Makindo Medical Notes

Related Subjects: |Colorectal cancer |Colorectal polyps |Ulcerative Colitis |Acute Severe Colitis |Crohn's disease

🧪 Suspected colorectal cancer cannot be excluded without definitive investigation. Options include barium enema + rigid sigmoidoscopy, CT pneumocolon, or colonoscopy. CEA (Carcinoembryonic Antigen) is useful for monitoring recurrence but not for diagnosis.

📖 About

• 💡 A leading cause of cancer in older adults, arising from accumulation of genetic mutations in colonic epithelium.
• ➡️ Most colorectal cancers (CRC) evolve from adenomatous polyps (adenoma–carcinoma sequence).
• Exceptions: HNPCC (Lynch syndrome) and colitis-associated CRC.

⚠️ Risk Factors

• 👨 Male sex.
• 🍖 Diet: low fibre, high fat/red meat intake.
• ⬆️ Sporadic cases (~70%).
• IBD: Ulcerative colitis >10 years, Crohn’s colitis (long duration).
• Hx cholecystectomy (↑ bile salts).

👨‍👩‍👧 Familial Risk (10–30%)

• HNPCC (Lynch syndrome): 2–3% of cases.
• Familial adenomatous polyposis (FAP): <1%.
• Gardner’s syndrome / hamartomatous polyposis: rare (<0.1%).

🧬 Aetiology & Genetic Mechanisms

• 🍔 Dietary: low fibre, high fat.
• 🧪 Oncogenes: K-ras, c-myc activation.
• 🛑 Tumour suppressors lost: APC, p53, DCC.
• Mismatch repair defects: hMSH2, hMLH1 → Lynch syndrome.
• Classical sequence: Normal mucosa → Dysplasia → Adenoma → Adenocarcinoma.
• Right-sided tumours are typical in familial syndromes (FAP, HNPCC).

🔎 Pathology Types

• 🩸 Ulcerating → bleeding, anaemia.
• 🌱 Polypoid type.
• 🌀 Annular (“apple-core”) → obstruction.
• Diffuse / infiltrating / colloid (mucus-secreting).

🌱 Polyps & Malignancy Risk

• Histology: Villous > Tubulovillous > Tubular.
• Size: Larger = ↑ risk.
• Dysplasia: Higher grade = ↑ malignancy risk.

📊 Histological Grades

• Grade I – Well differentiated.
• Grade II/III – Moderately differentiated.
• Grade IV – Anaplastic.

📍 Tumour Location

• Rectum + Sigmoid: ~60%.
• Ascending colon: ~20%.
• Transverse/descending colon: ~20%.

📡 Spread

• Direct invasion up to 2 cm from margin.
• 🩸 Haematogenous: Liver (commonest), lungs, adrenals, kidneys, bones.
• 🌿 Lymphatic: Para-aortic, supraclavicular.
• Krukenberg metastases → ovaries.
• May seed surgical wounds/ports.

🧾 Clinical Presentation

• Rectal: PR bleeding, tenesmus, altered bowel habit, palpable mass.
• Left colon: Constipation, altered habits, blood, iron deficiency anaemia, sigmoid mass.
• Right colon: Occult bleeding → anaemia, weight loss, late obstruction.
• 🚨 Acute: Obstruction, perforation, peritonitis, massive bleed, fistula (e.g., colovesical).

🧪 Investigations

• Bloods: FBC (anaemia), ferritin, folate, B12, LFTs (ALP for liver mets).
• Imaging: USS, CT, MRI, CXR for staging; Endorectal US for rectal cancer.
• Endoscopy: Colonoscopy + biopsy = gold standard. Alternatives: barium enema, CT pneumocolon.
• Marker: CEA – not diagnostic but valuable for monitoring recurrence.

📑 Duke’s (Modified) Staging

🛡 Prevention

• Colectomy in FAP → markedly increases survival.
• Aspirin/NSAIDs may be protective in some patients.

🔧 Definitive Management

• Surgical resections vary by site: Right/Left hemicolectomy, sigmoid colectomy, anterior resection (rectal), abdominoperineal resection (low rectal → colostomy).
• Solitary liver mets may be resectable → potential cure.

💊 Chemotherapy

• 5-Fluorouracil + Leucovorin mainstay (esp. Dukes C, some Dukes B).
• Other agents: Oxaliplatin, Irinotecan, Cetuximab (EGFR inhibitor), Bevacizumab (VEGF inhibitor).

🤲 Palliative Care

• Palliative surgery for obstruction, fistulas, bleeding (e.g., colostomy).
• Radiotherapy mainly for rectal tumours (pain/bleeding control, pre/post-op to ↓ recurrence).

Cases — Colorectal Tumours

• Case 1 (Right-sided colon cancer): A 72-year-old woman presents with fatigue and progressive pallor. Bloods reveal iron-deficiency anaemia. She denies abdominal pain or change in bowel habit. Colonoscopy reveals a large caecal mass. Biopsy confirms adenocarcinoma. CT staging shows no metastases. Management: Right hemicolectomy performed with curative intent. Iron supplementation and physiotherapy started peri-operatively. Outcome: Recovery is uneventful; discharged after 7 days. Histology: T3N0. Enters 5-year surveillance programme.
• Case 2 (Left-sided colon cancer): A 64-year-old man reports 3 months of altered bowel habit (loose stools alternating with constipation), tenesmus, and fresh rectal bleeding. Colonoscopy shows a friable sigmoid lesion. Biopsies confirm moderately differentiated adenocarcinoma. CT chest/abdomen shows no distant disease. Management: Left hemicolectomy with primary anastomosis performed. MDT decides no adjuvant chemotherapy needed. Outcome: Bowel function improves post-surgery; patient remains disease-free at 2-year follow-up.
• Case 3 (Rectal cancer with local spread): A 58-year-old woman presents with rectal bleeding, mucus discharge, and change in stool calibre. Digital rectal exam reveals a palpable mass 5 cm from the anal verge. MRI pelvis shows locally advanced rectal cancer (T3 with nodal involvement). Management: Neoadjuvant chemoradiotherapy given to downstage tumour, followed by low anterior resection with protective ileostomy. Post-op adjuvant chemotherapy completed. Outcome: Ileostomy reversed at 6 months. No evidence of recurrence at 18 months, though bowel frequency remains increased.

Teaching Commentary 🧑‍⚕️

Colorectal tumours vary by site: • Right-sided → occult bleeding, anaemia, often bulky. • Left-sided → change in bowel habit, obstruction, bleeding. • Rectal → tenesmus, mucus, altered stool calibre. Diagnosis is via colonoscopy with biopsy and staging (CT/MRI). Management is surgical resection ± adjuvant chemo/radiotherapy depending on site and stage. Long-term surveillance is vital, as recurrence risk is highest in the first 2–3 years. Screening (faecal immunochemical test, colonoscopy) is key to early detection.