To eat or not to eat? Effect of fasting prior to abdominal sonography examinations on the quality of imaging under routine conditions: A randomized, examiner-blinded trial

Objective. Although often recommended, it is unclear whether fasting enhances the imaging quality of abdominal sonography examinations. The aim of this study was to produce experimental evidence of the effect of fasting on the imaging quality of abdominal organs. Material and methods. Formally consenting medical inpatients who underwent elective abdominal sonography examinations at a university medical center were randomized to either a fasting or a non-fasting preparation. Blinded examiners evaluated the imaging quality of 11 anatomical regions. The primary end-point was the proportion of completely evaluable patients for each region. In secondary analyses, values of an imaging index reflecting the mean imaging quality of all regions (range 0-1) were compared. Results. Of 280 screened patients, 102 (36%) met the exclusion criteria and 35 (13%) declined participation. Of the 143 randomized patients, 130 (91%) were included in the primary analyses (66 fasting, 64 non-fasting). The proportion of completely evaluable patients did not differ significantly for any of the 11 regions, but a large nominal difference occurred for the gallbladder (45/66 (73%) fasting versus 34/64 (56%) non-fasting patients, p = 0.051). The median (range) imaging index was 0.57 (0.14-0.95) for fasting and 0.43 (0.00-1.00) for non-fasting subjects (p = 0.078). A significant (p = 0.002) difference favoring fasting was detected in the post-hoc subgroup analyses for male patients. Conclusions. For examinations of the gallbladder and for male patients, fasting might improve the sonographic imaging quality to some extent. Overall, no significant improvement in the imaging quality of abdominal organs was reached with a fasting preparation.