D. F. Martin

Benign Epithelial Tumours and Polyps

Morson and Dawson (1990)1 define an intestinal polyp as a mucosal projection into the lumen of the bowel. This does not indicate the underlying nature of the lesion. The polyps can be single or multiple and if multiple they may be in small numbers or in hundreds or thousands — polyposis. Different types of polyp are produced by different pathological processes: neoplasia leads to adenoma, inflammation to an inflammatory polyp, malformation leads to juvenile and Peutz—Jeghers polyps and dysmaturation to the hyperplastic (metaplastic) polyp. The gross and microscopic features of these different types are beautifully illustrated in Morson’s colour atlas (1988)2.

Large Bowel Carcinoma

The incidence of large bowel carcinoma varies greatly between countries but it is common in most developed countries (Boyle et al., 1985)1. In the UK it stands second in frequency as a cause of death amongst malignant diseases (Office of Population Censuses and Surveys, 1986)2. Levin and Dozois (1991)3 report a similar prevalence in the United States. They note a change in anatomical distribution of large bowel cancer in the last 40 years with an increase in right colonic tumours and a decrease in rectal tumours. At present about 60% of the tumours are in the rectum or sigmoid colon.

Perianal Abscess and Fistula

Perianal infection may present as an acute abscess or as a chronic discharging fistula but the two states are so interrelated that they are discussed together. These conditions have been recorded in writings for more than 2000 years. Fistulas were treated by ligatures, corrosives or laying open by the knife. John of Arderne in 1370 described the principles of surgical treatment which accord with modern ideas (Power, 1910)1.

Small Bowel Ischaemia

Marston (1986)1 reviews gut ischaemia which may be acute or chronic. It may be due to major or minor arterial blockage, venous occlusion or a low flow state. Wilson et al. (1987)2 reviewed acute superior mesenteric ischaemia in 102 cases and found that 33% were due to embolus, 26% to thrombosis and 24% to low flow states. The condition was depressingly lethal with a survival of only 8%. They emphasise the difficulty in diagnosis because there are no specific clinical signs or laboratory tests which are diagnostic. Diagnosis is often made late and this makes the prognosis even worse. Treatment is by bowel resection with or without revascularisation. The revascularisation procedures of embolectomy, aortomesenteric shunt or endarterectomy are only applicable to the early case. Ottinger (1978)3 reports that attempts at revascularisation often fail because of rethrombosis. Clavien (1990)4 emphasises the importance of urgent selective superior mesenteric angiography (SMA) both to establish the nature and extent of the blockage and to give access for vasodilators or thrombolytic drugs. Boley et al. (1981)5 report improved results in superior mesenteric artery vasodilatation with papaverine after revascularisation by embolectomy. Grendell and Ockner (1982)6 showed that mesenteric venous occlusion has a better prognosis than other forms of infarction but that the recurrence rate is high. Clavien et al. (1989)7 recommend contrast-enhanced computed tomography as the method of choice to demonstrate superior mesenteric vein thrombosis.

Highlights in Coloproctology

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Disorders of the Pelvic Floor

Included in this group of diseases are the following: idiopathic (neurogenic) incontinence, rectal prolapse, solitary rectal ulcer syndrome and idiopathic perineal pain. These conditions may be associated with disorders of the levator ani muscle and/or the internal and external sphincter ani muscles.

Tumours of the Small Intestine

It is not easy to subdivide tumours into benign and malignant categories in all cases. However, Olmsted et al. (1987)1 review those tumours which have little or no malignant predisposition. These tumours are often asymptomatic and are less common than malignant small bowel tumours. The common varieties are the lipoma, the leiomyoma and the adenoma. However, Olmsted excludes the latter two groups as they have a definite malignant potential. He does include Peutz-Jeghers polyps which now also appear to have malignant potential (Spigelman et al., 1989)2. The other tumours highlighted in Olmsted’s series are the neural tumours associated with neurofibromatosis, “adenoma” of Brunner’s glands and fibroid polyps. If benign tumours produce symptoms, they do so either due to causing an intussusception or by bleeding due to ulceration of the mucosa overlying them.

The Small Intestine: Normal Structure and Function

The small intestine is adapted for digestion and absorption. The various enzymes responsible for the breakdown of complex substances may pass into the lumen from surrounding exocrine glands or be produced by the gut directly. The small bowel in post mortem studies is 600 cm in length but is significantly shorter in life (Hirsch et al., 1956)1. The surface area for absorption is enormously increased by the valvulae conniventes and the villous configuration of the mucosa, well illustrated by Morson (1988)2 who describes the four types of mature cells covering the crypts and villi of the small bowel, namely enterocytes, goblet cells, enterochromaffin cells and Paneth cells. Under high magnification the enterocyte is seen to have a brush border (Zetterquist and Hendrix, 1960)3. The mucous membrane with its villi and crypts stands on the muscularis mucosa separating it from the muscularis propria. In the submucosal layer there is a plexus of small blood vessels, lymphatics, nerves and ganglia. The vascular arrangement is well illustrated by Carr and Schofield (1984)4. Morson (1988)2 indicates that the goblet cells are most numerous in the crypts and decrease over the villi. The enterochromaffin and Paneth cells are found in the base of the crypts. The cells ascend from this base to the tip of the villus rapidly, with cellular turnover being less than one week (Williamson, 1978)5. Griffiths et al. (1988)6 show that all the cells from a crypt villus unit are derived by division from a single stem cell at the base of the crypt. Unusual differentiation from the stem cell can occur under the influence of an abnormal stimulus, for example, Wright et al. (1990)7 show that mucosal ulceration induces the development of a cell which secretes epidermal growth factor — a potent stimulus of cell proliferation.

Other Forms of Colitis and Enterocolitis

Shepherd (1991)1 reviewed the histopathological appearances in a variety of colonic inflammatory conditions. He pointed out that these could be difficult to distinguish from ulcerative colitis or Crohn’s disease and that there are many causes of inflammatory change within the colon which are not caused by acute infection, ulcerative colitis or Crohn’s disease.

Intestinal and Colorectal Injury

Cox (1984)1 indicated that the commonest cause of blunt abdominal injury was road traffic accident and it was often part of multiple injuries which required careful assessment and resuscitation. He indicated that liver and/or spleen were the most likely to suffer intraabdominal injury. Intestinal injury came next in order of frequency.