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Page 4 of 12 Funahashi et al. Mini-invasive Surg 2018;2:27 I http://dx.doi.org/10.20517/2574-1225.2018.28

with 5% povidone-iodine solution. Division of the rectum on the posterior side was then performed, taking
care to preserve the IAS as much as possible. The rectum was circularly incised, closing the cut end with an
interrupted suture, and the rectum (including the tumor) was mobilized proximally, exposing the levator
ani muscle. If the surgeon suspected tumor invasion into the dissected plane, the procedure was immedi-
ately converted to an APR. The rectum, including the mesorectum, was divided and mobilized up to the
peritoneal reflection on the anterior side and to the rectosacral ligament on the posterior side. The 10 o’clock
and 2 o’clock positions around the prostate were dissected on the abdominal part of the organ in order to
avoid excessive dissection around these positions that could cause nerve injury and result in sexual dys-
[17]
function .

In the abdominal portion of a laparoscopic SPR, a Lap Disc Mini (Hakko Co., Ltd, Chikuma-shi, Japan)
was adapted to the anal canal to maintain pressure during laparoscopy. A camera port was inserted into
the umbilicus via a trocar; moreover, an operative port was inserted into the mid-lower abdominal region,
and 2 additional operative ports were inserted into the left and right McBurney’s points. During routine
intra-abdominal exploration, gauze was placed on the dissected plane as a landmark that could be identi-
fied, through the peritoneum, from the anterior side of the rectum. The sigmoid and descending colon
were completely mobilized from the subretroperitoneal fascia to ensure that the subsequent coloanal
anastomosis was free of tension. The sigmoid colon and its mesentery were then removed, and the lymph
nodes around the inferior mesenteric artery were dissected using a harmonic scalpel; additionally, the in-
ferior mesenteric artery was ligated at a high level using an endoclip. Denonvillier’s fascia was dissected,
exposing, on the anterior side, the seminal vesicles and prostate gland in male patients and the posterior
wall of the vagina in female patients. The lower rectum and mesorectum were mobilized from the sacrum,
through the anus, on the divided plane between the visceral and parietal endopelvic fascia. The lateral
ligaments of the rectum and the neurovascular bundle were gradually divided, using a harmonic scalpel,
from the inner limit of the inferior hypogastric nerve fibers. The rectum, including the entire mesorectum,
was completely removed from the pelvic floor. The colon and rectum were extruded through the umbilical
wound and resected. A coloanal anastomosis was sutured transanally. Reconstruction was performed with
a J-pouch or coloplasty, if possible. Finally, a diverting ileostomy was created; this was reversed 6 months
after surgery. Although most parts of the procedure during the abdominal portion were performed by the
surgical staff of the division of colorectal surgery, the anal portion of the surgery was performed only by
the senior author (KF).

Definition of ISR
The ISR procedure partially or totally resects the IAS by dissecting the intersphincteric space. In this study,
we defined partial ISR as a one-third resection of the upper part of the IAS between the dentate line and
the intersphincteric groove, and we defined a massive ISR as a more than two-thirds resection between the
dentate line and the intersphincteric groove. We take care to preserve the IAS as much as possible during
division of the rectum. Rectal dissection beyond the dentate line with coloanal anastomosis was defined as
a conventional coloanal anastomosis (conventional CAA).

Functional assessment
Anorectal function following ISR or conventional CAA was measured using structured questionnaires at
regular intervals following closure of the diverting stoma. Patients answered questions on daily stool fre-
quency and the presence of fecal urgency (incapacity to restrain defecation for more than 5 min). We also
[18]
[16]
used the Wexner incontinence (WI) score , the low anterior resection syndrome (LARS) score , and a
survey assessing the patients’ satisfaction with their daily bowel-movement habits that employed a visual
analogue scale (VAS). Complete incontinence was defined as a WI score of 20. In this study, the ISR pa-
tients were divided into 2 groups: partial ISR and massive ISR.

Postoperative follow-up
After surgery, patients were followed in the clinic every 3 months to be monitored for cancer recurrence