Segmental Arterial Mediolysis Associated with Renal Allograft Artery Dissection and Thrombosis During Kidney Transplantation

Background: Segmental arterial mediolysis (SAM) is a rare, non-inflammatory, non-atherosclerotic, non-hereditary arteriopathy of unknown etiology that typically affects medium-sized visceral arteries. The absence of reliable diagnostic criteria poses a significant challenge. Consequently, the diagnosis of SAM should be considered in the setting of a distinctive combination of clinical features, angiographic findings, and histopathology. Renal artery involvement is uncommon, and its occurrence in the donor graft during kidney transplantation (KT) has not previously been reported. Case presentation: We report the case of a kidney graft from a deceased donor in her seventh decade of life, transplanted into a recipient in her seventh decade of life. Donor–recipient ABO compatibility was confirmed, and both complement-dependent cytotoxicity crossmatch and flow cytometry crossmatch were negative. Cold ischemia time was 14 h, and warm ischemia time was 20 min. Immediately after declamping, massive thrombosis of the graft renal artery was observed and confirmed using an intraoperative flowmeter. The arterial anastomosis was taken down, the thrombus was removed, the artery was flushed with heparin, and the anastomosis was reconstructed using interrupted sutures. Despite revision, no arterial flow was detected, and the graft was deemed unsalvageable and explanted. Histopathological examination showed thinning of the tunica media, reduced smooth muscle cells on desmin staining, medial-adventitial dissection, and occlusive thrombosis, findings considered likely attributable to SAM. Conclusions: This case suggests that occult donor arterial wall disease compatible with SAM may present catastrophically during KT and may lead to immediate graft loss despite standard surgical salvage attempts. Although no validated strategy currently exists to screen for or prevent occult SAM in asymptomatic donors, awareness of this entity may assist transplant surgeons and pathologists in the evaluation of unexplained early graft arterial thrombosis, donor-graft vascular pathology, and communication with centres receiving paired organs from the same donor.