Some Clinical Problems in Small Intestinal Physiology Mackenzie Davidson Memorial Lecture, 1950

In the Mackenzie Davidson Lecture of 1950 we have presented some of the problems in abnormal small intestine physiology encountered in routine clinical work and have discussed possible physiological explanations for them. We have reviewed briefly some of the available knowledge of small intestinal physiology which has to do with motor function as demonstrable by X-ray methods. The movements of the intestine which propel forward its contents are reflexes which depend upon the intramural nervous system for their control and coordination, and upon proper balance of the two divisions of the autonomic nervous system. Electrical activity precedes contractions in the animal and the human intestine. Overactivity of the parasympathetic results in hypermotility and hypertonicity. It is given credit for being the basis of allergic reactions and for functional intussusceptions which are not infrequently demonstrable in the course of radiological study of the small intestine. The phenomena of parasympathetic overactivity have been observed in patients with anxiety and other emotional disturbances in whom no organic cause for the symptoms could be established. A new antiparasympathetic drug, banthine, retards the emptying of the stomach and intestinal movements. A parasympathomimetic drug, urecholine, increases the rate of emptying of the stomach and the movement of barium through the small intestine. Experimental use of these two drugs for appropriately selected patients has been followed by relief of symptoms but their practical clinical usefulness remains to be established. Electrolyte imbalance is associated with a type of paralytic ileus which we formerly attributed to hypoproteinemia with œdema of the intestine. This is relieved by restoring the serum potassium to a normal level, and does not occur when steps are taken to prevent the fall of serum potassium to critical levels. The study of the small intestine by X-ray methods is important not only for the detection of organic diseases such as neoplasms and inflammations, but also to disclose disorders of physiology which, although difficult to understand now, may in the future be of help in explaining the patient's symptoms. We who must do this work are well advised to follow carefully the fascinating investigations of the neurophysiologists and to search for physiological explanations for the phenomena we encounter.