Remodeling of Colonic Self-Expandable Nitinol Stent Using Low Power Argon Plasma Coagulation: A Brief Report

Abstract

Approximately 10%–40% of patients with colorectal cancer, especially those with left side or rectosigmoid cancer, debut with an acute bowel obstruction, and the use of self-expandable metal stents has increasingly become a valid alternative to emergency surgery, primarily in the palliative setting [1].

However, there are a few situations in which colonic stenting may be less effective, such as colonic flexures or rectum resulting in a higher risk of migration or patient's intolerance.

In this case report, we present a colonic stenting in metastatic cancer, where the stent caused rectal discomfort that has been effectively managed by the use of argon plasma coagulation (APC) to trim the distal portion of the stent with a lower power than usually applied.

A non-resectable rectosigmoid malignant stenosis in a 75-year-old man was successfully managed by placing an uncovered single-wire self-expandable Nitinol stent.

We intentionally left ~15 mm of stent distal to the stenosis to prevent pressure decubitus on the healthy wall immediately downstream of the distal end of the neoplasm, precisely at the rectosigmoid junction.

A follow-up endoscopy performed a few weeks later, confirmed the successful resolution of the stenosis although with a slight distal stent displacement. The patient reported normal bowel movements but experienced remarkable discomfort in the rectal area. This pain intensified in a few months and became poorly tolerated by the patient.

Thus, a new rectosigmoidoscopy was performed and it evidenced a considerable contact area between the distal portion of the stent and the rectal wall.

We decided to cut a distal portion of the stent using APC technique.

We employed the ERBE VIO 200-D, set at a power of 50 W and a flow rate of 2 L/min, to perform the cutting was performed first sagittally, then longitudinally near the boundary with the neoplasm (Figure 1). Some fragments were removed with forceps as foreign bodies, while others remained in the rectum, and their softness facilitated their spontaneous expulsion.

The procedure was well-tolerated by the patient without any complications (Figure 2).

Subsequently, the patient's previously reported rectal symptoms disappeared and his bowel transit was always regular without tenesmus or rectal discomfort until his death 12 months after the stent implantation due to tumor cachexia.

The trimming of the distal portion of self-expandable metal stents has been previously described, primarily for biliary types [2]. Few cases have been reported involving stents rectosigmoid malignant stenosis [3-7], which were made of cobalt-chromium-nickel-molybdenum alloys or nitinol (nickel-titanium): Nitinol is a member of the shape-memory alloy, which, in turn, are part of the even broader category of Smart Materials. The particular feature of these materials is the ability to change their properties when subjected to specific stimuli due to their intrinsic characteristics. Furthermore, few reports evidenced the use of YAG laser in this biliary context [8]. In literature, the APC settings were used with a power ranging from 70 to 100 W (in the last ablation setting of nouvelle VIO 3) and with 0.8 to 2 L/min for flow.

In our case the nitinol stent that we easily trimmed by a power of 50 W with a flow of 2 L/min. We believe that this cut setting is safer, more precise, and controlled even if it is slower compared to the above-mentioned techniques. In particular, in our case, no thermal injury of the mucosa occurred (Video S1).

The partial trimming of the distal end of a self-expanding nitinol stent implanted in rectosigmoid stenosis is simple and safe, as previously described in the literature. Nowadays, the majority of colonic stents are made up of a single-wire nitinol alloy, and they are easily moldable by APC. Furthermore, it is not mandatory to remove the fragments by forceps, as they are spontaneously expelled without any complications.

In conclusion, this is the first report on the use of APC for stent trimming at lower power setting. Further reports are necessary to confirm and validate the efficacy and safety of this procedure with this novel setting.

Patient signed the informed consent for the colonoscopies and for the use of his data for scientific purpose. CARE guidelines were followed for this case report. Institutional ethical committee approval was not required.

The authors declare no conflicts of interest.