Dehydration, antidiuretic hormone and the intravenous urogram

The efficacy and safety of attempts to dehydrate patients before intravenous urography in order to improve image quality have been called into question by several authors. Antidiuretic hormone (ADH) assays described here show that dehydration of outpatients as typically practised by radiology departments does not affect plasma ADH levels. Furthermore, the very act of contrast-agent administration causes a rapid rise in plasma ADH concentration to levels higher than would in any case be expected from modest dehydration. Since the likely effect on circulating ADH of attempted dehydration is dwarfed by the physiological response to a contrast agent, it is considered that such efforts are entirely superfluous.