Capsule Fecal Transplants Fail More Often Than Colonoscopy in 652-Patient Study

If you or someone you love has been through the misery of recurrent Clostridioides difficile (C. diff) infection, a nasty gut bacterium that causes relentless diarrhea and can keep coming back after antibiotics, you've probably heard about fecal microbiota transplant (FMT), the practice of transferring stool from a healthy donor to restore a disrupted gut microbiome. What you may not have heard is that how that transplant gets delivered, as a swallowed capsule or via colonoscopy, may matter more than doctors assumed.

A new prospective cohort study of 652 patients treated across four academic medical centers and two community practice groups found that capsule-delivered FMT failed to prevent C. diff recurrence significantly more often than colonoscopy-delivered FMT, especially in patients 65 and older. The finding is published in Gastro Hep Advances (DOI: 10.1016/j.gastha.2026.101051).

Key takeaways:

• In a 652-patient real-world study, capsule FMT recipients had an 18% recurrence rate at one month versus 7.4% for colonoscopy recipients.
• After adjusting for other factors, capsule delivery carried more than double the odds of recurrence (adjusted OR 2.37).
• The gap was concentrated in patients 65 and older; it did not reach statistical significance in younger patients.
• This is an observational study, not a randomized trial, so it cannot prove capsules cause worse outcomes, and it conflicts with an earlier, smaller randomized trial that found the two methods equivalent.

Capsule FMT Shows Higher C. diff Recurrence Than Colonoscopy Delivery

Researchers found that patients who received capsule FMT for recurrent C. diff had a one-month recurrence rate of 18%, compared with 7.4% for patients who received colonoscopic FMT (P=.002). After statistically adjusting for differences between the two groups, capsule delivery was independently associated with more than double the odds of recurrence (adjusted odds ratio 2.37, 95% CI 1.16 to 5.24, P=.02). The study, led by Belhasan and colleagues, tracked 652 individuals with recurrent C. diff infection (rCDI) who were treated with FMT between July 2019 and November 2023, with 644 included in the final analysis.

Why This Matters for Anyone Managing Recurrent C. diff

Recurrent C. diff is a punishing condition: about 1 in 5 patients with a healthcare-associated C. diff infection experiences a recurrence, according to CDC surveillance data, and repeated bouts mean repeated rounds of diarrhea, hospitalization risk, and antibiotic exposure. FMT capsules exist largely for convenience: no sedation, no bowel prep for a colonoscopy, no scheduling an endoscopy suite. If capsules genuinely carry a higher failure rate in real-world use, that convenience trade-off deserves a second look, particularly for older adults, who make up a large share of the recurrent C. diff population and who this study suggests may be driving most of the difference.

How the Study Was Designed

This was a prospective cohort study, meaning researchers followed real patients receiving routine clinical care rather than randomly assigning them to a treatment, across six sites (four academic centers, two community practice groups) over more than four years. Of the 652 patients, 421 received capsule FMT and 223 received colonoscopic FMT. Capsule recipients were notably older (median age 70 versus 59 in the colonoscopy group, P<.001) and less likely to be immunocompromised (16% versus 27%). The study was designed with enough patients to reliably detect a 7 percentage-point difference in recurrence between groups; the actual observed difference was 10.6 percentage points, giving the study strong statistical power to detect the effect it found.

When the researchers broke the results down by age, capsule FMT increased recurrence risk in patients 65 and older (odds ratio 2.7, 95% CI 1.2 to 6.4) but not clearly in patients under 65 (odds ratio 1.9, 95% CI 0.7 to 5.3, P=.2). Notably, the statistical test for whether age itself explained the difference between the two delivery methods (called an interaction test) did not reach significance, meaning the age pattern is suggestive but not formally confirmed. The researchers also found that dialysis patients had a substantially higher risk of recurrence regardless of delivery method (adjusted OR 9.44, 95% CI 2.75 to 32.3), and that beyond the first month, non-C. diff antibiotic exposure became the strongest predictor of relapse, with recurrence climbing from 24% at two months to 50% at six months to 89% at twelve months in patients exposed to other antibiotics, versus 11%, 25%, and 38% respectively in those who weren't.

What This Means if You're Considering FMT for Recurrent C. diff

This study does not mean capsule FMT is ineffective or that patients should refuse it. It means the choice of delivery method may be worth an explicit conversation with a gastroenterologist, especially for patients over 65, who appear to bear most of the added risk seen here. It's also a reminder that any antibiotic use after FMT, for an unrelated infection, can undercut the transplant's protective effect over time, a detail worth flagging to any prescribing doctor. Patients under 65 and those without dialysis or heavy antibiotic exposure may see little practical difference between the two methods based on this data.

Limitations Worth Knowing

This is an observational cohort, not a randomized controlled trial, so it can show an association between delivery method and recurrence but cannot prove that capsules themselves cause worse outcomes. Capsule recipients were older and healthier on other measures (less immunocompromised), which opens the door to selection bias: doctors may have steered certain patients toward one method over another for reasons the statistics can't fully capture, even after adjustment. The findings also sit in some tension with a smaller, earlier randomized trial by Kao and colleagues in JAMA, which enrolled 116 patients and found capsule FMT noninferior to colonoscopy, with 96.2% of patients in both arms free of recurrence at 12 weeks. That trial was smaller, enrolled a younger population, and may have been underpowered to detect the age-driven gap this new, larger cohort identified. A broader systematic review and meta-analysis of FMT delivery routes has generally found colonoscopy performs at least as well as capsule delivery, consistent with the new findings' direction if not their magnitude.

What Comes Next

The authors call for more individualized treatment decisions rather than a one-size-fits-all default to either method, and flag age as a factor clinicians should weigh when choosing how to deliver FMT. Confirming the finding, and settling whether age truly modifies the risk, will likely require either a randomized trial large enough to power an age-stratified analysis or further real-world cohorts pooling data across more sites.

It's also worth noting how this study was funded and who worked on it: it was supported by a donation from the nonprofit Achieving Cures Together, and several of the authors disclose financial relationships with FMT-related companies, including consulting, research support, or advisory roles with OpenBiome, Finch Therapeutics, Rebiotix, Seres, and Diasorin. These are common and disclosed relationships in a niche field where academic FMT researchers often collaborate with the small number of organizations that manufacture or distribute donor stool products, but they're worth knowing when weighing the study's conclusions.

Common Questions

Does this mean I should avoid capsule FMT? No. The study found a higher recurrence rate with capsules in this population, but it's an observational study that can't rule out other explanations, and capsules can still be a reasonable choice, particularly for patients under 65. Talk with your gastroenterologist about what fits your situation.

Why would swallowing a capsule work differently than colonoscopy delivery? The study doesn't establish a biological mechanism. Possibilities include differences in how much donor material reaches the colon, where it's deposited, or unmeasured differences between the patients typically chosen for each method.

What should I ask my doctor if I'm considering FMT? Ask about your age, kidney status (given the dialysis finding here), and any anticipated need for antibiotics after the procedure, since these all showed up as relevant to recurrence risk in this study.

Is FMT still considered effective overall for recurrent C. diff? Yes. Both delivery methods showed most patients did not experience recurrence at one month; the study is about a difference in degree between two effective options, not a verdict that either one fails.

References

1. Dina Belhasan, Nataliia Kuchma, Monika Fischer, et al. (2026). Colonoscopic or Capsule Fecal Microbiota Transplantation for Recurrent Clostridioides difficile Infection: A Prospective Cohort. Gastro Hep Advances. https://doi.org/10.1016/j.gastha.2026.101051
2. Jennifer Moisi (2022). Clostridioides difficile-Infection (CDI). VacciTUTOR. https://doi.org/10.33442/vt202159
3. Effect of Oral Capsule vs Colonoscopy-Delivered Fecal Microbiota Transplantation on Recurrent Clostridium difficile Infection: A Randomized Clinical Trial (Kao et al., JAMA 2017). NIH. https://pmc.ncbi.nlm.nih.gov/articles/PMC5820695/