[The problem of rheumatoid nephropathy]

To study clinical and morphological variants and frequency of renal involvement in patients with rheumatoid arthritis (RA).

Routine laboratory tests, device (urography, dynamic scintigraphy of the kidneys) and ultrasound investigations, lifetime and postmortem examinations of renal tissue using histological, immunohistochemical and electron-microscopic techniques, biopsy of gingival and rectal mucosa for amyloid detected renal lesions in 268 (46.2%) of RA patients followed up for 25 years meeting the ARA criteria. In 98 (37%) patients renal lesions were verified morphologically. Lifetime renal biopsies were made for 60 of them.

The diagnosis of chronic pyelonephritis was made in 117 patients, 42 patients had nephrolithlasis, nephroptosis and papillary necrosis were found in 49 and 3 patients, respectively. Arterial hypertension was present in 96 examinees, nephrotic syndrome was diagnosed in 19 and chronic renal failure--in 67 patients. Drug-related nephropathy occurred in 35 cases, in 26 cases symptoms of pyelonephritis arose prior to RA. Combination of renal diseases was found in 197 patients. Renal pathology was not verified morphologically only in 5 cases. Glomerulonephritis (GN) variants were present in 35 patients: mesangioproliferative (n = 27), membraneous (n = 5), mesangiocapillary (n = 3). 12 of them took Au preparations or D-penicillamin, therefore diagnosis of true rheumatoid GN was feasible only in 23 of them. GN was combined with renal amyloidosis (n = 28), minimal morphological changes (n = 19), interstitial/tubulointerstitial nephritis (n = 4), pyelonephritis (n = 4), arteriolosclerotic nephrosclerosis (n = 3). 41 patients with diagnosed pyelonephritis were found morphologically to have amyloidosis (n = 16), GN (n = 10), minimal morphological changes of renal tissue (n = 6), tubulointerstitial nephritis (n = 3), pyelonephritis, pyelonephritis alone (n = 4).

The above morphological findings point to high occurrence of renal pathology in RA. In many cases morphological signs are more serious than clinical symptoms. If RA activity is not controlled, nephritis of any type may transform into amyloidosis. When it is impossible to formulate morphological diagnosis in RA patients, it is proposed to use the term "nephropathy". Unrelated to RA nephropathy's diagnosis is valid in cases when renal pathology manifested before RA. Renal diseases arising in the presence of RA may be associated with this disease and should be reflected in its classification.