Fernand Widal (1862-1929) was a French scientist who worked at a defining period in the scientification of medicine when the basic sciences were being applied to clinical medicine. In the medical fashion of the time his early studies were centered on infectious diseases. He is best known for the diagnostic test that bears his name, the Widal agglutination test for the diagnosis of typhoid fever reported in 1896. Much like other investigators of the period he worked in several areas (shock, asthma, immunization, hemoglobinuria), ultimately focusing on the kidney during 1903-1906. He demonstrated that changes in blood non-protein nitrogen (NPN) level are induced by modification of protein intake, that edema is due to salt retention (from measurements of chloride), and that the prognosis of kidney disease is based on NPN levels. He staged the course of CKD on the gradual retention of NPN, which at 0.5-1 gm/L had a guarded prognosis (azotémie d’alarme); at 1-2 gm/L heralded death in 2 years (azotémie grave); at >2 gm/L had a fatal outcome worse than cancer; and at 5 gm/L death was imminent (azotémie fatale). He classified kidney disease as either associated with edema (chlorérumique), with elevated NPN (azotémique) or both. He recommended reduced intake of salt in edematous subjects and of protein in azotemics. One of his assistants in these studies was a grandson of Louis Pasteur, Pasteur Vallery-Radot (1886-1970), who maintained his interest in kidney disease and as professor of medicine in charge of Broussais hospital trained Jean Hamburger (1909-1992) and Gabriel Richet (1916-2014), the future founders of French nephrology and the International Society of Nephrology.
Keywords: Fernand Widal, edema, salt, CKD classification, nephritis