Inflammatory Disorders

Acute proctocolitis: infective or drug induced, e.g., antibiotics, there is preservation of the mucosal architecture and acute inflammation with biopsies only being submitted if symptoms persist beyond several weeks. Infective cases (Campylobacter, Shigella, Salmonella) are usually self-limited and culture-positive in only 40% of cases. Drug-induced inflammation often responds to its withdrawal.

Chronic proctocolitis: characterised by disturbance of the mucosal architecture and a chronic inflammatory cell infiltrate ± foci of active inflammation. Commonly due to idiopathic chronic inflammatory bowel disease (CIBD) but also seen overlying diverticulosis and pneumatosis coli, in infection (Shigella, amoebiasis, schistosomiasis), obstructive enterocolitis and with drugs. Microbiological culture, travel and drug history should always be ascertained in patients with chronic diarrhoea.

CIBD - ulcerative colitis and Crohn's disease: the latter has been discussed previously but can present either as isolated colonic disease or associated with ileitis. It is a segmental, transmural chronic inflammatory condition and there is often rectal sparing but anal disease (fissure, fistula, abscess) present. The segmental distribution, focality of inflammation, presence of granulomas and ileal component are all useful diagnostic pointers in colonoscopic biopsy or resection specimens. Recurrence elsewhere in the gut is not uncommon despite surgical resection and because of this Crohn's disease is a contraindication to pouch formation in restorative proctocolectomy. Occasionally it presents isolated to the appendix or sigmoid colon coexisting with diverticulitis.

In contrast to this, ulcerative colitis is a diffuse, chronic, active mucosal inflammatory condition involving the rectum and a contiguous length of large intestine, e.g., left-sided proctocolitis or pancolitis. It is of variable severity with episodic exacerbations and remissions - acute fulminant colitis may be complicated by severe haemorrhage, toxic dilatation or megacolon, perforation and peritonitis. Other complications include mucosal dysplasia and malignancy (usually adenocarcinoma) in extensive disease of long standing duration (pancolitis > 10 years). Villiform or polypoid DALMs (dysplasia-associated lesions or masses) can be difficult to distinguish from the much more common inflammatory mucosal polyps and may harbour underlying adenocar-cinoma. Alternatively, dysplasia may occur in flat mucosa, and colonoscopic surveillance of chronic colitis involves sequential mucosal sampling as well as target biopsy of any macroscopic abnormality. Biopsy orientation onto a polycarbonate strip aids subsequent localisation of any histological abnormalities. Macroscopically ulcerative colitis shows mucosal granularity, linear or confluent ulceration and polyps of varying size. The terminal ileum is only involved in severe pancolitis over a length of 1-2 cm (backwash ileitis) and although there is usually proctitis the rectum may be spared due to treatment effects, e.g., predsol enemas. Extraintestinal effects include arthritis, iritis and, in the liver, sclerosing cholangitis which can lead to cirrhosis and cholangiocarcinoma.

In a minority of cases clear distinction cannot be made between ulcerative colitis and Crohn's disease on macroscopic and microscopic examination - so-called indeterminate colitis.

Diversion proctocolitis: follows faecal stream diversion, e.g., after ileostomy or colostomy for tumour, trauma or CIBD. The defunctioned segment develops florid reactive lymphoid hyper-plasia which can be mucosal or transmural, mimicking or superimposed on an underlying inflammatory disorder such as CIBD. Persistent severe symptoms may neccessitate surgical excision of the segment, e.g., the rectal stump following colectomy for ulcerative colitis.

Microscopic colitis: minimal inflammation may be apparent grossly or histologically for various reasons, e.g., treated CIBD, post infection, drug ingestion, uraemia, stercoral trauma, etc. However, microscopic colitis which causes chronic, voluminous watery diarrhoea is radiologi-cally and colonoscopically normal. It occurs in middle-aged to elderly women and has variable associations with HLA type, autoimmune diseases and NSAID ingestion. Diagnosis is by histology with a normal architecture and transmucosal infiltrate of chronic inflammatory cells. Its main variants, collagenous and lymphocytic colitis, show a thickened subepithelial collagen band and excess surface intraepithelial lymphocytes, respectively. Not infrequently there is spontaneous resolution or response to anti-inflammatory therapy.

Infective proctocolitis: investigation includes microbiological culture with microscopy for cysts (amoebiasis) and ova (schistosomiasis). Infection should be considered particularly where there is a history of travel or immunosuppression, e.g., AIDS, chemotherapy or post transplant. In immunosuppression, infection with unusual opportunistic organisms can occur, e.g., cryp-tosporidiosis, atypical mycobacteria.

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