Since many, if not most, anal cancers derive from HPV infections, and since the HPV vaccine before exposure to HPV prevents infection by some strains of the virus and has been shown to reduce the incidence of potentially precancerous lesions, scientists surmise that HPV vaccination may reduce the incidence of anal cancer.

On 22 December 2010, the U.S. Food and Drug Administration approved Gardasil vaccine to prevent anal cancer and pre-cancerous lesions in males and females aged 9 to 26 years. The vaccine has been used before to help prevent cervical, vulvar, and vaginal cancer, and associated lesions caused by HPV types 6, 11, 16, and 18 in women.

The American Cancer Society estimated that in 2014 about 7,060 new cases of anal cancer would be diagnosed in the United States (4,430 in women and 2,630 in men) . It is typically found in adults, average age early 60s.

In the United States, an estimated 800 to 900 people die of anal cancer annually.

Some groups of women have been found to be at a higher risk of developing CIN:

- Women who become infected by a "high risk" type of HPV, such as 16, 18, 31, or 33

- Women who are immunodeficient

- Women who give birth before age 17

A number of risk factors have been shown to increase a woman's likelihood of developing CIN, including poor diet, multiple sexual partners, lack of condom use, and cigarette smoking.

Between 250,000 and 1 million American women are diagnosed with CIN annually. Women can develop CIN at any age, however women generally develop it between the ages of 25 to 35.

Breeds that may be more commonly affected include the English Cocker Spaniel, German Shepherd Dog, Alaskan Malamute, Dachshund, and Springer Spaniel. It is a disease of middle-age to older dogs and even though early reports described spayed females as more commonly affected, multiple recents studies have shown no gender overrepresentation.

Aggressive surgical removal of the tumor and any enlarged sublumbar lymph nodes is essential for treatment of the tumor and associated hypercalcaemia. There is a high recurrence rate, although removal of lymph nodes with metastasis may improve survival time. Radiation therapy and chemotherapy may be helpful in treatment. Severe hypercalcaemia is treated with aggressive IV fluid therapy using sodium chloride and medications such as loop diuretics (increased kidney excretion of calcium) and aminobisphosphonates (decreased calcium release from bones). A poorer prognosis is associated with large tumor size (greater than 10 cm), hypercalcaemia, and distante metastasis. Early, incidental diagnosis of small anal sac masses may lead to a better prognosis with surgery alone (ongoing study).

Digestive system neoplasms are tumors which affect the digestive system. Types include:

- esophageal cancer

- gastric cancer

- small intestinal cancer

- colorectal cancer

- anal cancer

Cancer of the stomach, also called gastric cancer, is the fourth-most-common type of cancer and the second-highest cause of cancer death globally. Eastern Asia (China, Japan, Korea, Mongolia) is a high-risk area for gastric cancer, and North America, Australia, New Zealand and western and northern Africa are areas with low risk. The most common type of gastric cancer is adenocarcinoma, which causes about 750,000 deaths each year. Important factors that may contribute to the development of gastric cancer include diet, smoking and alcohol consumption, genetic aspects (including a number of heritable syndromes) and infections (for example, "Helicobacter pylori" or Epstein-Barr virus) and pernicious anemia. Chemotherapy improves survival compared to best supportive care, however the optimal regimen is unclear.

Anal dysplasia is most commonly linked to human papillomavirus (HPV), a usually sexually-transmitted infection. HPV is the most common sexually transmitted infection in the United States while genital herpes (HSV) was the most common sexually transmitted infection globally.

Colorectal cancer is a disease of old age: It typically originates in the secretory cells lining the gut, and risk factors include diets low in vegetable fibre and high in fat. If a younger person gets such a cancer, it is often associated with hereditary syndromes like Peutz-Jegher's, hereditary nonpolyposis colorectal cancer or familial adenomatous polyposis. Colorectal cancer can be detected through the bleeding of a polyp, colicky bowel pain, a bowel obstruction or the biopsy of a polyp at a screening colonoscopy. A constant feeling of having to go to the toilet or anemia might also point to this kind of cancer.

Use of a colonoscope can find these cancers, and a biopsy can reveal the extent of the involvement of the bowel wall. Removal of a section of the colon is necessary for treatment, with or without chemotherapy. Colorectal cancer has a comparatively good prognosis when detected early.

Normally found in children or young adults, a common cause of conjunctival squamous cell papilloma is during childbirth, when the mother passes the virus to her child.

Anal dysplasia is a pre-cancerous condition which occurs when the lining of the anal canal undergoes abnormal changes. It can be classified as low-grade squamous intraepithelial lesions (LSIL) and high-grade squamous intraepithelial lesions (HSIL).

Most cases are not associated with symptoms, but people may notice lumps in and around the anus.

A squamous cell papilloma is a generally benign papilloma that arises from the stratified squamous epithelium of the skin, lip, oral cavity, tongue, pharynx, larynx, esophagus, cervix, vagina or anal canal. Squamous cell papillomas are a result of infection with human papillomavirus (HPV).

Cervical stenosis may be present from birth or may be caused by other factors:

- Surgical procedures performed on the cervix such as colposcopy, cone biopsy, or a cryosurgery procedure

- Trauma to the cervix

- Repeated vaginal infections

- Atrophy of the cervix after menopause

- Cervical cancer

- Radiation

- Cervical nabothian cysts

Cervical stenosis may impact natural fertility by impeding the passage of semen into the uterus. In the context of infertility treatments, cervical stenosis may complicate or prevent the use of intrauterine insemination (IUI) or in vitro fertilization (IVF) procedures.

Anorectal anomalies are medical problems affecting the structure of the anus and rectum. A person with an anorectal problem would have some sort of deformative feature of the anus or rectum, collectively known as an anorectal malformation.

Examples of anorectal anomalies include:

- Anal stenosis

- Imperforate anus

- Proctitis

- Anal bleeding

- Anal fistula

- Anal cancer

- Anal itching

- Hemorrhoid (piles)

Rectovestibular fistula is the most common defect of the rectum and anal canal in females.

When the fecal stream is diverted as part of a colostomy, a condition called diversion colitis may develop in the section of bowel that no longer is in contact with stool. The mucosal lining is nourished by short-chain fatty acids, which are produced as a result of bacterial fermentation in the gut. Long-term lack of exposure to this nutrients can cause inflammation of the colon (colitis). Symptoms include rectal bleeding, mucous discharge, tenesmus and abdominal pain.

One of the main causes is suggested to be excessive and repetitive straining during defecation. Other causes include weakness of the pelvic floor muscles (secondary to age related neuropathic degeneration or traumatic injury during pregnancy and labor.

Anal warts are irregular, verrucous lesions caused by human papilloma virus. Anal warts are usually transmitted by unprotected, anoreceptive intercourse. Anal warts may be asymptomatic, or may cause rectal discharge, anal wetness, rectal bleeding, and pruritus ani. Lesions can also occur within the anal canal, where they are more likely to create symptoms.

The incidence of anal fissures is around 1 in 350 adults. They occur equally commonly in men and women and most often occur in adults aged 15 to 40.

Most anal fissures are caused by stretching of the anal mucosa beyond its capability.

Superficial or shallow anal fissures look much like a paper cut, and may be hard to detect upon visual inspection, they will generally self-heal within a couple of weeks. However, some anal fissures become chronic and deep and will not heal. The most common cause of non-healing is spasming of the internal anal sphincter muscle which results in impaired blood supply to the anal mucosa. The result is a non-healing ulcer, which may become infected by fecal bacteria.

In adults, fissures may be caused by constipation, the passing of large, hard stools, or by prolonged diarrhea. In older adults, anal fissures may be caused by decreased blood flow to the area. When fissures are found laterally, tuberculosis, occult abscesses, leukemic infiltrates, carcinoma, acquired immunodeficiency syndrome (AIDS) or inflammatory bowel disease should be considered as causes. Some sexually transmitted infections can promote the breakdown of tissue resulting in a fissure. Examples of sexually transmitted infections that may affect the anorectal area are syphilis, herpes, chlamydia and human papilloma virus.

Other common causes of anal fissures include:

- childbirth trauma in women

- anal sex

- Crohn's disease

- ulcerative colitis

- poor toileting in young children.

A rectovestibular fistula, also referred to simply as a vestibular fistula, is an anorectal congenital disorder where an abnormal connection (fistula) exists between the rectum and the vulval vestibule of the female genitalia.

If the fistula occurs within the hymen, it is known as a rectovaginal fistula, a much rarer condition.

A group of conditions known as Mucosal prolapse syndrome (MPS) has now been recognized. It includes SRUS, rectal prolapse, proctitis cystica profunda, and inflammatory polyps. It is classified as a chronic benign inflammatory disorder. The unifying feature is varying degrees of rectal prolapse, whether internal intussusception (occult prolapse) or external prolapse.

Although SRUS is not a medically serious disease, it can be the cause of significantly reduced quality of life for patients. It is difficult to treat, and treatment is aimed at minimizing symptoms.

Stopping straining during bowel movements, by use of correct posture, dietary fiber intake (possibly included bulk forming laxatives such as psyllium), stool softeners (e.g. polyethylene glycol, and biofeedback retraining to coordinate pelvic floor during defecation.

Surgery may be considered, but only if non surgical treatment has failed and the symptoms are severe enough to warrant the intervention. Improvement with surgery is about 55-60%.

Ulceration may persist even when symptoms resolve.