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FISTULA IN ANO.
An abscess formed in the ischiorectal fossa, although opened early by free incision, and before the cavity becomes greatly distended with pus, frequently will not heal; it may fill up and contract to a certain extent, but it does not become entirely obliterated, a narrow tract remaining indisposed, from various causes, to yield further to reparative action without surgical interference. It is this sinus which constitutes the affection designated fistula in ano.
The disturbance to which the part is subject whenever the bowels are moved, and the action of the sphincter, are assigned by most surgeons as the reason why the healing process is arrested; but may it not be attributed, with more reason, to the nature of and the several disadvantageous circumstances attending on an abscess in this locality, such as the depending position, the numerous veins that exist there, and their liability to congestion, all of which tend to retard the process of granulation and cicatrization? Moreover, when these phenomena are slow in their progress, the surface of the internal cavity assumes a peculiar organization, which, save that it is destitute of villi, somewhat resembles mucous membrane in structure, function, and in the inaptitude of the opposed surfaces to unite. It is not alone in the neighbourhood of the rectum, but in other situations also, that we find sinuses form, when the healing process is tardy. In complete fistula in ano, the passage of particles of the less solid feculent matter, and the gases generated in the intestinal Canal, also prevent the healing process. Those who maintain the opinion that the action of the sphincter is the chief cause in preventing reparation, argue, a posteriori, that division of the muscle, whereby it is set at rest for a time, effects a cure; may not the successful result rather depend upon laying the sinus freely open, as when we have recourse to the same plan of proceeding in the treatment of sinuses occurring in other situations?
Fistula; in ano are described by most writers as perfect, fistula) ani completae,—and imperfect, fistula) ani incompletae; the former are those which have both an opening into the intestine and one externally; the latter have but one opening, which may either be internally in the mucous membrane of the intestine, or externally in the integument. When a fistula has no communication with the cavity of the bowel, it is called a blind external fistula; and when the opening exists only within the anus, and there is no external communication, it is known as a blind internal fistula. Blind external fistula is very rare, an internal opening almost always existing if the abscess has degenerated into that state to which the term fistulous may properly be applied. The opening into the intestine may be very small, or, from the sinuosity of the fistula, we may be unable to detect it on a first examination; yet on a second or third exploration, conducted with care and a due consideration of the position it is most likely to occupy, and the employment of a suitable probe, it will probably be discovered.
A difference of opinion exists between several eminent surgeons as to the formation of the internal opening in complete fistula. Sir Benjamin Brodie says: "I believe that this is the way in which fistulae in ano are always formed, namely, the disease is originally an ulcer of the mucous membrane of the bowel, extending through the muscular tunic into the cellular membrane external to the intestine; and I will state my reasons for entertaining that opinion. The matter is of great importance as a question of pathology, but it is one of great importance, as I shall show by-and-by, in connection with surgical practice. It is admitted by every one, that in the greater number of cases of fistulae in ano, there is an inner opening to the gut as well as the outer opening; and I am satisfied the inner opening always exists, because I scarcely ever fail to find it, now that I look for it in the proper place, and seek it carefully. I have, in a dead body, examined the parts where fistulae had existed several times, and in every instance I have found an inner opening to it. This affords a very reasonable explanation of the formation of these abscesses: it is almost impossible to understand, on any other ground, why suppuration should take place in the vicinity of the rectum more than in any other part of the body, and why the cellular membrane there should suppurate more than cellular membrane elsewhere. Moreover, the pus contained in an abscess near the rectum scarcely ever presents the appearance of laudable pus, it is always dirty coloured and offensive to the smell; sometimes highly offensive, and occasionally you find feculent matter in it quite distinct. There is no reason why an abscess, simply formed in the cellular membrane, should smell of sulphuretted hydrogen; but there is a good reason why it should do so if it be connected with the rectum.
"This being the case, it is easy to understand why these abscesses do not heal. The least quantity of mucus, even from the gut, or of feculent matter issuing into the cavity of the abscess, is sufficient to cause irritation, and to prevent it healing; and I have, more than once, in the living person, been able to trace the progress of the formation of one of these abscesses. For example, I was sent for to see a lady who complained of some irritation about the rectum, and on examining it, I found an ulcer on the posterior part. I ordered her to take Ward's paste, confect. piperis nigri, or cubeb pepper—I forget which. A month afterwards she again sent for me, and I found there was an abscess. I opened it, and from the outer opening a probe passed into the gut through the ulcer, which had been the original cause of the disease. The original opening of an abscess is generally very small indeed, but occasionally it is large, and when the ulceration has proceeded to some extent, large enough to admit the end of the little finger. The inner orifice is, I believe, always situated immediately above the sphincter muscle, just the part where the faeces are liable to be stopped, and where an ulcer is most likely to extend through both tunics." Mr. Syme* remarks: "I do not hesitate to affirm, that when a fistula in ano is formed, the mucous membrane always remains entire in the first * 'Diseases of the Eoctum,' Third Edition, p. 25.