Resectoscopic Metroplasty with Uterine Septum Excision: A Histologic Analysis of the Uterine Septum

Study Objective: To evaluate the histology of the uterine septum after its complete hysteroscopic excision. Design: Case series. Setting: Second Gynecological and Obstetric Unit and Pathological Anatomy Department of the University of Bari, Italy. Patients: Thirty-five patients aged between 25 and 41 years who were diagnosed with uterine septum by 3-dimensional ultrasound per the European Society for Human Reproduction and Embryology/European Society of Gastrointestinal Endoscopy 2013/Salim 2003 criteria. In addition, office hysteroscopy was performed to define the anatomy of the uterine cavity and to exclude the presence of other endometrial pathologic conditions. Interventions: Operative hysteroscopic septum resection was performed. The septum was initially incised with an “L-shape” bipolar electrode with a 5-mm bipolar mini-resectoscope (KARL STORZ SE & Co. KG, Tuttlingen, Germany). Then, using the bipolar loop, 2 triangles of the septum were excised in parallel, obtaining uninterrupted entire septum-long strips from the fundus to the apex of the septum. These strips were immediately removed from the uterus and reassembled in vitro to reconstruct a macroscopic, 3-dimensional structure of the septum for complete morphologic and histologic evaluations. Measurements and Main Results: Patients presented with an average body mass index of 24.8 kg/m2 and were all nulliparous. Histologic evaluation of the uterine septa showed a different conformation of the muscle bundles along the septum. Muscle cells in the apex and edges of the septum were arranged in nodules circumscribed by a thin area of collagen fibers. Medium-sized vessels were distributed in the collagen fibers around the muscle cells. Only few capillary vessels were present in the muscle nodules. This pattern was very similar to the cell arrangement in leiomyomas. In the core of the septa, near the base, the muscle bundles showed a linear course with concurrent collagen fibers and vessels. All the aforementioned characteristics were consistently present in every patient. On high-power histologic fields (200×), the muscle portion accounted for 48.3% ± 1.8% (mean, 6%) area in the apex and borders to 48.5% ± 1.3% (mean, 6%) area in the core. Collagen fibers accounted for 27.1% ± 1.1% (mean, 4%) area in the apex and borders to 26.7% ± 1.3% (mean 5%) area in the core. Conclusion: By removing the septum as a whole structure, this study allowed us to redefine the concept of the septum as a complex structure according to the islands of muscle fibers irregularly arranged in vertex, in a context of collagen tissue and similar to the structure of myomas. It appears to deeply involve the anterior and posterior uterine walls, resembling a “reverse letter H.”