Basal epithelial formalin pigment deposition in the kidneys--a useful marker for ketoacidosis at autopsy.

Basal vacuolization of renal epithelial cells occurs in diabetic and alcoholic ketoacidosis, hypothermia and starvation. The vacuoles contain triglycerides. Following a case where formalin pigment deposition within these vacuoles led to the identification of ketoacidosis, a retrospective review of a further 31 cases with ketoacidosis, was undertaken. There were 24 diabetics and 7 alcoholics (age range 21-80 yrs; mean 50.9 yrs; M:F ratio = 2:1. The post-mortem interval was 1-12 days (mean - 4.5 days). Characteristic basally-located pigment surrounding vacuoles was found in 16 cases (51.6%) (14 diabetic ketoacidosis; 2 alcoholic ketoacidosis). Fifteen cases had no formalin pigment deposition. No relationship could be found between the intensity of staining and the postmortem interval, degree of putrefaction, or level of vitreous humour β-hydroxybutyrate. No staining was demonstrated in control cases matched for postmortem interval. Although formalin pigment deposition occurred in only 51.6% of cases with proven ketoacidosis at autopsy, it appeared to be a highly specific phenomenon. As these deposits were identifiable after recognizable cellular morphology had been lost due to autolysis and putrefaction, this artefact of fixation may be of particular use in suggesting the possibility of ketoacidosis in decomposed bodies with compromised histology.