Unenhanced helical CT for renal colic--is the radiation dose justifiable?

AIM: The purpose of this study was to define and compare the radiation doses to patients undergoing computed tomography (CT) or intravenous urography (IVU) for the investigation of renal colic.

METHODS: The IVU dose was calculated from dose area product measurements for 27 abdominal films (AXR) and a review of 30 IVUs performed to investigate renal colic. The effective dose to a patient undergoing CT was calculated using anthropomorphic model data. Fifty patients underwent CT for the investigation of renal colic over a 6-week period.

RESULTS: CT following our protocol confers an average effective dose of 4.7 mSv. An IVU to investigate renal colic used 2.5 AXRs. A 3 film IVU gives an average dose of 1.5 mSv. Forty-two CT examinations were abnormal and the findings are described in the text.

CONCLUSION: Although unenhanced CT confers diagnostic advantages and avoids the risks of intravenous contrast medium, this should be considered against the increased radiation dose to the patient which in our institution is over three times that of an IVU.