Patent track sign
Native kidney biopsy for unexplained proteinuria.
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Sequential images from a native kidney biopsy. The lower pole was chose for the biopsy. After the needle was deployed and withdrawn, a "patent track" of color flow along the course of the biopsy indicates active bleeding. The patent track extends out into a small perirenal hemorrhage.
After two minutes of compression the kidney was re-imaged. The patent track was still present and the perirenal hemorrhage had increased slightly in size.
With 8 more minutes of compression, the patent track eventually closed and the size of the hematoma stabilized.
This case is a good example of the patent track sign: a color Doppler signal along the course of a biopsy, indicating that the track has not collapsed/coapted and that there is still active bleeding from the procedure. The track usually extends out of the biopsied organ into a surrounding hematoma, as in this case.