Melvin H. Farmelant

The renogram: Physiologic basis and current clinical use

Externally monitored radioisotopic renal function studies have proven to be diagnostically useful in a variety of urinary tract disorders. Controversy, however, concerning everything from equipment and patient preparation to information content and interpretation has surrounded the procedure since its inception. The theses presented here are that the choice of equipment is determined by the intended use, that a few major physiologic events determine the shape of the curves produced in the studies, that the information content exceeds what has been extracted to date, and that subtle renal abnormalities are better detected by intercomparison of a patients two kidneys than by comparison to values derived from a selected normal population. Choice of patient preparation and interpretation of the results depend on understanding the physiology involved in the procedure.

The use of radioactive isotopes in the diagnosis of hypertension

Summary Although radioisotopic technics for the diagnosis of renovascular hypertension have been available for less than a decade, they have been demonstrated to provide unique information with a minimum of inconvenience and discomfort to the patient. Kinetic data, obtained with I 131 -Hippuran, and scans, showing the anatomical location of a labeled mercurial, are of established value as screening procedures for renovascular hypertension and may, in addition, be useful in predicting the outcome of surgery in an individual patient.

Sensitivity and specificity of radioisotope renography in renovascular hypertension.

Effective drug therapy for hypertension modifies the urgency of establishing a diagnosis of renal arterial stenosis. The cost of establishing a diagnosis must be considered with other factors in determining the usefulness of renography in renovascular hypertension. Recently published studies estimate the cost effectiveness of this procedure based on some data from a cooperative study of renal vascular hypertension. The small but costly incidence of false positives contributes significantly to the total cost of patient screening. Careful attention to technical details that are presented here could reduce false positives without sacrificing the true positives. However, even with increased specificity economic considerations would indicate limiting a screening program to younger patients or those in whom a drug regimen is unsuccessful.