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NIHR Signal Transvaginal ultrasound and MRI achieve similar accuracy for diagnosing lower bowel endometriosis

Published on 16 July 2019

doi: 10.3310/signal-000791

Transvaginal ultrasound and magnetic resonance imaging (MRI) scans are both accurate ways to diagnose the most severe form of deep endometriosis affecting the bowel. By using both transvaginal ultrasound and MRI, the chance of non-invasively and accurately diagnosing endometriosis of the lower bowel rises to nearly 100%.

This review and meta-analysis looked at eight studies where both transvaginal ultrasound and MRI had been used to diagnose endometriosis in a total of 1,132 women. In each individual the investigation findings were compared with the reference standard, which was histological confirmation of endometriosis at surgery.

The quality of the studies was mostly high. Although none of these was a UK study, the results broadly support current UK practice. Also, they suggest that clinicians could consider using either of these examinations to non-invasively achieve an accurate diagnosis

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Why was this study needed?

Endometriosis, where tissue similar to the lining of the womb starts to grow in other places, affects around 10% of all women, and 20-50% of infertile women. In up to a third of cases, the bowel is affected, mostly the lower or recto-sigmoid portion of the intestine. Symptoms such as pelvic pain, painful sex and pain when urinating or passing stools persist for years before a diagnosis is made. The impact on women’s lives, and the economic burden on healthcare systems, is very significant.

Transvaginal ultrasound and MRI have been shown to be effective at detecting endometriosis. They are less invasive than surgical methods and don’t require sedation. While MRI is more complex and more expensive, transvaginal ultrasound is slightly more invasive as an ultrasound sensor is inserted vaginally and is operator-dependent.

This review aimed to compare their accuracy in the diagnosis of recto-sigmoid endometriosis.

What did this study do?

This systematic review and meta-analysis included eight studies with a total of 1,132 women, published between 2007 and 2018. Three studies were from Italy, the rest from Spain, France, Brazil and Iran.

All the women in the studies had both transvaginal ultrasound and MRI for suspected deep endometriosis, based on clinical history and/or physical examination. Diagnosis was confirmed at surgery with a biopsy.

The main outcome measure was accuracy: the combination of sensitivity (how good is this test at picking up people who have bowel endometriosis?) and specificity (how good is the test at excluding it in those who don’t have it?).

Overall, the quality of the studies was high. The results should be reliable, though there was a small risk of bias. Bowel preparation, which has been shown to increase the accuracy of intestinal lesion detection, was not taken into consideration.

What did it find?

  • MRI correctly identified 90% of cases (95% confidence interval (CI) 87 to 92%) in those who had endometriosis and correctly excluded bowel endometriosis in those without it for 96% of people (95% CI 94 to 97%).
  • Transvaginal ultrasound correctly identified 90% of cases (95% CI 87 to 92%) in those who had endometriosis and correctly excluded bowel endometriosis in those without it for 96% of people (95% CI 94 to 97%).
  • On average, prevalence was high: 47% of women in the studies had lower bowel endometriosis. So for individual women tested the chance of a positive test meaning that they indeed had endometriosis (the positive “post-test probability” or predictive value) was 94.8% for MRI and 93.9% for transvaginal ultrasound. The combined use of them yielded an even better post-test probability of 99.6%.

What does current guidance say on this issue?

The NICE 2017 guideline recommends transvaginal ultrasound as a first choice where endometriosis is suspected, or to identify deep endometriosis involving the bowel, bladder or ureter. If this is refused or not appropriate, they suggest trying a trans-abdominal ultrasound scan of the pelvis.

NICE does not recommend MRI as a first line choice but suggest using MRI to assess the extent of deep endometriosis involving the bowel, bladder or ureter. MRI scans should be interpreted by a specialist gynaecological radiologist.

Where endometriosis is suspected, NICE suggests that surgical investigation (laparoscopy) is considered even when an ultrasound is normal.

What are the implications?

The results of this useful update support UK current practice concerning a condition that can be difficult to diagnose.

The finding that when both MRI and transvaginal ultrasound are used together, positive predictive value increases to nearly 100% is worth consideration by clinicians, as it effectively makes the diagnosis. The authors suggest that both can be performed on the same day, requiring a single bowel preparation.

In terms of resource, ultrasound is a safe, low-cost and widely-used technique – but accuracy is more dependent on the operator’s experience. MRI is more expensive, but can be interpreted by a specialist remotely – potentially increasing accuracy.

Citation and Funding

Moura A, Ribeiro H, Bernardo W et al. Accuracy of transvaginal sonography versus magnetic resonance imaging in the diagnosis of rectosigmoid endometriosis: Systematic review and meta-analysis. PLoS One. 2019;14(4):e0214842.

No funding information was provided for this study.

Bibliography

European Society of Human Reproduction and Embryology (ESHRE). Management of women with endometriosis. Grimbergen, Belgium; 2013.

NHS website. Endometriosis. London: Department for Health and Social Care; updated 2019.

NICE. Endometriosis: diagnosis and management. NG73. London: National Institute for Health and Care Excellence; 2017.

Why was this study needed?

Endometriosis, where tissue similar to the lining of the womb starts to grow in other places, affects around 10% of all women, and 20-50% of infertile women. In up to a third of cases, the bowel is affected, mostly the lower or recto-sigmoid portion of the intestine. Symptoms such as pelvic pain, painful sex and pain when urinating or passing stools persist for years before a diagnosis is made. The impact on women’s lives, and the economic burden on healthcare systems, is very significant.

Transvaginal ultrasound and MRI have been shown to be effective at detecting endometriosis. They are less invasive than surgical methods and don’t require sedation. While MRI is more complex and more expensive, transvaginal ultrasound is slightly more invasive as an ultrasound sensor is inserted vaginally and is operator-dependent.

This review aimed to compare their accuracy in the diagnosis of recto-sigmoid endometriosis.

What did this study do?

This systematic review and meta-analysis included eight studies with a total of 1,132 women, published between 2007 and 2018. Three studies were from Italy, the rest from Spain, France, Brazil and Iran.

All the women in the studies had both transvaginal ultrasound and MRI for suspected deep endometriosis, based on clinical history and/or physical examination. Diagnosis was confirmed at surgery with a biopsy.

The main outcome measure was accuracy: the combination of sensitivity (how good is this test at picking up people who have bowel endometriosis?) and specificity (how good is the test at excluding it in those who don’t have it?).

Overall, the quality of the studies was high. The results should be reliable, though there was a small risk of bias. Bowel preparation, which has been shown to increase the accuracy of intestinal lesion detection, was not taken into consideration.

What did it find?

  • MRI correctly identified 90% of cases (95% confidence interval (CI) 87 to 92%) in those who had endometriosis and correctly excluded bowel endometriosis in those without it for 96% of people (95% CI 94 to 97%).
  • Transvaginal ultrasound correctly identified 90% of cases (95% CI 87 to 92%) in those who had endometriosis and correctly excluded bowel endometriosis in those without it for 96% of people (95% CI 94 to 97%).
  • On average, prevalence was high: 47% of women in the studies had lower bowel endometriosis. So for individual women tested the chance of a positive test meaning that they indeed had endometriosis (the positive “post-test probability” or predictive value) was 94.8% for MRI and 93.9% for transvaginal ultrasound. The combined use of them yielded an even better post-test probability of 99.6%.

What does current guidance say on this issue?

The NICE 2017 guideline recommends transvaginal ultrasound as a first choice where endometriosis is suspected, or to identify deep endometriosis involving the bowel, bladder or ureter. If this is refused or not appropriate, they suggest trying a trans-abdominal ultrasound scan of the pelvis.

NICE does not recommend MRI as a first line choice but suggest using MRI to assess the extent of deep endometriosis involving the bowel, bladder or ureter. MRI scans should be interpreted by a specialist gynaecological radiologist.

Where endometriosis is suspected, NICE suggests that surgical investigation (laparoscopy) is considered even when an ultrasound is normal.

What are the implications?

The results of this useful update support UK current practice concerning a condition that can be difficult to diagnose.

The finding that when both MRI and transvaginal ultrasound are used together, positive predictive value increases to nearly 100% is worth consideration by clinicians, as it effectively makes the diagnosis. The authors suggest that both can be performed on the same day, requiring a single bowel preparation.

In terms of resource, ultrasound is a safe, low-cost and widely-used technique – but accuracy is more dependent on the operator’s experience. MRI is more expensive, but can be interpreted by a specialist remotely – potentially increasing accuracy.

Citation and Funding

Moura A, Ribeiro H, Bernardo W et al. Accuracy of transvaginal sonography versus magnetic resonance imaging in the diagnosis of rectosigmoid endometriosis: Systematic review and meta-analysis. PLoS One. 2019;14(4):e0214842.

No funding information was provided for this study.

Bibliography

European Society of Human Reproduction and Embryology (ESHRE). Management of women with endometriosis. Grimbergen, Belgium; 2013.

NHS website. Endometriosis. London: Department for Health and Social Care; updated 2019.

NICE. Endometriosis: diagnosis and management. NG73. London: National Institute for Health and Care Excellence; 2017.

Accuracy of transvaginal sonography versus magnetic resonance imaging in the diagnosis of rectosigmoid endometriosis: Systematic review and meta-analysis

Published on 10 April 2019

Moura, A. P. C.,Ribeiro, Hsaa,Bernardo, W. M.,Simoes, R.,Torres, U. S.,D'Ippolito, G.,Bazot, M.,Ribeiro, Paag

PLoS One Volume 14 , 2019

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%.

Endometriosis is defined as the presence of endometrial-like tissue outside the uterine cavity.

Superficial endometriosis (also called ‘peritoneal endometriosis’): peritoneal infiltration is less than 5mm in depth.

Ovarian endometriosis: includes superficial ovarian implant and endometriomas.

Deep endometriosis: foci of depth greater than 5mm affecting the retrocervix, paracervix, recto-vaginal septum, digestive tract (e.g. recto-sigmoid), ureter, bladder. Exceptionally affects more distant sites, such as the lungs, liver, diaphragm and operative scars.

Expert commentary

A non-invasive diagnosis of recto-sigmoid endometriosis is desirable as management is complex requiring referral to tertiary care centres. Given the low cost, safety and widespread availability of transvaginal ultrasound, it should be considered as the first line investigation for recto-sigmoid endometriosis.

The limitation of transvaginal ultrasound is that it is inherently operator dependent and requires training and experience to reduce errors while MRI images can be interpreted remotely by an expert.

In case of doubt, both transvaginal ultrasound and MRI should be considered in the same patient as the combined approach raises the diagnostic accuracy to nearly 100%.

Lucky Saraswat, Consultant Gynaecologist and Minimal Access Surgeon, Aberdeen Royal Infirmary; Honorary Lecturer, Aberdeen Centre for Women’s Health Research, University of Aberdeen 

The commentator declares no conflicting interests