SummaryCoagulation studies were performed in 45 cases of nephrotic syndrome without uremia. The most striking features were an increase in the number of thrombocytes, and in the level of fibrinogen, factor V and factor VIII. Thrombin time was usually prolonged and the titre of antithrombin III was increased. No fibrin breakdown products were found in the serum. 13 patients developed thrombotic complications, with eventual death in 5 cases.

Renal biopsies obtained from 20 adult patients within 30 days after onset of acute renal failure with microangiopathic hemolytic anemia ("the hemolytic-uremic syndrome") were studied. Lesions were graded independently by two observers without knowledge of the clinical history. All patients who did not have refractory hypertension were treated with heparin. Ten of the patients died, and four developed end-stage renal failure requiring chronic dialysis. Six patients, however, had a relatively good outcome: two recovered completely and four developed mild-to-moderate chronic renal failure not requiring dialysis. The six patients with a good outcome had significantly less severe arterial intimal thickening on biopsy compared with the remaining patients with a poor outcome. The patients with a good outcome and those with a poor outcome did not differ in the severity of glomerular lesions. The clinical features did not allow a prediction of late outcome. These results suggest that early renal biopsies may be helpful in predicting prognosis in the "hemolytic-uremic syndrome." This clinical syndrome may occur either in apparently healthy people, or may complicate the course of a chronic essential hypertension.

Nephrotic syndrome (NS) is associated with several disorders of hemostasis: thrombocytosis and platelet hyperaggregability; increased plasma levels of factors V and VIII, and of fibrinogen with blood hyperviscosity; decreased plasma levels of natural anticoagulants: free protein S, and antithrombin III compensated by increased levels of α₂-macroglobulin; lowered fibrinolytic activity. Intensity of hypercoagulability is related to the degree of hypoalbuminemia; however, the role of hypercoagulability in the increased incidence of thromboembolic events, including renal vein thrombosis, is not proved. Clotting disorders are due to urinary losses of anticoagulants or to increased liver synthesis of procoagulants stimulated by hypoalbuminemia. Moreover, changes in clotting factors levels may be due to intravascular thrombin formation (marked by increased plasma levels of fibrinopeptide A). During active phases of glomerulonephritides (GN) with NS, thrombin formation might in fact arise in glomeruli, following activation of the glomerular hemostasis system. Isolated glomeruli from human crescentic GN, rabbit nephrotoxic GN and rat HgCl₂ autoimmune GN produce excessive amounts of procoagulant (tissue factor) activity (PCA). Sequential studies of the self-limited HgCl₂ GN showed that glomerular PCA, proteinuria and glomerular fibrin deposits peaked concomitantly at the acme of the disease, suggesting that immunologically mediated glomerular damage had triggered the extrinsic coagulation pathway.

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