Decreased filtration fraction during active proliferative lupus nephritis: relation to disease activity and reversibility of renal function.

Nine consecutive patients with systemic lupus erythematosus (SLE) were studied longitudinally for glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) during ten exacerbations of severe proliferative glomerulonephritis. At the onset of exacerbation, GFR decreased significantly whereas ERPF did not fall; the latter even increased in some patients. As a consequence mean filtration fraction (FF), the ratio of GFR and ERPF, fell from 0.20 to 0.10. At maximum exacerbation, both GFR and ERPF had decreased without change in FF. During remission FF rose to pre-exacerbation values as a result of increase in GFR without change in ERPF. We conclude that changes in FF reflect changes in renal haemodynamics in patients with SLE and active proliferative glomerulonephritis. Determination of FF may be of some value in assessing renal disease activity and the degree of reversibility of renal function in those patients.