Diarrhoe'a (Gr. dia, 'through,' and rheō, 'I flow') is the name applied to an increase in the discharges from the bowels, which are usually unduly liquid, sometimes overcharged with bile, and sometimes the contrary, and is, properly speaking, a symptom rather than a disease. Thus it often occurs in the course of diseases of the liver and spleen, of some forms of heart-disease, of many fevers and other acute diseases, and is a common complication of the advanced stage of Consumption (q.v.). Frequently, however, it is the most prominent, perhaps the only symptom of ill-health; and it may then take rank as a disease, or rather as the generic name of a group of diseases. In this aspect the subject will be discussed here.
Diarrhoea is either simple, bilious, or choleraic; the last form has already been discussed (see CHOLERA). The ancients applied the name lienty to a diarrhoea in which the dejections consisted of matters not digested, or very partially so; this form is, however, very unusual, at all events in Britain. Dysentery (q.v.) is also a form of diarrhoeal disease; as is the form of Fever (q.v.) called gastric, typhoid, or enteric fever. Simple and bilious diarrhoea probably often differ only in degree; they are both distinguished from the advanced stages of cholera and dysentery by the presence of abundance of biliary colouring matter in the stools, and by the absence of the distinctive features of the other two diseases as described elsewhere. Diarrhoea is almost always accompanied at first by pain in the abdomen, sometimes severe or even agonising in character. According to its cause and treatment, it may pass off in a few hours, or may persist for a few weeks or months; or it may even prove fatal.
Diarrhœa has many varieties and many causes; but the whole tribe of more or less epidemic diarrhœal diseases present certain relations in common, which have been studied of late years to a considerable extent from the preventive or sanitary point of view. Thus it is observed of all of these diseases, without exception, that they are more apt to prevail during summer and autumn than during the earlier seasons of the year; and it is also well established that their prevalence is to a great extent dependent on the intensity of the solar heat, so that a temperature above 60° F. seems to be almost essential, under ordinary circumstances, to their epidemic diffusion. Moreover, it has been shown that the decomposition of organic matters in the neighbourhood of human dwellings, and the introduction of the products of decomposition into the food, drink, or air used by the healthy, has been a direct exciting cause of diarrhœa in a great number of instances where the disease has been locally epidemic; from which it is inferred that the real source of diarrhœal diseases is usually to be found in a morbid poison closely associated with the process of putrefaction, although not, perhaps, necessarily generated during that process. It has been noticed that cold and wet seasons are the least favourable to the production of diarrhœa, which is explained on the theory above alluded to by the rapid removal in such seasons of all organic debris; and there is little doubt that this explanation is correct, as the converse is equally true, the combination of heat with long-continued drought being almost sure to waken into life the epidemic seeds of diarrhœa. Again it is noticed that where drainage is imperfect and drinking water impure, diarrhœal diseases are specially apt to occur (see CHOLERA); the class of the population most apt to be affected being those who occupy low levels, or who are otherwise exposed to the influence of this aqueous or gaseous poison. Infants are especially apt to suffer from diarrhœa, and a large number of the infantile deaths in many English towns are caused either directly by this disease, or by the abuse of stimulants and narcotics for its cure.
Besides these epidemic diarrhœas, isolated cases of simpler and more obvious origin are very frequent. In some persons diarrhœa is the usual result of catching cold—i.e. they suffer from catarrh of the digestive, instead of, as is most usual, the respiratory organs. But far more frequently diarrhœa results from unwholesome or indigestible food or drink, or from excessive indulgence even in what would otherwise not be hurtful. In all such cases the diarrhœa is to be regarded as beneficial; in fact it is the natural effort of the intestines to rid themselves of their objectionable contents, and should be encouraged rather than arrested. Diarrhœa occurring as an incident in prolonged constipation is to be explained in the same way, as due to irritation of the intestines by their hardened contents.
Acute diarrhœa should almost always be treated first by an aperient, as the unaided action of the intestines is often insufficient to expel irritating material. A full teaspoonful of Gregory's powder, or a tablespoonful of castor-oil with ten or fifteen drops of laudanum are especially useful. The food taken should be small in amount, and as easily digestible as possible. Milk, arrowroot, &c., beef-tea, toast, plain biscuits, are among the most suitable articles of diet. Pain may be alleviated by poultices or fomentations sprinkled with laudanum. A small dose of brandy often checks both the pain and the diarrhœa. Should the disease not yield to these measures, opium, carminatives, and astringents should be administered. In some cases, especially of febrile diarrhœa, an emetic of ipecacuanha at the very beginning will sometimes remove the disease with remarkable rapidity; and in most forms of diarrhœa it may be alleged that this medicine (in doses of from one to five or even ten grains) is well borne. Sometimes it is combined with opium in the form of Dover's powder. In chronic diarrhœa (not the consequence of serious organic disease) careful regulation of the diet is of prime importance, and is generally accompanied by the administration of astringents. But such cases are often very intractable, and no rules can be laid down that would apply to all. In a very large class of cases, especially of infantile diarrhœa, depending upon a too acid state of the secretions, the leading remedy is chalk, either in powder or in the very serviceable form of the mistura crete (mixture of chalk) of the pharmacopœias, from one to three dessert-spoonfuls of which may be given after every disturbance of the bowels. Lime-water, mixed with milk in the proportion of one to four or five, is easily given to very young children, and serves nearly the same purpose.
The astringents useful in diarrhœa are very various. Those of vegetable origin are usually first employed, alone or in combination. The most important are galls, oak-bark, kino, catechu, logwood. The mineral astringents are chiefly salts of the heavier metals, iron, bismuth, copper, lead, &c.; but also chalk and lime, and alum. Opium, one of the most powerful remedies, owes its usefulness to other than astringent properties, and is very frequently given in combination with astringents—e.g. in chalk and opium powder, compound kino powder, lead and opium pills. In many states of the system in which diarrhœa occurs, however, it is dangerous. It must never be given to young children, or in large doses to any one, without medical advice. In some forms of diarrhœa, especially in children, antiseptics are very useful—e.g. carbolic acid, creasote; and it is probably to its antiseptic properties that corrosive sublimate (bichloride of mercury) owes its value when administered in minute doses.