Assessment of Omission of Non-Contrast CT for CT Diagnosis of Abdominal Diseases in Patients Undergoing Non-Emergent Contrast-Enhanced CT Abdomen

To assess whether omission of non-contrast computed tomography (NCCT) in patients undergoing non-emergent contrast-enhanced CT (CECT) abdomen affects the final CT diagnosis in abdominal diseases. A total of 350 adult patients were selected for non-emergent CECT scan abdomen, and NCCT was omitted. Images were reviewed by two experienced radiologists (R1 and R2) to make primary and secondary CT diagnoses. In case of disagreement, the opinion of a third experienced radiologist (R3) was obtained. The concordance/discordance between the radiologists was calculated. Percentages of cases in which performing CECT alone did not affect the CT diagnosis were calculated. There was concordance between radiologists R1 and R2 for primary CT diagnosis of abdominal diseases in 340/350 patients undergoing non-emergent CECT abdomen, while NCCT was omitted. The secondary CT diagnosis was unaffected by omitting NCCT in 69 out of 70 cases, i.e., 98.57% concordance between R1 and R2. In 10/350 patients (2.86%), omission of NCCT prevented accurate primary CT diagnosis according to R2, while R1 and R3 opined that NCCT was not needed. In all these 10 patients, NCCT findings did not produce any major diagnostic changes. Omission of NCCT prior to non-emergent CECT abdomen does not prevent an accurate diagnosis in a vast majority of abdominal diseases, while reducing the radiation dose by almost half. No previous study is available in which the non-contrast phase has been omitted successfully in adults, before non-emergent CECT, in a large variety of infective and neoplastic abdominal diseases.