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Low-dose CT may be sufficient for appendicitis diagnosis

Roshini Claire Anthony
04 Oct 2017

Using a reduced computed tomography (CT) dose to diagnose appendicitis in adolescents and young adults does not appear to affect clinical outcomes, and could potentially reduce the long-term risk of radiation-related cancers, according to results of the LOCAT* trial.

“Our findings show that low-dose CT can be successfully delivered without impairing the negative appendectomy rate, appendiceal perforation rate, or other clinically important outcomes,” said the researchers.

“In view of the vast numbers of appendiceal CT scans done worldwide, use of low-dose CT could prevent a sizeable number of radiation-associated cancers in the future,” they said.

This noninferiority trial was conducted in 20 hospitals in South Korea that had limited experience using low-dose CT. Patients aged 15–44 years (mean age 28 years, about 45 percent male) with suspected appendicitis were randomized to receive either low-dose (2 mSv, median dose-length 132 mGy.cm, n=1,535) or standard-dose CT (3–8 mSv, median dose-length 486 mGy.cm, n=1,539).

Appendicitis was diagnosed in 524 and 564 patients from the low- and standard-dose groups, respectively. Appendectomies that produced surgical specimens with no evidence of mural neutrophil infiltration or mucosal neutrophils with ulcerations were considered negative or unnecessary.

Of the 559 and 601 patients who underwent appendectomy in the low- and standard-dose groups, respectively, 3.9 (n=22) and 2.7 percent (n=16) were deemed negative or unnecessary (difference, 1.3 percent, 95 percent confidence interval, -0.8 to 3.3; p=0.0022 for noninferiority). [Lancet Gastroenterol Hepatol 2017:doi:10.1016/S2468-1253(17)30247-9]

Incidence of adverse events in the entire cohort (n=3,074) was comparable between low- and standard-dose groups (n=43 and 41, respectively), with one incidence of life-threatening anaphylaxis due to iodinated contrast material reported in the low-dose group.

The appendiceal perforation rate in all cases of appendicitis was slightly higher among patients on low- compared with standard-dose CT (34.7 percent vs 31.2 percent; difference, 3.5 percent; p=0.023 for noninferiority).

The results of this study add to the existing literature on the noninferiority of low-dose CT in the diagnosis of appendicitis. [N Engl J Med 2012;366:1596-1605; Int J Surg 2016;31:71-79]

While the between-group differences were small, researchers suggested weighing the results against the benefits of radiation-related cancer prevention.

“A successful reduction of population radiation dose should entail judicious CT use and dose lowering in individual examinations. In this context, stepwise diagnostic protocols limiting CT use to clinically or ultrasonographically equivocal cases are most welcomed, and the protocols should ideally incorporate low-dose CT,” said the researchers, who cautioned against interpreting these results to increase rates of CT use with lower doses. The results may also not extend to hospitals in other countries, they said.

As previous studies have shown an elevated cancer risk among individuals exposed to CT scan-irradiation in adolescence or young adulthood, [BMJ 2013;346:f2360; Lancet 2012;380:499-505] there is interest in limiting the radiation dose exposure in individuals in this age group, said the researchers.

“The high incidence of acute appendicitis in adolescents and young adults emphasizes the need to reduce the CT dose, because younger patients are more sensitive to the late effects of radiation,” said Dr Paulina Salminen from Turku University Hospital, Turku, Finland, in a commentary. [Lancet Gastroenterol Hepatol 2017:doi:10.1016/S2468-1253(17)30282-0]

“[Low-dose CT protocols] should be implemented in all emergency departments according to the as-low-as-reasonably-achievable principle, to enable substantial reduction in radiation doses for patients with suspected appendicitis,” she said, and encouraged further research into identifying the capability of low- and standard-dose CT in differentiating between complicated and uncomplicated appendicitis.

 

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