Study of fallopian tube anatomy and mechanical properties to determine pressure limits for endoscopic exploration

Falloposcopy is the endoscopic examination of the fallopian tubes, which are challenging to access due to their deep body location, small opening from the uterus, and lumen filled with plicae. We and others have developed endoscopes that are inserted through the uterus guided by a hysteroscope into the tubal ostium. To better understand how to utilize these endoscopes either as standalone devices or in concert with everting delivery balloons, a preliminary study of anatomy and mechanical behavior was performed ex vivo on porcine and human fallopian tubes. Segments of fallopian tubes from the isthmus, ampulla and infundibulum were inflated with saline either to bursting or held at sub-burst pressures with saline or a saline-filled balloon. Formalin fixed, paraffin embedded tissue sections stained with Masson's trichrome were examined for damage to the mucosa and muscularis. Porcine fallopian tubes tolerated saline pressurization at 15 psi for 1 minute without morphological damage. Balloon inflation to 15 psi caused no apparent damage to the muscle layer or rupture of the fallopian tube, but balloon movement within the tube can denude the mucosal epithelial layer. Human fallopian tubes averaged higher burst pressure values than porcine tubes. Under pressurization, the external tube diameter expanded by minimal to moderate amounts. Human and porcine tissues were similar in histological appearance. These studies suggest that moderate pressurization is acceptable but will not appreciably expand the fallopian tube diameter. The results also indicate that pigs are a reasonable model to study damage from falloscopy as seen in human tissue.