Albuminuria refers to the presence of albumin, a type of protein, in the urine. Normally, the kidneys filter waste products and excess substances from the blood, and these are excreted as urine. However, under normal circumstances, proteins, especially albumin, should be retained in the blood and not pass into the urine.

Unit 7,

Reference: Oxford Concise Medical Dictionary (9th ed) Oxford University Press 2015 ISBN-13: 9780199687817, p765