Bilirubin Infarct

Bilirubin infarct, a focus of bilirubin deposition in the kidney in newborn jaundice. While in jaundice of adults diffuse coloring of the entire kidney tissue is observed by dissolved bile pigments (and only in rare cases does the appearance of amorphous lumps of bile pigments in the tubules occur), for newborn jaundice the deposition of crystalline bilirubin exclusively in the papillae of the kidney medulla is characteristic. To the naked eye, the bilirubin infarct on a section through the kidney appears as orange-red coloring in the papillae of the kidney medulla, and it is not difficult to notice that this coloring is based on the presence of orange-red stripes running radially in accordance with the direction of the medullary tubules [see separate table (pp. 487-488), fig. 3]. Under the microscope, ruby-red rhombic and needle-shaped crystals of bilirubin are found located in the lumens of the tubules, in the protoplasm of the epithelial cells, and in the interstitial connective tissue. Bilirubin infarcts very often combine with uric acid infarct (see) of the kidney (the latter indicates that the child lived for at least 1-2 days after birth; this has certain forensic medical significance).