Delayed diagnosis of a traumatic gluteal pseudoaneurysm with arteriovenous fistula and dual arterial supply mimicking a buttock abscess after a stab wound: a case report.

BACKGROUND: Traumatic arteriovenous fistulas (AVFs), with or without associated pseudoaneurysms, are uncommon complications of penetrating vascular injuries that may cause substantial morbidity and potentially fatal complications. Evidence is largely derived from case reports and case series, with important contributions from military experience. Delayed gluteal lesions may mimic a hematoma or abscess, creating a diagnostic pitfall.

CASE PRESENTATION: A 51-year-old male presented with a one-month history of a progressively enlarging painful left buttock mass following a stab wound that had been primarily sutured at a local hospital. Initial ultrasound suggested a hematoma, and the patient was admitted with a working diagnosis of "left buttock mass." Physical examination revealed a 7 × 7 cm fluctuant mass with tenderness but without overt signs of infection. Contrast-enhanced pelvic CT demonstrated a 6.8 × 3.2 cm intensely enhancing lesion within the left gluteus maximus with prominent feeding vessels, suggestive of an arteriovenous fistula or vascular malformation. Digital subtraction angiography confirmed a left gluteal pseudoaneurysm with an associated arteriovenous fistula supplied by branches of both the inferior gluteal and internal pudendal arteries, with early venous opacification. The patient underwent successful transcatheter embolization using fibered platinum coils and a cyanoacrylate-lipiodol mixture, with complete occlusion of the fistula confirmed on completion angiography. The patient recovered uneventfully and was discharged on postoperative day 2. At three-month follow-up, the patient reported no specific discomfort, and color Doppler ultrasonography showed a marked reduction in mass size with no detectable flow within the lesion.

CONCLUSION: Penetrating buttock trauma may cause a gluteal pseudoaneurysm with an associated AVF supplied by more than one internal iliac artery branch. Contrast-enhanced CT and selective angiography are important for recognizing the vascular lesion and delineating all feeding arteries. In this patient, embolization of both the inferior gluteal and internal pudendal arterial feeders achieved complete angiographic occlusion and a favorable clinical outcome, with a markedly smaller mass and no detectable intralesional flow on color Doppler ultrasonography at three months.