Double Dose Urography

Abstract

The evolution of contrast agents for urography has been briefly reviewed, the passage of the contrast in the plasma and extracellular space has been mentioned, and the nature of excretion in the nephron has been denned. The emphasis in the past on the dose of contrast agent, dehydration, compression and more recently a double dose and rehydration have been discussed. There is no evidence that rehydration has any value within the period of the examination while the double dose produces an osmotic diuresis with urine of maximum concentration. It is suggested that the dose of contrast agent for urography is the one which produces a maximum urinary concentration for the duration of the examination. In most patients this requires sufficient contrast to contain 15 grammes of iodine. More may be needed in very large patients and slightly less in smaller patients. There is no evidence that the larger dose leads to more reactions, while there is a considerable saving in the overall time for the examination and the films used. It can be anticipated that this is a suitable anatomical study for hypertensive patients, but it is unsuitable as a physiological study of differential renal function. However, the advantages of the double dose urogram are a better nephrogram and pyelogram; it may avoid the necessity for abdominal compression, provide a better study in the presence of poor renal function and a close correlation with true renal function. The latter is being currently reviewed. In conclusion, it is suggested that the double dose urogram should be considered “the Adequate Dose Urogram”.