[Xanthogranulomatous pyelonephritis. Our theory and discussion on the development of such an entity. Report of 9 cases].

The authors present 9 cases of xanthogranulomatous pyelonephritis observed in the "Juan XXIII" Hospital in Tarragona. They emphasize the relationship between lithiasis, chronic urinary infection and antigenic stimulation for the development of this entity, the progressive result of a lesion in the kidney tissue with immobilized infectious calcareous deposits. In the granulomatous lesion they find cells called antigen-antibody quartets, with foamy-type histiocytes, the nodular collections of which constitute the key to X.P. The formation of lymphocytic germinal centres is another antigenic stimulus in some parts of the kidney tissue. These structures are due to the storing of antibodies and therefore the immunoglobulins would not be released towards the blood stream, which would explain changes in the immunoglobulins in these patients' serum.