NOTE: This article was first published in Summer 2020 in Issue 9 of our Kidney Matters magazine

Kidney Matters asked Karen Stevenson, a Consultant Renal Surgeon in Glasgow, if a patient’s weight influences her decision to perform transplant surgery.

In terms of weight and body shape, there are two main practical considerations we have to make as surgeons when we are assessing a person’s suitability for a kidney transplant. As technology develops and more surgery using robots is carried out, this may well change, but currently we need to ask ourselves two questions:

• Can we place adequate separation or retraction(1) to expose the iliac vessels (the blood vessels at the top of the leg) and bladder?
• Can we safely access the iliac vessels to place clamps to control them?

Getting a good view of that iliac vessel

The transplanted kidney’s (or graft’s) artery needs to be joined together (anastomosed(2)) to the external iliac artery and vein in the recipient. The iliac vessels lie just on top of the muscles of the back of the abdominal cavity. The small and large intestines lie in front of them. In order to access the iliac vessels, a cut or incision is made through the front of the abdomen. If a potential recipient carries a lot of weight around their abdomen the distance to their iliac vessels is greater and this makes the vessels more difficult to access.

Surgical safety rules!

We need to keep you safe. During surgery, we need to ensure that the placement of the retractors we need to use does not compromise other organ systems. Whenever we put retractors into your body, they increase the pressure on the respiratory system and this impacts upon your ability to breathe and get enough oxygen during an operation. The key is we must be able to anaesthetise you safely.

So, does a high BMI number really matter?

Although units vary, we don’t use a maximum body mass index (BMI) number to determine whether you are a suitable candidate for kidney transplantation. For us, it is more about the distribution of your weight and its impact on how safely we can perform the transplant.

You can have very different fat and body shape distributions. The most difficult to transplant is the patient with a significant abdominal girth, or the ‘apple shape’.

We are far less bothered by a significant BMI number than we are by a very apple-shaped person over, say, a ‘pear-shaped’ person, who may be large at the top or bottom but who does not carry the majority of their weight around their waist.

So, for us it’s not about the BMI numbers, it’s about your weight distribution and how safely we can anaesthetise you and perform the necessary blood vessel anastomoses.

There are other weight-related considerations. Being overweight in the period immediately post-transplant can make diabetes difficult to manage. We also know that re-admissions to hospital and wound complications are significantly higher in patients who have a BMI over 35. There is also some evidence that a high BMI is associated with early graft loss. So, if you have a BMI over 35 we would encourage you to consider these additional risk factors. But we would still be talking!

Getting the right dietary advice

Accessing the right weight-loss dietary advice is always easy for kidney patients. There is plenty of generic advice out there. But very little of this is suitable for kidney patients who are not able to eat many of the foods recommended in these diets, mainly due to their potassium or phosphate content.

Good access to NHS weight management advice is also variable across the UK, as is access to weight loss or bariatric surgery(3). Bariatric teams are often involved in the management of diabetes to try to regress the disease, but are not yet involved in large numbers in the management of people with kidney disease. This is an area we are starting to look at.

It’s a balancing act

A high BMI should really be used as an indicator of higher risks associated with transplant surgery. But these risks must also be balanced against the risk of not getting a transplant and remaining on dialysis.

NHS Live Well offers information and advice for adults and children about healthy weight, including how to find out if you’re a healthy weight using a BMI calculator.

Explanation of terms

1. A retractor is a surgical instrument used to separate the edges of a surgical incision or cut so that body parts (or veins) under the incision may be accessed.
2. Anastomosis (plural, anastomoses) is a connection or opening between two things that are normally separate, such as between blood vessels and the transplanted kidney.
3. Bariatric surgery, such as gastric bypass, gastric sleeve, and laparoscopic adjustable gastric banding, work by changing the layout of your gastrointestinal tract (stomach and digestive system).