title: Recognizing purple bag syndrome at first look.
abstract: Purple urine bag syndrome is a clinical entity first described in 1978. Its typical discoloration is worrying for clinicians. In the past, these patients sometimes reached the emergency unit only because of this exceptional worrying urinary sign and underwent invasive diagnostic examinations including cystoscopy, without any abnormal finding. It is now clear that this astonishing phenomenon of double discoloration of the urine, appearing purple in the bag and dark blue in the test tube, results from the formation of 2 different pigments (indirubin and indigo) in very alkaline urines due to enzymes produced by gram-negative bacteria, such as indoxyl phosphatase/sulfatase, which can convert urinary metabolites of dietary tryptophan. Practicing physicians should identify purple urine bag syndrome as a usually benign medical condition diagnosed in asymptomatic patients, which only requires treatment of bacteriuria with antibiotics, prevention of constipation, substitution of catheter and acidification of the urine. After these measures, urine typically returns to its normal color.
authors.affiliation: Nephrology and Transplantation Unit, Department of Translational Medicine, and International Research Centre Autoimmune Disease, Amedeo Avogadro University, Novara, Italy. ccanavese@hotmail.com
authors.forename: Caterina
authors.initials: C
authors.lastname: Canavese
authors.forename: Andrea
authors.initials: A
authors.lastname: Airoldi
authors.forename: Marco
authors.initials: M
authors.lastname: Quaglia
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Barbè
authors.forename: Maddalena
authors.initials: M
authors.lastname: Brustia
authors.forename: Matteo
authors.initials: M
authors.lastname: Vidali
authors.forename: Marco
authors.initials: M
authors.lastname: Bagnati
authors.forename: Stefano
authors.initials: S
authors.lastname: Andreone
authors.forename: Tjibbo
authors.initials: T
authors.lastname: Corrà
authors.forename: Calogera
authors.initials: C
authors.lastname: Sciarrabba
authors.forename: Giorgio
authors.initials: G
authors.lastname: Bellomo
authors.forename: Piero
authors.initials: P
authors.lastname: Stratta
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001424:Bacterial Infections / Q000652:urine*; D003116:Color; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013577:Syndrome; D014546:Urinary Catheterization; D014552:Urinary Tract Infections / Q000652:urine*