body, sometimes proving extremely serious. Lymph dispersion in the intestinal lumen, causes not only diarrhoea, but often also lymphocytopenia and hypoproteinaemia, and therefore an immunodepression syndrome, which in the long term may give rise to intestinal and extraintestinal cancer.