The intussusception is formed not only by the intestinal tube, but also by the portion of mesentery in connection with it. This being drawn in with the invaging,ted portion, presses the latter to one side. Consequently, the foremost opening of the contained seirment is not in the middle line, but is twisted so as to rest against a part ofthe investing sheath. When once started, the invagination tends to increase by peristaltic action, the increase being always at the expense of the outermost portion, and may vary in degree from an extent of a few inches to several feet.
The consequences of the intussusception are occlusion of the intestinal canal, and obstruction of the circulation in the double layer of bowel which forms the invaginated portion. The two inner tubes become dark purple from congestion, and swollen ; and some effusion mixed with blood is poured out between the opposed mucous surfaces, and also into the canal beyond the point of obstruction. Lymph is afterwards exuded, and the opposed serous surfaces become adherent. In some rare cases, the inflammation extends beyond the seat of disease, and causes general peri tonitis ; in others, ulceration and perforation take place in the investing sheath, owing to irritation of the end of the contained portion ; and this is sometimes seen to protrude through the opening thus formed, into the cavity of the peritoneum. If the strangulation of the invaginated portion is complete, it becomes gangrenous, and, in favourable cases, may be de tached, piecemeal or in mass, and discharged through the anus. Should this happen, if the adhesions already formed remain firm, the sheath or invaginating segment, being united at its free end with the part of the bowel immediately above the point of intussusception, still forms with it a continuous tube, although the intervening portion has been removed. Sometimes, however, the adhesions give way, and then extravasation may take place into the peritoneum.
In infancy, it is usually the small intestine which becomes invaginated into the colon. The end of the ilium, with the ilio-ccal valve, is forced into the cmcum. This, as the intussusception increases, penetrates farther and farther into the colon, drawing behind it the ilium, and doubling first the mourn, then the ascending colon, and afterwards more and more of the larger bowel the farther it extends. At last, it may reach the rectum, and be feltby a finger introduced through the anus. In such a case, when the abdomen is opened, the larger bowel seems in great part to have disap peared, and a tumour is found occupying, usually, the left side, often the iliac fossa. This is of a slate-gray colour, is elongated in shape, and dmighy to the touch. By traction, the invaginated portion can be drawn out, although it is usually soft, and is apt to tear in the process. Before penetrating into the colon, the ilium may or may not pass through the valve ; usually, it does not do so, and if a portion pass between the lips of the valve, it is seldom more than a few inches.
Sometimes, even-in infancy, more often in older children, the intussus ception occurs in the course of the small intestine, the colon taking no part in the invagination. When this displacement occurs in a healthy child, it of course gives rise to symptoms of obstruction. It may, how ever, take place without producing symptoms. In examining the bodies of children, especially if they have died of intestinal catarrh, or of some form of brain disease, it is not uncommon to find portions of the bowel invaginated, often in several places, without any symptoms of this accident having been noticed during life. This form of intussusception usually oc
curs in the small intestine. It is supposed to take place immediately be fore death ; for the bowel is merely invaginated, and is not swollen or con gested, or altered in appearance in any way. Moreover, it can be readily drawn out by a very slight efibrt.
Symptoms. —There is some variety in the symptoms, ,according to the age of the child and the seat of the invagination. In infants the intussus ception is almost always at the expense of the larger bowel. In older children it may be confined to the jejunum or ilium, without involving the colon. The symptoms noticed in infants, and those arising in older children, must be therefore considered separately.
In the case of an infant the ordinary history given by the mother is that the baby was in his usual health, when suddenly be gave a scream, turned excessively pale, and then cried violently, writhing and drawing up his legs as if in great suffering. The pain is not constant, for the child, after a time, ceases to cry, and lies back, looking pinched and pale ; but in a short time the paroxysm returns, and he screams and writhes as before. When the pain first comes on, the infant vomits his last meal, and the vomiting is usually repeated, especially if food or medicine be given to him. In most cases, an aperient is at once ordered, and is returned di rectly it has been swallowed. The state of the bowels is important. If they are empty below the point of obstruction, they remain obstinately confined, and the straining efforts, which are usually made, merely expel mucus and blood. If the lower bowel contains any matter, this is discharged in a thin, loose state, shortly after the occurrence of the intus susception. The stool may contain blood, and the action of the bowels is usually followed, after a short interval, by further straining and the evacu ation of mucus and blood. At this time, the temperature is not elevated ; the belly is painless—indeed, drain.. the paroxysms of colic, gentle frictions to the belly seem to afford relief abdomen is neither full nor tense, and between the attacks of pain, the child may be often found in his cot lying upon his belly. Sometimes the secretion of urine is greatly dimin ished, but this is a very variable symptom, and apparently has no refer ence at all to the seat of obstruction. !Often, at this period, the most careful examination of the belly detects no localised swelling ; but after a time, if the abdomen be carefully palpated during an interval of rest from pain, a distinct swelling may be perhaps detected by the fingers pressed deeply into the left iliac fossa. There may be some tenderness at this point if some hours have elapsed since the occurrence of the accident. Later, the mass can often be reached by the finger introduced into the rectum, for its tendency is to travel farther and farther down the bowel. The child sleeps but little after the invagination has occurred. If, at the first, he sleeps between the attacks of pain, he soon ceases to do so, and re mains wakeful and restless, constantly whining and until exhausted. The temperature varies. Sometimes it is little altered from the normal level. In other cases, it begins to rise after a few hours, and may reach 102° or 1.03°. Directly symptoms of collapse are noticed, the tempera ture usually falls below the level of health.