Peritoneum (Gr. periteinein, 'to extend around'), a serous membrane, and, like all membranes of this class, a shut sac, which, however, in the female is not completely closed, as the Fallopian tubes communicate with it by their free extremities. The peritoneum more or less completely invests all the viscera lying in the abdominal and pelvic cavities, and is then reflected upon the walls of the abdomen, so that there is a visceral and a parietal layer. Numerous folds are formed by the visceral layer as it passes from one organ to another. They serve to hold the parts in position, and at the same time enclose vessels and nerves. Some of these folds are termed Ligaments, from their serving to support the organs. Thus, we have ligaments of the liver, spleen, bladder, and uterus formed by peritoneal folds. Others are termed Mesenteries (from the Gr. meson, 'the middle,' and enteron, 'the intestine'), and connect the intestines with the vertebral column. They are the Mesentery proper, the ascending transverse, and descending meso-colon, and the meso-rectum. Lastly, there are folds called Omenta, which proceed from one viscus to another. The great omentum always contains some adipose tissue, which in persons inclined to corpulency often accumulates to an enormous extent. Its use appears to be (1) to protect the intestines from cold by covering them anteriorly as with an apron, and (2) to facilitate their movement upon each other during their vermicular action.
DISEASES OF THE PERITONEUM.—The peritoneum often becomes the seat of dropsical effusion, both in cases of general dropsy and in cirrhosis of the liver. It may also be attacked by cancer, either primary or secondary, and, like all the serous membranes, readily takes on inflammation from various exciting causes. This inflammation is termed Peritonitis, and may be either an acute or a chronic disease.
Acute Peritonitis, inflammation of the coating of the bowels, but often popularly spoken of as 'inflammation of the bowels,' generally presents well-marked symptoms. It sometimes commences with a chill, but severe pain in the abdomen is usually the first symptom. The pain is at first sometimes confined to particular spots (usually in the lower part of the abdomen), but it soon extends over the whole abdominal region. It is increased, on pressure, to such an extent that the patient cannot even bear the weight of the bedclothes; and to avoid, as far as possible, internal pressure upon the peritoneum, he lies perfectly still, on his back, with the legs drawn up, and breathes by means of the ribs, in consequence of the pain occasioned by the descent of the diaphragm in inspiration. The breathing is naturally shallow in these cases, and, less air being admitted at each movement of respiration, the number of those movements is increased. There are perhaps forty or even sixty respirations executed in a minute, instead of eighteen or twenty. The pulse is usually very frequent, often 120 or more in the minute, and small and tense, though occasionally strong and full at the commencement of the attack; the temperature is usually raised, and vomiting is almost always an early symptom. After the disease has continued for a certain time the belly becomes tense and swollen; the enlargement being caused at first by flatus, and afterwards also by the effusion of fluid, as may be ascertained by percussion and palpation. The progress of the disease is in general rapid. In fatal cases death usually takes place within a week, and often sooner. The symptoms indicating that the disease is advancing towards a fatal termination are great distention of the abdomen, a very frequent and feeble pulse, a pinched and extremely anxious appearance of the face, and cold sweats.
Peritonitis rarely arises from exposure to cold alone. It is frequently the result of local violence, and of wounds penetrating the peritoneal sac, including various surgical operations. In the majority of cases it is due to extension of some inflammatory process in one of the abdominal viscera, particularly the hollow viscera (stomach, intestines, gall-bladder, urinary-bladder, womb). It is sometimes caused by Bright's disease. Two varieties call for special mention: puerperal peritonitis, due to extension of septic inflammation of the lining membrane of the womb after child-birth or miscarriage, a most fatal form of disease; and peritonitis from perforation of one of the hollow viscera, which is characterised by the suddenness of the attack, intense pain, incapable of mitigation by medicine, all at once arising in some part of the abdomen, the whole of which soon becomes tender in every part. This form of the disease is generally fatal, death usually ensuing within two days, and sometimes within a few hours. Perforation of the small intestine, in consequence of ulceration of its glands, is of not uncommon occurrence in typhoid fever, and sometimes occurs in phthisis. That apparently useless structure, the vermiform appendage of the cæcum, is a comparatively frequent seat of perforation. Sometimes it is the stomach which is perforated, and in these cases the patients are usually unmarried women (especially domestic servants), who may have previously appeared in good health, or at most have complained of slight dyspepsia.
At the onset of the disease it is not always easy to distinguish it from Colic (q.v.), but the progress of the case will soon settle the question. With this exception, the only disease with which peritonitis is likely to be confounded by the well-educated practitioner is a peculiar form of hysteria; but the age and sex of the patient, the presence of hysteria in other forms, and the general history of the patient and of her symptoms will almost always lead to a correct diagnosis of the disease.
The treatment of a case of peritonitis must depend upon the cause to which it is due. Perfect rest in bed is essential. In the great majority of cases opium should be given in full doses, to allay pain and keep the bowels at rest. But in some, particularly those following surgical operations on the female generative organs, the opposite plan, treatment by saline purgatives, introduced by Lawson Tait, gives excellent results. The diet must be light and fluid; in cases of perforation of the stomach no food or even drink must be given by the mouth. Light poultices, or hot fomentations, should be constantly applied to the abdomen; leeches are sometimes useful. In cases of perforation from disease or injury, and of suppurative peritonitis, life has frequently been saved during recent years by prompt surgical interference.
Chronic Peritonitis occurs in two forms, which differ in their origin and degree of fatality, but are very similar in their symptoms. In the first the inflammation is of the ordinary character, and, although the disease sometimes originates spontaneously, it is more frequently the sequel of an imperfectly cured acute attack; in the second it depends upon tubercular inflammation, and is generally met with in persons of a scrofulous constitution. The symptoms of chronic peritonitis are more obscure than those of the acute form. There is abdominal pain, often slight, and not always constant, which is increased by pressure, or sometimes is felt only when pressure is made. The patient complains of a sensation of fullness and tension of the belly, although its size is not visibly increased; of a loss of appetite; and of nausea and vomiting; and the bowels are usually more or less out of order. After a time the abdomen enlarges, and becomes tympanitic, or more or less filled with fluid; and death gradually ensues from debility and emaciation, unless the fatal issue is accelerated by an acute inflammatory attack. It is not always easy to determine, during life, whether the disease belongs to the first or second form. When its origin cannot be traced to a preceding acute attack, to local abdominal injury, or to chronic affections of the abdominal viscera, there is strong reason to believe it to be of the tubercular form, especially if the general constitution and the hereditary tendencies of the patient point in the same direction.
Little can be done in the way of medical treatment, especially in the tubercular form, further than mitigating the most distressing symptoms, and possibly retarding the final issue, though recovery sometimes follows the continuous application of mercurial liniment. In chronic, even tubercular peritonitis, however, as in the acute disease, surgical interference, either by aspiration or by free opening of the abdominal cavity, has given very encouraging results in many cases.