Orthostatic proteinuria: a harmless variant of protein loss?

A 28-year-old young woman was referred to our department of Internal Medicine for analysis of unintentional weight loss. At initial analysis, a persistent proteinuria was found with no evident relation to her weight loss. Anamnestic as well as additional studies showed no evidence of a primary kidney disease. After this exclusion, orthostatic proteinuria was confirmed by simple urine analysis. Since the weight loss had not yet been explained, an analysis followed at the Department of Gastointestinal and Liver Diseases where inflammatory bowel disease (IBD) was found. Literature study shows that proteinuria may be associated with IBD. This concerns mainly selective tubular protein loss, without a distinctive change in protein loss with a change in position. Orthostatic proteinuria, therefore, remained the most likely diagnosis. In this case, the patient was advised to check both urine and kidney function annually.