A brownish discoloration of the bladder mucosa on cystoscopy and the histological findings in a bladder biopsy specimen of submucosal vascular basement membrane thickening, pigment or chronic inflammatory changes in the absence of infection were present in various combinations in all our patients with analgesic-associated nephropathy. None of these findings was present in a control group of patients with other established causes of renal function impairment. More objective diagnostic aids may lead to a greater awareness and earlier diagnosis of this preventable cause of chronic renal failure.

Markedly increased concentrations of free fatty acids after a fatty meal and heparin injection already have been shown to falsely increase thyroxine values measured by competitive protein-binding techniques, where ethanol extraction in used. We report here the effect of lesser increases. In 10 patients receiving heparin during hemodialysis we found significant increases in serum thyroxine by competitive protein-binding (mean, 20 nmol/l) and in free fatty acid concentrations (164 micronmol/l). Thyroxine measured as iodine did not change significantly. In seven subjects who had fasted for 27 h, we also noted significant increases in thyroxine by competitive protein-binding (mean 63 nmol/l) and in free fatty acid concentrations (624 micronmol/l). In a single subjects, serial measurements showed a close association of the two variables and the overall correlation between the increases was good. This artefact limits the value of many currently used thyroxine methods because it imposes restrictions on transport of samples and selection of patients.