Relationship between the magnetic resonance imaging appearance of adenomyosis and endometriosis phenotypes

Abstract

STUDY QUESTION What is the relationship between endometriosis phenotypes superficial peritoneal endometriosis (SUP), ovarian endometrioma (OMA), deep infiltrating endometriosis (DIE) and the adenomyosis appearance by magnetic resonance imaging (MRI)? SUMMARY ANSWER Focal adenomyosis located in the outer myometrium (FAOM) was observed more frequently in women with endometriosis, and was significantly associated with the DIE phenotype. WHAT IS KNOWN ALREADY An association between endometriosis and adenomyosis has been reported previously, although data regarding the association between MRI appearance of adenomyosis and the endometriosis phenotype are currently still lacking. STUDY DESIGN, SIZE, DURATION This was an observational, cross-sectional study using data prospectively collected from non-pregnant patients who were between 18 and 42 years of age, and who underwent surgery for symptomatic benign gynecological conditions between January 2011 and December 2014. For each patient, a standardized questionnaire was completed during a face-to-face interview conducted by the surgeon during the month preceding the surgery. Only women with preoperative standardized uterine MRIs were retained for this study. PARTICIPANTS/MATERIALS, SETTING, METHODS Surgery was performed on 292 patients with signed consent and available preoperative MRIs. After a thorough surgical examination of the abdomino-pelvic cavity, 237 women with histologically proven endometriosis were allocated to the endometriosis group and 55 symptomatic women without evidence of endometriosis to the endometriosis free group. The existence of diffuse or FAOM was studied in both groups and according to surgical endometriosis phenotypes (SUP, OMA and DIE). MAIN RESULTS AND THE ROLE OF CHANCE Adenomyosis was observed in 59.9% (n = 175) of the total sample population (n = 292). Based on MRI, the distribution of adenomyosis was as follows: isolated diffuse adenomyosis (53 patients; 18.2%), isolated FAOM (74 patients; 25.3%), associated diffuse and FAOM (48 patients; 16.4%). Diffuse adenomyosis (isolated and associated to FAOM) was observed in one-third of the patients regardless of whether they were endometriotic patients or endometriosis free women taken as controls (34.2% (81 cases) versus 36.4% (20 cases)); P = 0.764. Among endometriotic women, diffuse adenomyosis (isolated and associated to FAOM) failed to reach significant correlation with the endometriosis phenotypes (SUP, 20.0% (8 cases); OMA, 45.2% (14 cases) and DIE, 35.5% (59 cases); P = 0.068). In striking contrast, there was a significant increase in the frequency of FAOM in endometriosis-affected women than in controls (119 cases (50.2%) versus 5.4% (3 cases); P < 0.001). FAOM correlated with the endometriosis phenotypes, significantly with DIE (SUP, 7.5% (3 cases); OMA, 19.3% (6 cases) and DIE, 66.3% (110 cases); P < 0.001). LIMITATIONS, REASONS FOR CAUTION There was a possible selection bias due to the specificity of the study design, as it only included surgical patients in a referral center that specializes in endometriosis surgery. Therefore, women referred to our center may have suffered from particularly severe forms of endometriosis. This could explain the high number of women with DIE (166/237-70%) in our study group. This referral bias for women with severe lesions may have amplified the difference in association of FAOM with the endometriosis-affected patients compared to women without endometriosis. Furthermore, according to inclusion criteria, women in the endometriosis free group were symptomatic women. This may introduce some bias as symptomatic women may be more prone to have associated adenomyosis that in turn could have been overrepresented in the endometriosis free group. Whether this selection could have introduced a bias in the relationship between endometriosis and adenomyosis remains unknown. WIDER IMPLICATIONS OF THE FINDINGS This study opens the door to future epidemiological, clinical and mechanistic studies aimed at better characterizing diffuse and focal adenomyosis. Further studies are necessary to adequately determine if diffuse and focal adenomyosis are two separate entities that differ in terms of pathogenesis. STUDY FUNDING/COMPETING INTEREST(S) No funding supported this study. The authors have no conflict of interest to declare.