Proctitis and Anusitis

Updated: Oct 25, 2022
  • Author: David E Stein, MD, MHCM; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Inflammation of the mucosal lining of the rectum is defined as proctitis, whereas anusitis is simply inflammation of the anal canal. Inflammation in these areas can cause symptoms, such as itching, burning, rectal bleeding, pelvic pressure, and foul-smelling discharge. The distinction between proctitis and anusitis is not overly pertinent, in that the etiology and the treatment of anusitis and proctitis are similar. For the purposes of this article, the term proctitis will be understood to include anusitis.

Several different etiologies exist, including inflammatory bowel disease (IBD), infectious organisms (eg, Neisseria gonorrhoeae, Salmonella, Shigella), noninfectious causes (eg, radiation, ischemic, diversion), and idiopathic causes. For convenience, these etiologies may be divided into three broad categories: IBD, infectious proctitis, and noninfectious proctitis.

Proctitis can occur in both the acute setting and the chronic setting and can cause significant anorectal complaints. Treatment is generally nonsurgical; however, in certain cases, surgery is indicated.



It is important to recognize that most inflammatory processes of the rectum also involve the adjacent colon and the anus. Controversy remains regarding the anatomy of the rectum and the anus. Some authorities say that the rectum starts at the level of the third sacral vertebra, whereas others consider the start of the rectum to be at the sacral promontory.

Where the rectum ends also is debated. Some say that it ends when it passes through the levator ani muscles, but most agree that the rectum transitions to the anus where the epithelial cells change from columnar cells to squamous cells.

The World Health Organization (WHO) and the American Joint Cancer Committee define the anal canal as the distal portion of the gastrointestinal (GI) tract that corresponds to the internal anal sphincter.

In proctitis and anusitis, the anatomy does not change therapy, because a significant overlap between anorectal inflammation and rectosigmoid inflammation exists.



The pathophysiology of proctits is dependent on the various etiologies and is not completely understood. In addition, some patients seem more susceptible to this inflammatory condition, with factors such as young age, previous abdominal surgery, hypertension, vasculopathy, and diabetes cited as possible contributing factors. The pathophysiology of proctitis in IBD is believed to be caused by an autoimmune process, though the specific antigen has not been elicited.

Infectious etiologies may be related to the organism itself or to a toxin produced by the organism.

Radiation proctitis may be due to cellular injury secondary to ischemia from radiation. Diversion proctitis is thought to be caused by a deficiency of short-chain fatty acids. Ischemic proctitis may be due to mesenteric venous occlusion, aortoiliac surgery, radiotherapy, vascular intervention, atherosclerotic disease, or drug use (eg, cocaine).

Regardless, all three categories of proctitis (ie, IBD, infectious, and noninfectious) result in an unrestrained inflammatory response, with the inflammatory cells being products that mediate cellular-tissue injury.



This article divides the etiologies of proctitis into the following three categories:

  • Proctitis due to inflammatory bowel colitides (eg, ulcerative colitis, Crohn disease)
  • Proctitis from infectious causes (eg, Clostridioides [Clostridium] difficile and Salmonella species); in most cases, the rectal inflammation caused by an infection most likely causes inflammation in the colon as well
  • Proctitis due to noninfectious conditions (eg, diversion, ischemia, and radiation)


The prevalence of proctitis in the general population has not been established through epidemiologic studies. However, one can ascertain the incidence of proctitis when analyzing specific disease states. For example, patients with ulcerative colitis displayed a 31-50% frequency of proctitis upon diagnosis, depending on age at diagnosis. A study in the pediatric ulcerative colitis population demonstrated a significant increase in the occurrence of proctitis in female children as compared with males. [1] The frequency of chronic radiation-induced proctitis has been reported to be in the range of 2-20% and is influenced by total radiation dose, mode of delivery, and dose fractionation. [2]



In the acute setting, most bouts of proctitis have a good outcome and prognosis. More specifically, once appropriately treated, infectious proctitis tends not to recur.

For the more chronic diseases, such as IBD, outcomes and prognoses vary. Clearly, in medically treated ulcerative colitis and proctitis, approximately 40-70% of cases do not require operation. If proctocolectomy is performed, the patient is cured of the disease. Crohn disease is another story: Because it can occur in all portions of the GI tract, even after a proctectomy, Crohn disease has a recurrence rate in the range of 45-90%.

Diversion proctitis generally has a good outcome and prognosis once the diversion is reversed.

The outcome and prognosis of radiation proctitis vary with the severity of proctitis. Outcomes range from requiring a few medical treatments in the form of enemas to surgery. Complication rates for surgical treatment have been reported to be as high as 75%.