Ultrasound detection of microembolic signals in hemodialysis accesses

Microembolic signals (MES) detected by ultrasound, thought to be of gaseous or solid origin, have been described with decompression illness and in the intracranial and cardiopulmonary circulation. We describe the first reported cases of MES occurring in hemodialysis accesses. Two hemodialysis patients, one with a synthetic graft and one with an arteriovenous fistula, showed MES during a dialysis session detected by duplex ultrasound. We postulate that these MES represent cavitation bubbles developing from turbulent blood flow around the venous needle in the access. However, other potential causes exist, including air introduced into the circulation from the dialysis circuit or microemboli arising from thrombus or atheroma.