After a colostomy, your anus and the remaining section of rectum below the stoma are effectively taken out of service. Stool is diverted to the bag on your abdomen, so nothing passes through the lower bowel anymore. But “out of service” does not mean nothing happens. The unused rectum and anus undergo a series of changes, some predictable and manageable, others surprising enough to catch people off guard. Whether you still have your rectum intact or it was removed entirely during surgery, the downstream effects are real and worth understanding before they show up unannounced.
The Rectum and Anus May Still Be There
Not every colostomy involves removing the rectum and anus. In a Hartmann’s procedure, for example, the surgeon diverts the colon to a stoma but leaves the rectal stump sewn shut inside the pelvis. This is common when surgery is done urgently for conditions like complicated diverticulitis or obstructing tumors. In other cases, such as an abdominoperineal resection for low rectal or anal cancer, the rectum and anus are removed entirely and the perineal opening is closed. What happens to your anus depends heavily on which of these paths your surgeon took.
If the rectum stays in place, it sits there empty, disconnected from the fecal stream but still lined with living tissue that has its own needs. If the rectum and anus were removed, you are instead dealing with a healing wound where the anus used to be. Both scenarios come with their own set of issues, and neither is a “set it and forget it” situation.
Mucus Discharge From a Quiet Anus
One of the most common and least discussed experiences after colostomy is mucus coming from the anus. The lining of the rectum continues to produce mucus even when nothing is passing through. Before surgery, this mucus was mixed into stool and went unnoticed. Now, with no stool to absorb it, the mucus accumulates and eventually passes on its own or needs to be expelled deliberately, sometimes by sitting on the toilet as though having a bowel movement.
The amount varies from person to person. Some people notice just a small amount on toilet paper; others deal with enough to warrant wearing a small pad. The mucus can occasionally be tinged with blood, especially if the rectal lining has become inflamed. This discharge is not dangerous in itself, but it can be alarming if nobody warned you about it. Many ostomates describe feeling blindsided by the idea that their backside still has things to say.
Diversion Colitis and Why the Unused Rectum Gets Inflamed
When the fecal stream is diverted away from the rectum, the lining of that segment loses its main source of nutrition. The cells that line the colon and rectum rely heavily on short-chain fatty acids, especially butyrate, which are produced when gut bacteria ferment fiber and other material passing through. Cut off that supply, and the tissue starts to deteriorate. This condition is called diversion colitis, sometimes referred to as diversion proctitis when it is confined to the rectum.
The inflammation is remarkably common. Microscopic changes consistent with diversion proctitis develop in most patients with a defunctioned rectum, with studies reporting incidence between roughly 70% and 100%.1PubMed Central. The Rectal Stump During and After Subtotal Colectomy for Ulcerative Colitis: A Narrative Review of Surgical Strategies, Medical Management Options, and Cancer Surveillance Recommendations Fortunately, only about 30 to 40% of those people develop noticeable symptoms. When symptoms do occur, they include rectal bleeding, mucus discharge that worsens, a feeling of pressure or discomfort in the pelvis, and occasionally mild pain.
At the tissue level, the picture is distinctive. Within three months of diversion, endoscopy reveals redness and a granular texture in the rectal lining, and biopsies show chronic inflammatory cells, tiny surface erosions, and an overgrowth of lymphoid tissue.2PubMed Central. Diversion colitis and involution of the defunctioned anorectum These changes look different from inflammatory bowel disease, which is important because many colostomy patients had IBD in the first place and the distinction matters for management decisions.
The mechanism boils down to nutritional starvation of the bowel wall. The diverted segment has negligible concentrations of short-chain fatty acids, and without incoming fiber, the remaining bacteria cannot produce more.3PubMed. Treatment of diversion colitis with short-chain-fatty acid irrigation The microbial community shifts as well: aerobic bacteria increase, while the fermentation-capable anaerobes that normally dominate decline.4PubMed Central. Evaluation of intestinal microbiota, short-chain fatty acids, and immunoglobulin a in diversion colitis There is also evidence that nitrate-reducing bacteria increase in the diverted segment, producing higher levels of nitric oxide, which at elevated concentrations becomes toxic to colonic tissue.5International Journal of Surgery. Pathophysiology, clinical presentation and management of diversion colitis: A review of current literature
Treating an Inflamed Rectal Stump
The most straightforward cure for diversion colitis is restoring the fecal stream, which means reversing the colostomy. When reversal is planned, the inflammation typically resolves on its own once stool passes through again. But many colostomies are permanent, or reversal is delayed months to years, so the inflammation needs to be managed in the meantime.
The approach that most directly addresses the underlying problem is instilling short-chain fatty acids into the rectum. In early clinical work, delivering a solution of these fatty acids twice daily led to complete resolution of symptoms and the inflammatory changes visible on endoscopy within four to six weeks.3PubMed. Treatment of diversion colitis with short-chain-fatty acid irrigation This treatment essentially feeds the starving tissue directly. In practice, short-chain fatty acid enemas are not widely available commercially, so clinicians often turn to anti-inflammatory enemas instead. Topical mesalamine, corticosteroids, or a combination of both can improve rectal bleeding and endoscopic findings.6PubMed Central. Efficacy of Combined Mesalazine Plus Corticosteroid Enemas for Diversion Colitis after Subtotal Colectomy for Ulcerative Colitis These treatments manage symptoms rather than fixing the root cause, but they work well enough for most people while awaiting reversal or living with a permanent stoma.
Phantom Rectal Sensations
If your rectum was removed during surgery, you might still feel it. Phantom rectum syndrome is strikingly similar to phantom limb sensations after an amputation: the brain continues to receive and interpret signals from nerves that once served the rectum, creating the sensation that the organ is still there. The most common phantom feeling is the urge to have a bowel movement, which can be deeply confusing and distressing when you know there is no rectum left to respond to.
This is not a rare curiosity. In one study of patients who had their rectum removed, about two-thirds reported phantom sensations. The urge to defecate was the most frequent complaint, and once established, these sensations were permanent in the majority of patients.7PubMed. Phantom sensations after excision of the rectum A separate study found that 96% of patients experienced some form of phantom rectal sensation within the first eight months after surgery, including both nonpainful feelings like a sense of fullness and painful ones described as pins and needles, stinging, or burning, especially while sitting.8PubMed. Perceptions of phantom rectum syndrome and health-related quality of life in patients following abdominoperineal resection for rectal cancer
The nonpainful sensations often appeared in connection with specific triggers: emptying the colostomy bag, irrigating the stoma, resting, or shifting positions. The painful sensations tended to worsen while sitting. For some people, these phantom sensations fade over months or years. For others, they persist indefinitely. Knowing to expect them can reduce the anxiety that comes with feeling an urge your body can no longer act on.
Structural Changes and Anal Stricture
An anus that goes unused for an extended period can undergo structural changes. The anal canal and the muscles surrounding it may gradually tighten or narrow without the regular passage of stool keeping them stretched. In extreme cases, this can progress to anal stricture, where the opening becomes significantly narrowed or even completely closed.
One case report documented a patient who developed complete anal stricture after a diverting colostomy performed for Fournier’s gangrene. After four months with the stoma in place, physical examination and colonoscopy revealed the anal canal had sealed shut entirely, requiring anoplasty (surgical reconstruction of the anal opening) at the time of stoma closure.9PubMed Central. Treatment of Complete Anal Stricture after Diverting Colostomy for Fournier’s Gangrene While complete stricture is rare, some degree of narrowing is more common, and it can complicate stoma reversal when the time comes. Surgeons sometimes recommend gentle dilation of the anal canal during the period a temporary stoma is in place, particularly if reversal is planned.
Rectal Stump Complications After Hartmann’s Procedure
When a colostomy is created via Hartmann’s procedure, the bottom of the remaining bowel is stapled or sewn shut, creating a rectal stump. This closed-off pouch can cause problems of its own. Mucus and secretions accumulate inside, and if the closure line breaks down, the contents can leak into the pelvis.
This complication, sometimes called rectal stump “blowout,” occurred in about 17% of patients within 90 days of surgery in one retrospective study. The breakdown happened at a median of 12 days after the operation. Roughly half of the affected patients had a visible defect in the closure line, while the other half developed a pelvic abscess without an obvious structural failure. Patients with more severe disease at the time of surgery and those with a history of pelvic radiation were at substantially higher risk.10PubMed Central. Incidence and risk factors of blowout within 90 days after a primary Hartmann’s procedure: a retrospective cohort study The same study found that placing a catheter in the rectal remnant during surgery to allow drainage significantly reduced the risk of blowout. Pelvic abscess from a stump leak is uncommon but serious, sometimes requiring prolonged treatment.11Journal of Biomedical and Clinical Research. Vacuum-assisted closure for treating chronic pelvic abscess following rectal stump leak after Hartmann’s procedure for low rectal cancer
Perineal Wound Healing When the Anus Is Removed
If your surgery involved removing the rectum and anus entirely, you are left with a wound in the perineum, the area where the anus used to be. Healing this wound is one of the most challenging aspects of recovery, and complications are common. The perineum sits in an anatomically awkward location for wound healing: it bears your weight when you sit, it is near bacterial sources, and it has limited blood supply, especially after radiation.
Risk factors for delayed perineal wound healing include prior radiation therapy, the surgical indication itself (cancer versus IBD), and patient factors like diabetes, obesity, and smoking.12PubMed Central. Perineal wound complications after abdominoperineal resection Low albumin levels, an indicator of poor nutritional status, were found to be an independent risk factor for delayed healing, and patients whose wounds healed slowly had a dramatically increased chance of prolonged hospitalization.13PubMed Central. Risk factors for delayed perineal wound healing and its impact on prolonged hospital stay after abdominoperineal resection Wound failure frequently requires extended care with daily dressing changes, home nursing visits, and sometimes hospital readmission.
Surgeons have explored various strategies to improve perineal closure, including biological mesh and muscle flap techniques, though trials have so far not demonstrated clear superiority over standard primary closure at the 30-day mark.14PubMed. Using a composite end-point and WIN-ratio analysis to evaluate perineal wound healing after abdominoperineal resection for rectal cancer: further insights from the BIOPEX trials Some perineal wounds take weeks to close; others drag on for months. For people recovering at home, sitting on a cushion with a cutout (like a donut pillow) and keeping the wound clean and dry are basic but meaningful parts of daily management.
Cancer Risk in the Retained Rectum
If you have a rectal stump left in place, especially after surgery for ulcerative colitis, there is a small but real risk of cancer developing in the leftover segment. The retained rectum still contains mucosa that was part of a diseased colon, and the chronic inflammation of diversion proctitis may add an additional layer of risk over time.
A systematic review and meta-analysis pooling data from over 9,000 patients with a defunctioned rectal stump found a pooled cancer diagnosis rate of 0.7%, with a cumulative incidence of about 0.3% at ten years after surgery.15PubMed Central. The incidence of malignancy in the residual rectum of IBD patients after colectomy: a systematic review and meta-analysis That sounds low, and it is, but individual studies have reported rates as high as 3% in ulcerative colitis patients followed for decades.16PubMed. The fate of the rectal stump after subtotal colectomy for ulcerative colitis Having had prior colorectal neoplasia is a major risk factor that pushes the numbers higher for some individuals.
The practical takeaway is that a rectal stump left behind is not something you can forget about. It needs periodic surveillance with endoscopy to catch any concerning changes early. Compliance with surveillance is a genuine challenge: one long-term follow-up study found that fewer than half the patients in a surveillance group were actually keeping up with their scheduled endoscopies. Two of those patients eventually required proctectomy for rectal cancer, at 11 and 16 years after the original colostomy.17PubMed. Fate of the rectal stump after subtotal colectomy for ulcerative colitis in the era of ileal pouch-anal anastomosis The alternative to long-term surveillance is completing the proctectomy, removing the rectal stump altogether, which eliminates the cancer risk but adds another surgery and its own recovery.
Sexual Function and Pelvic Nerve Damage
The surgery that creates a colostomy, particularly when it involves removing the rectum, can damage the autonomic nerves that run through the pelvis. These nerves control sexual arousal, erection, ejaculation, vaginal lubrication, and bladder function. Damage can come from the surgery itself, from tumor invasion, from radiation, or from post-operative pelvic inflammation and infection.18PubMed Central. Sexual Dysfunction after Colorectal Surgery
The result is that many patients experience sexual dysfunction after colorectal surgery. For men, this can mean difficulty achieving or maintaining erections and ejaculatory problems. For women, reduced lubrication, pain during intercourse, and decreased sensation are common. Both men and women can experience diminished libido, which often has both physical and psychological roots.19Surgeries. Rehabilitation for Women and Men Experiencing Sexual Dysfunction After Abdominal or Pelvic Surgery The presence of the stoma itself adds a layer of body image disruption that compounds the physiological issues.20PubMed Central. Sexual Dysfunction and Intimacy for Ostomates
These effects are not inevitable, and nerve-sparing surgical techniques have improved outcomes. But the topic is underreported because patients are often reluctant to bring it up, and surgical teams do not always ask. If you are facing colostomy surgery, asking your surgeon directly about the risk to pelvic nerves and what can be done to minimize damage is one of the most productive conversations you can have beforehand.
Changes to the Rectal Microbiome
The microbial community inside the diverted rectum shifts substantially once stool stops flowing through. Bacterial diversity drops, the balance between types of bacteria changes, and species that normally would not dominate begin to take over. Research comparing the microbiome before and after diversion found that defunctioning stomas were associated with lower overall microbial diversity and increases in bacteria like Pseudomonas and Streptococcus.21PubMed Central. Perioperative changes in the microbiome during rectal cancer surgery: exploratory analysis of the National Institute for Health and Care Research (NIHR) IntAct trial These shifts are closely linked to the inflammatory changes described in diversion colitis: when the bacteria that produce short-chain fatty acids decline, the tissue they were feeding goes hungry and becomes inflamed.
Whether these microbial changes are fully reversible after stoma reversal is still an active question. Early evidence suggests the microbiome begins to recover once the fecal stream returns, but whether it ever returns to its pre-diversion state, or how long that takes, is not well established. For people with permanent colostomies, the altered microbiome in the rectal stump is essentially the new normal, and managing any resulting symptoms is the practical focus rather than trying to restore the original bacterial community.