Study examines benefit of follow-up CT when abdominal ultrasound inconclusive

About one-third of CT examinations performed following an inconclusive abdominal ultrasound examination have positive findings, according to a study of 449 patients at Massachusetts General Hospital in Boston.

Opinions vary as to the need and relevance for further diagnostic imaging workup after an inconclusive abdominal ultrasound examination, said Supriya Gupta, MD, one of the authors of the study. "Our study found that 32.9% of follow-up CT examinations had positive findings, while 42.7% had findings that were not significant and 11.7% were equivocal. The remaining 12% had incidental findings, that is, important findings but not related to the clinical indication for the exam, said Dr. Gupta.

"While only about 33% of the CT examinations had positive findings it doesn't mean that the other CT exams were not valuable as sometimes even negative exams add a lot to patient management," noted Dr. Gupta.

The study found that follow-up CT was most useful in diagnosing renal lesions. The positivity rate for CT was 87.5% for renal cysts and 81.8% for renal stone, said Dr. Gupta. Renal cysts and renal stone were two of the more common indications for recommending follow-up CT.

CT had the least value as a follow up exam for indeterminate pancreatic and intestinal masses on ultrasound, with a less than 10% positivity rate" said Dr. Gupta.

The study results emphasize that the benefits of CT as a follow-up to inconclusive ultrasound examinations need to be more carefully reviewed; standardized guidelines for the use of follow-up CT need to be developed because the use of CT has cost and radiation implications, said Dr. Gupta.

The study will be presented on April 30 at the American Roentgen Ray Society Annual Meeting in Vancouver, Canada.