Adenomyosis is a common debilitating gynaecological disease. Transvaginal sonography (TVS) has been shown to be capable of diagnosing adenomyosis with an acceptable degree of accuracy. However, the reported appearances of adenomyosis on TVS are numerous and there is no consensus in the literature as to which image characteristics are unequivocally diagnostic; clarification would assist the sonographer in confidently providing a diagnosis. Following a thorough search of the electronic databases Embase and Medline, nine articles assessing the diagnostic accuracy of the sonographic features of adenomyosis on TVS against a gold standard reference test (histology post hysterectomy), using sensitivity and specificity, were selected for inclusion. The methodological quality of each of the nine included articles was assessed using a valid and reliable checklist tool. Four articles were considered suitable for inclusion in meta-analysis, which was facilitated by Meta-DiSc (Clinical Biostatistics Unit, Ramón y Cajal Hospital, Madrid, Spain). Meta-analysis showed that the heterogeneity between the studies was too great to allow statistical pooling of data. There was a wide between-study variation in the proficiency of six well-documented ultrasound characteristics of adenomyosis to correctly identify the disease, despite an apparent similarity in the studies’ populations, interventions and outcomes. This systematic review has been unable to draw a concise conclusion about which ultrasound image characteristics are most reliable in the correct diagnosis of adenomyosis. Further research is required into the sonographic features of adenomyosis with much larger study groups to attempt to establish those features that could enhance the reliability of ultrasound image interpretation.