Meta-analysisindependent cross-checkabstract checked I-ORG-125 standard review
Appendix removal and ulcerative colitis
Appendectomy and the development of ulcerative colitis: results of a metaanalysis of published case-control studies.
Overview
Koutroubakis IE et al.. Am J Gastroenterol 2000 · PMID 10638578 · DOI 10.1111/j.1572-0241.2000.01680.x
People who had their appendix removed were much less likely to develop ulcerative colitis.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Pool studies on appendectomy and UC
- How was the study done?
Meta-analysis of 13 case-control studies
- How many people, animals or samples were studied?
2770 UC patients, 3352 controls
- What was actually found?
69% lower odds of UC after appendectomy
- How large was the observed effect?
OR 0.31 (0.25-0.38)
- What do the results mean in everyday life?
The appendix seems to be involved in gut immune responses
- What are the study's limitations?
Case-control designs
- What does it say about Elawady's specific claim?
Supports the association; not 'proof' of a beneficial function
- Do the results apply to Germany and Europe?
Applicable
- What can explicitly not be concluded from this study?
Cannot prove causation
Scientific in-depth review
1. Full reference
- Authors
- Koutroubakis IE et al.
- Journal
- Am J Gastroenterol
- Year
- 2000
- Identifier
- PMID 10638578 DOI 10.1111/j.1572-0241.2000.01680.x
- Verification
- verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Not stated in abstract.
2. Research question
Is appendectomy associated with a lower risk of developing ulcerative colitis?
3. Study design and population
- Study design
- Meta-analysis – Meta-analysis of 13 case-control studies
- Population
2770 UC patients and 3352 controls
- Country
Multinational
- Period
Studies 1987 - January 1999
- Sample size
13 case-control studies
- Inclusion and exclusion criteria
Studies designed to evaluate appendectomy and UC
4. Methods and endpoints
- Exposure / intervention
Prior appendectomy
- Comparator
No appendectomy
- Endpoints
UC
- Statistical methods
Pooled OR, heterogeneity test
5. Actual results
- Results
Overall OR 0.307 (95% CI 0.249-0.377), i.e. 69% lower odds of UC (62-75%); no significant heterogeneity; confounding by smoking excluded according to the authors.
- Absolute risks
Not reported
- Authors' conclusion
The inverse association is strong and consistent; further studies needed to establish causality.
6. Strengths
- Consistent across 13 studies
7. Weaknesses
- Case-control designs (recall/selection bias)
- Old literature (to 1999)
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Early meta-analysis; limited assessment of primary-study quality.
9. Assessment of the statistical interpretation
OR CI log-symmetric (stats/C-ORG-04_05_06_assoc.py).
10. Relevance to the specific claim
Shows that the Andersson 2001 finding (A-ORG-04) fits a consistent body of evidence.
11. Independent contrary findings
ACCURE (I-ORG-126) shows appendicectomy can help, not harm, people with UC.
12. Transferability to Germany and Europe
Largely European studies.
13. Overall methodological judgement
Supports the association that the archive cites, but not that it 'proves' a protective immune role or that removal is harmful.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Causal mechanism.