CT angiograms have had a huge impact on the way in which we perform DIEP flaps. By providing a clear idea of the position and quality of vessels in every case, I order CT angiography for DIEP flaps make my operations faster and safer.

I was recently sent an email from a lady who had seen several other surgeons, asking me for advice.

One of the concerns this lady had was how likely it was that the surgeon (not me) would end up having to take muscle with an abdominally-based free flap.

The answer to that question depends on several issues. As I didn’t know the other surgeons involved, the chance of muscle being taken is often entirely dependent on how comfortable the surgeon is with perforator dissection techniques. And this is directly related to the number of DIEP flaps a surgeon has raised. But for me, I make my decision before an incision is ever made.

The decision is based on the CT scans that are performed as part of the pre-operative work-up. This usually involves the patient having a specialised CT scan, called a CT angiogram, several days before the procedure. A dye which can be detected by the CT scanner is injected into a vein, and this then circulates through the body into both the arteries and veins. Images are captured and can be used to create a detailed map of where the best perforating blood vessels pass through the muscle, into the fat and skin of the abdomen. If my radiologist is feeling friendly, the raw data can actually be used to create complicated 3D images which will offer me precise co-ordinates for the position of these perforating vessels, as well as the pattern of branching of the main artery. I can, using these images, determine exactly how and where I will chase these vessels when raising the DIEP flap.

Forgive my amateur image modifications, but this is a basic CT angiogram from one of my patients. The way to look at this is to imagine that you have been cut (like a loaf of bread) into thin (perhaps 1-2mm thickness) slices, and then one of those slices is laid out for us to look at. This slice passes just under the umbilicus, and I have made a few highlights to help:

1. The yellow outline shows the rectus muscles at the front of the abdomen
2. The green line shows the area of fibrous tissue that has stretched between the two muscles (this is “divarication”)
3. The blue lines show the lower edge of the umbilicus (the “tummy-button”)
4. And the red arrow shows our target, a perforating blood vessel passing through the rectus and into the fat and skin. This is the vessel I chose to chase through the muscle, and down into the groin so that I could disconnect the flap and transfer it to the chest for the microsurgery.

The benefits are (I hope) obvious. The procedure is safer, because I know where my target is and I can work methodically towards that without having to stop and check (and guess) at every vessel I come across which emerges from the muscle. For the very same reason, the procedure is faster. If I don’t have to deliberate unnecessarily, then I can be more efficient in raising the flap. And the CT is also a fantastic communication tool that I can use to reassure (and educate) my patients pre-operatively. It seems that knowing that there are good quality blood vessels available for the surgery is a major relief for many women.

“CT scans have been shown to make DIEP flap harvest safer and faster.”

There is a cost involved in having the CT scan done, but it isn’t large. And we have studies to suggest that if it saves me only 20 minutes in the operating theatre, then the costs are recouped. I suspect also that having a CT scan showing a good quality perforator means that there is a lower chance that muscle will be (needlessly) harvested with the flap, which may well translate into reducing the problems with bulge or weakness that can crop up after abdominal flaps are raised.

So, for me, ordering CT scans are a routine part of preparing my patients for this kind of surgery.

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