In this study, MRI and operative scores showed significant agreement regarding compartments A, B, O, and C, which was compatible with previous studies using the previous ENZIAN classification [10–12]. Our results demonstrated 100% specificity and sensitivity of MRI in the evaluation of rectovaginal septum and posterior vaginal fornix considering (compartment A) the #ENZIAN classification.
DIE procedures are one of the most complicated operations for gynecological surgeons. It may result in multiple complications and comorbidities such as bowel, bladder, and ureter injuries and bleeding from adhesion sites. The overall rate of severe complications for DIE operations is reported to be 7–9% [13–16]. Preoperative knowledge of the involved pelvic organs facilitates minimizing these complications as well as disease recurrence, providing an effective preoperative strategy via a multidisciplinary approach. Currently, TVS and MRI are effectively used in DIE diagnosis by experienced gynecologists and radiologists. TVS has 93% sensitivity and 96% specificity, whereas MRI has 95% sensitivity and 91% specificity in the diagnosis of DIE. Nonetheless, laparoscopy remains the gold standard for endometriosis diagnosis [17].
American Society of Reproductive Medicine (rASRM) classification has been the most widely used scoring system for defining the severity of the disease [18]. However, it does not define adherent organ involvement and the location of DIE lesions [19]. The relation between the rASRM classification and symptom severity has been evaluated in various studies; however, the lack of reliable correlation [20–23] has led physicians to seek a much more relevant classification model. The ENZIAN classification emerged for this purpose to provide a decent definition of DIE lesions. A correlation between ENZIAN and DIE symptoms was demonstrated in terms of location and severity [24, 25]. Moreover, ENZIAN demonstrated a correlation between DIE symptoms, the extent of the disease, and surgery length [25–27]. However, regardless of the intraoperative classification, MRI and TVS remain the most valuable preoperative diagnostic tools.
A meta-analysis evaluating the data of 20 studies reported an overall sensitivity and specificity of MRI for pelvic DIE diagnosis as 83% and 90%, respectively [6]. In another study, Dipaola et al. compared MRI and intra-operative ENZIAN scores in 115 patients, revealing a significant concordance between histopathologic results of excised tissues in vagina-rectovaginal space, uterosacral ligaments, rectum-sigmoid colon, and adenomyosis and MRI scores with accuracy reported as 96%, 98%, 96%, and 100%, respectively [12]. In addition, Burla et al. evaluated the correlation between preoperative MRI and ENZIAN score. They reported 95.2% sensitivity and 95.7% specificity for compartment A [10], which was 100% in our results.
In terms of modifications in the #ENZIAN classification, compartment B includes uterosacral ligaments (USL) and pelvic sidewall involvement. Besides, the #ENZIAN classification evaluates right and left pelvic sides separately, which is in contrast to the previous revised ENZIAN classification [8]. Another difference between the revised ENZIAN classification and the #ENZIAN classification is that in the latter, compartment B does not include ureter involvement or hydronephrosis, which has an incidence ranging from 0.3–12% and is often asymptomatic[28]. The clinical significance of ureteral endometriosis has led to the need for a separate classification of the condition. In our study, MRI had 97% sensitivity and 100% specificity in compartment B. A meta-analysis evaluating the data of 20 studies showed 85% sensitivity and 80% specificity of MRI in terms of USL [6]. Dipaola et al. found 97% sensitivity and 99% specificity in compartment B [12]. In contrast, a study comparing the previous ENZIAN classification to MRI findings reported a 78% sensitivity and 100% specificity for compartment B [10]. The reason behind this low sensitivity is not apparent; however, we may speculate that the accuracy of MRI could decrease in severe cases and is also related to the experience.
Regarding compartment C in our study, high sensitivity and specificity were achieved at 95% and 94%, respectively. It is worth mentioning that these results only include the rectum, which is described as a 16 cm segment of the colon adjacent proximally to the anal verge. In contrast to the rectosigmoid region, compartment C does not involve the sigmoid colon. A meta-analysis evaluating both rectum and sigmoid colon lesions reported 83% sensitivity and 88% specificity[7]. Two other studies evaluated MRI accuracy of DIE lesions using the revised ENZIAN score, and both reported 86% sensitivity in compartment C. Specificities of the compartment C in these studies were reported as 98% [12] and 89% [10].
Another improvement in #ENZIAN is the inclusion of the tubo-ovarian condition compartment. In this compartment, tubal and ovarian adhesions to pelvic sidewall, uterus, USL, and bowels are assessed. TVS has 93% sensitivity and 96% specificity in endometrioma diagnosis, which can be used as an indicator of the diagnostic accuracy of TVS in the tubo-ovarian condition compartment [29]. However, the presence of endometrioma and the tubo-ovarian condition compartment are different. Endometriomas may not cause adhesions by themselves. Also, adhesion of tuba and ovaries may occur without endometrioma. In our results, MRI has 86% specificity and 92% sensitivity, which is the only result assessing the tubo-ovarian compartment of the #ENZIAN classification to date and should be confirmed with further studies.
On the other hand, MRI had low accuracy and low sensitivity in peritoneal lesion detection, which was expected considering the dimension of the peritoneal lesions. Preoperative diagnosis of compartment P does not usually alter the surgical strategy, and therefore small undefined peritoneal lesions could be neglected.
In our study, extragenital organ involvements classified as FU, FB, and FI were not present and therefore not included except for adenomyosis, which is classified as FA. MRI accuracy, sensitivity, and specificity for adenomyosis in this study were 87%, 88%, and 87%, respectively, which is similar to previous studies [10, 30].
Limitations of this study are the low number of DIE patients, the retrospective nature of the study, and the lack of rASRM scores. The strengths of this study could be the evaluation of full-time surgery videos by experienced surgeons and the interpretation of MRI by radiologists familiar with DIE cases.
In conclusion, this study demonstrated that utilizing the #ENZIAN classification in MRI reports has significant sensitivity and specificity in compartments A, B, O, and C. For compartments T and FA, although sensitivity and specificity are not as high as in compartments A, B, C, and O, there was significant sensitivity and specificity for MRI. However, the accuracy of MRI is insufficient in compartment P. Currently our study is the only evaluation of MRI accuracy using the #ENZIAN classification system, and if future studies support our results, we believe that #ENZIAN could be used to diagnose DIE lesions preoperatively in MRI.