Symptoms such as diarrhea and painful defecation need to be systematically investigated and the underlying causes each carefully treated. Complications such as obstruction and fistulae may require surgery. Several other methods have been studied in attempts to lessen the effects of radiation proctitis. These include sucralfate, hyperbaric oxygen therapy, corticosteroids, metronidazole, argon plasma coagulation, radiofrequency ablation and formalin irrigation.

Treatment for proctitis varies depending on severity and the cause. For example, the physician may prescribe antibiotics for proctitis caused by bacterial infection. If the proctitis is caused by Crohn's disease or ulcerative colitis, the physician may prescribe the drug 5-aminosalicyclic acid (5ASA) or corticosteroids applied directly to the area in enema or suppository form, or taken orally in pill form. Enema and suppository applications are usually more effective, but some patients may require a combination of oral and rectal applications.

Another treatment available is that of fiber supplements such as Metamucil. Taken daily these may restore regularity and reduce pain associated with proctitis.

Proctitis has many possible causes. It may occur idiopathically (idiopathic proctitis). Other causes include damage by irradiation (for example in radiation therapy for cervical cancer and prostate cancer) or as a sexually transmitted infection, as in lymphogranuloma venereum and herpes proctitis. Studies suggest a celiac disease-associated "proctitis" can result from an intolerance to gluten.

A common cause is engaging in anal sex with partner(s) infected with sexual transmitted diseases in men who have sex with men. Shared enema usage has been shown to facilitate the spread of Lymphogranuloma venereum proctitis.

Prevention of radiation injury to the small bowel is a key aim of techniques such as brachytherapy, field size, multiple field arrangements, conformal radiotherapy techniques and intensity-modulated radiotherapy. Medications including ACE inhibitors, statins and probiotics have also been studied and reviewed.

Radiation proctitis (and the related radiation colitis) is inflammation and damage to the lower parts of the colon after exposure to x-rays or other ionizing radiation as a part of radiation therapy. Radiation proctitis most commonly occurs after treatment for cancers such as cervical cancer, prostate cancer, and colon cancer. Radiation proctitis involves the lower intestine, primarily the sigmoid colon and the rectum and is part of the conditions known as pelvic radiation disease and radiation enteropathy.

In people presenting with symptoms compatible with radiation enteropathy, the initial step is to identify what is responsible for causing the symptoms. Management is best with a multidisciplinary team including gastroenterologists, nurses, dietitians, surgeons and others.

Medical treatments include the use of hyperbaric oxygen which has beneficial effects in radiation proctitis or anal damage. Nutritional therapies include treatments directed at specific malabsorptive disorders such as low fat diets and vitamin B12 or vitamin D supplements, together with bile acid sequestrants for bile acid diarrhea and possibly antibiotics for small intestinal bacterial overgrowth. Probiotics have all been suggested as another therapeutic avenue.

Endoscopic therapies including argon plasma coagulation have been used for bleeding telangiectasia in radiation proctitis and at other intestinal sites, although there is a rick of perforation. Sucralfate enemas look promising in proctitis.

Surgical treatment may be needed for intestinal obstruction, fistulae, or perforation, which can happen in more severe cases. These can be fatal if patients present as an emergency, but with improved radiotherapy techniques are now less common.

Optimal treatment usually produces significant improvements in quality of life.

Pain relief is administered concomitantly to the treatment of the primary disease causing tenesmus. Methadone has been shown to be an effective pain-reliever.

Tenesmus is characterized by a sensation of needing to pass stool, accompanied by pain, cramping, and straining. Despite straining, little stool is passed. Tenesmus is generally associated with inflammatory diseases of the bowel, which may be caused by either infectious or noninfectious conditions. Conditions associated with tenesmus include:

- Amebiasis

- Coeliac disease

- Chronic arsenic poisoning

- Colorectal cancer

- Anal melanoma

- Cytomegalovirus (in immunocompromised patients)

- Diverticular disease

- Hemorrhoid, which are prolapsed

- Inflammatory bowel disease

- Irritable bowel syndrome

- Ischemic colitis

- Kidney stones, when a stone is lodged in the lower ureter

- Pelvic floor dysfunction

- Radiation proctitis

- Rectal gonorrhoea

- Rectal lymphogranuloma venereum

- Rectal lower gastrointestinal parasitic infection, particularly "Trichuris trichiura" (whipworm)

- Shigellosis

- Ulcerative colitis

Tenesmus (rectal) is also associated with the installation of either a reversible or non reversible stoma where rectal disease may or may not be present. Patients who experience tenesmus as a result of stoma installation can experience the symptoms of tenesmus for the duration of the stoma presence. Long term pain management may need to be considered as a result.

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.

About 21% of inflammatory bowel disease patients use alternative treatments. A variety of dietary treatments show promise, but they require further research before they can be recommended.

- Melatonin may be beneficial according to "in vitro" research, animal studies, and a preliminary human study.

- Dietary fiber, meaning indigestible plant matter, has been recommended for decades in the maintenance of bowel function. Of peculiar note is fiber from , which seems to contain soluble constituents capable of reversing ulcers along the entire human digestive tract before it is cooked.

- Fish oil, and eicosapentaenoic acid (EPA) derived from fish oil, inhibits leukotriene activity, the latter which may be a key factor of inflammation. As an IBD therapy, there are no conclusive studies in support and no recommended dosage. But dosages of EPA between 180 and 1500 mg/day are recommended for other conditions, most commonly cardiac. Fish oil also contains vitamin D, of which many people with IBD are deficient.

- Short chain fatty acid (butyrate) enema. The epithelial cells in the colon uses butyrate from the contents of the intestine as an energy source. The amount of butyrate available decreases toward the rectum. Inadequate butyrate levels in the lower intestine have been suggested as a contributing factor for the disease. This might be addressed through butyrate enemas. The results however are not conclusive.

- Herbal medications are used by patients with ulcerative colitis. Compounds that contain sulfhydryl may have an effect in ulcerative colitis (under a similar hypothesis that the sulfa moiety of sulfasalazine may have activity in addition to the active 5-ASA component). One randomized control trial evaluated the over-the-counter medication "S"-methylmethionine and found a significant decreased rate of relapse when the medication was used in conjunction with oral sulfasalazine.

- Helminthic therapy is the use of intestinal parasitic nematodes to treat ulcerative colitis, and is based on the premises of the hygiene hypothesis. Studies have shown that helminths ameliorate and are more effective than daily corticosteroids at blocking chemically induced colitis in mice, and a trial of intentional helminth infection of rhesus monkeys with idiopathic chronic diarrhea (a condition similar to ulcerative colitis in humans) resulted in remission of symptoms in 4 out of 5 of the animals treated. A randomised controlled trial of Trichuris suis ova in humans found the therapy to be safe and effective, and further human trials are ongoing.

- Curcumin (turmeric) therapy, in conjunction with taking the medications mesalamine or sulfasalazine, may be effective and safe for maintaining remission in people with quiescent ulcerative colitis. The effect of curcumin therapy alone on quiescent ulcerative colitis is unknown.

Many hypotheses have been raised for environmental factors contributing to the pathogenesis of ulcerative colitis. They include the following:

- Diet: as the colon is exposed to many dietary substances which may encourage inflammation, dietary factors have been hypothesized to play a role in the pathogenesis of both ulcerative colitis and Crohn's disease. Few studies have investigated such an association; one study showed no association of refined sugar on the prevalence of ulcerative colitis. High intake of unsaturated fat and vitamin B6 may enhance the risk of developing ulcerative colitis. Other identified dietary factors that may influence the development and/or relapse of the disease include meat protein and alcoholic beverages. Specifically, sulfur has been investigated as being involved in the etiology of ulcerative colitis, but this is controversial. Sulfur restricted diets have been investigated in patients with UC and animal models of the disease. The theory of sulfur as an etiological factor is related to the gut microbiota and mucosal sulfide detoxification in addition to the diet.

- Breastfeeding: Some reports of the protection of breastfeeding in the development of inflammatory bowel disease contradict each other. One Italian study showed a potential protective effect.

- One study of isotretinoin found a small increase in the rate of ulcerative colitis.

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.

Mild cases usually do not require treatment and will go away after a few days in healthy people. In cases where symptoms persist or when it is more severe, specific treatments based on the initial cause may be required.

In cases where diarrhoea is present, replenishing fluids lost is recommended, and in cases with prolonged or severe diarrhoea which persists, intravenous rehydration therapy or antibiotics may be required. A simple oral rehydration therapy (ORS) can be made by dissolving one teaspoon of salt, eight teaspoons of sugar and the juice of an orange into one litre of clean water. Studies have shown the efficacy of antibiotics in reducing the duration of the symptoms of infectious enteritis of bacterial origin, however antibiotic treatments are usually not required due to the self-limiting duration of infectious enteritis.

Diseases of the hepatobiliary system affect the biliary tract (also known as the "biliary tree"), which secretes bile in order to aid digestion of fats. Diseases of the gallbladder and bile ducts are commonly diet-related, and may include the formation of gallstones that impact in the gallbladder (cholecystolithiasis) or in the common bile duct (choledocholithiasis).

Gallstones are a common cause of inflammation of the gallbladder, called cholecystitis. Inflammation of the biliary duct is called cholangitis, which may be associated with autoimmune disease, such as primary sclerosing cholangitis, or a result of bacterial infection, such as ascending cholangitis.

Disease of the biliary tree may cause pain in the upper right abdomen, particularly when pressed. Disease might be investigated using ultrasound or ERCP, and might be treated with drugs such as antibiotics or UDCA, or by the surgical removal of the gallbladder.

In Germany, 90% of cases of infectious enteritis are caused by four pathogens, Norovirus, Rotavirus, "Campylobacter" and "Salmonella". Other common causes of infectious enteritis include bacteria such as "Shigella" and "E. coli," as well as viruses such as adenovirus, astrovirus and calicivirus. Other less common pathogens include "Bacillus cereus, Clostridium perfringens, Clostridium difficile" and "Staphylococcus aureus".

"Campylobacter jejuni" is one of the most common sources of infectious enteritis, and the most common bacterial pathogen found in 2 year old and smaller children with diarrhoea. It has been linked to consumption of contaminated water and food, most commonly poultry and milk. The disease tends to be less severe in developing countries, due to the constant exposure which people have with the antigen in the environment, leading to early development of antibodies.

Rotavirus is responsible for infecting 140 million people and causing 1 million deaths each year, mostly in children younger than 5 years. This makes it the most common cause of severe childhood diarrhoea and diarrhea-related deaths in the world. It selectively targets mature enterocytes in the small intestine, causing malabsorption, as well as inducing secretion of water. It has also been observed to cause villus ischemia, and increase intestinal motility. The net result of these changes is induced diarrhoea.

Enteritis necroticans is an often fatal illness, caused by β-toxin of "Clostridium perfringens". This causes inflammation and segments of necrosis throughout the gastrointestinal tract. It is most common in developing countries, however has also been documented in post-World War II Germany. Risk factors for enteritis necroticans include decreased trypsin activity, which prevent intestinal degradation of the toxin, and reduced intestinal motility, which increases likelihood of toxin accumulation.

Gastrointestinal diseases refer to diseases involving the gastrointestinal tract, namely the esophagus, stomach, small intestine, large intestine and rectum, and the accessory organs of digestion, the liver, gallbladder, and pancreas.

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.

Localised disease (carcinoma-in-situ) and the precursor condition, anal intraepithelial neoplasia (anal dysplasia or AIN) can be ablated with minimally invasive methods such as Infrared Photocoagulation.

Previously, anal cancer was treated with surgery, and in early-stage disease (i.e., localised cancer of the anus without metastasis to the inguinal lymph nodes), surgery is often curative. The difficulty with surgery has been the necessity of removing the internal and external anal sphincter, with concomitant fecal incontinence. For this reason, many patients with anal cancer have required permanent colostomies.

Current gold-standard therapy is chemotherapy and radiation treatment to reduce the necessity of debilitating surgery. This "combined modality" approach has led to the increased preservation of an intact anal sphincter, and therefore improved quality of life after definitive treatment. Survival and cure rates are excellent, and many patients are left with a functional sphincter. Some patients have fecal incontinence after combined chemotherapy and radiation. Biopsies to document disease regression after chemotherapy and radiation were commonly advised, but are not as frequent any longer. Current chemotherapy consists of continuous infusion 5-FU over four days with bolus mitomycin given concurrently with radiation. 5-FU and cisplatin are recommended for metastatic anal cancer.

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)

Unfortunately mesna is ineffective as a treatment once hemorrhagic cystitis has developed. Although rare, once a case of radiation-induced hemorrhagic cystitis is diagnosed there is no empirically-proven treatments to heal this type of condition, which can severely degrade a patient's quality of life and might possibly lead to renal failure with risk of death.

Viral hemorrhagic cystitis in children generally spontaneously resolves within a few days.

The first step in the treatment of HC should be directed toward clot evacuation. Bladder outlet obstruction from clots can lead to urosepsis, bladder rupture, and renal failure. Clot evacuation can be performed by placing a wide-lumen bladder catheter at bedside. The bladder can be irrigated with water or sodium chloride solution. The use of water is preferable because water can help with clot lysis. Care must be taken to not overdistend the bladder and cause a perforation.. Hyperbaric oxygen (HBO2) therapy has been proven to be effective in treating radiation-induced hemorrhagic cystitis.

Immunotherapy with immune checkpoint inhibitors is being investigated in head and neck cancers.

The treatment of choice is a large resection or amputation of the affected limb. Radiation therapy can precede or follow surgical treatment. Tumors that have advanced locally or have metastasized can be treated with mono or polychemotherapy, systemically or locally. However, chemotherapy and radiation therapy have not been shown to improve survivorship significantly.

Treatment involves antibiotics and may involve drainage of the buboes or abscesses by needle aspiration or incision. Further supportive measure may need to be taken: dilatation of the rectal stricture, repair of rectovaginal fistulae, or colostomy for rectal obstruction.

Common antibiotic treatments include: tetracycline (doxycycline) (all tetracyclines, including doxycycline, are contraindicated during pregnancy and in children due to effects on bone development and tooth discoloration), and erythromycin. Azithromycin is also a drug of choice in LGV.

Gay bowel syndrome was a medical term first used by Henry L Kazal and colleagues in 1976 to describe the various sexually transmitted perianal and rectal diseases and sexual traumas seen in Kazal's proctology practice, which had many gay patients.

Prognosis is highly variable. Spontaneous remission is common. Complete cure can be obtained with proper antibiotic treatments to kill the causative bacteria, such as tetracycline, doxycycline, or erythromycin. Prognosis is more favorable with early treatment. Bacterial superinfections may complicate course. Death can occur from bowel obstruction or perforation, and follicular conjunctivitis due to autoinoculation of infectious discharge can occur.