Proctitis, or inflammation of the rectal lining, develops through several distinct pathways: sexually transmitted infections, inflammatory bowel disease, radiation therapy, reduced blood flow, physical trauma, and certain medications. The cause depends heavily on your age, medical history, and exposure risks. Here’s a breakdown of each one.
Sexually Transmitted Infections
Infectious proctitis is the most common form among otherwise healthy adults, and it’s almost always sexually acquired. It occurs predominantly in people who have receptive anal contact, whether genital-anal, oral-anal, or digital-anal. The four most common STI pathogens that cause rectal inflammation are gonorrhea, chlamydia (including a more aggressive strain called LGV), genital herpes, and syphilis.
Any of these infections can take hold in the rectal lining and trigger pain, discharge, bleeding, or an urgent feeling of needing to use the bathroom. Herpes tends to cause especially sharp rectal pain along with small ulcers, while gonorrhea and chlamydia often produce mucus or pus-like discharge. Some people with STI-related proctitis have mild symptoms or none at all, which means the infection can go undetected and be passed to partners. Using condoms or other barrier methods during anal contact significantly reduces the risk.
Inflammatory Bowel Disease
Ulcerative colitis and Crohn’s disease both cause chronic inflammation in the digestive tract, and either one can target the rectum specifically. In fact, between 25% and 55% of people diagnosed with ulcerative colitis initially present with disease confined entirely to the rectum. This form, called ulcerative proctitis, is the mildest extent of ulcerative colitis, though it can progress over time to involve more of the colon.
Crohn’s disease can inflame any part of the digestive tract from mouth to anus, and when it settles in the rectum it produces similar symptoms: bleeding, urgency, and a persistent feeling of rectal pressure. Unlike STI-related proctitis, IBD-related proctitis is a chronic autoimmune condition. It isn’t caused by an infection or behavior, and it requires ongoing management to control flare-ups.
Radiation Therapy for Pelvic Cancers
Radiation aimed at cancers in the pelvic area (prostate, cervical, rectal, or bladder cancers) can damage the rectal lining as a side effect. This is called radiation proctitis, and it comes in two forms with very different timelines.
Acute radiation proctitis develops during treatment or within the first three months afterward. It’s relatively common and often resolves on its own once radiation ends. Chronic radiation proctitis is a different story. It can appear starting three months after treatment, typically within the first year, but has been documented decades later. The estimated incidence of chronic radiation proctitis ranges from 2% to 20%, depending on the type of cancer treated and the radiation dose used.
The long-term numbers are sobering. Large studies with extended follow-up suggest that 10% to 20% of pelvic radiation patients develop gastrointestinal complications over a ten-year period. About half of those patients say the symptoms affect their quality of life, and 20% to 40% describe that impact as moderate or severe. Symptoms typically include rectal bleeding, diarrhea, urgency, and sometimes pain during bowel movements.
Reduced Blood Flow to the Rectum
When blood supply to the rectum drops, the tissue becomes inflamed and damaged. This ischemic form of proctitis is less common but tends to affect specific groups. Elderly and bed-ridden patients with atherosclerotic (hardened artery) disease are at highest risk. It also occurs after aortic or pelvic vascular surgery, which can temporarily disrupt blood flow to the lower digestive tract.
Cocaine use is a notable and sometimes overlooked cause. Cocaine is a potent vasoconstrictor, meaning it forces blood vessels to narrow dramatically. The blood vessels supplying the rectum are densely packed with nerve fibers that respond to this kind of stimulation, making the area especially vulnerable to sustained constriction. The result can be focal rectal ischemia, essentially a localized injury from oxygen deprivation. Blood clots in the veins draining the rectum (mesenteric venous thrombosis) account for a separate subset of cases and can occasionally affect younger patients without typical cardiovascular risk factors.
Diversion After Ostomy Surgery
When part of the bowel is surgically rerouted through an ostomy (a stoma in the abdominal wall), the remaining rectum no longer receives stool. This sounds harmless, but the cells lining the rectum depend on nutrients produced when bacteria in the gut break down dietary fiber. Without fecal flow, the rectal microbiome shifts, the nutrient supply to those cells drops, and inflammation sets in. This is called diversion proctitis, and it develops in a significant portion of people who retain their rectum after ostomy surgery. It typically causes mild bleeding or mucus discharge and often improves if the bowel is reconnected.
Medications and Physical Trauma
Certain medications can irritate the rectal lining directly. NSAIDs (common over-the-counter painkillers like ibuprofen and naproxen) are the most frequently cited culprits when taken long-term or in high doses. Antibiotic use creates a different pathway: by disrupting the normal bacterial balance in the gut, antibiotics can allow C. difficile bacteria to overgrow and infect the colon and rectum, causing inflammation that may include proctitis. This typically happens during or shortly after a course of antibiotics.
Physical trauma is a more straightforward cause. Foreign objects or chemicals introduced through the anus can directly injure the rectal lining. Some enema solutions contain chemicals that act as irritants, triggering inflammation even when used as directed. Frequent or forceful use of enemas increases this risk.
Foodborne Infections
While STIs dominate the infectious category, bacteria that cause food poisoning can also inflame the rectum. Salmonella, Shigella, and Campylobacter infections all involve the lower digestive tract and can produce proctitis as part of a broader gastrointestinal illness. In these cases, rectal inflammation is usually one piece of a larger picture that includes diarrhea, cramping, and fever. It resolves as the infection clears.
Who Is Most at Risk
Your risk profile depends on the type of proctitis. For infectious proctitis, the primary risk factor is unprotected receptive anal contact with an infected partner. People living with HIV may be more susceptible to certain less common pathogens. For radiation proctitis, anyone receiving pelvic radiation therapy is at risk, with higher doses and certain cancer types carrying greater odds. For IBD-related proctitis, the risk factors are the same as for ulcerative colitis and Crohn’s disease: a combination of genetics, immune system dysfunction, and environmental triggers that researchers are still working to fully map.
Ischemic proctitis clusters in older adults with cardiovascular disease and in people who use cocaine. Diversion proctitis is specific to the post-surgical population. And medication-related proctitis is most likely in people on long-term NSAIDs or recent antibiotic courses. Because the causes are so varied, identifying the right one is essential for getting effective treatment.