Colic, or painful half spasm, half paralysis of the large intestines, is the best example of a kind of spasmodic pains to which some authors accord the name of neuralgia, as it seems to me without good reason. They appear to be quite independent of the operation of the neurotic temperament, and to be caused entirely by the operation of some local irritant, or narcotic irritant, upon the muscular fibres of the viscus. In the case of colic this influence is most frequently and most powerfully exerted by lead, which undoubtedly becomes locally deposited in chronic poisoning with that metal; at other times it is produced by the irritation of indigestible food passing along the alimentary canal.
That there may be such a thing as enteralgia, of really neuralgic character, I do not deny; on the contrary, so far as regards the rectum, I have myself seen such a case. But true neuralgia of the large bowel is exceedingly uncommon; what goes by the name is usually either colic from local irritation of the viscus; or a mere hysterical hyperæsthesia of the lining membrane, which is one of the occasional phenomena of spinal irritation; or else it is a case of neuralgia of the abdominal wall, such as is included in the description of "lumbo-abdominal neuralgia," in Part I. of this work.
There is no occasion to describe minutely the symptoms of so familiar a disease as lead-colic, or as colic from irritation by indigestible food, when they occur in their typical forms. In the former case the marked constipation which ushers in the attack of pain, and the peculiar greenish-yellow sallowness nearly always seen in the countenance, ought to be sufficient to direct examination to the gums (for the blue line) and inquiry as to any possible impregnation of the system with lead, owing either to the nature of the patient's occupation, or to some accidental entry of the poison into the drinking-water, or its inhalation from the walls of newly-painted rooms, etc. In the latter case, the fact that the attack of colic was shortly preceded by a meal, either of obviously indigestible food, or too copious in quantity and heterogeneous in kind, or too hastily eaten without sufficient mastication, supplies a clew.
But there are a few cases representing minor degrees of either of these kinds of colic, that are much less easy to diagnose distinctly.
Lead-poison sometimes enters the system continuously, for a long period, but in proportions too minute to produce the effects which we identify as an attack of lead-colic. I believe that for the production of the latter complaint it is necessary that the poisoning shall be sufficiently intense completely to paralyze a considerable piece of bowel, thus altogether hindering peristalsis, or, rather, making the peristaltic acts of the non-paralyzed portions above worse than fruitless. But there is a minor degree in which it may happen that the local affection (owing, I believe, to a less extensive deposit of lead in the bowel) does not reach the decidedly paralytic stage; the state then is one of irregular and painful spasm of individual fibres (quite possibly intermingled with paralysis of a few others), and the practical result is irregularity of evacuation—now diarrhœa, and again constipation—and the frequent recurrence of twinges of pain that are easily mistaken for abdominal neuralgia. Such symptoms as these are nearly always found to have occurred, if proper inquiry be made, in those examples of chronic lead-poisoning in which the toxic process goes on to the development of epilepsy, or marked symmetrical paralysis of the wrist-extensors, without the patient having ever suffered an attack of ordinary colic. In these slow and insidious cases the constitutional affection may not have reached the height at which the complexion and general aspect of the patient suggests metallic poisoning: and the case may present very neuralgia-like features. The absence of the points douloureux is not, as we have seen, conclusive against neuralgia in its early stages. It is therefore an excellent rule, in all cases of chronic recurrent spasmodic pain in the abdomen, especially in men, to investigate the possibilities of lead-poisoning; and, if the slightest suspicious appearance of the gums be found, this track of inquiry must be followed up exhaustively before we abandon the idea. The absence of all special neurotic history in a patient's family should increase our suspicions respecting pains of this character that continue with an obstinacy which makes it unlikely they are due to improper food.
Pains of abdominal irritation are, however, without doubt produced in some cases by unsuspected faults of diet, and may even recur in such a quasi-periodic manner as to strongly suggest the idea of neuralgia in the lumbo-abdominal nerve. One special variety of this happens, I believe, much more often than is thought. A patient will habitually take considerable quantities of some article of food which he does not readily digest, but which is not at all acutely irritant: under these circumstances a simple accumulation is apt to take place in the colon, especially at the top of the ascending colon, the top of the descending colon, or just above the sigmoid flexure, or else in the cæcum. The result of accumulation in the last of these places is not unfrequently typhlitis and perityphlitis, this part of the bowel having (for some reason) a special tendency to inflammation. Deposits in the other localities named are rarely the cause of inflammation, but they very frequently give rise to violent pain, which is exceedingly apt to be taken for the pain either of gall-stone, of renal calculus, or else of some abdominal neuralgia. In cases, therefore, where there is any possibility that accumulation is the cause of pain, it is highly desirable to commence with a dose of castor-oil and laudanum, followed up, if needful, by the administration of a large warm-water enema, given through an O'Beirne's tube. The most violent and recurrent attacks of pain in the renal region, the flank, the abdomen, or the groin, will sometimes be instantly cured by such means, sufficiently proving the non-neuralgic character of the complaint.
I have elsewhere explained that the impaction of a renal or an hepatic calculus, in the ureter or the ductus choledochus, may set up a true neuralgia in persons with the requisite congenital predisposition. The passage of renal or hepatic calculi may give rise to symptoms falsely suggesting neuralgia, which require just to be mentioned here. But there is no need to dwell much upon the diagnosis, for the passage of renal or hepatic calculi has always attendant symptoms and features of constitutional history, which ought to preserve the physician from mistake. The sensation of constriction, of nausea and vomiting, the faintness approaching to collapse, the persistent and constantly increasing severity of the pain up to the moment at which mechanical relief occurs, to say nothing of other phenomena, are distinctive to the skilled observer, and, when taken in conjunction with the history of past attacks, if any, will always prevent mistakes. In the few cases which might still be doubtful it will be well to try the effect of a relaxing dose of chloroform, which, in the case of calculus, will often put an end to the paroxysm at once and finally.