This is a chronic granulomatous inflammatory condition that
can involve any part of the gastrointestinal tract . it may occur at any age and the sex distribution is equal the most common site affected is the terminal ileum . this is involved in 70% of patients , giving rise to the soubriquet of (terminal ileitis) or (regional ileitis) the colon may also be involved and crohn,s colitis is the only manifestation of the disease in 20%of cases . multiple sites are common . crohn,s disease occurs in a discontinuous pattern within the bowel such that affected areas may be separated by quite normal bowel . these affected areas are termed skip-lesions 
,Macroscopically the bowel wall becomes grossly thickened and enveloped in mesenteric fat (fat wrapping). the histological hallmark is non - caseating granuloma . this may not be found in up to 40%of specimens however . there is transmural chronic inflammation of the affected bowel with local lymphadenopathy . various aetiological theories exist , including genetic autoimmune viral and mycobacterial infections though a complex polygenic aetiology is the most likely . there appears to be strong relationship with smoking
  1. crohn,s disease presents in a varied fashion . in children , failure to thrive and loss of weight may be the only features . in adults the most common presentation is diarrhoea , which occurs in 80% of cases . perianal lesions are present in 70%and this may be the presenting feature of the disease . abdominal pain is present in 60%of cases . other features include abdominal distension , rectal bleeding pyrexia abdominal mass or abdominal wall fistula
  2. Clinical manifestations and complications of chronic
  3. inflammatory bowel disease there are many extra intestinal manifestations of conhn,s disease many of which occur in ulcerative colitis 1- oral and rectal aphthous ulceration 2- clubbing of the nails 30- pyoderma gangrenosum 4- erythema nodosum 5- large joint mono-arthritis and sarcoileitis 6- uveitis and episcleritis 7- renal oxalate stones hepatobiliary complications of both crohn,s disease and ulcerative colitis include cholelithiasis , fatty change of the liver penicholangitis cirrhosis chronic active hepatitis cholangiocarcinoma sclerosing cholangitis and amyloid deposition
  4. investigations a barium enema may reveal characteristic features of crohn,s rose thorn ulceration deep fissures skip lesions fistula thickened bowel string sign of kantor (terminal ileal stricture ) or a featureless(drain pipe ) colon . the  ESR  and c- reactive protein are invariably raised in acute episodes anaemia is common and LETs are often elevated 
  5. complications 1- acute inflammation this can result in peritonitis and any of its squelea particularly intra abdominal abscess formation rarely involved bowel may perforate . cronhn,s colitis as with any form of colitis can become fulminant and develop into a toxic megacolon 2- bleeding this may be a feature of a cronhn,s colitis but rarely occurs if small bowel is involved alone and it rarely requires emergency surgery 3- recurrence up to 30% of patients have a bowel resection for crohn,s  disease will require further procedures for recurrent disease . it has a predilection for recurring at anastomoses from previous resections 4- bowel obstruction this results from a stricture which is common in crohn,s particularly in the small intestine . these are best treated by either a conservative bowel resection or stricturoplasty if the strictures are multiple or there have been previous resection . it has been shown that bowel healing is not affected by the presence of crohn,s disease therefore wide resection of affected bowel are both unnecessary and counterproductive in the long term 5- perianal disease anal conditions such as perianal tags perianal abscess chronic fissures and fistula in ano are common . acute perianal conditions need to treated as they arise . there may be numerous fistula 6- malignancy there is risk of developing cacinoma in colon or small bowel affected  with crohn,s disease the prognosis is poor as the diagnosis is usually made late because the symptoms are put down to existent inflammation the risk of malignancy in crohn,s disease is less than the risk of developing colonic carcinmoa in ulcerative colitis 7- abdominal mass persistent inflammation in the affected bowel may results in a phlegmanous mass . this usually occurs in the right iliac fossa representing terminal ileal disease but may occur at any site an inflammatory mass may resolve with continued anticolitic drugs and metronidazole but persistent despite these measures is an indication for bowel resection 8- fistula crohn,s disease has a tendency to form fistula entero- enteric entero-colic - and entero-cutaneous fistulae are the most commonly encountered these frequently follow surgery however carefull undertaken

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