A retrospective single-centre study investigating Onyx-18-only superior rectal artery embolisation for bleeding-predominant internal haemorrhoids demonstrated technical success across all nine performed procedures and complete cessation of rectal bleeding in all six treated patients at final follow-up. The research evaluated consecutive patients treated between October 2023 and April 2026, tracking clinical outcomes and procedure-level technical variables to assess the feasibility, safety, and durability of this liquid embolic approach.
While most reported techniques employ microcoils, particles, or combined regimens, ethylene–vinyl alcohol copolymer permits slow, controlled delivery under continuous fluoroscopic visualisation of cast progression and reflux, theoretical properties that may assist distal vessel occlusion but have not established the agent as a standard treatment for this condition.
The study cohort consisted of six consecutive patients comprising five men and one woman with a median age of 43 years, ranging from 24 to 80 years. Baseline severity according to the Goligher classification was grade I in one patient, grade II in two patients, grade III in two patients, and grade IV in one patient, with all six experiencing rectal bleeding either daily or several times per week prior to endovascular intervention.
Before undergoing embolisation, all patients received proctological evaluation and colonoscopy to rule out alternative luminal causes of bleeding, while individuals with portal hypertension or liver cirrhosis were excluded due to the distinct venous congestion mechanism underlying anorectal bleeding in portal hypertension. Regarding previous care, two patients had required medical iron therapy and one had undergone red blood cell transfusion, with three having received prior haemorrhoid-directed treatments including sclerotherapy, rubber-band ligation, or surgery, though none had undergone Doppler-guided haemorrhoidal artery ligation or transanal haemorrhoidal dearterialisation.
All endovascular interventions were performed via right common femoral arterial access followed by catheterisation of the inferior mesenteric artery, where digital subtraction angiography identified the superior rectal artery branches supplying the haemorrhoidal plexus. Interventional radiologists advanced a dimethyl-sulfoxide-compatible microcatheter superselectively into the target vessels and administered Onyx-18 slowly under continuous fluoroscopic monitoring without using adjunctive coils or particulate embolic agents.
Initial treatment protocols varied, with three patients receiving bilateral embolisation of both right- and left-sided superior rectal artery territories during their first session, while the remaining three patients received unilateral embolisation. Among the three patients initially treated unilaterally, two developed persistent or recurrent bleeding from untreated contralateral arterial supply that required staged contralateral embolisation, whereas none of the patients treated bilaterally at the outset required secondary embolisation.
Technical assessment confirmed satisfactory target devascularisation and radiopaque cast formation in all nine procedures, which had a median duration of 38 minutes ranging from 28 to 53 minutes. Fluoroscopy generated a median radiation dose of 838 mGy across a range of 267 to 2026 mGy, and the volume of administered Onyx-18 documented in six procedures showed a median of 1.6 mL ranging from 0.3 to 4.0 mL, with quantities from three early procedures unrecorded in procedural reports.
At the updated telephone follow-up conducted on 12 August 2026, all six patients reported complete freedom from recurrent rectal bleeding after completion of their treatment courses. The median follow-up duration from initial embolisation was 19.5 months, ranging from 4 to 34 months, with five of the six patients maintaining at least 12 months of post-procedural surveillance.
Safety assessments identified no major adverse events, non-target embolisation, or clinically evident tissue ischaemia throughout the follow-up period, although one patient experienced a transient episode of self-limiting rectal pain following bilateral embolisation. Additionally, three patients presenting with baseline Goligher grade III or IV disease subsequently underwent complementary surgical resection for residual or prolapsing tissue pedicles after bleeding had resolved, confirming that supplementary surgery was not prompted by recurrent haemorrhage.
The study authors highlighted several methodological limitations, including the retrospective single-centre design, the small sample size of six individuals, the absence of a control comparator, and an operator learning curve that accounted for the temporal shift toward initial bilateral treatments. Furthermore, internal iliac angiography was not routinely performed to assess potential middle rectal artery contributions, and validated longitudinal metrics such as the French Bleeding Score, formal quality-of-life questionnaires, and patient satisfaction surveys were not prospectively collected.
From a methodological and governance perspective, the investigation was organized as a retrospective service review conducted in strict adherence to the Strengthening the Reporting of Observational Studies in Epidemiology reporting framework. In accordance with institutional policy governing the evaluation of anonymized routine-care data, formal approval from an institutional ethics committee and individual patient consent to participate were not required for this clinical review. Additionally, the study documentation outlines explicit computational and editorial provenance, noting that the authors utilized OpenAI’s ChatGPT as a supportive tool for language editing, structural refinement, and formatting assistance. However, all underlying data, procedural metrics, anatomical interpretations, reference citations, and final textual phrasings were independently examined, verified, and approved by the clinical investigators prior to publication. Regarding data availability, the complete datasets generated and evaluated throughout the retrospective analysis remain restricted from public repositories to comply with institutional patient privacy policies and data protection regulations, though anonymized procedural records may be accessed from the corresponding author upon reasonable request and institutional authorization.
The mechanistic premise underlying endovascular occlusion of superior rectal artery branches aligns directly with the physiological principles that govern established surgical dearterialisation procedures. The investigators identify haemorrhoidal artery ligation and transanal haemorrhoidal dearterialisation as the closest surgical analogues to endovascular embolisation, as both surgical and catheter-based strategies share the identical foundational objective of curtailing arterial inflow to the hypervascular haemorrhoidal plexus. None of the patients in this cohort had previously undergone Doppler-guided haemorrhoidal artery ligation or transanal haemorrhoidal dearterialisation before receiving endovascular therapy. This inflow-reduction principle also provides a biologically plausible explanation for the distinct rebleeding patterns observed across the cohort. When patients received unilateral embolisation during their initial session, untreated superior rectal artery branches on the contralateral side continued to deliver arterial blood into the interconnected vascular plexus, thereby sustaining rectal haemorrhage and prompting staged secondary interventions. Conversely, treating bilateral territories simultaneously addressed the primary inflow pathways, preventing immediate rebleeding from untreated contralateral feeding vessels.
Despite the clear biological rationale supporting bilateral target occlusion, the researchers explicitly urge caution against inferring causal superiority for upfront bilateral embolisation over unilateral management. In their procedural analysis, the investigators emphasize that the chronological shift toward treating both right- and left-sided superior rectal artery branches evolved alongside expanding operator experience and procedural familiarity. Because the earliest endovascular cases were predominantly performed unilaterally while subsequent procedures incorporated bilateral catheterisation as technical confidence matured, this temporal evolution represents a classic operator learning curve rather than a controlled comparison between competing interventional strategies. Consequently, the observed association between bilateral embolisation and the avoidance of secondary staged procedures must be classified as hypothesis-generating rather than definitive evidence of clinical advantage. The investigators note that complete bilateral devascularisation appears beneficial primarily when both anatomical territories can be safely and superselectively catheterised, but prospective trials with standardized procedural assignments are necessary to isolate the true therapeutic effect from operator skill progression.
The technical characteristics of ethylene–vinyl alcohol copolymer distinguish this liquid agent from traditional mechanical and particulate embolic materials, offering specific handling dynamics within delicate pelvic vasculature. In particular, Onyx-18 permits an operator to pause and resume the slow injection process while maintaining continuous real-time fluoroscopic visualization, allowing precise observation of polymer precipitation, cast progression, and proximal reflux. Nevertheless, the study authors emphasize that these physical handling characteristics remain purely theoretical advantages. Because comparative clinical data pitting liquid polymers against conventional microcoils, particles, or combination regimens are currently lacking, existing evidence does not prove that Onyx-18 delivers superior clinical efficacy or greater procedural reliability than traditional embolic materials for haemorrhoidal disease.
The safety profile and clinical durability observed in this series also require critical contextualization within the broader literature on endovascular proctology. While no major adverse events, non-target polymer dispersion, or clinically evident tissue ischaemia occurred, aside from one transient episode of rectal pain after bilateral treatment, the investigators caution that uneventful outcomes in six patients do not establish procedural safety. Furthermore, the authors highlight that preliminary bleeding control must be interpreted cautiously, as recent evidence demonstrates that haemorrhoidal embolisation outcomes may decline over time. Because validated tools such as the French Bleeding Score, formal quality-of-life instruments, and patient satisfaction surveys were not prospectively collected, and routine internal iliac angiography was omitted, middle rectal artery supply was not systematically classified. Consequently, the authors conclude that prospective studies utilizing standardized bleeding instruments and comprehensive angiographic protocols are required before long-term durability or parity with surgical techniques can be confirmed.
Subject of Research: Onyx-only superior rectal artery embolisation for bleeding internal haemorrhoids
Article Title: Onyx-only superior rectal artery embolisation for bleeding internal haemorrhoids: initial single-centre experience
Article References: Loureiro, L., Almeida, P., Cardoso, S., Loffroy, R., & Machado, R. (2026). Onyx-only superior rectal artery embolisation for bleeding internal haemorrhoids: initial single-centre experience. CVIR Endovascular, 9(1), Article 116. https://doi.org/10.1186/s42155-026-00767-8
Image Credits: AI Generated
DOI: 10.1186/s42155-026-00767-8
Keywords: haemorrhoids, superior rectal artery, embolisation, Onyx-18, rectal bleeding, interventional radiology, endovascular procedures, Onyx-only, superior, rectal, artery, bleeding
News Source: Ophelia Keating. (November 7, 2026). Initial Study Finds Onyx Embolisation Controls Bleeding in Internal Haemorrhoids. Scienmag.
