## Epidemiology of Colorectal Cancer in India **Key Point:** The rectosigmoid region (rectum and sigmoid colon) accounts for approximately 60–70% of all colorectal cancers in India, making it the most common site. ### Anatomical Distribution | Site | Frequency in India | Global Frequency | Clinical Significance | |------|-------------------|------------------|----------------------| | Rectosigmoid (rectum + sigmoid) | 60–70% | 50–60% | Most common; presents with bleeding, tenesmus | | Caecum & ascending colon | 15–20% | 20–25% | Occult bleeding, anaemia; later presentation | | Transverse colon | 5–10% | 10–15% | Rare; often advanced at diagnosis | | Descending colon | 5–10% | 5–10% | Uncommon; stricturing pattern | **High-Yield:** The rectosigmoid predominance in India is attributed to: - Lower dietary fibre intake historically - Higher incidence of inflammatory bowel disease in this region - Genetic predisposition in certain populations - Chronic irritation from parasitic infections (historically) **Clinical Pearl:** Rectosigmoid tumours typically present earlier with visible bleeding and altered bowel habits, whereas right-sided (caecal) tumours present late with anaemia and abdominal mass. ### Why Rectosigmoid? 1. **Anatomical factors:** Narrower lumen, increased intraluminal pressure 2. **Longer transit time:** Increased mucosal contact with carcinogens 3. **Stasis:** Promotes bacterial overgrowth and secondary bile acid metabolism **Mnemonic:** **RECTUM FIRST** — Rectosigmoid cancers are the earliest-presenting and most-frequent colorectal malignancy in Indian populations.
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