The cobweb sign: percutaneous silastic long line tip placement in tributaries of superficial veins.

We report a method for preventing misplacement of percutaneous silastic catheters in superficial vein tributary or venous plexus. Catheters inserted less than the length calculated by surface anatomy measurement due to resistance were studied in three patients. Contrast X-rays (Omnipaque, Nycomed Imaging AS, Oslo, Norway) of the catheters was performed to confirm the catheter tip placement position. On initial assessment, the catheter tip placement was thought to be satisfactory and infusion of TPN commenced. Following signs of extravasation, re-examination of the contrast X-rays demonstrated that multiple thin rays of omnipaque could be traced in different directions like a cobweb. In the third infant, we recognised the "cobweb" sign and prospectively withdrew the catheter tip 2 cm. Repeat contrast X-ray confirmed that the catheter tip was in a major superficial vein, infusion continued without further complication. We conclude that when the "cobweb" sign is noticed then the catheter should be removed or withdrawn 2 to 3 cm and repeat contrast X-ray performed..