Special Surgery 17. Anorectal Tumors: Symptoms, Diagnosis, Treatment
I. Rectal Cancer
Definition and Etiology
- Rectal cancer: malignant tumor from epithelial lining of rectum
- Mostly adenocarcinoma
- Develops through adenoma-carcinoma sequence
- Risk factors:
- Low-fiber diet, fatty/red/processed meat
- Alcohol, smoking, obesity, type 2 diabetes mellitus
- IBD: ulcerative colitis, Crohn colitis
- FAP: APC tumor suppressor gene mutation
- Lynch syndrome / HNPCC: mismatch repair defect → microsatellite instability
Clinical Features
- Rectal bleeding, bright red or mixed with stool
- Change in bowel habits: constipation, diarrhea, alternating pattern
- Tenesmus / incomplete evacuation
- Mucus discharge
- Painful defecation, especially low tumors
- Iron-deficiency anemia from chronic bleeding
- Palpable rectal mass on DRE if low/mid rectum
- Weight loss, anorexia, pelvic pain in advanced disease
Diagnosis
- History and physical examination
- Digital rectal examination: palpable mass, distance from anal verge, mobility/fixation, sphincter involvement
- Colonoscopy + biopsy: gold standard
- CT colonography: alternative if colonoscopy incomplete, but cannot biopsy
- Labs: CBC for anemia; renal/liver function before treatment
- CEA: baseline and follow-up marker, not diagnostic
- MRI pelvis: best local staging test
- T/N stage
- Mesorectal fascia / circumferential resection margin
- Sphincter/levator involvement
- CT chest/abdomen/pelvis: distant metastasis staging
- Endorectal US/EUS: useful for early T1/T2 lesions and local excision planning
Staging
TNM
- Tis: carcinoma in situ / lamina propria
- T1: submucosa
- T2: muscularis propria
- T3: perirectal/mesorectal tissue
- T4a: visceral peritoneum
- T4b: adjacent organs/structures
- N0: no regional lymph node metastasis
- N1: 1-3 regional lymph nodes
- N2: 4 or more regional lymph nodes
- M1: distant metastasis
Stage Groups
- Stage 0: Tis
- Stage I: T1-2 N0
- Stage II: T3-4 N0
- Stage III: N+
- Stage IV: M1
II. Rectal Cancer Treatment
Treatment by Stage
- Stage 0-I: surgical resection
- Selected very early low-risk T1 tumors: transanal/local excision possible
- Stage II-III: neoadjuvant chemoradiotherapy → surgery with total mesorectal excision (TME) → ± adjuvant chemotherapy
- Stage IV: systemic therapy; palliative surgery/intervention for obstruction, perforation, bleeding or severe symptoms
Surgical Approaches
1. Transanal Excision
- Endoscopic/transanal local excision
- Selected early stage I, small (<3 cm), mobile low rectal cancers without suspicious nodes
- Unfavorable pathology → radical resection
2. High / Low Anterior Resection: Dixon Operation
- Removal of all/part of rectum with mesorectum
- Anastomosis between remaining left colon and rectum/anus
- Upper and middle rectal cancers; selected low tumors if sphincter can be preserved
- High anterior resection: anastomosis above peritoneal reflection
- Low anterior resection: anastomosis below peritoneal reflection
- Spare anal sphincter; temporary diverting ileostomy often used for low anastomosis
3. Abdominoperineal Resection: Miles Operation
- Removal of lower rectum, anal canal and sphincter complex
- Permanent end colostomy
- Indication: very low rectal cancer involving anal sphincters/levator or impossible safe sphincter-preserving margin
4. Hartmann Procedure
- Rectal/rectosigmoid resection + end colostomy + closed rectal stump
- Mainly emergency/high-risk cases: obstruction, perforation, unstable patient, unsafe anastomosis
Follow-Up
- CEA monitoring if initially elevated/useful
- Colonoscopy: metachronous cancer/polyps, anastomosis/local recurrence
- CT chest/abdomen/pelvis: metastasis surveillance according to stage/protocol
- DRE/endoscopy/pelvic MRI in selected high local recurrence risk or watchful follow-up situations
III. Anal Cancer
Definition and Risk Factors
- Anal cancer: malignant tumor of anal canal or anal margin
- Most common histology: squamous cell carcinoma
- Risk factors:
- HPV infection, especially 16 and 18
- Immunosuppression, e.g. HIV
- History of anal warts / condyloma
- Receptive anal intercourse, smoking
Clinical Features
- Rectal/anal bleeding
- Anal pain
- Tenesmus
- Perianal mass or ulcer
- Pruritus or discharge
- Palpable anal canal mass on DRE
- Inguinal lymphadenopathy
- Can be mistaken for hemorrhoids
Diagnosis and Treatment
- Inspection, DRE and palpation of inguinal nodes
- Anoscopy/proctoscopy + biopsy: diagnostic confirmation
- Labs: CBC for anemia; HIV/HPV-related disease assessment when appropriate
- MRI pelvis or endoanal US: local staging
- CT chest/abdomen/pelvis or PET-CT: nodal/distant staging and radiotherapy planning
- First-line treatment for most non-metastatic anal SCC: definitive chemoradiotherapy
- Nigro-type protocol: radiotherapy + 5-FU/capecitabine + mitomycin C
- High cure rate and sphincter preservation in many patients
- Surgery is reserved for persistent/recurrent disease after chemoradiotherapy or selected small anal margin lesions
- Salvage operation: abdominoperineal resection (APR/Miles) with permanent colostomy
IV. Benign Anorectal Tumors / Exam Summary
Benign Anorectal Tumors
- Rectal adenomas/polyps: may be asymptomatic or cause minor bleeding, mucus, tenesmus or prolapse
- Treatment: colonoscopic polypectomy, EMR/ESD, or transanal excision for selected rectal adenomas
- Radical resection if invasive cancer or high-risk malignant polyp features
- Anal condylomas: HPV-related warty lesions
- Giant condyloma / Buschke-Lowenstein tumor: extensive locally destructive lesion, high recurrence, possible malignant transformation
- Treatment of condylomas: topical therapy/ablation for small lesions; surgical excision for large or suspicious lesions
Exam Summary
- Rectal cancer is usually adenocarcinoma; colonoscopy + biopsy confirms diagnosis
- MRI pelvis is key for local rectal staging; CEA is for baseline/follow-up, not diagnosis
- Stage II-III rectal cancer: neoadjuvant chemoradiotherapy → TME surgery → ± adjuvant chemotherapy
- Dixon operation preserves sphincter; Miles/APR removes sphincter and creates permanent colostomy
- Anal cancer is usually SCC and HPV-related
- Anal SCC first-line treatment is chemoradiotherapy; surgery is mainly for persistent/recurrent disease