In patients with Median Arcuate Ligament Syndrome (MALS), significant external compression of the coeliac artery (CA) by the median arcuate ligament (MAL) increasing mucosal ischemia (1,2) is assumed to cause chronic disabling postprandial abdominal pain, weight loss, and consequently lethargy and social deprivation (3,8). The majority of these patients have had a long medical journey before the diagnosis MALS is considered resulting in a substantial burden of disease and high healthcare and societal costs.

Although a Systematic Review have shown a sustainable symptom relief of 68% and a significant and durable improvement of quality of life after surgical treatment for MALS (4), there is still no (inter)national consensus on the existence and treatment of MALS (1, 5, 6, 7).

Two recent guidelines (3, 8) concluded that patients with MALS might be considered for surgical CA release (Recommendation 25 GRADE 2D; expert agreement 96%, Terlouw 2020). To end the ongoing debate and to enable the development of evidence-based guidelines for the management of MALS, both guideline committees recommend to perform a blinded, randomised controlled trial comparing a CA release with a sham operation. The proposed Coeliac Artery Release or Sham Operation study will either underline the usefulness of eCAR as a minimal invasive (cost)effective treatment for MALS or it will prohibit a meaningless intervention in patients with disabling abdominal symptoms.

If the CARoSO study proves that the treatment of MALS by eCAR is effective, to 490 patients with chronic disabling abdominal symptoms per year can be treated in the Netherlands. Effective treatment of MALS is expected to result in mean health gain of 6.05 Quality Adjusted Life Years (QALYs)/patient and has the potency to reduce the substantial productivity loss and healthcare consumption caused by MALS, resulting in a saving up to M€4.3/year. The outcome of the CARoSO study will be translated into strong recommendations in the coming updates of the relevant (inter)national multidisciplinary guidelines and will be adapted in daily practice.

The involved professions and the patient representatives unanimously recommend as primary endpoint for this study the proposed disease specific outcome measure: symptom relief measured on a VAS and PGI-I scale. This clinical outcome parameter can be reliable assessed within 6 months after the CA release (1, 9, 10). A two years follow up is suggested to extinguish the positive effect of attention in the diagnostic phase (11).

This study design allows for patient and observer blinding and for the sham group the eCAR approach is still feasible if the CARoSO outcome support this without applying additional scar tissue. A sham operation without skin incisions results in unblinding for the patient and the observer and thus undermines the basis of the evidential value of this study. There are no known cases where irreversible damage such as the intestinal infarction has occurred due to not treating this condition. Possible risks of not treating are continuous (pain) complaints and weight loss. The patients who undergo the sham operation and who still have complaints after unblinding of the study and proven effectivity of eCAR can still undergo the endoscopic AC release.

Inclusion Criteria:

• Patients with a consensus diagnosis of MALS based on a multidisciplinary discussion in the two Dutch expert centers for Mesenteric Ischemia (Medisch Spectrum Twente and Erasmus Medical Centre). The multidisciplinary team contains of a vascular surgeon, gastroenterologist, radiologist as recommended in the guidelines.
• Typical complaints: post-prandial pain and at least two of the following: dietary modification, unexplained weight loss, unexplained diarrhea.
• Eccentric stenosis of ≥70% of the AC at the medial arcuatum ligament, demonstrated by two imaging techniques (duplex, MRA, CTA or DSA), including at least an inspiration and expiration CTA with 1mm sections. (Definition percent stenosis according to ECST 1998 formula: % stenosis = (1 - [diameter at the site of stenosis/estimated original diameter at the site of the stenosis]) x 100).
• Ultrasound Abdomen without other more common abnormalities.
• Gastroscopy-duodenoscopy without abnormalities, unless appropriate for mucosal ischemia.

Exclusion Criteria:

• Patient not suitable for endoscopic AC release (e.g. previous surgery in the operating area).
• Pregnancy.
• Previous (endovascular) intervention of the visceral arteries.
• A significant stenosis in the superior or in the inferior mesenteric artery.

Patients are randomized in a 1:1 fashion (stratified on preoperative abdominal pain VAS, psychiatric comorbidities and gender) for either endoscopic Coeliac Artery Release (eCAR) or a sham operation.The randomization takes place in the operating room by a randomization program. Except for the surgical team, all care providers are blinded. To maintain the blinding, there will be no (substantive) contact between the members of the operating team and the patient postoperatively (or in follow up).

In the event of an emergency in a patient included in the CARoSO study envelopes will be 24/7 available to break the blind. Furthermore the study will be unblinded when the difference in effectiveness as described in the hypothesis is achieved for the primary outcome after the analyses on the 6 months outcomes (both primary and secondary) have been completed for all included subjects. This decision will be made by the Data Safety and Monotoring Board.