The management of malignant obstruction of the colon distal to the splenic flexure is controversial. The 'traditional' three-stage procedure is marred by frequent failure to complete the planned sequence of operations and a resulting high permanent stoma rate. At each stage the mortality rate (7 per cent) and morbidity rate (30 per cent) are significant. The mortality rate following primary resection with delayed anastomosis (Hartmann's procedure) is 10 per cent. However, many patients experience complications and only 60 per cent have the stoma reversed. Primary anastomosis may be performed after subtotal or segmental colonic resection. The reported mortality rate is about 10 per cent with anastomotic leakage in 4-6 per cent, but cases are often carefully selected. It is difficult to suggest clear guidelines based on existing data. Although there are strong arguments in favour of a single-stage procedure, surgeons must decide whether available resources and local circumstances permit this. The alternative is Hartmann's procedure or referral to a surgeon with an interest in emergency colorectal surgery.

Neoplasms occur in 0.5 per cent of appendices. Ultrasonography or computed tomography is beneficial, but preoperative detection is rare. At operation, the diagnosis is considered in under half of cases. Mucocele, localized pseudomyxoma peritonei, benign tumours and most appendiceal carcinoids are cured by appendicectomy alone. Right hemicolectomy is indicated for: (1) invasive adenocarcinoma; (2) tumours close to the caecum; (3) lesions larger than 2 cm; (4) mucin production; (5) invasion of the lymphatics, serosa or mesoappendix; and (6) cellular pleomorphism with a high mitotic rate. Tumours of 1-2 cm, small mucinous carcinoids, adenocarcinoma confined to the mucosa, and tumours in children may be treated by appendicectomy alone at the surgeon's discretion. The 5-year survival rate associated with classical carcinoid is more than 90 per cent. The prognosis of mucinous carcinoid is intermediate between that of classical carcinoid and well differentiated adenocarcinoma. The prognosis of adenocarcinoma is determined by Dukes' stage and is similar, stage for stage, to that of colorectal carcinoma.

The prognostic power of the extent of tumour invasion is indisputable; Dukes' classification has repeatedly been proven to be strongly correlated with patient survival. Modifications have led only to confusion, resulting in caution being required in the classification of patients with Dukes' A tumours. In the UK, the American tumour node metastasis and Australian clinicopathological systems are frequently considered too complex for routine clinical use. Meanwhile, Jass's classification may be complicated by observer variation between pathologists, and recent evidence suggests that it offers no advantage over that of Dukes. All the conventional staging systems also fail to take the skill of the surgeon into account when determining outcome. Attempts at quantifying tumour structure have not heralded the expected major advance. For instance, the expense and uncertain prognostic value of tumour DNA content assessed by flow cytometry are likely to restrict widespread use of this technique. It may soon be possible, however, to provide optimum treatment for patients based on individual tumour doubling times. Classification using knowledge of how a small number of cells in the tumour have the ability to invade locally, enter blood vessels and metastasize would also provide important prognostic information on which treatment could be based. Until then, the ease of use and high prognostic power of Dukes' classification ensure that, after 60 years, it is still the 'gold standard' against which all other prognostic classifications in colorectal cancer should be assessed.

Anal tumours represent 5 per cent of anorectal cancers and exist as two clinical entities: tumours of the anal canal and those of the anal margin. Smoking and sexual behaviour, particularly homosexual anal intercourse, are important aetiological factors. This association is related to anal warts and human papillomavirus infection, notably type 16, which is found in around 70 per cent of warts. Symptoms are non-specific and are frequently attributed to benign conditions. Rectal examination reveals a characteristically infiltrating lesion and any suspicious anal area should be biopsied. There are two histological types. Squamous carcinoma comprises approximately 95 per cent of anal tumours and includes the 35 per cent of tumours derived from the anal transition zone (cloacogenic tumours), containing a mixture of squamous and mucinous elements. The remaining 5 per cent of anal tumours are adenocarcinoma. Squamous cell tumours of the anal canal are probably best treated using radiotherapy (with chemotherapy) as complete response rates, 5-year survival rates, and incidences of normal sphincter function and significant toxicity are around 80, 70, 75 and 20 per cent respectively. Treatment failures may be salvaged by surgery. The 5-year survival and local recurrence rates for radical surgery are around 60 and 25 per cent respectively; there are few indications for local excision. In contrast, 60 per cent of anal margin tumours are suitable for local excision, the 5-year survival rate being in excess of 80 per cent. Combining radiotherapy with surgery may give additional benefit. Current randomized controlled trials should further clarify the relative merits and demerits of the treatment options.

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