Sonographic signs of snakebite

Crotaline snakebites are routinely assessed with serial external examinations. We sought to correlate external findings with changes observed on ultrasound imaging.

This was a prospective, observational study of consecutive rattlesnake envenomation in patients treated at a single hospital in central California. Information recorded for each case included clinical data, gross external examination, and ultrasound images of tissue edema, localized fluid collections, and video footage of muscle fasciculations.

Thirteen patients were enrolled. Ultrasound imaging of the bitten extremity was consistent with external examination of the bitten limb. The most common sonographic finding was subcutaneous tissue edema. Edema and necrosis in 3 patients with rapidly progressive leg swelling spared the deeper muscle layers and fascial planes. In 2 patients with bites on the fingers, edema and tendon involvement were readily visualized using a water-bath technique (placement of the hand in a pool of water, allowing more detailed examination of the tissue planes).

Ultrasound imaging may allow for a more complete understanding of the local effects of snakebite. We were also able to document normal deeper muscle integrity in cases with diffuse leg edema. More studies are needed to fully elaborate the strengths and limitations of bedside ultrasound as a diagnostic adjunct in envenomation assessment.