Use of Methotrexate in Gynecologic and Obstetric Practice: What the Radiologist Needs to Know.

Methotrexate (MTX) is the primary pharmaceutical agent that is used for management of disorders arising from trophoblastic tissue. Its widespread international use is mostly attributable to its noninvasive, safe, and effective characteristics as a treatment option for ectopic pregnancy (EP) and gestational trophoblastic disease (GTD), with the large added benefit of fertility preservation. Although the effects of MTX usage are well documented in the gynecologic and obstetric literature, there is a scarcity of radiologic literature on the subject. Depending on the type of EP, the route of MTX administration and dosage may vary. US plays an essential role in the diagnosis and differentiation of various types of EPs, pregnancy-related complications, and complications related to MTX therapy, as well as the assessment of eligibility criteria for MTX usage. A knowledge of expected imaging findings following MTX treatment, including variability in echogenicity and shape of the EP, size fluctuations, changes in vascularity and gestational sac content, and the extent of hemoperitoneum, is essential for appropriate patient management and avoidance of unnecessary invasive procedures. A recognition of sonographic findings associated with pregnancy progression and complications such as tubal or uterine rupture, severe hemorrhage, septic abortion, and development of arteriovenous communications ensures prompt patient surgical management. The authors discuss the use of MTX in the treatment of disorders arising from trophoblastic tissue (namely EP and GTD), its mechanism of action, its route of administration, and various treatment regimens. The authors also provide a focused discussion of the role of US in the detection and diagnosis of EP and GTD, the assessment of the eligibility criteria for MTX use, and the identification of the sonographic findings seen following MTX treatment, with specific emphasis on imaging findings associated with MTX treatment success and failure. Online supplemental material is available for this article. ©RSNA, 2021.