Endometriosis and its coexistence with irritable bowel syndrome and pelvic inflammatory disease: findings from a national case–control study—Part 2

Objective To investigate whether the increased chances of having a diagnosis of irritable bowel syndrome (IBS) and pelvic inflammatory disease (PID) in women with endometriosis is due to misdiagnosis or co‐morbidity. Design A case–control study of women aged 15–55 years with endometriosis and matched controls. Setting Data from the UK’s General Practice Research Database for the years 1992–2001. Sample A total of 5540 women aged 15–55 years, diagnosed with endometriosis, each matched to four controls without endometriosis. The index date was defined as the date of diagnosis. Methods Data were analysed to determine whether women with endometriosis were more likely to receive a diagnosis of PIDor IBS than women without endometriosis. Odds ratios were calculated for endometriosis associated with IBS and PID before and after the index date. Main outcome measures Diagnosis of IBS or PID before and after the index date. Results Compared with the controls, women with endometriosis were 3.5 times more likely to have received a diagnosis of IBS (OR 3.5 [95% CI: 3.1–3.9]). Even after women had been diagnosed with endometriosis, they were still two and a half times more likely to receive a new diagnosis of IBS when compared with the controls (OR 2.5 [95% CI: 2.2–2.8]). Similarly, women with endometriosis were more likely than those without endometriosis to have been treated for PID both before (OR 5.9 [95% CI: 5.1–6.9]) and after (OR 3.8 [95% CI: 3.1–4.6]) being diagnosed with endometriosis. Conclusions Women with endometriosis are more likely to be diagnosed with IBS and PID than controls, even after a definitive diagnosis of endometriosis has been reached.