Chapter 8f
HAEMORRHOIDS
1. DEFINITION
Haemorrhoids are varicosities of the veins of the haemorrhoidal plexus, often accompanied by inflammation, thrombosis and bleeding with ICD 10AM Codes I84,022.4 and 0.87.2. There are external, internal and mixed haemorrhoids.
•Internal haemorrhoids develop above the dentate line and so are covered by simple columnar epithelium lacking sensory innervation.
•External haemorrhoids arise below the dentate line and so are covered by stratified squamous epithelium with innervation by the inferior rectal nerve.
•Mixed haemorrhoids are confluent internal and external haemorrhoids.
Internal haemorrhoids drain via the superior rectal vein into the portal system whereas external haemorrhoids drain via the inferior rectal vein into the inferior vena cava. Haemorrhoids basically are dilated arterio venous complexes. The pathophysiology is quite obscure but although many theories have been suggested, the vascular cushion theory of the origin of haemorrhoids is the best accepted. Anatomically there are anal cushions within the submucosa of the anal canal that contain blood vessels in the form of arterioles, venules, arteriolar-venous shunts together with muscle and connective tissue. These vascular cushions at the ano-rectal junction above the dentate line are anatomically normal and are present in adults, children and even in the embryo. The best explanation is that the distal displacement of these cushions by loss or weakening of the supportive tissue leads to the production of haemorrhoids which can prolapse, bleed or thrombose.
1334 Chapter 8 Haemorrhoids which prolapse at the anus and are irreducible (strangulated) may create a surgical emergency.
2. FREQUENCY
They are very common; the frequency is increased among whites and in persons of high socioeconomic status and in rural dwellers and there is no sex preponderance. They are seen most commonly in young and middle aged adults but the prevalence increases with age until the sixth decade and then slightly diminishes. The prevalence of haemorrhoids varies greatly in tt
various reports and in part depends upon the definitions employed. In Africa prevalences of about 20% and of 40% in western societies are quoted.
3. CAUSATION
The causation of haemorrhoids is not clearly understood and the data are confusing.
4. PREGNANCY
Pregnancy is well known both to initiate and aggravate the symptom of haemorrhoids particularly during labour. They may complicate 40% of pregnancies. They are less frequent after caesarean section and a large American study showed that 30% of women one month after delivery had haemorrhoids falling to 7.8% at twelve months whereas after a caesarean section the respective figures were 14% falling to 1.3%.
5. CONSTIPATION AND DIARRHOEA
A large prospective study (1) showed that constipation was not associated with haemorrhoids; Likewise, frequent laxative use was not associated. By contrast the subjective complaint of diarrhoea was significantly associated with haemorrhoids. There was a statistically significant trend with an increased haemorrhoid rate with increased frequency of diarrhoea from once per month to once per week or more. It is likely that constipation does not cause haemorrhoids but that hard stools may
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HAEMORRHOIDS 135 traumatise haemorrhoids to cause the characteristic red arteriolar bleeding of haemorrhoids.
6. PORTAL HYPERTENSION
Although it is traditional to regard haemorrhoids as a complication of portal hypertension, recent studies distinguish haemorrhoids - enlarged vascular channels with fibromuscular tissue - from the enlarged venous channels of portal hypertension: the distinguishing features are that if compression is applied and then released, varices rapidly refill (2).
7. SPINAL CORD INJURY
There is a significant association of haemorrhoids and spinal cord injuries (3).
8. PROSTATISM
Although a link is traditional, there are no epidemiological studies in support.
9. STRAINING AT STOOL
Increased internal and sphincter tone appear to be associated with the production of haemorrhoids (4).
10. G FORCES
There is anecdotal evidence of an increased prevalence of haemorrhoids in fighter plane pilots exposed to high G forces but no objective data in support : the subject cries out for investigation.
1336 Chapter 8 11. PRACTICAL IMPLICATIONS
In view of the paucity of data of any scientific value on the causation of haemorrhoids apart from pregnancy little help can be offered in terms of their prevention. Particularly in view of the high frequency of haemorrhoids in the population there is a significant field open to investigation.
References
1. Johanson JF, Sonnenberg A. The prevalence of hemorrhoids and chronic constipation: am epidemiological study. Gastroenterology 98,380-6 (1990).
2. McCormack TT, Bailey HR, Simms JM et al. Rectal varices are not piles. Brit. J. Surg.
171,163 (1984).
3. Delco F, Sonnenberg A. Associations between hemorrhoids and other conditions. Dis.
Colon. 41,1534-42 (1998).
4. Hancock BD. Internal sphincter and the nature of haemorrhoids. Gut 18,651-5 (1977).
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