Internal haemorrhoids are found in the right anterior, right posterior and left lateral positions within the anal canal. This was originally thought to be due to the terminal branching of the superior mesenteric artery, however recent studies have refuted this. The position of haemorrhoids within the anal canal however remains remarkably consistent.
Haemorrhoids can be divided into those originating above the dentate line, which are termed internal; those originating below the line are termed external. External haemorrhoids or piles are rarely symptomatic unless a thrombus builds up in the plexus.
Haemorrhoids are thought to represent engorgement or enlargement of the normal fibro-vascular plexus cushions lining the anal canal. It has been postulated that chronic straining secondary to constipation, gas passing or diarrhoea results in a pathologic response in haemorrhoids.
Internal haemorrhoids are classified by history and not by physical examination.
Grade I – bleeding without prolapse
Grade II – prolapse with spontaneous reduction
Grade III – prolapse with manual reduction
Grade IV – incarcerated, irreducible prolapse
This system has been in place for many years and correlates relatively well with treatment algorithms (ie Grade I and II haemorrhoids are often successfully treated by non operative means while Grade III and Grade IV haemorrhoids are more likely to require surgery).