[Pathomorphology of transplant rejection and kidney biopsy diagnosis of the transplant].

Rejection processes concerning transplanted kidneys are traditionally classified as hyperacute, acute and chronic. It is, however, generally felt, that this time related classification is not satisfactorily in every respect. In order to come to a more differentiated histological diagnosis in the individual case, we resolved the time related classification categories and tried to specify rejection processes exclusively according to pathomorphological aspects. Thus 3 morphological rejection patterns or types can be differentiated: (1) a necrotizing-thrombotic rejection type (nth-rej), (2) a cellular rej (cell-rej) and (3) a sclerosing rej (scl-rej). These morphological rejection types match only partially with the time related categories. Especially it becomes apparent, that many cases have mixed rejection patterns. The pure as well as the mixed rejection patterns can exactly be defined in the histological diagnosis when the morphological categories are applied (e.g. severe cell-rej with moderate nth- and slight scl-component). This procedure is favourable in our opinion because a) the histological diagnosis now precisely informs the clinician about the whole spectrum of lesions present and b) individual cases can be compared with one another more effectively. In biopsy interpretation especially the following causes of functional deterioration have to be considered besides rejection processes: shock kidney, ureter stenosis, pyelonephritis, renal artery thrombosis and various types of glomerulonephritis (GN) in the transplant (de novo-GN, recurrent GN and others).