Diarrhoea in general practice: a sixteen-year report of investigations in a microbiology laboratory, with epidemiological assessment.

Results are presented of the laboratory examination of faeces specimens from 20,273 patients with acute diarrhoea. These were household index cases seen in general practice in a London borough during the years 1953-68. An annual average of about 2 per cent of households in the area were affected, but there was considerable fluctuation with year and season. Half the patients were children although only one-fifth of the population at risk was under 15 years of age. The greatest incidence of diarrhoea was among children under 5 years old. Male children, but female adults predominated. Specimens were sent for laboratory diagnosis at the discretion of the general practitioner. The laboratory found some abnormality in nearly a third and there were indications that transmissible infection was involved in about one-fifth of patients. The most common diagnosis was Sonne dysentery (9 per cent) which came in epidemic waves and made its greatest impact among young school children. Microscopy was useful, and giardiasis was diagnosed in 1-4 per cent of index patients. Other parasites were less commonly found. Fatty globules characteristic of an infectious condition we have called 'fatty diarrhoea' were frequently observed by microscopy in stools from young children and occasionally from older persons. Blood or pus cells were seen in less than half the shigella and salmonella infections and in a much smaller proportion of the remainder. A test for occult blood performed on specimens from all patients of 40 years or older was positive, in the absence of visible red cells, in a tenth of these cases. Other studies on the bacteriology of diarrhoea in general practice are referred to and some epidemiological comparisons made. The possible place of unidentified infective agents in the aetiology of undiagnosed diarrhoeas and of 'fatty diarrhoea' is discussed.