Systemic methotrexate treatment of interstitial pregnancy - Magnetic resonance imaging (MRI) as a valuable tool for monitoring treatment

Objective. Interstitial pregnancy occurs in 2-4% of ectopic pregancies and is defined as implantation of the trophoblast in the interstitial part of t he tuba uterina. Therefore the term intramural pregnancy can also be found in the literature. In 20% of the cases that progress beyond 12 weeks of ame norrhea a potentially life-threatening rupture of the uterus occurs, leadin g to a maternal mortality rate of 2.5%. According to the literature until a few years ago diagnosis was mainly made intraoperatively, and resulted in cornual resection or hysterectomy per laparotomy. Better methods of diagnos is and treatment of interstitial pregnancy can help to decrease morbidity a nd mortality associated with this condition. Patients. We describe two cases of interstitial pregnancies that were event ually diagnosed and also monitored by magnetic resonance imaging (MRI) afte r systemic methotrexate treatment. Both patients were uniparous and experie nced their second spontaneous pregnancy. Methods: Treatment consisted of fo ur doses (50 mg /m(2) body surface area) of systemic intramuscular methotre xate alternating with four doses (6 mg) of intramuscular folio acid. When b eta-hCG levels were undetectable, MRI results were compared with pre-therap eutic MRI findings. Results: In patients A and B, beta-hCG levels were undetectable 64 and 88 d ays after initiation of methotrexate treatment, while magnetic resonance im aging revealed nearly equally persisting interstitial pregnancies. They ini tially presented as hyperintense lesions with hypointense zones and changed into a hypointense lesion with a central hyperintense area for patient A, and a completely hyperintense lesion for patient B at the time of negative beta-hCG levels in follow-up MRI. Conclusion: Systemic methotrexate treatment with an intramuscular regimen i s effective in the treatment of interstitial pregnancy. MRI has the ability of correct tissue differentiation and objective three-dimensional measurin g of interstitial pregnancy. We therefore propose this imaging modality as a valuable tool for monitoring systemic methotrexate treatment of interstit ial pregnancy that should be used additionally to beta-hCG clearance curves .