Rectal Cancer Surgery | Dr. Cai Sanjun (Colorectal Surgery) | CMCS Shanghai

About Dr. Cai Sanjun

Dr. Cai Sanjun is Director of Colorectal Surgery at Fudan University Shanghai Cancer Center — China's foremost oncology institution and one of the highest-volume colorectal cancer surgical centres in the country. He is a nationally recognised leader in laparoscopic colorectal oncology, sphincter-preserving surgery for ultra-low rectal cancer, and the integration of neoadjuvant chemoradiotherapy into multimodal rectal cancer management. Dr. Cai's practice is defined by the philosophy that a permanent colostomy is not an inevitable consequence of low rectal cancer — that with precise pre-operative staging, appropriately selected neoadjuvant therapy, and technically demanding intersphincteric dissection, the majority of patients with tumours within 5 cm of the anal verge can achieve both oncological cure and sphincter preservation. His department at Fudan University Shanghai Cancer Center has established one of China's most comprehensive colorectal oncology programmes, integrating high-resolution MRI staging, multidisciplinary treatment planning, laparoscopic total mesorectal excision, and structured pelvic floor rehabilitation into a unified care pathway.

Case Overview

Mr. James Harrington, a 52-year-old British financial executive based in Shanghai, presented with a three-month history of rectal bleeding and altered bowel habit. Digital rectal examination identified a firm mass approximately 4 cm from the anal verge. Colonoscopy confirmed an ulcerating tumour at 4 cm, and biopsy demonstrated moderately differentiated adenocarcinoma. High-resolution pelvic MRI staged the tumour as cT3N1M0 — a locally advanced ultra-low rectal cancer with a threatened circumferential resection margin (CRM). The multidisciplinary team led by Dr. Cai Sanjun recommended neoadjuvant long-course chemoradiotherapy (CAPEOX plus 50.4 Gy in 28 fractions) before surgical resection, both to downstage the tumour and to convert the threatened CRM to a clear margin — creating the conditions for sphincter-preserving surgery.

Following neoadjuvant therapy, MRI restaging confirmed significant tumour regression: the lesion reduced from cT3N1 to ypT2N0, the CRM converted from threatened to clear, and CEA normalised from 12.5 to 4.2 ng/mL. Dr. Cai performed laparoscopic intersphincteric resection (ISR) — dissecting the plane between the internal and external anal sphincters under direct vision, excising the internal sphincter with the tumour to achieve a clear distal margin while preserving the external sphincter and puborectalis muscle for continence. A hand-sewn coloanal anastomosis was constructed and a defunctioning loop ileostomy fashioned to protect the low anastomosis. Final pathology confirmed ypT2N0M0 (Stage II after neoadjuvant therapy), all 16 lymph nodes negative, and CRM greater than 2 mm. The patient was discharged on day ten and commenced structured pelvic floor rehabilitation at two weeks.

Patient Background

• Name / Nationality: Mr. James Harrington (pseudonym) — British; senior financial executive based in Shanghai; strong preference for sphincter preservation and avoidance of permanent colostomy
• Age / Sex: 52-year-old male
• Chief Complaint: Rectal bleeding and increased stool frequency (4–5 times daily) with tenesmus for 3 months; no prior investigation
• Family history: Father diagnosed with colon cancer at age 65 — first-degree relative history of colorectal cancer
• Past medical history: No hepatitis, no tuberculosis; no prior abdominal surgery
• Digital rectal examination: Firm mass palpable approximately 4 cm from the anal verge in the knee-chest position, involving approximately half the circumference of the rectal wall; blood on examining finger
• Tumour markers: CEA 12.5 ng/mL (elevated); CA19-9 within normal limits

Diagnostic Workup and Staging

Colonoscopy and Biopsy

• Findings: Ulcerating tumour at 4 cm from the anal verge, occupying approximately two-thirds of the luminal circumference
• Biopsy pathology: Moderately differentiated adenocarcinoma — confirmed primary rectal malignancy

High-Resolution Pelvic MRI — Critical Staging Findings

• Tumour location: Lower pole of tumour 3.5 cm from the anal verge (above the dentate line) — ultra-low rectal cancer by definition
• T stage: cT3 — tumour penetrating through the muscularis propria into the mesorectal fat; no invasion of adjacent organs
• N stage: cN1 — two enlarged mesorectal lymph nodes with malignant morphological features
• Extramural vascular invasion (EMVI): Negative — no tumour cells identified within mesorectal blood vessels; favourable prognostic indicator
• Circumferential resection margin (CRM): Threatened positive — tumour within 1 mm of the mesorectal fascia; direct surgery would carry high risk of CRM involvement and local recurrence
• Clinical stage: cT3N1M0 — Stage III; ultra-low location with threatened CRM

Staging CT (Chest and Abdomen)

• No hepatic lesions, no pulmonary nodules, no peritoneal deposits — distant metastasis excluded
• No retroperitoneal or inguinal lymphadenopathy

Dr. Cai's pre-operative assessment: The MRI tells us three things that define the entire treatment strategy. First, the tumour is 3.5 centimetres from the anal verge — this is the most challenging location in colorectal surgery. Second, the circumferential margin is threatened — if we operate now, the probability of a positive CRM is high, and a positive CRM means a local recurrence rate of 20 to 30 percent. Third, the patient has no distant metastasis and his EMVI is negative — this is a curable cancer. The question is not whether to cure it. The question is how to cure it while preserving the sphincter. The answer is neoadjuvant chemoradiotherapy first, then reassess. If the tumour responds — and in cT3N1 rectal cancer with no adverse features, the majority do — we will have a clear margin and a preserved sphincter. That is the goal.

Multidisciplinary Team Discussion and Neoadjuvant Strategy

The MDT convened by Dr. Cai Sanjun included colorectal radiology, radiation oncology, medical oncology, and pathology. The consensus recommendation was neoadjuvant long-course chemoradiotherapy followed by restaging MRI at six weeks and surgical resection if response was adequate — the standard approach for locally advanced rectal cancer with threatened CRM per ESMO and NCCN guidelines.

Neoadjuvant regimen: CAPEOX chemotherapy (capecitabine plus oxaliplatin) concurrent with long-course radiotherapy — 50.4 Gy delivered in 28 fractions over 5.5 weeks. The concurrent chemotherapy serves as a radiosensitiser, enhancing the local tumour response to radiation while providing systemic micrometastasis control.

Rationale for long-course over short-course radiotherapy: Long-course chemoradiotherapy (50.4 Gy over 28 fractions) produces greater tumour downstaging than short-course radiotherapy (25 Gy over 5 fractions) — a critical advantage when the surgical goal is sphincter preservation in an ultra-low tumour. The six-week interval between completion of radiotherapy and surgery allows maximum tumour regression before the resection is performed.

Restaging MRI — Six Weeks Post-Chemoradiotherapy

• Tumour regression: Significant reduction in tumour volume; residual lesion now 3 cm from the anal verge
• T stage: Downstaged to ypT2 — tumour confined within the muscularis propria on MRI
• N stage: Lymph nodes reduced in size; no nodes with malignant morphological features
• CRM: Converted from threatened to clear — tumour now greater than 2 mm from the mesorectal fascia
• CEA: Normalised from 12.5 to 4.2 ng/mL — biochemical response confirmed
• Tumour regression grade (MRI-TRG): Grade 2 — moderate response with residual tumour signal; surgical resection indicated

Dr. Cai's restaging assessment: The MRI response is exactly what we hoped for. The CRM is now clear. The tumour has downstaged from T3 to T2. The nodes have responded. This patient is now a candidate for intersphincteric resection — a procedure that would not have been safe or oncologically sound six weeks ago. The neoadjuvant therapy has done its job. Now it is our turn.

Operative Procedure

Anaesthesia and Positioning

Anaesthesia: General anaesthesia with endotracheal intubation. Epidural catheter placed for post-operative analgesia — reducing systemic opioid requirement and facilitating early mobilisation per ERAS protocol.

Positioning: Lithotomy position — simultaneous abdominal and perineal access without repositioning. This is essential for ISR, which requires coordinated abdominal laparoscopic dissection and perineal transanal dissection in the same operative session.

Phase 1 — Laparoscopic Abdominal Dissection and Total Mesorectal Excision (TME)

Abdominal exploration: Laparoscopic survey of the peritoneal cavity confirmed no peritoneal deposits, no hepatic surface lesions, no unexpected findings. The magnified laparoscopic view provided superior visualisation of the pelvic anatomy compared with open surgery — critical for the precise fascial plane dissection that defines TME quality.

Vascular ligation: The inferior mesenteric artery was divided at its origin from the aorta with preservation of the left colic artery — high ligation for adequate lymph node harvest combined with left colic preservation to optimise blood supply to the coloanal anastomosis.

TME dissection — the oncological foundation: Sharp dissection was performed in the embryological plane between the visceral mesorectal fascia and the parietal pelvic fascia — the holy plane of rectal cancer surgery. This plane, when correctly entered and maintained, allows complete en bloc removal of the rectum and its entire mesorectal envelope containing the regional lymph nodes, while preserving the pelvic autonomic nerves that control bladder function, sexual function, and defaecation.

Autonomic nerve preservation: The hypogastric nerves, the pelvic nerve plexus, and the neurovascular bundles of Walsh were identified and preserved under laparoscopic magnification throughout the posterior, lateral, and anterior dissection. Nerve preservation in ultra-low rectal cancer surgery requires meticulous dissection at the level of the levator ani — where the nerves are closest to the tumour and most vulnerable to inadvertent injury.

Dr. Cai's operative note: TME is not a technique. It is a discipline. The plane exists in every patient — it was defined by embryology, not by the surgeon. Our job is to find it and stay in it. When you are in the correct plane, the dissection is almost bloodless and the nerves are visible. When you are outside the plane, you are bleeding and you cannot see the nerves. The laparoscope shows you the plane more clearly than any open incision — the magnification reveals tissue planes that are invisible to the naked eye. That is why laparoscopic TME produces better CRM rates than open TME in experienced hands.

Phase 2 — Transanal Intersphincteric Dissection (ISR Core)

Perineal approach: With the abdominal dissection complete to the level of the levator ani, the perineal surgeon commenced the transanal component of the ISR — the defining technical step that distinguishes this procedure from conventional low anterior resection.

Mucosal incision at the dentate line: A circumferential mucosal incision was made just above the dentate line — the junction between the columnar rectal mucosa and the squamous anal mucosa. This incision enters the intersphincteric space: the anatomical plane between the internal anal sphincter (smooth muscle, involuntary) and the external anal sphincter (striated muscle, voluntary). The internal sphincter is the distal extension of the rectal circular muscle layer and must be excised with the specimen to achieve a clear distal margin in ultra-low rectal cancer. The external sphincter and puborectalis muscle — the primary determinants of voluntary continence — are preserved.

Intersphincteric dissection: Under direct vision, the intersphincteric plane was developed circumferentially — separating the internal sphincter from the external sphincter with sharp dissection. The dissection proceeded proximally until it met the abdominal dissection plane, completing the circumferential mobilisation of the specimen. Approximately 1 cm of the puborectalis muscle was included in the resection to ensure an adequate distal margin — a partial ISR technique appropriate for this tumour location.

Distal margin confirmation: The distance from the tumour lower pole to the distal mucosal incision was measured at 1.2 cm — exceeding the 1 cm minimum required for oncological adequacy in ISR.

Dr. Cai's operative note: The intersphincteric plane is the most demanding dissection in colorectal surgery. It is a narrow space — a few millimetres wide — between two muscle layers that must be separated without damaging either. The internal sphincter must come out with the specimen. The external sphincter must stay. If you damage the external sphincter, the patient will have permanent incontinence — a worse outcome than a colostomy. If you leave internal sphincter on the specimen side, you risk a positive distal margin. The margin between these two errors is measured in millimetres. That is why ISR requires not just laparoscopic skill but a thorough understanding of anorectal anatomy and years of experience in high-volume sphincter-preserving surgery.

Phase 3 — Specimen Extraction, Coloanal Anastomosis, and Defunctioning Ileostomy

Specimen extraction: The fully mobilised rectum and mesorectum were delivered transanally — avoiding any abdominal extraction incision and eliminating the associated wound pain, hernia risk, and cosmetic impact of a conventional specimen extraction site.

Coloanal anastomosis: The proximal colon was delivered to the perineum and a hand-sewn coloanal anastomosis constructed between the descending colon and the anal canal at the level of the dentate line. A hand-sewn technique was used rather than a stapled anastomosis — because the anastomosis is at the dentate line, below the reach of any circular stapler, and because the hand-sewn technique allows precise mucosal apposition at this critical level.

Defunctioning loop ileostomy: A loop ileostomy was fashioned in the right iliac fossa through a separate 3 cm incision — diverting the faecal stream away from the coloanal anastomosis during the healing period. Ultra-low coloanal anastomoses have a higher leak rate than standard colorectal anastomoses because of the limited blood supply at the dentate line level and the mechanical stress of the pelvic floor musculature. The defunctioning ileostomy converts a potential anastomotic leak from a life-threatening pelvic sepsis into a manageable wound complication — the single most important safety measure in ISR surgery.

Operative data: Total operative time 210 minutes; blood loss approximately 50 mL; one pelvic drain placed; no abdominal extraction incision.

Post-operative Course and ERAS Outcomes

ERAS Milestones

• Post-operative day 1: Urinary catheter removed; patient mobilised to chair; oral fluids commenced
• Post-operative day 3: Semi-liquid diet commenced; ileostomy functioning with gas and liquid output
• Post-operative day 7: Water-soluble contrast enema via the ileostomy confirmed no anastomotic leak; pelvic drain removed
• Post-operative day 10: Discharged with ileostomy bag; community stoma nurse follow-up arranged; ileostomy reversal planned for 3–6 months post-operatively

Pelvic Floor Rehabilitation

• Week 2 post-operatively: Structured pelvic floor rehabilitation commenced — Kegel exercises (anal sphincter contraction training) and biofeedback therapy to strengthen the external sphincter and puborectalis muscle before ileostomy reversal
• Goal: Achieve Wexner Continence Score of 8 or below (socially acceptable continence) before ileostomy reversal — ensuring the patient has adequate sphincter function to manage without the defunctioning stoma
• Rationale: Post-ISR continence depends not only on the preserved external sphincter anatomy but on the neuromuscular rehabilitation of the pelvic floor. Structured biofeedback therapy accelerates this rehabilitation by providing real-time electromyographic feedback during sphincter contraction exercises — training the patient to recruit the correct muscle groups and optimise squeeze pressure before the faecal stream is restored

Final Pathology

• Specimen: Total mesorectal excision specimen — complete mesorectal envelope intact; no surgical defects or perforations (TME quality Grade 1)
• Tumour: Residual invasive adenocarcinoma 1.2 cm × 0.8 cm — significant downstaging from the pre-treatment 4 cm mass
• ypT stage: ypT2 — tumour confined within the muscularis propria; no mesorectal fat invasion after neoadjuvant therapy
• Distal margin: Negative — clear
• Proximal margin: Negative — clear
• Circumferential resection margin (CRM): Negative — tumour greater than 2 mm from the mesorectal fascia; R0 resection confirmed
• Lymph nodes: 0/16 nodes positive — all 16 harvested nodes negative; complete nodal clearance
• Pathological stage: ypT2N0M0 — Stage II after neoadjuvant therapy; downstaged from clinical Stage III
• Tumour regression grade (pathological TRG): Grade 2 — moderate response; residual viable tumour with extensive fibrosis

Expert Commentary — Dr. Cai Sanjun

1. Neoadjuvant Chemoradiotherapy: Converting the Inoperable to the Curable

For ultra-low rectal cancer with a threatened circumferential resection margin, neoadjuvant chemoradiotherapy is not optional — it is the foundation of the entire treatment strategy. A positive CRM after direct surgery carries a local recurrence rate of 20 to 30 percent, regardless of how technically perfect the resection appears. Neoadjuvant therapy addresses this risk at its source: by shrinking the tumour away from the mesorectal fascia before surgery, it converts a threatened margin into a clear margin and transforms a patient who would have required abdominoperineal resection with permanent colostomy into a candidate for sphincter-preserving intersphincteric resection. In our centre's experience, 60 to 70 percent of patients with cT3N1 ultra-low rectal cancer achieve sufficient downstaging after long-course chemoradiotherapy to undergo ISR. The six-week interval between radiotherapy completion and surgery is not a waiting period — it is the period during which the maximum tumour regression occurs. Operating too early sacrifices the full benefit of the radiation response. The restaging MRI at six weeks is the decision point: if the CRM has converted to clear and the tumour has downstaged, we proceed with ISR. If the response is insufficient, we reassess the surgical options.

2. Intersphincteric Resection: The Technical Frontier of Sphincter Preservation

Intersphincteric resection is the most technically demanding procedure in colorectal surgery. It requires the surgeon to operate simultaneously in two anatomical planes — the mesorectal plane from above and the intersphincteric plane from below — and to join these two dissections precisely at the level of the levator ani. The margin for error is measured in millimetres: too close to the internal sphincter and the distal margin is positive; too close to the external sphincter and continence is permanently compromised. At Fudan University Shanghai Cancer Center, our ISR programme has demonstrated that with appropriate patient selection — tumours responding to neoadjuvant therapy, adequate sphincter muscle bulk on pre-operative MRI, and motivated patients committed to post-operative rehabilitation — the majority of patients achieve Wexner scores of 5 to 8, representing socially acceptable continence that allows normal daily activities without restriction. This outcome is not guaranteed by the surgery alone. It requires the complete pathway: neoadjuvant therapy to downstage, precise ISR to preserve the external sphincter, defunctioning ileostomy to protect the anastomosis, and structured pelvic floor rehabilitation to restore neuromuscular function. Each component is necessary; none is sufficient alone.

3. TME Quality: The Non-Negotiable Oncological Standard

Total mesorectal excision is not a surgical technique — it is an oncological standard. The mesorectum is the anatomical compartment that contains the primary tumour, the regional lymph nodes, and the lymphovascular channels through which rectal cancer spreads locally. Complete removal of the mesorectal envelope as an intact unit — without disruption, perforation, or incomplete excision — is the single most important determinant of local recurrence in rectal cancer surgery. A complete TME specimen with a clear CRM reduces local recurrence to below 5 percent in most series. An incomplete TME with a positive CRM carries a local recurrence rate of 20 to 30 percent regardless of adjuvant therapy. The laparoscope enhances TME quality by magnifying the fascial planes that define the correct dissection plane — planes that are difficult to visualise in the narrow male pelvis through an open incision. In our department, all rectal cancer resections are performed laparoscopically, and TME quality is assessed on every specimen by a dedicated colorectal pathologist using the Quirke grading system. Quality control of the specimen is as important as quality control of the operation.

4. Defunctioning Ileostomy: The Safety Net That Enables Ambition

The defunctioning loop ileostomy is the reason ISR is safe. Without it, a coloanal anastomosis at the dentate line — the lowest possible anastomotic level in colorectal surgery — carries an anastomotic leak rate of 15 to 20 percent, and a leak at this level causes pelvic sepsis, anastomotic stricture, and frequently the permanent colostomy that the entire operation was designed to avoid. With a defunctioning ileostomy, a leak becomes a manageable wound complication rather than a surgical catastrophe. The ileostomy is temporary — reversed at 3 to 6 months once the anastomosis has healed and the patient has completed pelvic floor rehabilitation. The reversal is a straightforward 45-minute procedure under general anaesthesia. The net result is a patient who avoids a permanent colostomy, achieves socially acceptable continence, and returns to full professional and social function. That outcome justifies the temporary inconvenience of the ileostomy without reservation.

How CMCS Shanghai Coordinated This Case

CMCS Shanghai supported Mr. Harrington from initial symptom presentation through ileostomy reversal planning, including: urgent coordination of colonoscopy and biopsy at Fudan University Shanghai Cancer Center with same-week appointment scheduling; bilingual review of colonoscopy findings and biopsy pathology with written summary for the patient and his family physician in London; specialist referral to Dr. Cai Sanjun with priority MDT scheduling; coordination of high-resolution pelvic MRI, staging CT of chest and abdomen, and tumour marker panel with results translation and clinical interpretation; bilingual interpretation throughout all MDT discussions, neoadjuvant therapy consent, and surgical planning sessions; coordination of CAPEOX chemotherapy scheduling and radiotherapy planning with the radiation oncology department; weekly bilingual updates during the five-and-a-half-week chemoradiotherapy course covering tolerability, side effect management, and nutritional support; restaging MRI coordination at six weeks with results communicated to the patient and his oncologist in the United Kingdom; real-time surgical updates to the patient's wife and his colorectal surgeon in London during the 210-minute ISR procedure; post-operative daily bilingual updates covering drain output, ileostomy function, anastomotic leak assessment, and discharge planning; stoma nurse coordination and ileostomy management education in English before discharge; pelvic floor rehabilitation scheduling including biofeedback therapy sessions with bilingual physiotherapy support; ileostomy reversal planning coordination at three to six months with pre-reversal contrast enema and surgical scheduling; and establishment of a long-term surveillance protocol with direct liaison between Dr. Cai's team and the patient's colorectal surgeon in London.

For international patients with rectal cancer, colorectal malignancy, or complex lower gastrointestinal disease requiring expert surgical evaluation in Shanghai, Dr. Cai Sanjun's team at Fudan University Shanghai Cancer Center represents colorectal oncological expertise at the international frontier — combining high-resolution MRI staging, neoadjuvant chemoradiotherapy, laparoscopic total mesorectal excision, and intersphincteric resection to achieve sphincter preservation and oncological cure in cases where permanent colostomy was previously considered inevitable. CMCS ensures that expertise is accessible: in the patient's language, with overseas physicians informed at every step, from the first diagnostic colonoscopy through long-term oncological surveillance.

This case report is de-identified and published for educational purposes. All clinical details have been anonymized in accordance with patient privacy standards. CMCS Shanghai is a medical concierge service and does not provide direct medical care.