Spray Coagulation (SprayCoag) is a noncontact thermoablative mode producing superficial tissue effects and operating on the same principles as Argon plasma coagulation (APC). Although SprayCoag has long been used for hemostasis in Surgery and dissection in ESD or POEM, its use in first-space endoscopy remains limited. A recent case series suggested that SprayCoag applied with a conventional polypectomy snare tip across different gastrointestinal locations may be a safe, economical, and less polluting alternative to APC (1). However, a major gap that should be filled is the lack of documented SprayCoag settings for first-space endoscopy.

We propose SprayCoag as an alternative to APC for ablating rectal angiodysplasias in chronic radiation proctitis (CrP). Accordingly, we conducted a single-blind randomized controlled trial using an ex-vivo porcine rectal model to identify the SprayCoag settings that most closely replicate APC-induced tissue effects. Intervention: Two electrosurgical units (ESU), the VIO-300D (Erbe Elektromedizin GmbH, Tübingen, Germany) and the ESG-300 (Olympus, Tokyo, Japan) were used for both APC and SprayCoag. APC was set according to recommended settings for CrP and SprayCoag was tested at 3 settings (effect/power): VIO-300D-Erbe: 2/50, 1/60 and 1/50; ESG-300-Olympus: 1/40, 2/30 and 2/40. All electrofulgurations were performed by the same endoscopist and tissue effects were blindly assessed by the same anatomopathologist. Main outcome measure: The tissue effects of SprayCoag.

Four rectums were included. For each rectum and generator, 3 APC and 3 SprayCoag electrofulgurations per setting were performed (N = 96).

VIO-300D-Erbe: APC produced mean thermal injury of 2.4mm (2.0-2.7) in diameter and 1.3mm (0.2-1.8) in depth, Volume: 2.0mm³ (0.3-2.8). These values were similar to SprayCoag-1/50: 2.6mm (2.2-2.8) in diameter and 1.4mm (0.7-2.0) in depth, Volume: 2.3mm³ (1.2-3.5), p=0.272 (95%CI -3.3-1.1), p=0.251 (95%CI -0.2-0.9), p=0.525 (95%CI -1.6-3.2), respectively. SprayCoag-2/50 and 1/60 caused significantly higher damage.

ESG-300-Olympus: APC produced injury of 2.3mm (1.8-2.6) in diameter and 1.2mm (0.3-1.7) in depth, Volume: 1.8mm³ (0.3-2.9) similar to SprayCoag-2/30: 2.5mm (1.9-2.8) in diameter and 1.2mm (0.9-1.8) in depth, Volume: 1.9mm³ (0.8-3.3), p=0.217 (95%CI -0.3-1.2), p=0.386 (95%CI -0.3-0.7), p=0.417 (95%CI -0.8-1.9), respectively. SprayCoag-1/40 showed a trend toward greater volume damage: 2.2mm³ (0.6-4.1), p=0.271 (95%CI -0.6-2.1) and a more erratic effect, 3/12 (25%) yielding no measurable injury. SprayCoag-2/40 produced significantly greater thermal damage in diameter and volume: 2.8mm (2.5-3.2), p=0.021 (95%CI 0.1-1.6) and 3.3mm³ (2.0-4.7), p=0.017 (95%CI 0.3-3.1), respectively. No electrofulguration reached the muscle layer.

SprayCoag 1/50 with the VIO-300D and SprayCoag 2/30 with the ESG-300 produce tissue injury comparable to APC and may therefore be suitable alternatives for the treatment of chronic radiation proctitis.