Renal concentrating capacity test using desmopressin at bedtime

Abstract 

A crossover trial was undertaken to evaluate the bedtime administration of desmopressin (Minirin) as a renal concentrating capacity test (RCCT). Medication was given intranasally as a single 20-µg dose to 58 children ranging from 3 to 15 years of age with suspected or known renal impairment. The night-time test was shown to be a simple and effective means of assessing renal concentrating capacity. Comparison with the standard daytime test resulted in a 60 mosmol/kg higher mean osmolality in the night-time test. The results were reproducible, with a 95% confidence interval of –26 to 43 mosmol/kg. The procedure was easy to perform, with 51 of 52 patients (or their parents) preferring the night-time regimen compared with the daytime test. Night-time desmopressin therefore offers the potential of a user-friendly RCCT in patients with suspected impairment of renal tubular function.