In the Chilandar monastery (Mount Athos, Greece) library, a collection of medical texts written in the Old Serbian Slavonic language was discovered in 1952. Because of its size and comprehensiveness, this manuscript was named the Chilandar Medical Codex. The Collection contains several manuscripts, which according to modern medical terminology, the manuscripts can be classified as texts on Internal Medicine, Infectious diseases, Toxicology, Pediatrics, Pharmacology and Surgery, belonging to different time periods. The oldest part, Text on uroscopy, is considered to have been written in 13th or 14th century and consists of 35 text pages divided into 62 paragraphs. Following the popular uroscopy methodology of macroscopic examination of urine, this text contains detailed descriptions of urine characteristics (color, consistency, sediment, odor), as well as a convincing Hippocratic description of urine formation from the filtration of metabolic and waste materials (involving the four humors) rather than blood and fumes (toxic metabolites) according to the theory of Theophilus Protospatharius and Isaac Israeli. Precise descriptions of normal and pathological urine characteristics are provided. Although kidney anatomy and function is unclear, the urinary bladder is very undoubtedly described as an organ for urine collection. In the Chilandar Medical Codex, there are about one hundred descriptions of kidney and urinary tract diseases and disorders. Many symptoms and syndromes such as hematuria, dysuria, pyuria, renal colic, anuria, polyuria, edema and dropsy, urine retention and fever, are incorporated in the broader clinical pictures of lithiasis of the kidney and/or bladder, pyelonephritis, cystitis, necrotic renal disease indicative of renal tuberculosis and tumors, acute and chronic nephritis, renal failure, and gout. Specific pharmacological prescriptions, mostly simple or compound herbal medicines, are given for each of those renal ailments.