・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