Over-the-catheter endoscope replacement for stenting in patients with inaccessible malignant colonic obstruction with coexisting peritoneal carcinomatosis.

Although a large-caliber endoscope (LCE) is indispensable for through-the-scope placement of a self-expandable metallic stent (SEMS) in patients with malignant colonic obstruction (MCO), inaccessibility of the target obstructing lesion (TOL) by the endoscope is a significant cause of unsuccessful procedures. We herein present a novel salvage procedure when the TOL is not directly accessible by an LCE in conditions such as coexisting peritoneal carcinomatosis involving the colon. The salvage procedure, termed over-the-catheter endoscope replacement (OCER), starts with an ultraslim endoscope suitable for deep insertion beyond a tortuous colon for traversing a guidewire through the TOL. The ultraslim endoscope is then withdrawn and replaced by an LCE through the following steps. An endoscopic retrograde cholangiopancreatography catheter is preloaded in the LCE, the catheter alone is passed over the guidewire already traversed through the TOL, and the LCE is navigated over the catheter as far as possible toward the TOL to deliver the SEMS delivery system in a standard through-the-scope manner or further in an over-the-wire manner even if LCE insertion is incomplete. Among the 165 patients with MCO who underwent stenting during our study period, OCER led to successful procedures in all nine patients whose TOLs were initially inaccessible because of colon-involving peritoneal carcinomatosis. By utilizing the functions of distinctive endoscopes in a unique and complementary way, OCER can be a practical salvage option for challenging cases of MCO that are highly prone to unsuccessful palliation by conventional SEMS placement.