Mechanism of bilirubin elimination in urine: insights and prospects for neonatal jaundice

Clin Chem Lab Med. 2021 Jan 15;59(6):1025-1033. doi: 10.1515/cclm-2020-1759. Print 2021 May 26.

Abstract

Despite a century of research, bilirubin metabolism and the transport mechanisms responsible for homeostasis of bilirubin in serum remain controversial. Emerging evidence on the hepatic membrane transporters and inherited disorders of bilirubin metabolism have contributed to a greater understanding of the various steps involved in bilirubin homeostasis and its associated excretory pathways. We discuss these recent research findings on hepatic membrane transporters and evaluate their significance on the newborn bilirubin metabolism and excretion. New insights gained speculate that a proportion of conjugated bilirubin is excreted via the renal system, as an alternative to the intestinal excretion, even in normal physiological jaundice with no associated pathological concerns. Finally, this paper discusses the clinical relevance of targeting the altered renal excretory pathway, as bilirubin in urine may hold diagnostic importance in screening for neonatal jaundice.

Keywords: bilirubin metabolism; bilirubin – urine; conjugated bilirubin; hepatic membrane transporters; neonatal jaundice; unconjugated bilirubin.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Bilirubin / metabolism
  • Humans
  • Infant, Newborn
  • Jaundice*
  • Jaundice, Neonatal* / diagnosis
  • Liver / metabolism
  • Membrane Transport Proteins

Substances

  • Membrane Transport Proteins
  • Bilirubin