Rationale and Objectives
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.
Materials and Methods
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.
Results
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).
Conclusions
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.
Introduction
Computed tomography (CT) is the imaging modality of choice for the diagnosis of many causes of acute abdominal pain. CT protocols for evaluating patients presenting with acute nontraumatic abdominal pain commonly include the use of oral and intravenous (IV) contrast agents. This widely used protocol is considered to provide the most diagnostic information but is based on data from the earliest days of abdominal CT imaging. The introduction of helical and multidetector CT scanners has made the utility of oral contrast uncertain. The use of both oral and IV contrast materials is remarkably sensitive and specific for the diagnosis of bowel-related pathologies, but is not necessarily the most efficient and safe protocol . There are no formal definite guidelines regarding the optimal use of oral contrast in patients presenting to the emergency department (ED) with acute nontraumatic abdominal pain, and this has led to a wide variation in clinical practice .
The use of oral contrast material for abdominal CT examinations may have several disadvantages, including potential adverse effects of the oral contrast material to the patients, nasogastric tube insertion in patients who are unable to tolerate orally administered contrast material, prolonged ED stay and possible delays in diagnosis, treatment, and operative intervention. Prolonged ED stay also results in increased health-care costs and patient discomfort . Many studies have suggested that IV contrast alone is sensitive and specific for the diagnosis of appendicitis . However, insufficient attention has been given in the literature to the impact of oral contrast material on the diagnosis of other bowel-related causes of acute abdominal pain . To the best of our knowledge, no large prospective randomized trial has focused on this influence.
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Materials and Methods
Patients
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CT Technique
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Image Analysis
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Statistical Analysis
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Results
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TABLE 1
The Clinical Characteristics of Our Patients
Study Group ( N = 174) Control Group ( N = 174)P Value Age (mean years ± SD) 48.3 ± 17 48 ± 17.1 0.860 S/P abdominal operation, n (%) 41(23.6) 53(30.5) 0.147 Change in bowel habits, n (%) 18(10.3) 28(16.1) 0.113 Nausea or vomiting, n (%) 35(20.1) 63(36.2) 0.001 Fever(>37.5°C), n (%) 6(3.4) 7(4) 0.777 Neutrophils(mean % ± SD) 69.3 ± 12.6 69.1 ± 12.4 0.876 CRP(median) 7.3 12.7 0.043 Tenderness, n (%) Located 135(77.6) 146(83.9) 0.377 Diffuse 15(8.6) 13(7.5)
CRP, C-reactive protein; S/P, status post; SD, standard deviation.
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TABLE 2
Technical Adequacy of the Studies
Study Group ( N = 174) Control Group ( N = 174)P Value Excellent, n (%) 149(85.6) 157(90.2) 0.134 Good, n (%) 15(8.6) 14(8) Fair, n (%) 10(5.7) 3(1.7)
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TABLE 3
Specific Findings of the Main Bowel-related Pathologies in Both Groups
Study Group Control Group Appendicitis 28 33 Distention Yes/maybe 27 33 No 1 0 Wall thickening Yes 26 32 No 2 1 Wall enhancement Yes/maybe 24 26 No 4 7 Fat stranding Yes/maybe 27 30 No 1 3 Appendicolith Yes 8 7 No 20 26 Collection Yes 3 3 No 25 30 Diverticulitis 17 19 Diverticulosis Yes 17 19 Wall thickening Yes/maybe 17 18 No 0 1 Wall enhancement Yes/maybe 14 16 No 3 3 Fat stranding Yes/maybe 17 19 Specific diverticulum dilatation Yes 8 10 No 9 9 Collection Yes 0 2 No 17 19 Colitis 9 5 Wall thickening Yes/maybe 9 5 Wall enhancement Yes/maybe 6 4 No 3 1 Fat stranding Yes/maybe 8 4 No 1 1 Collection Yes 1 0 No 8 5
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TABLE 4
Cases in which Oral Contrast Material Was Considered Useful or Probably Useful
Type of Diagnosis Number of Cases Reason Study group Appendicitis 3 Two cases—low INAF index
One case—unusual location of the appendix between small-bowel loops Enteritis 1 Suspected bowel obstruction Colitis 1 Suspected inflammatory bowel disease No bowel pathology 1 Small-bowel malrotation Control group Appendicitis 2 One case—low INAF index
One case—appendix not filled with OCM Diverticulitis 2 Diverticulum not filled with OCM Colitis 2 OCM filled the entire colon No bowel pathology 1 OCM filled the entire colon Small-bowel obstruction 1 OCM did not fill the bowel distal to the transition point
INAF, intra-abdominal fat; OCM, oral contrast material.
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Discussion
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