Accuracy of Ultrasound in Diagnosing Retained Products of Conception

The presence of an echogenic mass on ultrasound is the most sensitive and specific sonographic indicator of retained products of conception (RPOC) following any pregnancy event, according to a systematic review and meta-analysis from the United Kingdom, published in The American Journal of Obstetrics and Gynecology.¹

The study aimed to evaluate and synthesize existing evidence on the diagnostic accuracy of various ultrasound modalities in detecting RPOC. Researchers conducted an extensive search of multiple databases, including Ovid SP, CINAHL, EBSCO, PubMed, BMJ Best Practice, Google Scholar, and several grey literature sources such as CORE, Trip, and the GreyLit Report. Eligible studies included prospective or retrospective cross-sectional or cohort studies that correlated ultrasound findings with histopathological confirmation of RPOC, across all gestational ages and pregnancy outcomes.

A total of 11 studies involving 1,567 participants were included. Participants had symptoms suggestive of RPOC after term or preterm delivery, miscarriage, or pregnancy termination. The analysis assessed three sonographic features:

• Presence of an echogenic mass
• Endometrial thickness >10 mm
• Color Doppler flow

Key Findings:

• Echogenic mass had the highest diagnostic accuracy:
• Sensitivity: 91.5%
• Specificity: 84.3%
• Diagnostic odds ratio (DOR): 57.8
• Endometrial thickness >10 mm showed:
• Sensitivity: 66.7%
• Specificity: 86.6%
• DOR: 12.9
• However, the correlation with RPOC was statistically weak.
• Color Doppler flow demonstrated:
• Sensitivity: 85.0%
• Specificity: 40.6%
• DOR: 3.89

These results highlight that echogenic mass is the most reliable ultrasonographic finding for diagnosing RPOC. In contrast, endometrial thickness alone is a poor predictor, and color Doppler, while sensitive, lacks specificity.

The authors emphasize that RPOC remains a diagnostic challenge, and accurate identification is crucial to avoid unnecessary surgical interventions and their associated reproductive risks. They also advocate for a standardized definition of the sonographic appearance of RPOC to improve diagnostic consistency.

Source: Am J Obstet Gynecol. 2024 May;230(5):512-531.e3. doi: 10.1016/j.ajog.2023.11.1243.