Patients With IBD Who Undergo Colon Cancer Surgery Have Higher Blood Clot Risk

A large, retrospective study by Cleveland Clinic researchers, in collaboration with colleagues at other institutions, shows that patients with inflammatory bowel disease are at elevated risk of blood clots after colon cancer surgery.

The findings support increased vigilance in these patients, says Miguel Regueiro, MD, Chief of Cleveland Clinic’s Digestive Disease Institute, and a coauthor of the study.

While both IBD and surgery are known to increase clot risk, it’s the first study to quantify risk specifically for colorectal cancer surgeries, he notes.

“For patients with IBD who get bowel surgery, especially for cancer, it gives us a heightened awareness,” he says. “We should be telling these patients not to ignore warning signs like shortness of breath or swelling in the legs, especially if it’s only in one leg.”

Delayed risk

Using data from the TriNetX database, researchers compared outcomes for more than 24,000 patients who underwent surgery for colorectal cancer. Half had IBD, and half did not.

Researchers found that rates of venous thromboembolism were similar in the first 30 days after surgery. However, between 31 and 90 days after surgery, the risk for IBD patients jumped to more than one-and-a-half times that of patients without IBD. This increased risk was mainly driven by increased rates of deep vein thrombosis, researchers noted. Elevated risk persisted for up to a year after surgery.

Dr. Regueiro says they couldn’t explain why the increased risk for IBD patients seemed to be delayed, noting it warranted further study. But he says, overall, the findings were not a surprise.

“It confirmed our suspicions,” he says.

Previous studies have found that patients undergoing surgery for IBD are at increased risk of venous thromboembolism.

“This is especially the case with active inflammation from ulcerative colitis,” Dr. Regueiro says. “There’s something about the inflammation that’s prothrombotic; it seems to lead to more clots. So, there’s the inflammation itself plus the surgery, which is a known factor that contributes to the higher clot risk as well.”

Researchers suspected that cancer surgery in this patient group would also carry an increased risk.

Dr. Regueiro notes that guidelines call for prescribing IBD patients undergoing surgery with a low dose of low-molecular-weight heparin to prevent clots. Cleveland Clinic takes that precaution a step further by continuing anti-coagulation therapy for one month after surgery in some patients, he said.

Increased vigilance and patient counseling

While prospective studies are needed before considering preventative treatments across the board, the new findings suggest that both providers and patients should be aware of increased risk. Any warning signs should prompt an ultrasound to check for DVT “at the bare minimum,” Dr. Regueiro says. In addition, patients with IBD who undergo cancer surgery should be counseled about risks, including avoiding long flights or car rides or taking steps to prevent blood clots, like calf exercises or compression stockings.

The group hopes to follow up with additional studies, such as using ultrasound proactively to determine how many patients may be experiencing asymptomatic clots, and how often clots may resolve on their own versus requiring treatment.

The study, “Postoperative Venous Thromboembolism Following Colorectal Cancer Surgery in Patients With and Without Inflammatory Bowel Disease: A US-Based Collaborative Network Propensity-Matched Cohort Study,” was presented at the 2026 Digestive Disease Week Conference.