Some Effects of Ionizing Radiation on the Physiology of the Gastrointestinal Tract: A Review

by evidence of early histological damage, functional alterations, and signs and symptoms such as anorexia, nausea, vomiting, and diarrhea, which are prominent features of the radiation syndrome. In considering the nature of the altered physiology of the gastrointestinal tract produced by radiation, one is dealing with a very complicated system of the body. Digestion and absorption of food are complex and poorly understood. Symptoms related to the gastrointestinal tract are reflected via a complex system of nervous control through the autonomic sympathetics and parasympathetics. To complicate matters further, the gut has an enteric nervous system of its own which allows for autonomous movements. Gastrointestinal symptoms may stem from diseases of the gastrointestinal tract itself, from diseases of other parts of the body via complex nerve pathways, from impulses arising in the central nervous system, or from a combination of these sources. Gastrointestinal symptoms of central origin are frequent and complex in character. Such complexity is exemplified in the phenomenon of vomiting which may be produced by the sight of blood, extreme fear, or a shocking experience. Other gastrointestinal functional disturbances of a more chronic nature may result from psychic imbalance. It is often difficult to distinguish between organic disease of the gastrointestinal tract and functional disturbances which are purely psychic in origin. In addition, disturbances of central origin are said to be produced by toxins affecting the vomiting and other higher centers. Many acute infectious diseases are ushered in with gastrointestinal symptoms which are believed to be due to central toxic as well as local effects. Disease or trauma of other viscera or parts of the body may produce gastrointestinal symptoms by reflex mechanisms through the central nervous system. Very little is yet known about the part the afferent and efferent nervous elements play in the symptomatology related to radiation injury of the gastrointestinal tract.