Page 597 - Textbook of Pathology, 6th Edition

MISCELLANEOUS LESIONS Haemorrhoids (Piles) 581

Diverticulosis Coli Haemorrhoids or piles are the varicosities of the haemorrhoi-
dal veins. They are called ‘internal piles’ if dilatation is of
Diverticula are the outpouchings or herniations of the mucosa superior haemorrhoidal plexus covered over by mucous
and submucosa of the colon through the muscle wall. membrane, and ‘external piles’ if they involve inferior
Diverticular disease, as it is commonly known, is rare under haemorrhoidal plexus covered over by the skin. They are
30 years of age and is seen more commonly as the age common lesions in elderly and pregnant women. They
advances. Multiple diverticula of the colon are very common commonly result from increased venous pressure. The
in the Western societies, probably due to ingestion of low- possible causes include the following:
fibre diet but is seen much less frequently in tropical countries 1. Portal hypertension
and in Japan. Diverticulosis is often asymptomatic and may 2. Chronic constipation and straining at stool
be detected as an incidental finding at autopsy. However, a 3. Cardiac failure
proportion of patients develop clinical symptoms such as 4. Venous stasis of pregnancy
low abdominal pain, distension, constipation and sometimes 5. Hereditary predisposition
intermittent bleeding. 6. Tumours of the rectum.
Based on the etiologic role of low fibre diet, pathogenesis
of diverticular disease of the colon can be explained as under: Microscopically, thin-walled and dilated tortuous veins
1. Increased intraluminal pressure such as due to low fibre are seen under the rectal mucosa (internal piles) or anal
content of the diet causing hyperactive peristalsis and thereby skin (external piles). Secondary changes and complications
sequestration, of mucosa and submucosa. that may occur include: thrombosis, haemorrhage,
inflammation, scarring and strangulation (prolapsed piles).
2. Muscular weakness of the colonic wall at the junction of
the muscularis with submucosa. Angiodysplasia
MORPHOLOGIC FEATURES. Grossly, diverticulosis is Angiodysplasia is a submucosal telangiectasia affecting
seen most commonly in the sigmoid colon (95%) but any caecum and right colon that causes recurrent acute and
other part of the entire colon may be involved. They may chronic haemorrhage. The condition is more common in the CHAPTER 20
vary in number from a few to several hundred. They elderly past 6th decade. The pathogenesis is obscure but is
appear as small, spherical or flask-shaped outpouchings, possibly due to mechanical obstruction of the veins.
usually less than 1 cm in diameter, commonly extend into
appendices epiploicae and may contain inspissated faeces. MISCELLANEOUS INFLAMMATORY CONDITIONS
They are connected to the intestinal lumen by a narrow ‘Fistula-in-ano’ is a well known and common condition
neck.
in which one or more fistulous tracts pass from the internal
Histologically, the flask-shaped structures extend from opening at the pectinate line through the internal sphincter
the intestinal lumen through the muscle layer. The colonic on to the skin surface. The condition probably results from
wall in the affected area is thin and is composed of atrophic infection of the anal glands.
mucosa, compressed submucosa and thin or deficient Histologically, nonspecific inflammatory changes are seen. The Gastrointestinal Tract
muscularis. However, muscularis propria in between the
diverticular protrusions is hypertrophied. While diverti- ‘Anal fissure’ is an ulcer in the anal canal below the level
cular disease may remain asymptomatic, inflammatory of the pectinate line, mostly in midline and posteriorly. The
changes in the diverticula (diverticulitis) produce clinical common cause is trauma due to passage of hard stools,
symptoms. followed by chronic infection.
‘Solitary rectal ulcer syndrome’ is a condition charac-
The complications of diverticulosis and diverticulitis are terised usually by solitary, at times multiple, rectal ulcers
perforation, haemorrhage, intestinal obstruction and fistula with prolapse of rectal mucosa and development of proctitis.
formation. The histological appearance is quite characteristic. Besides
ulceration and inflammation of the rectal mucosa, lamina
Melanosis Coli propria is occupied by spindle-shaped fibroblasts and smooth
muscle cells. The condition is also called as ‘localised form of
Melanosis coli is a peculiar condition in which mucosa of
the large intestine acquires brown-black colouration. The colitis cystica profunda’ and must be differentiated from ‘diffuse
form of colitis cystica profunda’ seen in cases of ulcerative colitis.
condition is said to occur in individuals who are habitual Submucosal cysts lined by foreign body giant cells and
users of cathartics of anthracene type.
containing gas are also seen in ‘pneumatosis cystoides
Grossly, the mucosal surface is intact and is pigmented intestinalis’.
brown-black.
Microscopically, large number of pigment-laden LARGE INTESTINAL POLYPS AND TUMOURS
macrophages are seen in the lamina propria. The nature Large bowel is the most common site for a variety of benign
of this pigment is found to be both melanin and lipofuscin. and malignant tumours, majority of which are of epithelial