Study: Non-contrast abdominal CT – an alternative to CT with contrast for nontraumatic acute abdominal pain

Acute abdominal pain is a major reason for admission to emergency departments. In 2007-2008, the number of emergency department visits for non-injury abdominal pain reported to the U.S. Department of Health and Human Services (HHS) was 7,000,000, an increase of 31.8% since 1999-2000.¹ CT is the imaging modality primarily used to diagnose abdominal pain, with the Division of Health Statistics reporting that 44.3% of all patients with this symptom had an advanced imaging procedure in 2008.

The majority of these abdominal CT scans are performed with contrast: intravenous, oral and/or rectal. Intravenous contrast agents can produce mild to severe allergic reactions; administration of rectal contrast agents take manpower and time to administer; oral contrast agents can add hours to a timely diagnosis while waiting for the agent to travel through the gastrointestinal tract.

A non-contrast abdominal CT would eliminate these problems. But is it diagnostically appropriate? Emergency department physicians and residents of Tampa’s University of South Florida Department of Emergency Medicine and radiologists at Tampa General Hospital conducted a study to find out. They determined that with appropriately vetted patients, diagnostic findings were comparable.

The study, published online August 22, 2015 in the Journal of Emergency Medicine, followed 72 patients from time of emergency department admission through a week of follow-up. Lead author Austin Payor, D.O. and colleagues stated any missed emergent acute pathology would continue to progress and worsen within a seven day observational time period. A repeat CT scan – this one using contrast – or a decision to perform abdominal surgery would reveal the true etiology of abdominal pain.

Over a 90-day period commencing August 1, 2013, 485 patients presented with symptoms of nontraumatic, non-injury abdominal pain to the emergency department of Tampa General Hospital. A total of 72 patients were enrolled who met the criteria established for the ordering of a non-contrast abdominal CT.

In addition to agreeing to participate in the study, which a large percentage of patients were not, patient selection criteria included:

• 18 years of age and over, not pregnant, experiencing acute abdominal pain for 72 hours or less;
• Had a body mass index (BMI) of less than 18;
• No history of prior abdominal or pelvic trauma or surgery within the past 30 days;
• Were not suspected of having a renal stone or an unstable condition as determined by an emergency physician;
No history of abdominal or pelvic primary or metastatic cancer.

The attending emergency physician could overrule a patient’s enrollment if he/she felt that a CT exam with contrast was needed to rule out such conditions as abdominal aortic aneurysm.

A total of 39 patients, or 54%, had a positive CT scan. Forty-one patients were admitted to the hospital, of whom eight underwent abdominal surgery. Three of the patients had a contrast CT performed within the seven day time period. The findings – a pelvic mass, colitis, and pancreatitis – were identified on both the non-contrast and the contrast CT examinations.

Performing non-contrast CT instead of contrast CT on even a small portion of these patients would save time in emergency departments to make an accurate diagnosis, reduce overcrowding, and provide cost-savings. The authors write, “The practicing physician remains always cognizant of the ever-looming threat of legal action as they try to provide care to the patient…For the busy emergency physician, the ideal test is not one that would provide the diagnosis every time, but one that would guarantee that no disease process is missed when disease is present.”

They concluded that the study, even with its small sample size, shows that “With our given inclusion and exclusion criteria, noncontrast CT of the abdomen and pelvis is likely a reliable diagnostic modality for nontraumatic abdominal pain in the ED. We hope additional studies are conducted to validate our findings.”

REFERENCES

1. Bhuiya FA, Pitts, SR, McCaig LF. Emergency Department Visits for Chest Pain and Abdominal Pain: United States, 1999-2008. 2010 NCHS Data Brief; 43:1-8.
2. Payor A, Jois P, Wilson J, et al. Efficacy of noncontrast computed tomography of the abdomen and pelvis for evaluating nontraumatic acute abdominal pain in the emergency department. J Emerg Med. Published online August 22, 2015.