INTRODUCTION: Intestinal endometriosis is considered the most severe form of 
deep endometriosis, the rectosigmoid being involved in about 90% of cases of 
bowel infiltration. Transvaginal sonography (TVS) and magnetic resonance imaging 
(MRI) have been used for noninvasive diagnosis and preoperative mapping of 
rectosigmoid endometriosis (RE), but no consensus has been reached so far 
regarding which method is the most accurate in this setting.
OBJECTIVE: We aimed at performing a systematic review and meta-analysis to 
compare the accuracy of TVS versus MRI in the diagnosis of RE in a same 
population.
METHODS: A systematic review was conducted in accordance with the PRISMA 
guidelines. Studies were identified by searching the MEDLINE, Embase, and LILACS 
databases, as well the reference lists of retrieved articles, through February 
2019. We included all cross-sectional studies that evaluated the accuracy of TVS 
versus MRI in the diagnosis of RE within a same sample of subjects and that used 
surgical findings with histological confirmation as the gold standard. The 
QUADAS-2 instrument was used to evaluate study quality. Sensitivity, 
specificity, positive likelihood ratios (LR+), and negative likelihood ratios 
(LR-) for the diagnosis of RE were calculated. This study is registered with 
PROSPERO, number CRD42017064378.
RESULTS: Eight studies (n = 1132) were included in the meta-analysis. The pooled 
sensitivity, specificity, LR+, and LR- values of MRI for RE were 90% (95% CI, 
87-92%), 96% (95% CI, 94-97%), 17.26 (95% CI, 3.57-83.50), and 0.15 (95% CI, 
0.10-0.23); values of TVS were 90% [95% CI, 87-92%], 96% (95% CI, 94-97%), 20.66 
(95% CI, 8.71-49.00) and 0.12 (95% CI, 0.08-0.20), respectively. Areas under the 
S-ROC curves (AUC) showed no statistically significant differences between MRI 
(AUC = 0.948) and TVS (AUC = 0.930) in the diagnosis of RE (P = 0.13). Moreover, 
considering the average prevalence among the studies of 47.3%, both methods 
demonstrated similarly high positive post-test probabilities (93.9% for TVS and 
94.8% for MRI), and the combined use of them yielded a post-test probability of 
99.6%.
CONCLUSION: MRI and TVS have similarly high accuracy and positive post-test 
probabilities in the noninvasive diagnosis of RE. Combination of MRI and TVS may 
increase even further the positive post-test probabilities to near 100%.