Incidence and Etiologies of Proctitis

Abstract

Proctitis is an inflammatory condition affecting the rectal mucosa. While sexually transmitted infections (STIs) are known risk factors for proctitis, up to 50% of individuals with proctitis do not have an STI. We leveraged data from ExGen, a 48-week natural history study of extragenital gonorrhea (GC) and chlamydia (CT) conducted among 140 MSM in Seattle, Washington, 2016-2018. Each week, participants collected a rectal swab and completed an electronic diary which included questions on behavioral exposures and rectal symptoms. Rectal swabs were tested for GC, CT, and Mycoplasma genitalium (MG) at the end of the study. We defined proctitis symptoms as reporting rectal pain or pain on defecation and either rectal discharge or rectal bleeding. We calculated the incidence and duration of proctitis symptoms. To evaluate the association between behavioral exposures and rectal STIs with proctitis symptoms, we conducted a nested, matched case-control study: cases were participants who had proctitis symptoms and controls were participants without proctitis, matched to cases 2:1 by study week. We used conditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). Of 140 ExGen participants, there were 44 episodes of proctitis symptoms among 24 participants (cumulative incidence=17%; 95% CI=0.12-0.25); the mean duration of symptoms was 1.32 weeks. Rectal CT and GC were more common among cases (n=22) than controls (n=44) (CT: 23% vs. 0%; GC: 14% vs. 2%), but rectal MG prevalence was similar (27% vs. 23%); 54.5% of cases tested negative for rectal CT, GC, and MG. Rectal douching, use of non-saliva lubricant, and number of receptive anal sex acts were associated with proctitis symptoms in univariable analyses but only number of receptive anal sex acts remained significantly associated with proctitis symptoms in multivariable analyses (aOR = 23.34, 95% CI: 1.78 – 306.44 comparing >5 receptive anal sex acts to 0). Rectal GC and CT were more common among proctitis cases compared to controls but more than half of symptomatic individuals did not have a rectal STI. Frequent anal sex could contribute to symptom development or may also represent an increased exposure to biological risk factors. Further studies exploring additional behavioral and biological factors that may lead to development of proctitis symptoms among MSM are needed.