Rectal neoplasms

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Rectal neoplasms refer to abnormal growths in the rectum, which can be benign (e.g., adenomas, hyperplastic polyps) or malignant (rectal cancer, most commonly adenocarcinoma).

Aetiology

Rectal neoplasms primarily arise from uncontrolled cell growth in the rectal mucosa due to genetic and environmental factors. The main types include:

  • Adenocarcinoma (90% of cases): develops from adenomatous polyps.
  • Neuroendocrine tumours: rare but aggressive.
  • Squamous cell carcinoma: uncommon, associated with HPV infection.
  • Benign neoplasms: includes adenomas and hyperplastic polyps.

Pathophysiology

  • Most rectal cancers develop via the adenoma-carcinoma sequence, where genetic mutations lead to malignant transformation.
  • Invasive cancers grow into the rectal wall and may spread via lymphatics or haematogenous routes.
  • Advanced disease can cause obstruction, perforation, or distant metastases.

Risk factors

  • Age >50 years.
  • Personal or family history of colorectal cancer or polyps.
  • Inflammatory bowel disease (e.g., ulcerative colitis, Crohn’s disease).
  • Obesity and sedentary lifestyle.
  • Diet high in red and processed meats.
  • Smoking and alcohol consumption.
  • Hereditary conditions (e.g., Lynch syndrome, familial adenomatous polyposis).

Signs and symptoms

  • Rectal bleeding: bright red blood or mixed with stools.
  • Change in bowel habits: persistent diarrhoea or constipation.
  • Tenesmus: feeling of incomplete evacuation.
  • Weight loss: unexplained and progressive.
  • Abdominal pain: usually in later stages.
  • Iron-deficiency anaemia: may indicate chronic occult bleeding.

Investigations

  • Blood tests:
    • Full blood count: may show anaemia.
    • Liver function tests: to assess for metastatic spread.
    • Carcinoembryonic antigen (CEA): tumour marker for prognosis and monitoring.
  • FIT (Faecal Immunochemical Test) stool test: detects hidden blood in stool, used for screening and risk assessment.
  • Colonoscopy with biopsy (gold standard): allows direct visualisation and histological confirmation.
  • CT colonography: alternative if colonoscopy is not possible.
  • MRI pelvis: used for local staging of rectal cancer.
  • CT chest/abdomen/pelvis: assesses for metastatic disease.

Management

1. Early-Stage Disease (Localised Cancer):

  • Endoscopic removal: for small, low-risk polyps.
  • Surgical resection (gold standard): total mesorectal excision (TME) via anterior resection or abdominoperineal resection (APR) if distal rectum is involved.

2. Locally Advanced Disease:

  • Neoadjuvant chemoradiotherapy: given before surgery to reduce tumour size.
  • Surgical resection: with lymph node dissection.

3. Metastatic Disease:

  • Palliative chemotherapy: e.g., FOLFOX (5-FU, leucovorin, oxaliplatin).
  • Radiotherapy: for symptomatic control.
  • Targeted therapy: EGFR inhibitors (cetuximab) if RAS wild-type.
GastroenterologymypanotesRectal neoplasms