・Outcome and follow-up
The postoperative course was good, and the patient was discharged on the 16th postoperative day with a final histopathologic diagnosis of Stage I (pT2, N0 [0/12], M0) carcinoma of lower rectum, margins of resection clear. One month after the surgery, a recto-anal pressure test and rectal-anal sensation test were performed, the results of which were similar to those before the surgery, suggesting no problems. No obvious recurrence was observed 6 months after the surgery.
・Discussion
In recent years, ICG-guided surgery has gained popularity in the field of gastrointestinal surgery (4) given that it allows for enhanced real-time intraoperative visualization of anatomical structures, vascular perfusion, and lymph node navigation. To achieve the mentioned purposes, ICG has generally been administered intravenously. During gastrointestinal surgery, the intraoperative ICG navigation system is often used mainly for evaluating blood flow at the distal end of the gastrointestinal tract (5). Intraoperative ICG fluorescence imaging has been proven very useful for evaluating blood flow at the anastomotic site even during laparoscopic surgery for colorectal cancer, especially rectal cancer, and contributes toward reducing the risk of anastomotic leakage (5). During rectal cancer surgery, performing the dissection procedure at the appropriate pelvic layer is just as important as the evaluation of the anastomotic site condition (7). Appropriate nerve preservation with maximum consideration for lymph dissection is of course important; however, proper dissection of the pelvic floor muscles to preserve defecation function is also critical for future patient quality of life (8). In particular, surgery to preserve the anus of patients with lower rectal cancer requires preserving the appropriate pelvic floor muscles, with an emphasis on defecation function and curative surgery. ISR is the ultimate sphincter-preserving surgery for very low rectal cancers (7). We discussed how the ISR can help secure a proper dissection line and preserve the external anal sphincter. After examining ISR cases thus far, we found that it was important to smoothly connect the dissociated layer from the transanal approach to that from the transperitoneal approach (9). We believed that this problem could be solved by visualizing the dissected layer of the transanal approach from the abdominal cavity side and navigating via ICG intraoperative fluorescence imaging. A problem with this procedure is that ICG impregnated into the gauze exudes into the surrounding tissue where the gauze is placed, which makes distinguishing the dissociation layer becomes challenging. To address this problem, we mixed ICG with sodium arginine to make it viscous and then forcefully squeezed the gauze as much as possible to eliminate excess moisture. With this approach, the ICG could be visualized transabdominally without exuding into the surroundings. To the best of our knowledge, no reports have used ICG intraoperatively in this manner. Another merit of using this approach for ICG is that it is not administered intravenously, which potentially reduces allergic reactions and the burden on the patient’s body. Confirmation of the dissected layer via intraoperative fluorescence imaging with a gauze containing ICG seems to be applicable to other types of cancers aside from rectal cancer and may also be suitable for obese patients in whom identifying the dissected layer may be difficulty.
We herein reported a unique and advantageous method of using ICG during surgery. Nonetheless, more similar cases should be accumulated in order to establish a consensus on the treatment strategy.
・Declarations