SPECIFIC INTRODUCTORY COMMENTS
"Where is all the wisdom we have lost in knowledge? Where is all the knowledge we have lost in information". T S Eliot, 1888-1965.
"Discovery.........is a byproduct of making things simpler" Jerome Bruner.
The general aim of the following chapters is to illustrate the way clinical problems can be solved in a number of different areas. In this respect, neither the chapters nor the topics are meant to be complete, because we just cannot cover all aspects. But they are meant to give sufficient information to allow you to solve important individual patient problems. In most chapters, relevant background physiology is first set out as a prelude to the discussion of clinical problem-solving.
To help you in your approach to problem-solving a number of relevant clinical problems are set out at the end of each chapter and solved by our method within the four diagnostic categories discussed. The questions which follow should then be easy to answer without your having to go back to the clinical data on each occasion. Where problem solutions are not in the text, they will be made available to the Clinical Library after the relevant session. Part of your end-of-year written paper will consist of such problem-solving exercises. [The other part of the end-ofyear paper will consist of situations where you are given a diagnosis and asked (multiple-choice) questions on whether various features would be compatible with it. This is certainly not an artificial situation in clinical practice, because we are often sent patients by other doctors (e.g. Hospital admitting officers) with diagnostic labels already attached, and our job then is to see that the diagnosis is both correct and complete.]
The first part of the monograph deals with the solving of problems using clinical information alone, which is often sufficient in organs which declare themselves well on history and examination (for example the cardiovascular system, the respiratory system and the central nervous system). But this is not always so, for example with acidbase balance, electrolyte abnormalities and other metabolic disturbances, which often give subtle and nonspecific clinical changes; nor with dysfunction of relatively hidden organs, as in intestinal malabsorption. In such cases, physiological and biochemical investigations are often needed to complete each diagnostic category and this general area will be covered in later chapters. A In the previous section on clinical problem-solving, I pointed out that we should make clinical diagnoses initially
in four separate categories, namely (a) Anatomical diagnosis; (b) Pathological diagnosis; (c) Functional diagnosis; and (d) Aetiological diagnosis. As we go along, I hope you will see not only how this can be done, but how a conclusion in one category may help you reach a decision in another (e.g. CNS Anatomical diagnosis is entirely dependent on your assessment of the Functional derangements clinically), and also how they may overlap (e.g. if we know that a cerebral abnormality came on abruptly, it is most probably, in pathological terms, a vascular event, so we can then go back and reconsider our anatomical diagnosis in terms of vascular neuro-anatomy, e.g. acute right middle cerebral artery ?embolism). Such diagnostic category overlap may also help in a rather different way, namely by suggesting caution in one of your already-established diagnoses.
For example, we typically build up our pathological diagnosis of whether a condition is acute, chronic, etc. on the basis of the history, but remember that we are referring here to clinical pathology, and the actual pathology underlying this may have been developing for much longer than the clinical symptoms and signs suggest. This is largely because most organs have a large reserve of function, so a pathological process such as hepatic cirrhosis or pulmonary emphysema may be present long before the patient notices symptoms, particularly if he rarely puts the organ concerned under load (e.g. shortness of breath on effort in emphysema). A good example of this dissociation between function and pathology can be seen with myocardial ischaemia related to atherosclerosis, where patients have often been building up atherosclerotic coronary narrowings for years, but because these narrowings are short and focal, they initially offer very little resistance to blood flow (the same is true of moderate cardiac valvular stenosis), so that the degree of atheromatous narrowing can be quite severe before symptoms (e.g. angina) occur. Moreover, in some cases, it is not the mere march of natural functional sequelae such as angina which eventually give rise to the presentation from which we make our clinical pathological diagnosis (acute, chronic, etc.) but the occurrence of complications; for example acute myocardial infarction (which may be the first clinical presentation of coronary artery disease) is thought to be most usually due to the occurrence of a sudden thrombus complicating, and super-imposed upon, an injured or ruptured atherosclerotic plaque, so converting a partial arterial narrowing into a complete one.
Notwithstanding these reservations, the four diagnostic categories most often do overlap in a way which helps us reach a diagnosis within each. In difficult cases you should always remember to look at combinations of them both ways around, particularly in relation to cause and effect; for example is the mitral valve incompetence you have diagnosed the primary anatomical diagnosis and the left heart failure and cardiac dilatation a secondary functional consequence, or is it the other way round? Again, determining from the history which came first in time should resolve these questions.
It is also worth re-emphasising that where, anatomically, a number of systems seem to be involved, always try first to apply the principle of Occam's razor, i.e. is there one primary organ system involved with the rest of the symptoms and signs being secondary functional consequences? Take the case of a patient with hepato-splenomegaly, spider naevi, parotid swellings, gynaecomastia, testicular atrophy, jaundice, bruising, finger clubbing, palmar erythema, ascites, oedema, flapping tremor, and clouding of consciousness. Such disease seems to involve almost every organ and yet, with thought, it can be seen as primary hepatic disease with all the secondary functional consequences of that. Hence the importance of knowing the clinical (functional) physiology of all organs. [Of course, there are times when this attempted reduction to a primary involvement of a single system will not work, and then you may have to consider a multi-system disease (e.g. systemic lupus erythematosis). And if that doesn't work, it may be that the patient has multiple and quite separate problems (as commonly occurs in the elderly); in that event you should build up each of your four-category diagnoses quite separately.]
Practical Problem-Solving. N.B. At each weekly Clinical Diagnostic Problem-solving session, one class group will present their four-columned solution to a problem at the end of a chapter nominated the previous week. There will be time made for class interaction along the way, so make sure you all read the relevent chapter and problem before each session. Practise the approach not only using the guidelines here, but also those at the end of Chapters 1 and 2.
Practical tips. When doing these problems: Always give an Interim diagnosis - in all four columns if you can, whenever: (i) The time-course of the disease changes, e.g. a) Chronic (years) shortness of breath - ? due to obstructive airways disease. b) worse dyspnoea for 2 months - ? due to the administration of beta-blockers (started recently for angina) causing bronchiolar spasm (asthma). c) 1 day sudden severe shortness of breath. - ? due to the complication of rupture of hyper-inflated lung into the pleural space (pneumothorax). (ii). Whenever a new symptom appears. This not only gives you a chance to summarise as you go along, but time to pause and reflect on why (Aetiology) things are changing.
Also, whenever you allocate a phrase of information to a column, try to draw some inference from it, however tentative at first. Moreover, as you work through the problem, always link (by arrows) pieces of information pointing in the same direction. And when you have enough information to draw a definate conclusion, highlight it in some way so that you won't overlook it subsequently when making either an interim diagnosis or, at the end, your final overall four-columned conclusion/diagnosis.
All of this must seem rather like being given a written description of how to tie a neck-tie, where illustration would far better demonstrate the points. We will therefore go on to develop examples on a background of clinical physiology etc., in each of the various following chapters. Practice problem-solving at the end of each chapter. Each chapter in this book is followed by a practice problem for you to solve. In the initial chapters, a tabulated solution is given at the end, so that you can compare your efforts with mine, and so come to terms with the method. Later chapters, however, have problems which stand alone ie. do not have any tabled solution for you to compare.