OBJECTIVE: To evaluate the role of the equilibrium phase in abdominal computed tomography. MATERIALS AND METHODS: A retrospective, cross-sectional, observational study reviewed 219 consecutive contrast-enhanced abdominal computed tomography images acquired in a three-month period, for different clinical indications. For each study, two reports were issued - one based on the initial analysis of non-contrast-enhanced, arterial and portal phases only (first analysis), and a second reading of these phases added to the equilibrium phase (second analysis). At the end of both readings, differences between primary and secondary diagnoses were pointed out and recorded, in order to measure the impact of suppressing the equilibrium phase on the clinical outcome for each of the patients. The extension of the exact Fisher's test was utilized to evaluate the changes in the primary diagnosis (p < 0.05 as significant). RESULTS: Among the 219 cases reviewed, the absence of the equilibrium phase determined change in the primary diagnosis in only one case (0.46%; p > 0.999). As regards secondary diagnoses, changes after the second analysis were observed in five cases (2.3%). CONCLUSION: For clinical scenarios such as cancer staging, acute abdomen and investigation for abdominal collections, the equilibrium phase is dispensable and does not offer any significant diagnostic contribution.

Keywords: X-ray computed tomography; Ionizing radiation; Neoplasm staging; Acute abdomen.

OBJECTIVE: To evaluate the diagnostic capacity of abdominal computed tomography in the assessment of hepatic steatosis using the portal phase with a simplified calculation method as compared with the non-contrast-enhanced phase. MATERIALS AND METHODS: In the present study, 150 patients were retrospectively evaluated by means of non-contrast-enhanced and contrast-enhanced computed tomography. One hundred patients had hepatic steatosis and 50 were control subjects. For the diagnosis of hepatic steatosis in the portal phase, the authors considered a result of < 104 HU calculated by the formula [L - 0.3 × (0.75 × P + 0.25 × A)] / 0.7, where L, P and A represent the attenuation of the liver, of the main portal vein and abdominal aorta, respectively. Sensitivity, specificity, positive and negative predictive values were calculated, using non-contrast-enhanced computed tomography as the reference standard. RESULTS: The simplified calculation method with portal phase for the diagnosis of hepatic steatosis showed 100% sensitivity, 36% specificity, negative predictive value of 100% and positive predictive value of 75.8%. The rate of false positive results was 64%. False negative results were not observed. CONCLUSION: The portal phase presents an excellent sensitivity in the diagnosis of hepatic steatosis, as compared with the non-contrast-enhanced phase of abdominal computed tomography. However, the method has low specificity.

Keywords: Fatty liver; Steatosis; Liver disease; Tomography; Multidetector computed tomography; Contrast media.

OBJECTIVE: To evaluate the necessity of the non contrast-enhanced phase in abdominal computed tomography scans. MATERIALS AND METHODS: A retrospective, cross-sectional, observational study was developed, evaluating 244 consecutive abdominal computed tomography scans both with and without contrast injection. Initially, the contrast-enhanced images were analyzed (first analysis). Subsequently, the observers had access to the non-contrast-enhanced images for a second analysis. The primary and secondary diagnoses were established as a function of the clinical indications for each study (such as tumor staging, acute abdomen, investigation for abdominal collection and hepatocellular carcinoma, among others). Finally, the changes in the diagnoses resulting from the addition of the non-contrast-enhanced phase were evaluated. RESULTS: Only one (0.4%; p > 0.999; non-statistically significant) out of the 244 reviewed cases had the diagnosis changed after the reading of non-contrast-enhanced images. As the secondary diagnoses are considered, 35 (14%) cases presented changes after the second analysis, as follows: nephrolithiasis (10%), steatosis (3%), adrenal nodule (0.7%) and cholelithiasis (0.3%). CONCLUSION: For the clinical indications of tumor staging, acute abdomen, investigation of abdominal collections and hepatocellular carcinoma, the non-contrast-enhanced phase can be excluded from abdominal computed tomography studies with no significant impact on the diagnosis.

Keywords: Computed tomography; Ionizing radiation; Abdomen; Contrast media.