These are non specific inflammatory conditions of the alimentary canal. Chron’s disease can effect any part of the alimentary canal where as ulcerative colitis is limited to large intestine only.
There is strong evidence to support genetic influence in both the diseases. A variety of infective agents like virus and bacteria have been proposed but there is little evidence. Auto immunity remains a aetiological possibility. smoking is more common in chron’s disease and less common in ulcerative colitis than compared to general population.
In chron’s disease the sites which are involved are terminal ileum, right side of colon,colon alone,terminal ileum alone,ileum and jejunum. Characteristically the entire wall of the bowel is oedematous and thickened. There are deep ulcers which often appear as linear fissures and thus,the mucosa between them is described as ‘cobblestone’. Deep ulcers may penetrate through the bowel wall and initiate abscesses of the fistulas. Fistulas may develop between effected segment of bowels and bladder, uterus or vagina. Characteristically the changes are patchy, even when a relatively short segment of bowel is affected. There are skip lesions and mesenteric lymph nodes are enlarged. Microscopically non caseating granulomas are characteristic of crohn’s disease.
Features of crohn’s disease are pain which may be due to peritoneal involvement or obstruction, it may be associated with tenderness and guarding. Recurrent episodes of colic due to obstruction are a prominent feature in the life history of a patient with crohn’s disease. Pain might be some times accompanied by diarrhoea and fever. Steatorrhea and malabsorption of nutrients and drugs are common. Most patients suffer from malnutrition and weight loss, contributing factors being reduced food intake because anorexia, malabsorption and increased catabolism. Malabsorption of iron, folic acid and vitamin b12 commonly leads to anaemia.
Ulcerative colitis involves the rectum and colon and is continuous. In early stage haemorrhagic and granular after that ulceration develops. The ulcers might be superficial or deep. In severe disease the mucosa may slough in parts exposing granulation tissue while the remaining mucosa becomes oedematous,hyperplastic and raised,giving the appearance of pseudopolyposis.
In ulcerative colitis the main symptom is diarrhoea with loose bloody stools. Defeacation is always associated with pain in the lower abdomen.
In severe cases of ulcerative colitis or crohn’s disease there is exhaustive diarrhoea with upto 20 liquid stools per 24 hrs,dehydration,fever and tachycardia.
In chronic ulcerative colitis the bowel is permanently damaged by fibrosis and behaves as a rigid tube.
Relapse is often associated with emotional stress, intercurrent infection or the use of antibiotics.
Cancer of the colon can occur if there is total colitis of 10 years duration.