ICG is the most widely used uorophore in clini­cal practice. The compound is a heptamethine cyanine uorophore. It circulates bound to albu­min when injected intravenously, due to its hydrophobicity. The half-life in serum is 3–5min­utes [7], after which ICG undergoes biliary excre­tion. This uorophore has a peak excitation wavelength of 807nm and a peak emission wave­length of 822 nm [5]. Allergic reactions have been described, but the overall frequency is low (0.103%), and they are generally mild [8]. Hypotension may occur in 0.034% of patients. Due to ICG’s structure containing iodine, patients with previously documented iodine allergy (e.g. allergy to CT contrast) should avoid contact with ICG as there is considerable cross-reactivity.

to 91.6% of rectal cancers operated through this approach as demonstrated by the data submitted to the taTME registry [16]. The registry has cap­tured data on 1594 patients submitted to surgery through the transanal platform with a docu­mented leak rate of 15.7% [16]. Previous work has shown that a blood ow reduction in the rec­tal and colonic stumps was associated with an increase in AL [17]. Perfusion angiography using ICG offers a method of reducing this complica­tion and is currently the most studied application of uorescence in colorectal surgery. By assess­ing the proximal colonic transection point and the anastomosis itself in a more objective man­ner, perfusion can be optimized. Most data pub­lished to date has been on the effect of using PA for left-sided bowel resections, although data on right-sided resections has been accruing recently.

Perfusion angiography can be used at the point of bowel transection to identify where the bowel remains ischaemic. ICG is given intravenously and acts rapidly (often within a minute) allowing the surgeon to make an assessment of the bowel using the NIR equipment. A clear demarcation between perfused and non-perfused tissue is gen­erally evident and used as a guide for the proximal transection [11, 18, 19]. For left- sided resections, the proximal colon needs to be mobilized to achieve the adequate position for a tension-free anastomosis, and the conduit relies purely on per­fusion from the marginal artery [20]. It is plausi­ble that the need for more proximal bowel mobilization entails an increased risk of vascular insufciency that could lead to AL based on a vas­cular cause. This is a fundamental consideration when using a NOSE (natural orice specimen extraction) technique for colonic surgery – the favoured method of specimen extraction in taTME.A review has shown that transrectal spec­imen extraction when compared with open extrac­tion results in less pain, comparable operative time and length of hospital stay [21]. The degree of mobility required from the proximal colon is higher in this setting because it is necessary to consider enough extension to be able to transect the specimen extracorporeally through the anus. As demonstrated in Figs.35.1 and 35.2, the mar­ginal artery may be torn due to shear stress