In classical Greek medicine, neither Hippocrates nor Galen considered the condition of the urine to be an important sign of systemic diseases, and they did not relate its characteristics to definite illnesses, except in obvious cases of urinary tract disease. In their teaching, urine was used together with other physical signs as a prognostic indicator. With Theophilus, however, uroscopy gained an important role, and the appearance of the urine became pathognomonic of specific diseases. De Urinis owed its popularity to this new approach and to its didactic character, as it was written as a practical handbook. After the 12th century, De Urinis occupied an assured position among the few ancient medical treatises that in Latin translation formed a worldwide teaching canon for medieval and Renaissance medical schools.