Modified ultrasound scanning is a cost-effective method for the detection of deep infiltrating endometriosis

20 01 2009

To the Editor:

We were very pleased to read the well-written study of Bazot et al (1), which compares the value of physical examination, transvaginal sonography (TVS), rectal endoscopic sonography, and magnetic resonance imaging (MRI) for the assessment of different locations of deep infiltrating endometriosis (DIE). Unfortunately, the conclusion that MRI provides a more reliable map of DIE than TVS seems to be misleading and not completely justified by the results. Certain points in their study need to be clarified to the readers. As a matter of fact, the differences of accuracies between TVS and MRI are not statistically significant due to the large overlap of 95% confidence intervals for all locations. In particular, the sensitivity in the diagnosis of DIE in uterosacral ligaments showed a wide overlap of values. Furthermore, the low specificity (67%) reported in the present study, in comparison with previous studies of the same group (range 96-75%)(2), can further explain these results.

Re-evaluating the results in vaginal and rectovaginal septum endometriosis applying the McNemar test, we found an absence of difference between the two methods (p value: 0.136). In addition it is difficult for a reader to understand how MRI can better visualize DIE in these locations in comparison with TVS, in which the probe is so near to target. Recent reports of modified ultrasound scanning seem to have a good predictive value (3-5). The modified tenderness-guided approach proposed by Guerriero et al (3) consisted not only of particular attention in the eventual painful sites in the posterior fornix but also in the introduction of more ultrasound  transmission gel in the probe cover to better visualize the near-field area. Using this approach, a specificity of 89% with a sensitivity of 91% was obtained in the detection of vaginal endometriosis (4). Also, in the evaluation of rectovaginal septum involvement Guerriero et al (4) report a sensitivity of  74% (higher than the , 55% reported using MRI in the present study), and Abrao et al (5) using a simple bowel preparation before the examination reported a sensitivity of 98%.

In the absence of statistically significant differences, the use of MRI to examine all symptomatic women before surgery can increase the cost of preoperative evaluation without a true increase of diagnostic performance. For these reasons, modified TVS seems to be not only a first-line technique examination but also a cost-effective method for the assessment of different locations of DIE.

Stefano Guerriero, MDa
Juan Luis Alcazar, MDb
Silvia Ajossa , MDa
Gian Benedetto Melis, MDa

aDepartment of Obstetrics and Gynecology
University of Cagliari
Cagliari, Italy

bClinica Universitaria de Navarra
University of Navarra
Pamplona, Spain

References
1. Bazot M, Lafont C, Rouzier R, Roseau G, Thomassin-Naggara I, Daraï E. Diagnostic accuracy of physical examination, transvaginal sonography, rectal endoscopic sonography, and magnetic resonance imaging to diagnose deep infiltrating endometriosis. Fertil Steril. 2008 Nov 17. [Epub ahead of print].

2. Bazot, M, Detchev R, Cortez A, Amouyal P, Uzan S, Darai E. Transvaginal sonography and rectal endoscopic sonography for the assessment of pelvic endometriosis: a preliminary comparison. Hum. Reprod 2003; 18:1686-1692.

3. Guerriero S, Ajossa S, Gerada M, D’Aquila M, Piras B, Melis GB. : “Tenderness-guided” transvaginal ultrasonography: a new method for the detection of deep endometriosis in patients with chronic pelvic pain.  Fertil Steril 2007;88:1293-7.

4. Guerriero S, Ajossa S, Gerada M, Virgilio B, Angioni S, Melis GB. Diagnostic value of transvaginal ‘tenderness-guided’ ultrasonography for the prediction of location of deep endometriosis. Hum Reprod 2008;23:2452-7.

5. Abrão MS, Gonçalves MO, Dias JAJr., Podgaec S, Chamie LP, Blasbalg R.  Comparison between clinical examination, transvaginal sonography and magnetic resonance imaging for the diagnosis of deep endometriosis. Hum. Reprod. 2007;  22:3092-97.

Published online in Fertility and Sterility  doi: 10.1016/j.fertnstert.2009.01.124

The Authors Respond:

We read with great interest the letter from Guerriero et al. regarding our recent article. Guerriero et al suggest not only that “modified TVS” is a first-line examination of choice for assessing the different locations of DIE, but also that it is cost-effective.

On re-analyzing our results, Guerriero et al conclude that we found no significant difference between TVS and MR imaging for the evaluation of uterosacral ligament, vaginal and rectovaginal septum endometriosis. In fact, we demonstrated that MRI performed similarly to TVS and RES for the diagnosis of intestinal endometriosis, and that it had better sensitivity and higher likelihood ratios for uterosacral ligament and vaginal endometriosis. In addition to morphological findings (thickening, irregular and stellar aspects) present on both MRI and TVS, MRI provides features based on signal intensity (e.g. tiny hemorrhagic spots on T1WI and low-intensity areas on T2WI), thus increasing its accuracy, particularly for endometriotic involvement of small vaginal and uterosacral ligaments (1). We are somewhat surprised that Guerriero et al found uterosacral ligament involvement in only one third of their patients, as this is the most frequent target of DIE. On the other hand, they detected vaginal endometriosis in half their patients, yet the prevalence of this form is lower than that of uterosacral ligament involvement.

All these discrepancies raise several issues. One is the possible existence of a selection bias, leading to over-representation of patients with extensive pelvic endometriosis. Second, different teams may use different TVS definitions of uterosacral ligament endometriosis. Third, when a doubt persisted, we performed sonovaginography at the end of our TVS examination (2). In our experience, excessive filling of the posterior vaginal fornix can hinder visualization of the entire deep posterior compartment, thus complicating the examination of the uterosacral ligaments and rectosigmoid colon.

With respect to cost-effectiveness, systematic MRI cannot currently be recommended for women with suspected endometriosis because of its high cost and low availability. Although TVS remains the first-line imaging technique for DIE screening, it is wrong to claim that modified ultrasound scanning is cost-effective for the detection of DIE. Although the modified tenderness-guided approach and sonovaginography improve the detection of rectovaginal and vaginal endometriosis, Guerriero et al reported only 50% sensitivity for uterosacral ligament involvement and 67% for intestinal endometriosis (1). Recently, Abrao et al found that TVS was more sensitive than MR imaging for the diagnosis of intestinal endometriosis (98% versus 83%) (3). Discrepancies with other studies could be partly explained by differences in the protocols, such as systematic rectal enema before TVS examination. In contrast, when examining the “retrocervical area”, Abrao et al were unable to evaluate the different specific deep posterior endometriotic locations (uterosacral ligaments, vagina, and rectovaginal septum) in all their patients (3). Yet documentation of all specific locations of DIE is particularly important for surgical planning and for informing patients of the potential risks of the different operations.

In conclusion, TVS is an appropriate screening technique for pelvic endometriosis, but MRI provides a complete map of DIE locations. Further studies are required to evaluate the cost-effectiveness of the different imaging techniques, especially when surgery is planned.

Marc Bazot, MDa
Emile Daraï, MD, PhDb
Departments of aRadiology and bObstetrics and Gynecology
Hôpital Tenon 4
Paris, France

References
1. Bazot M, Darai E, Hourani R, Thomassin I, Cortez A, Uzan S, et al. Deep pelvic endometriosis: MR imaging for diagnosis and prediction of extension of disease. Radiology 2004; 232:379-89.

2. Dessole S, Farina M, Rubattu G, Cosmi E, Ambrosini G, Nardelli GB. Sonovaginography is a new technique for assessing rectovaginal endometriosis. Fertil Steril 2003; 79:1023-7.

3. Abrao MS, Goncalves MO, Dias JA, Jr., Podgaec S, Chamie LP, Blasbalg R. Comparison between clinical examination, transvaginal sonography and magnetic resonance imaging for the diagnosis of deep endometriosis. Hum Reprod 2007; 22:3092-7.

Published online in Fertility and Sterility  doi: 10.1016/j.fertnstert.2009.01.123

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