Multi-Detector Row CT of Acute Non-traumatic Abdominal Pain: Contrast and Protocol Considerations

AbdCT for the evaluation of AAP in the ED in the US may be excessive and is potentially (although rarely) misleading and harmful. A selective policy of ‘AbdUS first’ combined with an observation unit and/or surgeon evaluation prior to AbdCT is preferred to a ‘routine AbdCT’ policy. Repeated AbdCTs for abdominal pain are not recommended because of cumulative radiation exposure. Standardized and complete history and physical examination, such as that originally designed for computer-aided diagnosis of AAP, along with select laboratory testing and higher utilization of AbdUS lessens the necessity of AbdCT. ‘Routine AbdCT’ is particularly not necessary for the evaluation of suspected appendicitis. ‘Routine AbdCT’ lowers the negative appendectomy rate but at the expense of exposure to radiation. Right lower quadrant US and selective use of observation prior to AbdCT for suspected appendicitis, particularly in children, adolescents, and young adults, are warranted. MRI should substitute for AbdCT for the evaluation of suspected appendicitis during pregnancy.

This study aims to compare the diagnostic performance of abdominal computed tomography (CT) performed with and without oral contrast in patients presenting to the emergency department (ED) with acute nontraumatic abdominal pain.

Between December 2013 and December 2014, 348 adult patients presenting to the ED of a large tertiary medical center with nontraumatic abdominal pain were evaluated. Exclusion criteria for the study were history of inflammatory bowel disease, recent abdominal operation and suspected renal colic, abdominal aortic aneurysm rupture, or intestinal obstruction. All patients underwent intravenous contrast-enhanced abdominal CT on a Philips Brilliance 64-slice scanner using a routine abdomen protocol. The study group included 174 patients who underwent abdominal CT scanning without oral contrast, recruited using convenience sampling. A control group of 174 patients was matched to the cohort groups' gender and age and underwent abdominal CT with oral contrast material during the same time period. The patients' medical records were reviewed for various clinical findings and for the final clinical diagnosis. The CT exams were initially reviewed by a senior attending radiologist to determine the exams' technical adequacy and to decide whether an additional scan with oral contrast was required. Two senior radiologists, blinded to the clinical diagnosis, later performed consensus reading to determine the contribution of oral contrast administration to the radiologists' diagnostic confidence and its influence on diagnosing various radiological findings.

Each group consisted of 82 men and 92 women. The average age of the two groups was 48 years. The main clinical diagnoses of the pathological examinations were appendicitis (17.5%), diverticulitis (10.9%), and colitis (5.2%). A normal CT examination was found in 34.8% of the patients. There was no significant difference between the groups regarding most of the clinical parameters that were examined. None of the examinations of all of the 174 study group patients was found to be technically inadequate, and therefore no patient had to undergo additional scanning to establish a diagnosis. The consensus reading of the senior radiologists determined that the lack of oral contrast was insignificant in 96.6% of the cases and that contrast material might have been useful in only 6 of 174 study group patients (3.4%). The radiologists found oral contrast to be helpful only in 8 of 174 control group patients (4.6%). There was no significant difference between the clinical and radiological diagnoses in both groups (study group, P = 0.261; control group, P = 0.075).

Our study shows that oral contrast is noncontributory to radiological diagnosis in most patients presenting to the ED with acute nontraumatic abdominal pain. These patients can therefore undergo abdominal CT scanning without oral contrast, with no effect on radiological diagnostic performance.