Origin of urinary fibrin-fibrinogen degradation products in renal glomerular disease

The origin and mechanism of renal clearance of urinary 'fibrin-fibrinogen degradation products' (FDP) were studied in patients with renal glomerular diseases associated with heavy, non-selective proteinuria and high levels of urinary FDP. The results indicated that the urinary FDP arose primarily by the filtration of unaltered plasma fibrinogen through a damaged and abnormally permeable glomerular basement membrane and that a variable degree of lysis of the filtered fibrinogen occurred in the urine. The lysis of cross-linked fibrin in intraglomerular deposits, as evidenced by the presence of dimeric fragment D in the urine, appeared to contribute only a small amount to the total urinary FDP excretion.