FLuOrescence to Identify the Thoracic Duct During Oesophageal Resections

The thoracic duct is the largest vessel of the lymphatic system in the body. It transports chyle (a liquid containing both lymph and emulsified fats) from most of the body, including the gastrointestinal tract, into the left internal jugular vein. It is largely located in the thorax and is at risk of injury during the thoracic part of an oesophagectomy.

The reported incidence of thoracic duct injury during oesophagectomy is between 0.2 and 10.5%, although it may be under-reported in the literature. A review of prospective collected complication data from 292 consecutive oesophagectomies performed in Oxford over a 5 year period revealed a chyle leak rate of 9.9%. Chyle leak was associated in a doubling of median length of post-operative stay from 8 to 16 days in these patients. Chylothorax has been associated with a mortality of up to 30%.

Over the years, a number of attempts have been made to visualise chyle leakage following thoracic duct injury including administration of enteral fat containing feed (e.g. double cream), methylene blue and lymphoscintigraphy, but no studies have been published showing a mechanism to aid thoracic duct identification at the index operation, and so prevent injuries.

Fluorescence is a technique which uses fluorescent dyes (fluorophores) that emit invisible (near infra-red (NIR)) light when they are excited by light at a particular wavelength. In order to use this technique, a fluorescence-enabled camera is required in order to shine light at that particular wavelength on the fluorophore and to capture the light emitted. This is then displayed on a screen for the surgeon to see.

Indocyanine green (ICG) is a fluorescent molecule that is approved by the FDA (Food and Drug Administration) and the MHRA for use in humans. It is a widely used near infra-red dye for numerous operations. Near infra-red guided lymphatic mapping with ICG has gained much attention over recent years and its use has widely been published in breast and colorectal surgery. ICG has also been successfully used to identify the thoracic duct in a number of case reports in both adults and children.