Anal Intraepithelial Neoplasia Detection on Routine Colonoscopy: Review of 3550 Patients.

Background: Human papillomavirus (HPV) is prevalent in the general population with lifetime risk of about 80% whom didn't receive HPV vaccine. AIN publications have been focusing on high risk patients for developing AIN. It is usually asymptomatic especially during the early phases; 60-70% of anal squamous cell carcinomas (ASCC) are seen in an advance stage. Materials and Methods: We performed a retrospective review of 3550 colonoscopies done at a single institution in Henry Ford Providence Hospital. All patients underwent routine colonoscopy which had the anorectum and transition zone were inspected for AIN lesion with narrow band imaging (NBI) during retroflexion. Any suspected abnormalities were biopsied then reviewed by gastrointestinal pathologist. Any patient with confirmed AIN was referred for high resolution anoscopy with definitive treatment. Results: Our study covered 3550 patient of whom 41 patients (1.2%) resulted in suspicious lesion for AIN (19 males, 22 females; median age 52.25 years). The pathology result was 24 lesion (58%) had AIN 1, 16 patients (39%) had AIN 2-3 and one patient (2.4%) had invasive squamous cell carcinoma. Of these patients 48.8% were negative for HIV and immunocompetent. There was no complication related to the biopsy during colonoscopy. Conclusions: Even though AIN lesions are infrequently detected during routine colonoscopy, it is still feasible and valuable even in immunocompetent patients. Retroflexion plus NBI during colonoscopy can be used as an opportunity for AIN detection. Treating AIN lesion and detection them may lead to ASSC prevention. Routine colonoscopy presents a valuable opportunity for opportunistic detection of AIN lesions.