How does colorectal cancer present, and how does this differ between right colon, left colon, and rectum?

Clinical relevance. Recognising site-specific presentations (anaemia for right, obstruction/bleeding for left, tenesmus for rectum) speeds diagnosis.

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Presentation of colorectal cancer by site

The presentation depends on the tumour's location because of differences in luminal calibre and stool consistency.

Right (proximal) colon

• Wide lumen and liquid stool, so obstruction is late - presents with iron-deficiency anaemia, weight loss, fatigue, or a palpable mass.

Left colon

• Narrower lumen and formed stool, so change in bowel habit, rectal bleeding (often mixed with stool), and large-bowel obstruction.

Rectum

• Rectal bleeding (fresh, on/around stool), tenesmus, a sensation of incomplete emptying, and mucus.

Other

• About 20% present as emergencies (obstruction or perforation), with a worse prognosis.
• May present with metastatic disease (e.g. liver).