Skip to main content

Saturn Medic

Colorectal Cancer

Clinical Subject Page

Colorectal Cancer

Colorectal cancer (CRC) is a malignant tumor arising from the colon or rectum, most commonly developing from adenomatous polyps through the adenoma–carcinoma sequence. It is one of the most common cancers worldwide and is highly treatable when detected early

Also called

Colorectal Carcinoma

ICD-10

C19

Specialty

Gastroenterology

Onset

Chronic

Reviewed

July 2026

On This Page

Overview

Colorectal cancer develops through the progressive accumulation of genetic mutations that transform normal colonic mucosa into adenomatous polyps and eventually invasive carcinoma. Most tumors are adenocarcinomas. Patients may present with rectal bleeding, altered bowel habits, iron-deficiency anemia, abdominal pain, or bowel obstruction. Diagnosis is confirmed by colonoscopy with biopsy, and staging is performed using CT imaging. Treatment depends on the stage and typically includes surgery, chemotherapy, radiotherapy (for rectal cancer), and targeted or immunotherapy in selected patients.

Etiology & Risk Factors

Aetiology

Most colorectal cancers arise from adenomatous polyps through the adenoma–carcinoma sequence involving progressive genetic mutations.

Risk Factors

Non-Modifiable

  • Age >50 years

  • Family history of colorectal cancer

  • Familial adenomatous polyposis (FAP)

  • Lynch syndrome (HNPCC)

  • Personal history of colorectal cancer

  • Personal history of adenomatous polyps

  • Long-standing ulcerative colitis

  • Long-standing Crohn’s colitis

Modifiable

  • Diet high in red or processed meat

  • Low-fiber diet

  • Obesity

  • Physical inactivity

  • Smoking

  • Heavy alcohol consumption

  • Type 2 diabetes

Pathophysiology

Most colorectal cancers develop through the adenoma–carcinoma sequence. Progressive genetic mutations, including alterations in APC, KRAS, and TP53, transform normal colonic epithelium into adenomatous polyps, which gradually progress to invasive adenocarcinoma. As the tumor enlarges, it invades the bowel wall, spreads to regional lymph nodes, and may metastasize to distant organs, particularly the liver and lungs

Clinical Presentation

Symptoms

  • Rectal bleeding

  • Occult gastrointestinal bleeding

  • Iron-deficiency anemia

  • Change in bowel habits

  • Constipation

  • Diarrhea

  • Narrow stools

  • Abdominal pain

  • Bloating

  • Tenesmus (rectal cancer)

  • Weight loss

  • Fatigue

Signs

    • Pallor

    • Abdominal mass

    • Rectal mass

    • Hepatomegaly (liver metastasis)

    • Ascites (advanced disease)

    • Intestinal obstruction

    • Cachexia

History Taking

Ask about:

    • Rectal bleeding
    • Stool color
    • Change in bowel habits
    • Duration of symptoms
    • Abdominal pain
    • Weight loss
    • Fatigue
    • Symptoms of anemia
    • Family history of colorectal cancer
    • Personal history of polyps
    • Inflammatory bowel disease
    • Previous colonoscopy

Physical Examination

General Examination

Look for:

  • Pallor

  • Weight loss

  • Cachexia

  • Lymphadenopathy

Abdominal Examination

Assess for:

  • Abdominal tenderness

  • Distension

  • Palpable abdominal mass

  • Hepatomegaly

  • Ascites

Digital Rectal Examination (DRE)

Assess for:

  • Rectal mass

  • Blood on the glove

  • Rectal tenderness

  • Anal pathology

Other Examination

Look for:

  • Virchow’s node

  • Signs of liver metastases

  • Signs of bowel obstruction

Investigations

-Laboratory Tests

  • Complete blood count

  • Iron studies

  • Liver function tests

  • Renal function

  • Electrolytes

  • CEA (Carcinoembryonic antigen)

-Colonoscopy

Gold standard investigation

Allows:

  • Direct visualization

  • Biopsy

  • Detection of synchronous lesions

  • Polypectomy when appropriate

-Histopathology

Confirms:

  • Adenocarcinoma

  • Tumor grade

  • Histological subtype

-Imaging

CT Chest, Abdomen and Pelvis

Used for:

  • TNM staging

  • Detecting metastases

  • Surgical planning

MRI Pelvis

Preferred for:

  • Rectal cancer staging

  • Circumferential resection margin assessment

Endorectal Ultrasound

Useful for:

  • Early rectal cancer staging

PET-CT

Selected cases:

    • Suspected metastatic disease

    • Recurrent disease

Diagnosis

Early Disease (Stage I)

  • Surgical resection

  • Endoscopic resection for selected very early lesions

Localized Disease (Stage II–III Colon Cancer)

  • Curative surgical resection

  • Adjuvant chemotherapy for selected Stage II and most Stage III patients

Rectal Cancer

May require:

  • Neoadjuvant chemoradiotherapy or total neoadjuvant therapy

  • Surgical resection

  • Adjuvant chemotherapy when indicated

Metastatic Disease

Treatment may include:

  • Systemic chemotherapy

  • Targeted therapy

  • Immunotherapy (MSI-H/dMMR tumors)

  • Liver or lung metastasectomy in selected patients

  • Palliative surgery when necessary

Supportive Care

    • Nutritional support

    • Pain management

    • Stoma care

    • Psychological support

    • Palliative care for advanced disease

Home / Home / Clinical Cases / Gastrointestinal System Clinical Cases / Colorectal Cancer

Related Topics

Management

  • 1. Control Gastroesophageal Reflux

    • Give a proton pump inhibitor (PPI), usually once daily.

    • Increase to twice daily when reflux symptoms remain uncontrolled or during endoscopic treatment when indicated.

    • Encourage:

      • Weight reduction when overweight

      • Smoking cessation

      • Avoiding late meals

      • Elevating the head of the bed for nocturnal reflux

      • Avoiding individual reflux triggers

    Antireflux surgery is considered for persistent reflux despite optimized medical therapy, but it is not recommended solely to prevent cancer.

    2. Endoscopic Surveillance

    Non-dysplastic Barrett’s Esophagus

    • No immediate ablation is required.

    • Continue PPI therapy.

    • Perform periodic surveillance upper endoscopy with systematic biopsies.

    • Surveillance intervals are usually based on the length of the Barrett’s segment:

      • <3 cm: approximately every 5 years

      • ≥3 cm: approximately every 3 years

    Indefinite for Dysplasia

    • Confirm the diagnosis with an expert gastrointestinal pathologist.

    • Optimize acid suppression, often with twice-daily PPI.

    • Repeat endoscopy with biopsies after approximately 6 months.

    • Persistent indefinite dysplasia requires closer surveillance.

    3. Low-Grade Dysplasia

    • Confirm the diagnosis by a second expert gastrointestinal pathologist.

    • Endoscopic eradication therapy is generally preferred.

    • Endoscopic surveillance remains an alternative in selected patients after discussing risks and benefits.

    Common eradication treatment:

    • Endoscopic resection of visible lesions

    • Radiofrequency ablation of the remaining Barrett’s mucosa

    4. High-Grade Dysplasia

    • Refer to an experienced specialist or high-volume center.

    • Perform careful endoscopic assessment.

    • Remove visible or nodular lesions using:

      • Endoscopic mucosal resection

      • Endoscopic submucosal dissection in selected cases

    • Ablate the remaining Barrett’s epithelium, commonly with radiofrequency ablation.

    High-grade dysplasia should generally receive endoscopic eradication therapy because of its substantial risk of progression to adenocarcinoma.

    5. Early Esophageal Adenocarcinoma

    For superficial cancer limited to the mucosa:

    • Endoscopic resection of the cancer

    • Ablation of the remaining Barrett’s mucosa

    • Close surveillance afterward

    Esophagectomy may be required when there is:

    • Deep submucosal invasion

    • Lymphovascular invasion

    • Poor differentiation

    • Positive deep resection margins

    • Suspected lymph-node involvement

    • Disease unsuitable for endoscopic treatment

    6. Surveillance After Eradication

    Even after complete eradication of intestinal metaplasia:

    • Continue PPI therapy.

    • Perform scheduled surveillance endoscopy.

    • Carefully inspect the gastroesophageal junction and previous Barrett’s segment.

    • Biopsy suspicious areas because recurrence can occur.

Complications

  • Bowel obstruction
  • Bowel perforation
  • Gastrointestinal bleeding
  • Iron-deficiency anemia
  • Liver metastases
  • Lung metastases
  • Peritoneal metastases
  • Local recurrence
  • Cancer cachexia
  • Venous thromboembolism

Prognosis

  • The prognosis depends primarily on the TNM stage at diagnosis. Early-stage disease has an excellent prognosis following complete surgical resection, whereas metastatic disease has a significantly poorer outcome. Regular surveillance after treatment improves the detection of recurrence and new primary tumors.

Key Points / Clinical Pearls

  • Colorectal cancer usually develops from adenomatous polyps.
  • Adenocarcinoma accounts for over 90% of cases.
  • Rectal bleeding and altered bowel habits are common presenting symptoms.
  • Right-sided tumors often cause iron-deficiency anemia.
  • Colonoscopy with biopsy is the diagnostic gold standard.
  • CT is used for staging, while MRI is preferred for rectal cancer staging.
  • Surgical resection is the main curative treatment.
  • Chemotherapy, radiotherapy, targeted therapy, and immunotherapy are used according to disease stage.
  • Early detection through screening significantly improves survival.