Study Links Appendectomy to 58% Lower Colorectal Cancer Risk

Dr. Valentine Nfonsam, MD, MS, FACS, FASCRS, professor and executive vice chair of the department of surgery at Morehouse School of Medicine, wanted the longer view. Appendicitis is inflammation of the appendix, the small, narrow organ that sits near the junction of the small and large intestines. For years the answer had been removal. Then antibiotic therapy entered as a real choice for selected patients.

“The management of acute appendicitis has changed significantly over the last decade, and antibiotic therapy is now an accepted option,” Nfonsam said. The field had measured that change in the short term: whether a patient could skip the operating room, whether the inflammation returned, what complications followed, how quality of life held up afterward. Those questions mattered. They did not exhaust the list.

Leaving an inflamed appendix in place after a course of antibiotics might spare a patient an incision and a recovery, yet the organ would remain where the gut’s immune traffic and microbial communities already concentrated. No one had systematically asked what that permanence might mean years later for cancer risk in the colon and rectum. “However, most of the discussion has focused on short-term outcomes: avoiding surgery, recurrence, complications, and quality of life,” he said. “We wanted to ask a different question: Are there potential long-term oncologic implications of leaving the appendix in place after appendicitis?”

To find one, Nfonsam and his colleagues turned to the charts. They drew the cases from the TriNetX Global Collaborative Network, electronic health records spanning 168 health care organizations. The design was a retrospective matched cohort: more than 30,000 patients diagnosed with acute appendicitis, one group treated by appendectomy, the other by antibiotics alone. After the groups were matched on characteristics, each arm contained 15,774 patients. Once anyone already carrying a colorectal cancer diagnosis was excluded from the outcome window, the final counts stood at 15,616 in the appendectomy group and 15,295 in the antibiotic-only group.

Working alongside Nfonsam were Meghana Akula, BS; Syed Fahad Gillani, MD; Miriannie Rivera Valerio, MD, MS; Ahmad Zeineddin, MD; Cassie Bowers, BS; Miriam Michael, MD; Quyen D. Chu, MD, MBA, FACS; Christine E. Nembhard, MD, FACS; and May C. Tee, MD, MPH, FACS. Together they set the two cohorts side by side and followed what the records showed next—not the short-term endpoints the field already knew, but later diagnoses of cancer in the colon and rectum, adjusted for each patient’s individual risk factors.

Colorectal cancer is cancer that arises in the colon or the rectum, the lower reaches of the large intestine. In the years after the index episode of appendicitis, it was diagnosed in 110 patients who had undergone appendectomy, or 0.7 percent of that group. Among patients treated with antibiotics alone, the diagnosis reached 254, or 1.7 percent. The comparison adjusted for individual risk factors. Appendectomy carried a 58 percent lower relative risk of a subsequent colorectal cancer diagnosis.

Relative risk is the chance of an outcome in one group divided by the chance in another. A 58 percent reduction meant patients who had the appendix removed went on to receive a colorectal cancer diagnosis far less often than similar patients whose appendicitis had been managed with antibiotics alone. The two arms had begun from the same acute inflammation. They did not finish with the same oncologic record.

The appendix had once been written off as vestigial, a leftover from evolution with nothing left to do. That reading no longer holds. The small, narrow organ holds a substantial amount of lymphoid tissue, the immune tissue thought to help the body defend itself. It also takes part in the gut microbiome, the community of bacteria and other microorganisms that live in the digestive tract, and in the local immune system that works along that stretch of bowel.

“The appendix is more than a vestigial organ,” Nfonsam said. “It is rich in lymphoid tissue and participates in the intestinal microbiome and immune system in that area. Whether persistent inflammation or changes in the local microbial environment contribute to the development of cancer is biologically plausible, but our study cannot answer that question.”

The gap the charts recorded could travel more than one path. One is earlier detection of an underlying malignancy. Another is the simple removal of a source of inflammation. A third runs through the appendix’s place in the gut microbiome and the immune traffic around it. Changes in inflammation and in the local microbial environment have been linked to processes involved in colorectal cancer, so those biological functions remain open ground. The study could measure the association. It could not name the mechanism.

Nfonsam drew a hard line around what the numbers could mean for the next patient in clinic. “These results should not be interpreted to mean that everyone with appendicitis needs an appendectomy to prevent cancer,” he said. Antibiotic therapy had earned its place as a real choice for selected cases. “Antibiotic management remains an important option. But when we discuss nonoperative management, we should also think beyond the immediate episode of appendicitis and consider potential long-term oncologic risk and appropriate monitoring.”

The findings were presented as a research abstract and had not yet undergone peer review. They recorded a difference in later cancer diagnoses; they did not rewrite the standard of care. What followed from the charts, Nfonsam argued, was not a single rule but a wider conversation about who sat in front of the surgeon and how far the follow-up should reach.

“Treatment should not be one size fits all,” he said. “Age, genetic predisposition, family history, and other colorectal cancer risk factors may all be relevant as we study how to select patients and plan follow-up.”

The American College of Surgeons Clinical Congress 2026 convened in Washington from September 26 through September 29. On September 25, the day before the first sessions opened, the college released the abstract findings. The citation was set as Akula M, et al., “Risk of Colorectal Cancer Following Appendectomy.” The assignment was the Scientific Forum of the ACS Clinical Congress 2026, the portion of the congress reserved for original research abstracts. Under that title, on those dates, the work took its scheduled place on the program. Thousands of surgeons gathered in Washington. The Scientific Forum held the abstract on the floor.