EVALUATION OF RENAL MASSES DETECTED BY EXCRETORY UROGRAPHY - COST-EFFECTIVENESS OF SONOGRAPHY VERSUS CT

OBJECTIVE. The purpose of this study was to compare the cost-effective ness of sonography and CT for the evaluation of renal masses discovere d at excretory urography. MATERIALS AND METHODS. The records of 225 pa tients with a renal mass shown by urography who then had either sonogr aphy or CT within 3 months were reviewed retrospectively. The number, location, and size of lesions; initial and subsequent imaging tests; a nd final diagnoses were determined. Using the current Medicare reimbur sements for sonography and CT, we calculated the economic implications of using sonography or CT as the initial examination. Any effect of t he location or size of the lesion on the most cost-effective examinati on was also determined. RESULTS. Twenty-one percent of patients had bo th initial sonography and followup CT because of indeterminate finding s or detection of a solid mass that required further staging. When CT was done first, CT findings were equivocal in 12%, necessitating follo w-up sonography. At the prevailing charges, CT would have to be needed in 70% of patients initially imaged with sonography to justify the us e of CT as the initial examination. The location and size of the lesio n did not affect the need for CT at a rate (greater than 70%) that wou ld economically justify use of CT as the first imaging test. Eighty-si x percent of patients with a mass detected by urography had either a s imple cyst or no evidence of a mass on sonography or CT. CONCLUSION. S onography is the most cost-effective imaging method for the workup of a renal mass detected at urography. The number of sonographic examinat ions in which findings are indeterminate or positive (for a solid mass ) is not sufficiently high to warrant replacement of sonography by CT, regardless of the size and location of the lesion. CT should be reser ved for a limited number of specific indications.