title: Unenhanced helical CT for renal colic--is the radiation dose justifiable?
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Radiology, Guys Hospital, Guys and St Thomas' Hospitals Trust, London, UK.
authors.forename: E R
authors.initials: ER
authors.lastname: Denton
authors.forename: A
authors.initials: A
authors.lastname: Mackenzie
authors.forename: T
authors.initials: T
authors.lastname: Greenwell
authors.forename: R
authors.initials: R
authors.lastname: Popert
authors.forename: S C
authors.initials: SC
authors.lastname: Rankin
mesh_terms: D003085:Colic / Q000000981:diagnostic imaging*; D006801:Humans; D007669:Kidney Calculi / Q000000981:diagnostic imaging; D007674:Kidney Diseases / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011856:Radiographic Image Enhancement; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*