Objective
It was reported that nocturnal polyuria in cervical cord injured patients may be due to attenuation of diurnal variation of antidiuretic hormone (ADH) level. However, it has been unclear whether the attenuation of diurnal variation of ADH level caused nocturnal polyuria and bladder overdistension. To improve the management of neurogenic bladder with overdistension during the night, we investigated whether the attenuation of diurnal variation of ADH level is the cause of nocturnal polyuria or bladder overdistens-ion in patients with cervical cord injury.

Method
The subjects consisted of 17 patients with cervical cord injury. The age distribution ranged from 31 to 63 years with an average of 41.5 years. The duration of illness ranged from 5 months to 4 years. Oral intake was restricted below 2,000 ml per day. We measured urine volume and urine osmolarity during the day (8 AM∼8 PM) and night period (8 PM∼8 AM) and the level of plasma ADH and serum osmolarity at 2 PM and 2 AM.

Results
Plasma ADH level was 0.81⁑0.51 pg/ml during the day and 1.04⁑0.65 pg/ml during the night (p=0.17). Urine volume was 1050⁑410 ml during the day and 970⁑550 ml during the night (p=0.92). The average of urine osmolarity was 450.4⁑182.8 mosm during the day and 558.4⁑359 mosm during the night (p=0.25). The average of serum osmolarity was 292.4⁑14.5 mosm during the day and 290.4⁑9.3 mosm during the night (p=0.53).

Conclusion
This study showed that there was no significant difference in each parameter for two periods and urine volume was not increased in spite of attenuation of diurnal variation of ADH level. Therefore this indicated that attenuation of diurnal varia-tion of ADH was less likely responsible for nocturnal polyuria in patients with cervical cord injury.