Surgery chapters
Rectum: rectal cancer, prolapse and polyps
Surgical anatomy of the rectum, rectal polyps, rectal cancer (symptoms, spread, MRI staging, neoadjuvant treatment, anterior resection, TME and abdominoperineal excision), and mucosal and full-thickness rectal prolapse with their operations.
- Rectal cancer presents with bright red bleeding, tenesmus and early-morning bloody diarrhoea; most low tumours are felt on PR. Local staging is by MRI (circumferential margin, nodes).
- Treatment is total mesorectal excision by anterior resection when a sphincter-saving margin is possible, or abdominoperineal excision for very low tumours; chemoradiotherapy before surgery shrinks threatened tumours.
- Rectal prolapse: mucosal (children, under 4 cm, two layers) vs full-thickness (elderly women, concentric rings, weak sphincter); full-thickness needs rectopexy (abdominal) or Delorme/Altemeier (perineal).
On this page
Overview
The rectum is the last 12–15 cm of the large bowel, between the sigmoid colon and the anal canal. It is the commonest single site of large bowel cancer (about one-third of cases). Other surgical problems include polyps, prolapse, solitary rectal ulcer, proctitis and injury.
Bleeding per rectum must never be blamed on piles without examining the rectum.
Surgical anatomy
- Begins at about the level of the sacral promontory, where the taeniae coli spread into a complete outer longitudinal coat. No taeniae, haustra, appendices epiploicae or mesentery in the usual sense.
- Ends at the anorectal junction, where puborectalis slings around it, creating the anorectal angle (about 120° at rest).
- Three lateral curves with internal folds: valves of Houston.
- Divided into thirds: upper third covered by peritoneum front and sides; middle third in front only; lower third below the peritoneal reflection.
- Mesorectum: fatty envelope with vessels and lymph nodes, wrapped in the mesorectal fascia; removed whole in TME.
| Relation | Male | Female |
|---|---|---|
| Anterior (upper) | Rectovesical pouch, bladder | Pouch of Douglas, uterus |
| Anterior (lower) | Denonvilliers fascia, seminal vesicles, prostate | Rectovaginal septum, vagina |
| Posterior | Waldeyer fascia, sacrum, coccyx, presacral veins | Same |
| Lateral | Lateral ligaments with middle rectal artery, pelvic autonomic nerves, ureters | Same |
Blood supply and drainage
| Vessel | Origin | Notes |
|---|---|---|
| Superior rectal artery | Continuation of the IMA | Main supply; runs in the mesorectum |
| Middle rectal artery | Internal iliac | In the lateral ligaments; often small or one-sided |
| Inferior rectal artery | Internal pudendal (in Alcock canal) | Supplies the anal canal and sphincters |
- Superior rectal vein → IMV → portal system (hence liver metastases); middle and inferior rectal veins → systemic. This is a portosystemic junction.
- Lymph flows mainly upwards along the superior rectal vessels to IMA and para-aortic nodes. Low tumours can also spread laterally along the middle rectal vessels to pelvic side-wall nodes. Spread to groin nodes happens only if the tumour reaches the lower anal canal.
Lateral and inguinal node spread is the exception; upward spread is the rule. That is why the IMA is tied high.
Clinical assessment of rectal symptoms
- History: bleeding, mucus, change in bowel habit, tenesmus, pain, prolapse, incontinence, weight loss, family history.
- Digital rectal examination: tumours within about 7–8 cm of the anal verge can be felt; note mobility, fixation, distance from the sphincters.
- Rigid sigmoidoscopy and proctoscopy in clinic; flexible sigmoidoscopy; colonoscopy to examine the whole colon (synchronous lesions).
Rectal polyps
| Polyp | Key facts |
|---|---|
| Tubular / tubulovillous adenoma | Commonest polyp; risk rises above 1 cm |
| Villous adenoma | Soft, frond-like, may be huge; highest malignant risk; copious potassium-rich mucus → hypokalaemia, dehydration |
| Hyperplastic | Tiny (2–4 mm), pale, multiple, harmless |
| Juvenile polyp | Child; bright red "cherry" on a stalk; painless bleeding or prolapse; hamartoma with mucus-filled cysts; no malignant potential when solitary; often self-amputates |
| Inflammatory pseudopolyp | Colitis (UC), tropical infections |
| Serrated adenoma | Mainly right colon; alternative "serrated" route to cancer |
- Any rectal polyp → colonoscopy to find others.
- Remove for histology: snare polypectomy, endoscopic mucosal resection (lift with injected fluid; a cancer fails to lift), or transanal endoscopic microsurgery (TEMS) for large lesions.
Rectal cancer
Pathology and risk
- Nearly all are adenocarcinomas; signet-ring and mucinous types behave worse.
- Risks and genetics as for colon cancer (adenoma, FAP, Lynch, IBD, diet, age).
- Usually over 55 years, but young patients are often misdiagnosed as having piles.
Symptoms
| Symptom | Features |
|---|---|
| Bleeding | Earliest and commonest; bright red, with or separate from stool; easily confused with piles |
| Tenesmus | Feeling of incomplete emptying; typical of low tumours |
| Early-morning bloody diarrhoea | Passing blood and mucus ("bloody slime") on rising; spurious diarrhoea |
| Change in habit | Usually looser; rectosigmoid tumours may cause constipation |
| Pain | Late: invasion of sacral plexus, bladder or prostate |
| Weight loss, hepatomegaly, ascites | Advanced disease |
A patient over 50 with rectal bleeding plus a change in bowel habit needs urgent endoscopy. Never treat as piles without a rectal examination and sigmoidoscopy.
Spread
- Local: mainly circumferential (around the wall and into the mesorectum), little downward spread (a few centimetres at most). Anteriorly into prostate, seminal vesicles, bladder or vagina; posteriorly to sacrum.
- Lymphatic: upward along superior rectal vessels; lateral pelvic nodes for low tumours.
- Venous: liver most often, then lungs, adrenals.
- Transperitoneal from upper rectal tumours.
Investigations and staging
- Biopsy (sigmoidoscopy or colonoscopy) and colonoscopy of the whole colon (CT colonography if obstructed).
- CT chest, abdomen and pelvis for metastases.
- MRI pelvis: local staging of choice; shows T stage, circumferential resection margin (CRM) and nodes.
- Endoanal (endorectal) ultrasound: best for early (T1/T2) tumours being considered for local excision.
- CEA baseline.
Staging is by TNM (T1 submucosa, T2 muscularis propria, T3 through the muscle into perirectal fat, T4 other organs or peritoneum; N1 1–3 nodes, N2 4 or more). Dukes (A within wall, B through wall, node-negative, C nodes positive) is still asked.
Tumour within 1 mm of the circumferential (mesorectal) margin (CRM-threatened or positive) predicts local pelvic recurrence. It is the main reason to give neoadjuvant chemoradiotherapy.
Treatment principles
All cases are discussed by a multidisciplinary team.
| Situation | Treatment |
|---|---|
| Early T1 (and selected T2), favourable features | Local full-thickness excision (TEMS or transanal laparoscopic platform) |
| Upper rectum / rectosigmoid | High anterior resection with mesorectum taken at least 3 cm below the tumour |
| Mid and low rectum, sphincters can be saved | Low anterior resection with total mesorectal excision (TME), often with a temporary loop ileostomy |
| Very low tumour invading sphincters or levators | Abdominoperineal excision (APE/APR): rectum and anus removed, permanent end colostomy in the left iliac fossa |
| Frail, poor sphincters | Hartmann's operation (resection, end colostomy, closed rectal stump) |
| Threatened CRM or locally advanced | Long-course chemoradiotherapy (5-FU based, about 6 weeks), then surgery after a recovery interval |
| Lower-risk but node-positive, CRM clear | Short-course radiotherapy (5 days), then surgery soon after |
| Complete clinical response to chemoradiotherapy | "Watch and wait" surveillance in selected patients |
| Obstructing upper tumour, palliative | Stent or defunctioning colostomy |
- A sphincter-saving operation is usually possible if the lower edge is about 2 cm or more above the anorectal junction; a distal margin of at least 1 cm of clear bowel is acceptable with TME.
- Total mesorectal excision: sharp dissection in the "holy plane" around the mesorectal fascia, removing rectum, mesorectum and nodes intact. It sharply reduces local recurrence.
- The IMA is tied (high tie) and the splenic flexure mobilised so the anastomosis lies without tension.
- Stapled colon-to-rectum or coloanal anastomosis; a colonic J-pouch improves function after very low joins.
- Adjuvant chemotherapy for node-positive disease. Resectable liver metastases are removed in a specialist unit.
TME is the standard operation for mid and low rectal cancer. APR is reserved for tumours too low to save the sphincter.
Complications of rectal surgery
- Anastomotic leak (higher for low anastomoses, after radiotherapy; hence a defunctioning ileostomy).
- Pelvic autonomic nerve injury: sympathetic (hypogastric) → ejaculatory problems; parasympathetic (pelvic splanchnic) → erectile and bladder dysfunction.
- Low anterior resection syndrome: urgency, frequency, clustering, incontinence.
- Ureteric injury; presacral venous bleeding; perineal wound problems after APR.
- Local recurrence: pelvic pain, bleeding; found by CEA and CT/MRI follow-up.
The commonest site of large bowel cancer is the rectum, and most low rectal tumours can be felt with a finger, so a digital rectal examination is part of every assessment of rectal bleeding.
Overall 5-year survival is about 50%, strongly linked to stage and node status.
Rectal prolapse
| Feature | Mucosal (partial) prolapse | Full-thickness prolapse (procidentia) |
|---|---|---|
| Layers | Mucosa and submucosa only | All layers of the rectal wall |
| Length | About 1–4 cm | Over 4 cm, often 10–15 cm |
| Feel between finger and thumb | Thin, two layers of mucosa | Thick, double layer of the whole wall |
| Mucosal folds | Radial | Concentric rings |
| Sphincter | Usually normal | Patulous, weak; incontinence in about half |
| Who | Young children and adults with piles | Elderly women (about 6 times more than men), multiparous, chronic straining; also psychiatric illness, anorexia |
| Peritoneal pouch | No | A long prolapse holds a peritoneal sac in front that may contain small bowel |
Radial folds = mucosal; Rings = whole wall (concentric).
Causes
- Children: straight course of the rectum (sacral curve not yet formed), diarrhoea, malnutrition, worms (Trichuris), straining, cystic fibrosis (always consider a sweat test), Hirschsprung disease, polyps.
- Adults: weak pelvic floor, chronic straining and constipation, multiparity, previous anal surgery, neurological disease. Full-thickness prolapse starts as an internal intussusception of the rectal wall.
Treatment
Children (mucosal): usually conservative: treat the cause (diarrhoea, constipation, worms), teach parents to reduce it digitally. If it persists, submucosal injection (phenol in almond oil) or banding under anaesthesia.
Adults with mucosal prolapse: banding, injection, or excision of redundant mucosa.
Full-thickness prolapse: surgery is needed.
| Approach | Operation | Points |
|---|---|---|
| Abdominal (open or laparoscopic) | Rectopexy: rectum mobilised and fixed to the sacrum (sutures or mesh); ventral mesh rectopexy; resection rectopexy (with sigmoid colectomy if constipated) | Lowest recurrence; for fitter patients; risk of pelvic nerve damage (avoid in young men if possible) |
| Perineal | Delorme: strip the mucosa and plicate the muscle into a ring | For frail, elderly patients; regional anaesthesia; higher recurrence |
| Perineal | Altemeier: perineal rectosigmoidectomy (full-thickness excision and anastomosis) | Choice for incarcerated or strangulated prolapse |
| Perineal | Thiersch: wire or tape encircling the anus | Largely obsolete (sepsis, stenosis, obstructed defaecation) |
A mass coming out of the anus in a child may be an intussusception rather than a prolapse. In prolapse the mucosa is continuous with the perianal skin; in intussusception a finger passes into a groove between the mass and the anal wall.
Other rectal conditions
- Solitary rectal ulcer syndrome: young adults who strain; ulcer on the anterior wall about 8 cm from the anal verge; linked to internal intussusception; can look like cancer, so biopsy; treat with biofeedback, bulk, stop straining; rectopexy for some.
- Proctitis: ulcerative proctitis, infective (gonorrhoea, chlamydia, amoebiasis), radiation proctitis (bleeding after pelvic radiotherapy).
- Rectal injury: impalement, gunshot, foreign bodies. Intraperitoneal tears are repaired with a defunctioning stoma; extraperitoneal ones get a diverting colostomy, drainage and washout, with anaerobic cover.
Expect: where the rectum starts (taeniae spread out) and its blood supply (superior rectal from the IMA, middle from internal iliac, inferior from internal pudendal); Denonvilliers fascia in front; earliest symptom of rectal cancer (bleeding) and tenesmus; MRI for local staging and the circumferential resection margin predicting local recurrence; TME, anterior resection versus abdominoperineal excision; neoadjuvant chemoradiotherapy; villous adenoma with hypokalaemia; juvenile polyp in a child; mucosal versus full-thickness prolapse and the operations (rectopexy, Delorme, Altemeier); prolapse in children with diarrhoea, worms or cystic fibrosis.
Quick revision
- Rectum: no taeniae; main artery superior rectal (IMA); upward lymph spread.
- Cancer: bleeding first, tenesmus, morning bloody diarrhoea; feel it on PR.
- Colonoscopy + CT chest/abdomen/pelvis + MRI pelvis.
- CRM threatened → chemoradiotherapy first.
- Upper: anterior resection; mid/low: TME + low anterior resection + loop ileostomy; very low: APR with permanent colostomy.
- Villous adenoma: frond-like, mucus, hypokalaemia, highest malignant risk.
- Juvenile polyp: cherry-red, child, painless bleeding, benign.
- Prolapse: mucosal = radial folds, child, conservative. Full-thickness = concentric rings, elderly woman, rectopexy or Delorme.
Written by The House Job from standard references (Bailey & Love).
FAQ
What is the earliest symptom of rectal cancer?
Bleeding per rectum, usually bright red and painless. Tenesmus and early-morning passage of blood and mucus are also typical of low tumours.
Why is MRI used to stage rectal cancer?
It shows how far the tumour has spread through the wall, the involvement of nodes and how close it is to the mesorectal fascia (circumferential margin). This decides whether chemoradiotherapy is given before surgery.
What is the difference between anterior resection and abdominoperineal excision?
Anterior resection removes the rectum and joins the colon to the remaining rectum or anal canal, keeping the sphincters. Abdominoperineal excision removes the rectum and anus together and leaves a permanent end colostomy.
How is full-thickness rectal prolapse distinguished from mucosal prolapse?
Full-thickness prolapse is longer, feels thick between finger and thumb and shows concentric folds. Mucosal prolapse is short, thin and has radial folds.
Which operation suits a frail elderly woman with full-thickness prolapse?
A perineal operation such as Delorme's procedure, which can be done under regional anaesthesia. Fitter patients usually have an abdominal rectopexy, which recurs less often.