We would like to draw attention to a useful radiological sign indicating that a percutaneous central venous catheter may be in the ascending lumbar vein. In our neonatal unit there have been two confirmed cases where the ascending lumbar vein had inadvertently been cannulated. In both these cases a loop in the line had been noted in the region of the ileo-femoral vein (see figs 1⇓ and 2⇓). This “looping” or bend in the line is also seen in the picture recently published by De,⁵ and in other papers.^1–,³

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Figure 1

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Figure 2

That this complication occurs almost exclusively on the left² has been attributed to the unique anatomy of the left ileo-femoral vein compared to the right.¹ We believe that the local anatomy of the left ileo-femoral vein may also explain why the line loops when inadvertently entering the left ascending lumbar vein (fig 3⇓). One can appreciate that, when the ascending lumbar vein is seen on the lateral¹ and lateral-oblique view,⁴ and compared with the anterior posterior view, the vein can be seen to descend into the pelvis and then enter the ascending lumbar vein at an angle. On an x ray the line will then project a loop or bend.

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Figure 3

 Reproduced with kind permission from British Journal of Radiology: RS Oeppen and K Tung. Retrograde venous invasion causing vertebral metastases in renal cell carcinoma. Br J Radiol2001;74:759–61OpenUrlAbstract/FREE Full Text.

Another factor that may contribute to the appearance of the loop or bend is that it is probably difficult to advance the line up the narrow ascending lumbar vein, and therefore when trying to thread the line to its calculated length the line will “buckle” at this point.

Any loop or bend of a contrast filled line in the left ileo-femoral region should be regarded as a sign that the line has entered the ascending lumbar vein and pull the line back because the lumbar venous plexus will not always be visualised with contrast. There are serious complications of an unrecognised malpositioned long line.² We feel that awareness of this radiological sign would facilitate early recognition and would prevent serious morbidity.