Published online Sep 6, 2020. doi: 10.12998/wjcc.v8.i17.3679
Peer-review started: January 3, 2020
First decision: January 18, 2020
Revised: May 15, 2020
Accepted: August 1, 2020
Article in press: August 1, 2020
Published online: September 6, 2020
The use of 18F-fluorodeoxyglucose (18FDG) positron-emission tomography/computed tomography (PET/CT) has increased in oncology and in the management of infectious or inflammatory diseases. As a result of the increased indications for and availability of 18FDG PET/CT, unexpected 18FDG uptake has been identified in a variety of sites. In the field of gastroenterology, several studies have focused on incidental focal colorectal 18FDG uptake. No studies to date have investigated incidental anal 18FDG uptake. Anorectal examinations are nevertheless simple and minimally invasive, and the diagnosis of anal pathologies is often based on the patient’s history or data obtained during the clinical examination.
It seems important to assess the rate of incidental anal 18FDG uptake and to identify their aetiologies. Finally, no recommendations have been established in this particular situation.
The objectives of this study were as follows to assess the rate of incidental anal 18FDG uptake, to identify the aetiologies of incidental anal 18FDG uptake, and to evaluate the correlation between 18FDG PET/CT parameters and the diagnosis of an anorectal disease and the management of the disease.
We carried out a retrospective observational single-centre study. The data from patients with incidental anal 18FDG uptake were analysed. Patients who underwent anorectal examinations were identified and compared to those who did not undergo examinations. Patients who were offered treatment were then identified and compared to those who did not receive treatment. Comparisons between patients were performed using the Wilcoxon test and the chi-squared test or Fisher’s exact test, as appropriate. A P value < 0.05 was considered statistically significant.
Among the 43020 18FDG PET/CT scans performed, 197 18FDG PET/CT scans of 146 patients reported incidental anal uptake: The rate of incidental anal 18FDG uptake was 0.45%. Among the 134 patients included, 48 (35.8%) patients underwent anorectal examinations and anorectal diseases were diagnosed in 33 (69.0%) of these patients haemorrhoidal disease (n = 22), anal fissure (n = 6), recurrence of rectal adenocarcinoma on the coloanal anastomosis (n = 1), condyloma (n = 3), faecal impaction (n = 1), suppuration (n = 2) and solitary rectal ulcer syndrome (n = 1). Eighteen/48 (37.5%) received treatment. Among the examined patients, those with a pathology requiring treatment had significantly smaller metabolic volumes (MV) 30 and MV41 values and higher maximal and mean standardized uptake value measurements than those who did not require treatment.
Incidental anal 18FDG uptake is a rare event and is rarely explored. However, when explored, a diagnosis is made in more than two-thirds of the cases, and treatment is proposed in more than one-third of the cases. Some metabolic parameters associated with a therapeutic impact have been identified. These data should encourage practitioners to explore incidental anal 18FDG uptake systematically because some patients may recover well from an anal pathology.
Further large-scale prospective studies are needed. We would like to investigate a control group of patients without anal 18FDG uptake to better demonstrate the diagnostic and therapeutic impact of anal 18FDG uptake.