If the blood clots were in the vein where her dialysis catheter
was, this can be a catheter-related thrombosis
, estimated to occur with as many as 8% of central lines.
If she was on dialysis because of a serious illness where she was bedridden for some period of time, she could have developed DVT in the legs because of inactivity. This is also fairly common (2-15% of pts with critical illness).