[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Gastrointestinal tract](https://durgical.com/en/general-pathology/areas/gi/) › The anal canal: haemorrhoids, condyloma and anal carcinoma # The anal canal: haemorrhoids, condyloma and anal carcinoma - Lesion Swollen anal veins cause bright red bleeding; HPV can cause warts and, with high-risk types, cancer of the anal canal. Updated Nov 12, 2026 ## Key points - Haemorrhoids: straining with constipation and venous stasis of pregnancy are the main causes; also portal hypertension, where anorectal varices connect portal and caval systems. - Internal haemorrhoids (above the pectinate line) bleed painlessly; external ones hurt when they thrombose. - Bright red blood on the toilet paper: colon cancer must still be excluded. - Condyloma acuminatum: low-risk HPV (types 6 and 11). - Anal squamous cell carcinoma: high-risk HPV (type 16 above all); anal sex and HIV raise risk. - Basaloid tumours arise from immature cells of the transitional zone; they count as squamous carcinomas. ## What it is The anal canal has three zones: an upper zone lined by columnar rectal epithelium, a middle transitional zone and a lower zone of stratified squamous epithelium. Tumours mirror these linings: adenocarcinoma, squamous cell carcinoma and basaloid squamous carcinoma (the old cloacogenic carcinoma). Haemorrhoids are dilated collateral veins of the anal and perianal venous plexuses, caused by persistently raised venous pressure. ## Structure - Haemorrhoids: thin-walled dilated submucosal vessels, often with thrombosis, haemorrhage and recanalization. - Condyloma: papillary squamous proliferation with koilocytes. - Squamous cell carcinoma: nests of malignant squamous cells, often from anal intraepithelial neoplasia. - Basaloid carcinoma: small dark immature cells with peripheral palisading. ## Step by step - Venous pressure in the anal cushions rises (straining, pregnancy, portal hypertension). - Vessels of the haemorrhoidal plexus dilate and supporting tissue weakens. - Cushions slide down and bleed; thrombosis causes pain. - Separately, HPV infects the transitional zone; high-risk types integrate and inactivate p53 and RB. - Intraepithelial neoplasia progresses to invasive squamous carcinoma. ## Clinical notes - Haemorrhoids are rare under thirty except in pregnancy. - Anal varices of portal hypertension are more common and much less dangerous than oesophageal varices. - Distal anal cancers drain to inguinal nodes and systemic veins, bypassing the liver. ## Memory aid Above the line: painless bleeding and glandular tumours; below it: pain, squamous tumours and the groin nodes. ## Test yourself Think of the answer, then tap the question to see it. ## What is the main pathogenic factor in haemorrhoids? Persistently raised venous pressure in the haemorrhoidal plexus, mostly from straining at stool and pregnancy. ## Which virus is linked to anal squamous cell carcinoma? High-risk human papillomavirus, especially type 16. ## From which zone does basaloid (cloacogenic) carcinoma arise? From immature basal cells of the transitional zone of the anal canal. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/the-anal-canal-haemorrhoids-condyloma-and-anal-carcinoma/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Large intestine, appendix and anal canal](https://durgical.com/en/histology/large-intestine-appendix-and-anal-canal/) - [Hindgut and cloaca: the urorectal septum and the pectinate line](https://durgical.com/en/embryology/hindgut-and-cloaca-the-urorectal-septum-and-the-pectinate-line/) ## Connections ## Related 4 - [Oesophageal varices: portosystemic collaterals and why they bleed](https://durgical.com/en/general-pathology/oesophageal-varices-portosystemic-collaterals-and-why-they-bleed/) - [Colorectal adenocarcinoma](https://durgical.com/en/general-pathology/colorectal-adenocarcinoma/) - [Oncogenic viruses and H. pylori: the table to know](https://durgical.com/en/general-pathology/oncogenic-viruses-and-h-pylori-the-table-to-know/) - [Portal hypertension](https://durgical.com/en/general-pathology/portal-hypertension/) ## Related conditions 8 - [Haemorrhoids](https://durgical.com/en/conditions/haemorrhoids/) - [Anal cancer](https://durgical.com/en/conditions/anal-cancer/) - [Anal fissure](https://durgical.com/en/conditions/anal-fissure/) - [Human papillomavirus (HPV) infection](https://durgical.com/en/conditions/human-papillomavirus-infection/) - [Portal hypertension](https://durgical.com/en/conditions/portal-hypertension/) - [Anorectal abscess and fistula](https://durgical.com/en/conditions/anorectal-abscess-and-fistula/) - [Lower gastrointestinal bleeding](https://durgical.com/en/conditions/lower-gastrointestinal-bleeding/) - [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/) ## Microorganisms 1 - [Human papillomavirus](https://durgical.com/en/microbiology/human-papillomavirus/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Internal Hemorrhoid](https://www.ncbi.nlm.nih.gov/books/NBK537182/) (StatPearls (NCBI Bookshelf), 2025); [Anatomy, Abdomen and Pelvis: Anal Canal](https://www.ncbi.nlm.nih.gov/books/NBK554531/) (StatPearls (NCBI Bookshelf), 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/the-anal-canal-haemorrhoids-condyloma-and-anal-carcinoma/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/the-anal-canal-haemorrhoids-condyloma-and-anal-carcinoma/