Anal intraepithelial neoplasia (AIN) is a premalignant lesion for anal cancer. It is more commonly found in high-risk patients (e.g., human papilloma virus (HPV)/human immunodeficiency virus infections, post-organ transplantation patients, and men who have sex with men) and development is driven by HPV infection. The incidence of AIN is difficult to estimate, but is heavily skewed by preexisting conditions, particularly in high-risk populations. The diagnosis is made from cytology or biopsy during routine examinations, and can be performed at a primary care provider’s office. A pathologist can then review and classify cells, based on nucleus-to-cytoplasm ratios. The classification of low or high grade can better predict progression from AIN to anal cancer. There is little debate that AIN can develop into anal cancer, and the main rationale for treatment is to delay the progression. Significant controversy remains regarding screening, surveillance, and treatment for AIN. Management options are separated into surveillance (watchful waiting) and interventional strategies. Emerging data suggest that close patient follow up with a combination of ablative and topical treatments may offer the greatest benefit. HPV vaccination offers a unique treatment prior to HPV infection and the subsequent development of AIN, but its use after the development of AIN is limited. Ablative treatment includes excision, fulguration, and laser therapy.

Hemorrhoids, anal fissures, and fistulas are common benign anorectal diseases that have a significant impact on patients' lives. They are primarily encountered by primary care providers, including internists, gastroenterologists, pediatricians, gynecologists, and emergency care providers. Most complex anorectal disease cases are referred to colorectal surgeons. Knowledge of these disease processes is essential for proper treatment and follow up. Hemorrhoids and fissures frequently benefit from non-operative treatment; they may, however, require surgical procedures. The treatment of anorectal abscess and fistulas is mainly surgical. The aim of this review is to examine the etiology, diagnosis, medical, and surgical treatment for these benign anorectal diseases.

Therapeutic study, level IV.