The farsighted studies of the Italian Carlo L. Rovida (1844-1877) on the nature of urinary casts

Abstract

Carlo L. Rovida (1844-1877) was an Italian physician who graduated in Pavia (1866) and worked in Milan (1868) and Turin (1874), where he ran the Institute of Clinical Medicine at the university. Between 1870 and 1876 Rovida published several studies on the nature of urinary casts, which can still be considered valid today. He distinguished two main types of casts, i.e., "colorless" (hyaline) and "yellowish" (waxy). By painstaking microscopic observation of the urine, performed mainly by microchemical techniques, and histological examination of the kidneys, he came to the conclusion that both types of casts were produced by tubular cells. In addition, he found that the colorless casts were composed of a unique protein, which was different from any other protein known at the time, and which he called "cilindrina" (cylindrine). Instead, Rovida found that the yellowish casts contain a different, ill-defined protein, which was also present in the lateral and basal membrane of the tubular cells. Rovida should be remembered today because his views were much ahead of the prevailing theories of the time, which considered the casts as coagulated fibrin (a view sustained mainly in Germany) or as elements derived from either tubular degeneration or tubular production (a view sustained mainly in the United Kingdom and Sweden); his results concerning the site of production of hyaline casts and their unique nature were confirmed 90 years later, in the early 1960s, when it was demonstrated that these casts are made of Tamm-Horsfall glycoprotein, a protein which is produced by the cells of Henle's loop; and his conclusions about the special nature of waxy casts were also correct. In fact, even though the true composition of these casts is still not yet totally clear, there is now evidence that they contain a substance different from Tamm-Horsfall protein. Rovida is also a paradigm of how the progress of science is strictly dependent on the development of technology. In fact, it was only when appropriate techniques (e.g., electrophoresis, immunoelectrophoresis, and immunofluorescent microscopy) became available that the nature of casts could be defined with certainty.