Objective Abdominal lymphatic malformations (ALM) are benign macro-, microcystic or mixed lesions that originate from defects in vascular development. Depending on size and location, clinical symptoms vary from asymptomatic to potentially life-threatening. Standardized diagnostic and therapeutic guidelines for ALM do not exist. Current literature focuses on imaging characteristics rather than symptoms for indication of invasive treatment strategies, including sclerotherapy and surgery. Sirolimus is evolving as a medical treatment option, while a watchful waiting approach for asymptomatic and low-risk ALM patients is not yet established as a conservative strategy. Methods We retrospectively characterized a multicenter cohort of 21 ALM treated 1996 - 2024. Items included clinical symptoms, imaging findings, and management strategies, including resection, sclerotherapy, sirolimus or a watchful waiting approach. Results ALM patients were categorized based on symptoms and lesion characteristics with potentially associated complications depending on lesion size and anatomical location: 9/21 (43%) patients were observed in the asymptomatic and low-risk group with regular clinical and radiological follow-up intervals. Acutely symptomatic (7/21; 33%), symptomatic or high-risk patients (5/21; 24%) underwent resection (10/21; 48%), sclerotherapy (1/21, 5%), or were treated with sirolimus (1/21, 5%). All patients had favorable long-term outcomes. Conclusions We developed a multidisciplinary diagnostic and therapeutic algorithm for ALM based on clinical presentation and lesion characteristics to ensure a standardized, yet patient-centered symptom- and risk-based approach for the most beneficial treatment and outcome. Importantly, our study is the first to demonstrate that watchful waiting is an adequate strategy for asymptomatic ALM patients with a low anticipated risk for complications. Validation of our proposed algorithm is warranted in a prospective study.

The authors have declared no competing interest.

This study was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, grant 458322953), and by the charity cycling tour Tour der Hoffnung and received funding from the German Federal Ministry of Education and Research (BMBF): EJPRD Joint Transnational Call 2023, NARRATIVE; FKZ 01GM2405.

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Ethics committee of the University of Freiburg, Faculty of Medicine gave ethical approval for this work.

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