A colon stricture is a narrowing of the large intestine that partially or completely blocks the passage of stool. The narrowing happens when the colon wall thickens inward, shrinking the open channel (called the lumen) that digested food normally moves through. Strictures can develop gradually over months or years, and some people have no symptoms until the opening becomes small enough to cause problems.
How Strictures Form
The colon wall narrows through two basic processes, and most strictures involve a mix of both. The first is active inflammation, where the tissue is swollen, has increased blood flow, and retains extra fluid. The second is fibrosis, where the body lays down scar tissue (primarily collagen) as part of an excessive repair response to repeated or chronic inflammation. Over time, this collagen buildup stiffens and thickens the wall permanently.
The distinction matters because inflammatory narrowing can sometimes be reversed with medication, while fibrotic narrowing generally cannot. Imaging techniques can help distinguish between the two: inflamed tissue shows increased blood flow and fluid on scans, while fibrotic tissue lacks those signs and instead shows higher concentrations of collagen.
Common Causes
Several conditions can trigger the chronic inflammation or tissue damage that leads to a stricture:
- Crohn’s disease is one of the most frequent causes, particularly in the lower part of the small intestine and colon. The repeated cycles of flare and healing in Crohn’s make stricture formation common over the course of the disease.
- Diverticulitis can cause scarring in the sigmoid colon (the S-shaped section on the left side) after repeated infections in small pouches along the colon wall.
- Colorectal cancer can narrow the colon as a tumor grows inward. Any new stricture needs to be evaluated to rule out malignancy.
- Previous surgery is a surprisingly common cause. Strictures form at the connection point (anastomosis) after a segment of colon is removed. The incidence ranges from near zero to 30% depending on technique and healing, though only about 5% of those patients develop symptoms. Impaired blood flow to the surgical site, suture problems, and prior radiation therapy all raise the risk.
- Radiation therapy to the pelvis or abdomen can damage the colon lining and trigger fibrosis months or even years after treatment ends.
- Ischemic colitis, where reduced blood flow injures a section of the colon, can leave behind scar tissue that narrows the passage.
What a Stricture Feels Like
Symptoms depend on how narrow the colon has become and where the stricture sits. Many strictures cause no symptoms at all until they reach a critical point. The most common sign is abdominal bloating and distension, a feeling of fullness or tightness that comes and goes. You may also notice constipation that worsens over time, thinner-than-usual stools, cramping abdominal pain (especially after eating), or episodes where the bowel seems partially blocked and then clears on its own.
These symptoms often develop slowly, which is why some people adapt without realizing something has changed. A partial blockage can go on intermittently for weeks or months before it becomes severe enough to seek care.
When a Stricture Becomes an Emergency
A complete blockage is a medical emergency. When nothing can pass through the narrowed segment, the colon upstream of the stricture begins to stretch and fill with gas and fluid. Warning signs include sudden severe abdominal pain, an inability to pass gas or stool (called obstipation), rapid heart rate, low blood pressure, and a visibly swollen abdomen that feels rigid or tender to touch.
If the distension continues, it can compromise blood flow to the colon wall, leading to tissue death and perforation. A perforated colon causes widespread abdominal tenderness with rebound pain. Signs of perforation, loss of blood flow to the colon, or infection spreading into the bloodstream all require emergency intervention.
Cancer Risk in IBD-Related Strictures
One important concern with strictures in people who have Crohn’s disease or ulcerative colitis is the possibility that the narrowed area harbors cancer. A multicenter study found that 8% of patients with colonic strictures from Crohn’s disease were eventually diagnosed with cancer at the stricture site. In most of those cases, the cancer was discovered at or very close to the time the stricture was first identified. This is why doctors will almost always biopsy a colon stricture, particularly if it’s new, if it develops in someone with longstanding inflammatory bowel disease, or if it has features on imaging that raise suspicion.
How Strictures Are Diagnosed
Colonoscopy is the gold standard because it lets the doctor see the narrowed area directly, measure how tight it is, and take tissue samples to check for cancer or active inflammation. CT scans play a major supporting role. They can show the location and length of the stricture, the thickness of the colon wall, and whether there are signs of complications like upstream dilation or perforation. CT is also useful for distinguishing between inflammatory and fibrotic strictures based on patterns of blood flow and fluid in the bowel wall.
In some cases, MRI is used, particularly for people with Crohn’s disease who need repeated imaging over time. MRI can detect fluid buildup (a marker of active inflammation) and increased collagen content (a marker of established scarring) without radiation exposure.
Balloon Dilation
For benign strictures, the first treatment attempted is usually endoscopic balloon dilation. During a colonoscopy, a deflated balloon is threaded through the scope to the narrowed area, then inflated to stretch the colon open. Technical success at the first attempt reaches about 87%, and nearly all patients have a successful dilation by the second attempt. Clinical improvement, meaning relief of symptoms, occurs in about 93% of patients.
The main limitation is recurrence. Roughly 27% of patients experience re-narrowing, typically within a couple of months. Still, long-term data show that about 87% of patients remain free of repeat procedures at 10 years. For many people, one or two dilations are enough to manage the problem without surgery.
Stenting
Self-expanding metal stents are sometimes placed inside the colon to hold a stricture open. This is most commonly done for strictures caused by cancer, either as a bridge to surgery (keeping the bowel open until the tumor can be removed) or as a long-term palliative measure when surgery isn’t an option. The overall complication rate in one study was about 19%, with perforation occurring in roughly 13% of cases and stent migration occurring less frequently. These risks mean stenting is generally reserved for situations where the alternatives carry even higher risk.
Surgery
When dilation fails, when cancer is found, or when a stricture causes a complete obstruction, surgery becomes necessary. The two main approaches are bowel resection (removing the narrowed segment and reconnecting the healthy ends) and strictureplasty (cutting into the scarred area and reshaping it to widen the channel without removing any bowel).
Strictureplasty preserves bowel length, which is particularly important for people with Crohn’s disease who may need multiple surgeries over their lifetime. Losing too much bowel can lead to short bowel syndrome, a condition where the intestine can no longer absorb enough nutrients. For this reason, strictureplasty is typically chosen when patients are at high risk for short bowel syndrome. In most other situations, resection is preferred because it removes the diseased tissue entirely.
After any colon surgery, there’s a chance of developing a new stricture at the surgical connection site. When this happens, it can often be managed with balloon dilation rather than a second operation.