Read with two objectives: first to acquaint yourself with the current knowledge on the subject and the steps by which it has been reached; and secondly, and more important, read to understand and analyze your cases.
—SIR WILLIAM OSLER
“The Student Life”
DeGowin’s Diagnostic Examination provides the introductory knowledge base, describes the skills, and encourages the reader to acquire the experience and judgment needed to become a master clinical diagnostician. Despite recent advances in testing and imaging, the clinician’s skills in taking a history and performing a physical examination are needed now more than ever.
The history is the patient’s story of his or her illness related as the time course of their symptoms; the physical examination reveals the signs of disordered anatomy and physiology. The symptoms and signs of disease form temporal patterns, which the clinician recognizes from experience and knowledge of anatomy, physiology, and diseases. From the history and physical examination, the clinician generates testable pathophysiologic and diagnostic hypotheses—the differential diagnosis. Proficiency and confidence in differential diagnosis should improve with regular use of DeGowin’s Diagnostic Examination.
The differential diagnosis is subjected to laboratory testing. Proper use of the laboratory and imaging are based upon accurate diagnostic hypotheses generated while taking the history and performing the physical examination. Undisciplined use of both laboratory tests and imaging modalities is a major cause of increasing healthcare costs and leads to further inappropriate testing and patient harm. Over-reliance on technology has contributed to loss of clinical bedside skills.
DeGowin’s Diagnostic Examination is intended to assist the student and clinician in making reasonable diagnostic hypotheses from the history and physical examination. Part 1, Chapters 1 to 3, discusses the diagnostic framework in detail. Chapter 1 discusses the importance of diagnosis and the process of forming a differential diagnosis specific to each patient. Chapter 2 discusses the process of history taking and documentation of the findings in the medical record. Chapter 3 outlines the screening physical examination.
The heart of DeGowin’s Diagnostic Examination is Part 2, Chapters 4 thru 15. It is organized in the sequence in which the clinician traditionally performs the examination. Chapter 4 discusses the vital signs. Chapter 5 introduces some systems to keep in mind throughout the examination since they present with symptoms and signs not easily referable to a specific body region. Chapters 6 thru 13 discuss the diagnostic examination by body region: the skin (Chapter 6), the head and neck (Chapter 7), the chest and breasts (Chapter 8), the abdomen (Chapter 9), the urinary system (Chapter 10), the female genitalia and reproductive system (Chapter 11), the male genitalia and reproductive system (Chapter 12), the spine and extremities (Chapter 13), the neurologic examination (Chapter 14), and the psychiatric and social evaluations (Chapter 15).
Parts 3 and 4 provide supplemental information. Chapter 16 discusses the preoperative examination. The intent is to give the reader a framework for evaluating the medical risks in the perioperative period and an approach to communicating those risks to the patient and surgeon. Chapter 17 introduces the principles of laboratory testing and imaging critical to an efficient use of the laboratory and radiology. Chapter 18 lists many common (not “routine”) laboratory tests that provide important information about the patient’s condition not accessible from the history or physical examination. More specialized tests used to evaluate specific diagnostic hypotheses are not discussed.
Chapters 6 thru 14 have a uniform organization: (A) each chapter begins with a brief overview of the major organ systems to be considered; (B) next is a discussion of the superficial and deep anatomy of the body region; (C) the physical examination of the region or system is described in detail in the usual order of performance; (D) the symptoms particularly relevant to the body region and systems are presented; (E) the physical signs in the region or system examinations are listed (some findings can be both symptoms and signs; discussion of a finding is in the section where it is most likely to be encountered, then cross-referenced in the other section); and (F) discusses diseases and syndromes commonly in the differential diagnosis of symptoms and signs in the body region and systems under discussion. To avoid duplication, the text is heavily cross-referenced.
Brief discussions of many diseases and clinical syndromes are included so the reader can appreciate the patterns of symptoms and signs they commonly manifest. This will help the clinician determine whether that disease or syndrome should be included in the differential diagnosis of the symptoms and signs in their specific patient. Particularly useful points of differentiation are listed after the DDX symbol.
DeGowin’s Diagnostic Examination is not a textbook of medicine. The reader must use this with a comprehensive textbook of medicine to fully understand the diseases and syndromes. We strongly recommend Harrison’s Principles of Internal Medicine as a companion text.
We emphasize the characteristics of diseases because a clinician who knows the manifestations of many diseases will ask the right questions, obtain the key history, and elicit the pertinent signs distinguishing one disease from another. Instructions on how to elicit the specific signs are included in the physical examination section for each region; if the maneuver is not part of the usual examination, it is discussed with the sign itself. Following the descriptions of many symptoms and signs is a highlighted CLINICAL OCCURRENCE section. This is a list of diseases often associated with the symptom or sign. The organization of the Clinical Occurrence section is based upon the approach to the differential diagnosis of the symptom or sign felt to be most clinically useful.
Where a broad differential exists, we have introduced an organizational scheme for the CLINICAL OCCURRENCE based upon the pathophysiologic mechanisms of disease. The clinician can often narrow their differential diagnosis to one or a few basic mechanisms of disease: congenital, endocrine, degenerative/idiopathic, infectious, inflammatory/immune, mechanical/traumatic, metabolic/toxic, neoplastic, neurologic, psychosocial, or vascular. This facilitates the creation of a limited yet reasonable differential diagnosis. The categories in this scheme are not mutually exclusive; a congenital syndrome may be metabolic, infections are usually accompanied by inflammation, and a neoplastic process may cause mechanical obstruction. Although not rigid, this is a useful conceptual construct for thinking about the patient’s problems.
Symptoms, signs, syndromes, and diseases that may indicate an emergent condition requiring immediate and complete evaluation are noted by the • marginal symbol.
Use your understanding of normal and abnormal anatomy and physiology as the basis for thinking within clinical medicine, you can avoid the trap of “word-space.” This is the term one of us (RFL) has given to the common practice of using lists and word association as an approach to diagnosis: associating a word (for instance, cough) with a memorized list of other words (pneumonia, bronchitis, asthma, postnasal drip, gastroesophageal reflux, etc.). The inherent emphasis on memorization in this scheme is the bane of all medical students; fortunately, it is not only unnecessary, it is counterproductive. Cough is a protective reflex arising from sensory phenomena in the upper airway, bronchi, lungs, and esophagus mediated through peripheral and central nervous system pathways and executed by coordinated contraction of the diaphragm, chest wall, and laryngeal muscles. With this physiologic context, and our understanding of the mechanisms of disease, we can hypothesize the irritants most likely to be relevant in each specific patient.
New diseases are being encountered with surprising frequency. They present not with new symptoms and signs, but with new combinations of the old symptoms and signs. It is our hope that the reader will learn to recognize the patterns of known diseases and to be alert for patterns that are unfamiliar (those not yet in their knowledge base) or previously unrecognized (the new diseases). HIV/AIDS was recognized as an unprecedented clinical syndrome with a new pattern of familiar symptoms (weight loss, fever, fatigue, dyspnea, cough) and signs (wasting, generalized lymphadenopathy, mucocutaneous lesions, Kaposi’s sarcoma, opportunistic infections) in a unique population (homosexual males and IV drug users). Continuous expansion of our personal knowledge of the known while welcoming the unfamiliar and unknown is the excitement of clinical practice.
The testing of specific diagnostic hypotheses is beyond the scope of this book. It is subject to constant change as new tests are developed and their usefulness evaluated in clinical trials. Part 4 discusses the principles of laboratory testing (Chapter 17) and some common laboratory tests (Chapter 18). The reader should consult Harrison’s Principles of Internal Medicine and the current literature when selecting specific tests to evaluate their diagnostic hypotheses [Guyatt G, Rennie D, eds. Users’ Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice. Chicago, IL: AMA Press; 2002; Guyatt G, Rennie D, Meade MO, Cook DJ, eds. Users’ Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice. 2nd ed. New York, NY: McGraw-Hill; 2008].