The Importance of Medical Theory for Development of Diagnostics

The importance of medical theory for the general development of diagnostics, for elaboration of examination methods, and for assessment of the disease and the patient's condition is a commonplace. It is important that a diagnosis should be worded in the generally accepted terms and that the meaning of these concepts should correspond to the modern status of the medical science, i.e. diagnosis should be correct not only in form but in content as well.

History of medicine shows that, depending on the general concept of disease and its forms, physicians devise and use the corresponding diagnostic methods and give the various assessment of the observed phenomena. Beginning with Hippocrates and almost until the 19th cen­tury, diseases were regarded as a combination of symptoms, and simple observation was sufficient to arrive at a diagnosis. This empirical period of the descriptive clinical and symptomatological trend, which existed from the times of Morgagni's clinico-anatomical studies (1761), was then replac­ed by a deeper approach to the study of the disease. Physicians began com­paring the phenomena observed during the life time of the patient with the changes in his organs observed after his death. They noted that almost each disease was connected with visible changes in certain organs and believed that the cause of the disease should be looked for in the anatomical changes in organs. Diagnostic methods of examinations now included the study of anatomical changes in the patient's organs. These were the methods of Physical diagnosis (percussion, auscultation, palpation). A microscope was mvented and histological studies improved accordingly. Physicians could now detect very fine changes in tissues and cells of organs of dead patients. A new science, pathological anatomy, was thus initiated. It became the foundation for the study of diseases.

Diseases were now considered as being dependent on affections of

^" ious organs, and organolocalistic classification of diseases thus emerg-

* • Most diseases were given definite names depending on the site (localiza-

•on) of major changes: the inflammation of the pleura was given the name

Pleurisy, of the lung pneumonia, of the kidneys nephritis, etc.

Pathological anatomy discovered many new facts and explained many

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Chapter 4. General Methodology of Diagnosis

symptoms of diseases. But the creators of this science, Rudolf Virchow and his disciples, concentrated their attention on the finest changes occurring in the cells and forgot about man as a whole, about the integrity of the organism; in their opinion, the life of a body is a simple sum of the lives of cells; they understood disease as a simple sum of changes in the structure of cells, i.e. as a local affection of the body. This anatomical localistic medical thinking was not widely accepted in the Russian clinical medicine. Since the time of discovery of blood circulation by William Harvey (1578-1657) scientists began to be interested not only in the structure but also the function of various organs. Physiology was thus started. This was the science of life and function of various organs and systems of the body (Claude Bernard and others). Works of an outstanding scientist, the father of Russian physiology I. M. Sechenov (1829—1905), a prominent internist of the middle of the 19th century S. P. Botkin (1832-1889), the great Soviet physiologist, materialist, the creator of the teaching of higher ner­vous activity I. P. Pavlov (1849—1936), and of many others greatly con­tributed to the development of medical science. It was established that the function of organs (the heart, lungs, brain, etc.) is decisive for the life of man and animal, and that anatomical changes in an organ or cell is only partial manifestation of the disease. The living body was now understood as an integral system, and the activity of the nervous system was admitted to play a decisive role in regulation of the functions of the human body. " Physiology and medicine are fundamentally inseparable. If the physi­cian is in his actual practice, and even more important, in his ideals, a mechanic of the human organism, then inevitably every fresh discovery in physiology will sooner or later increase his power over this extraordinary machine, his power to conserve and repair this organism." (Lectures on Conditioned Reflexes by Ivan Petrovich Pavlov. New York, 1928,

pp. 95-96.)

Scientists began studying human diseases by modelling them in animals. Experimental study of diseases has given a start to a new science, pathological physiology, which treats of the changes in the function of an affected body and the developmental mechanisms of diseases. Pavlov wrote that " only through experiment shall medicine become what it should actually be: conscious and hence fully purposeful active science".

The function of organs in the sick became an important object of studies in practical medicine. New diagnostic methods for the study of the blood and urine, digestion, methods for measuring blood pressure, etc. were devised. Functional methods of studies became very important in diagnostics. The functional trend in medical science thus developed in its struggle against the one-sided anatomical (localistic) medical thinking.

The invention of the microscope has enriched medicine not only with

the information on the structure of the human body. The discovery of multitude of microbes in the human environment and also inside man himself (microbes were found in the organs and the blood of patients with various diseases) was an outstanding event. Microbes were found in the lungs of patients with pneumonia (pneumococci) and tuberculosis (tuber­culosis bacillus*), in the throat of diphtheria patients, and in the blood in sepsis, etc. It was then proved that many infectious diseases develop because of pathogenic microbes which get inside the body of healthy peo­ple. Bacteriology owes its birth to the wonderful discoveries of Luois Pasteur (" Fermentasions et generasions dites pontanees", 1858), Robert Koch (" Die Aetiologie der Tuberculose", 1882), I. I. Mechnikov (" In­flammation", 1892), and others. Later D. I. Ivanovsky opened the epoch of virology. Diagnostics was thus enriched with new methods of investiga­tion: bacteriological, virological, and immunological. The discovery of the cause of infectious diseases opened wide prospects for their control: prevention of infection (prophylaxis) and treatment. It became evident that an important condition for correct treatment is the discovery of the cause of the disease (aetiology). Microbes, poisons, and other factors were regarded as the cause of human diseases.

The discovery of causes of diseases, and of the role that microbes and other factors play in development of diseases of internal organs provided the basis for a new, aetiological trend in medical thinking. Classification of diseases, together with organopathological principle, became enriched with the determination of their aetiology.

But further study of the causes and aetiology of various diseases show­ed that penetration of microbes into a healthy body is not enough for the disease to develop. Not all persons who were in contact with patients dur­ing epidemics got affected with the disease. Tuberculosis mycobacterium is present inside many healthy persons but only some of them get affected with the disease. Some persons carry pathogenic microbes but do not develop the disease (bacteria carriers). It was found that the condition of the body is the decisive factor for the development of a disease; this factor is decisive in the attitude of man to bacteria: the body of a particular per­son should be sensitive to harmful effects and his resistance to this harmful effects should be weakened in order to develop a particular disease.

It was shown that various symptoms and the course of a given disease depend mainly on the patient's response to the harmful factors. For exam-P pneumonia in a young person is accompanied with high temperature soon ends in complete recovery, while elevation of temperature is in-

Today these microbes are called mycobacteria.

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significant in the old in whom the disease has a protracted course and com­plications develop. It was discovered that infection with a certain microbe, e.g. a streptococcus, can be manifested by various functional and mor­phological changes in the body, i.e. one disease may have different forms, from catarrh of the mucosa to suppuration and even sepsis.

Development of immunology (Mechnikov, Pirquet, and others) ex­plained many aspects of the clinical course of diseases up to auto-aggression and auto-immune processes in non-infectious diseases. Louis Pasteur, the founder of microbiology, was the author of a paradoxical say­ing that microbe is nothing but soil is everything for the development of a disease.

The discovery of various aetiological factors did not thus contradict the valuable clinical observations which showed that one and the same factor can cause a disease in one person and cannot in the another, and that the course of the disease of the same aetiology differs in various persons. The condition and reactivity of the body are the decisive factors in the onset of the disease. Under exposure to a conventionally pathogenic factor (most infections, physical or psychic factors), the development and course of the disease largely depend on the features of the body, hereditary factors and acquired traits. Study of this aspect of the clinic, the forms and stages of the development of pathological processes are the subject matter of the science treating of the mechanism of development of the disease, which is called pathogenesis. The term can be given a simplified interpretation: " how the disease attacks man". But along with pathogenesis, one can always find phenomena which can be interpreted as protective or adapta-tional response of the body, i.e. sanogenesis.

It was easier to discover the specific cause of the disease (e.g. tuber­culosis mycobacterium, streptococcus, injury) than to reveal the entire se­quence of functional and morphological changes occurring in the develop­ment of pathology. Pathogenesis proper, which is prerequisite for understanding disease, stood therefore next to aetiology in importance. The primitive notion of the mechanism of the development of a disease as " microbe—disease" as a direct causal link was replaced with time by the understanding of the role of the predisposing conditions, predisposition or resistance of the body to the pathogenic factor. But this came with the clinical experience. Aetiological trend implies the search of causative fac­tors in each case, which should then be followed by evaluation of the inner factors of the patient. On the whole it had lead to the understanding of the relations between the cause and the body response. It should be remembered that disease is not only a somatic but also psychic suffering, not only a biological but also a social phenomenon. The appropriate

medical and social studies widen the field of investigations from an in­dividual patient to social conditions which can favour the development of the disease. Study of the pathogenesis of a disease resulted in description of new groups of diseases (allergic diseases, collagenoses, etc.) and in the development of new methods for determination of reactivity of the body (allergic and biological tests, immunological, genetic, hormonal studies, etc.).

A powerful impetus to the development of medicine, diagnostics in­cluded, was given by the development and acceptance of the theory of ner­vism by S. P. Botkin and I. P. Pavlov. The theory substantiates the hypothesis that the nervous system accomplishes the most perfect connec­tion between separate parts of the body to account for its integrity, and also connection between the body and the environment, i.e. the nervous system is the leading and decisive system in the vital activity of the sick and a healthy person. The vigorous development of endocrinology from the time of its foundation by Brown-Sequard (1818-1894) stimulated the development of the theory of general pathology in which the decisive role in the development of disease is given to the organs of internal secretion (Selye theory, 1950), which rivalled the theory of nervism. Of course, the role of the humoral factors in the pathogenesis of diseases cannot be disregarded, but this does not diminish the role of the nervous system. The study of the nervous and the humoral regulation of the functions of a human body in health and pathology is a valuable source of facts for a practitioner.

The twentieth century was marked by the event of the greatest historical importance, the Great October Socialist Revolution in Russia in 1917. The revolution gave birth to a new health care system. The Soviet science was enriched by the method of social analysis of problems in medicine and medical sociology. The importance of governmental support of practical medicine was vividly demonstrated to all other countries.

At each stage of its development medicine was enriched with new data and deeper understanding of human diseases. From simple description of disease medicine came to the study of anatomical changes occurring in the affected body, and further to the study of the functional condition of a sick organism and discovery of the causes of the disease, and still further to the study of susceptibility of the subject to a disease, the importance of the en-^vironment and the leading role of the nervous system in the life of man in health and pathology. At the same time, each new stage of development of clinical thinking originated from the previous stage (anatomical, aetiological, etc.) and included it as an indispensible part for a wider, understanding of pathology.

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Chapter 4. General Methodology of Diagnosis