ART AND SCIENCE OF DIAGNOSIS

12 May

The triumphs of medical microbiology tend to overshadow another important aspect of nineteenth-century medicine that  grew out of what we might think of as the unhappy  intersection between clinical medicine practiced  at the patient’s  bedside and  pathological  investigations  con- ducted  in the autopsy  room.  Achieving a more  precise understanding of the nature  and seats of disease within the dead body was eventually coupled with more precise diagnosis of disease in living patients.  Symp- toms were correlated  with internal localized lesions, but, until the devel- opment of instruments  such as the stethoscope, the lesions could only be detected at the postmortem.

The gradual  development  and recent enthusiastic  reception  of the

technological  aids used in the diagnosis of disease represent  remarkable aspects of the evolution  of medical practice over the course of the last two hundred  years. Beyond their obvious  role in transforming the art of diagnosis, medical instruments  have profoundly affected the relation- ship between patient and physician, the education  and practical training of physicians, the demarcation between areas of medical specialization, the locus of medical practice, and even the financial structure  of medical care and  treatment. From  the time of Hippocrates until  well into  the nineteenth century, the average physician relied on essentially subjective information, such as the patient’s  own account  of the course of illness and the physician’s observations of notable signs and symptoms. Which signs and symptoms were considered notable was determined by prevail- ing medical philosophy,  tempered  by the experience of the individual physician.  In  general,  physical  examinations that  involving  touching the  patient  were extremely  limited,  except  for  some  attention to  the quality  of the  pulse.  Under  these  circumstances,  the  physician  could diagnose and prescribe by letter without even seeing the patient.  Indeed, the fee for advising the patient  by letter was often higher than  that  for an office visit.

During  the  nineteenth  century,  even  the  average  physician  was being encouraged  to follow the path  marked  out by the great clinicians and morbid  anatomists of the previous  century  towards  a more active role in obtaining  objective information concerning signs and symptoms of illness by direct  physical  examination. In  1761, the  year  in which Giovanni   Battista   Morgagni   (1682–1771) published  his  monumental five-volume examination  of The Seats and Causes of Diseases, Leopold Auenbrugger (1722–1809) of Vienna published another  landmark in the history  of  medicine  entitled  Inventum Novum. In  little  more  than  20 pages, Auenbrugger set forth  an account  of a new diagnostic  method called ‘‘chest percussion.’’ Using this method,  the physician could gain insight into the internal  state of the chest cavity by carefully evaluating the  sounds  produced  by tapping  or  thumping  the  patient’s  chest.  Of course a great  deal of experience was needed  before  a doctor  learned to distinguish  between the sounds  of a healthy  chest and  those  which betrayed  the earliest  signs of tuberculosis  or pneumonia produced  by a ‘‘morbid chest.’’

Auenbrugger, who was considered  a gifted amateur  musician and composer,  presumably  had  a better-trained ear  than  most  physicians. Chest  percussion,  which  depends  on  the  differences  in  sound  trans- mitted  through  air and fluid, is rather  like tapping  a wine cask or beer barrel  to  determine  whether  it is empty  or  partially  full. Because his father  was a tavern  keeper,  Auenbrugger was probably  quite  familiar with this phenomenon. Although  Auenbrugger considered  his method revolutionary, some physicians saw little difference between percussion and other  methods  of diagnosis by auscultation (listening) dating  back to the time of Hippocrates, such as shaking the patient  and listening for the sound of fluid sloshing about  in the chest, or placing the physician’s ear on the patient’s chest. Indeed, Auenbrugger’s  teacher had employed percussion of the abdomen  in cases of ascites (fluid accumulation in the peritoneal  cavity).

Few physicians expressed any interest in Auenbrugger’s work until

Jean-Nicolas Corvisart  (1755–1821) published  a translation and  com- mentary  in 1808. By this time, thanks  to the work of the so-called Paris school of morbid anatomy,  humoralism  had been essentially eclipsed by the concept of localized pathological  anatomy.  Corvisart’s disciples, especially Rene´ The´ophile  Hyacinthe  Lae¨nnec (1781–1826), established the value of direct (immediate)  and indirect (mediate) auscultation and transformed the art  and  science of physical  examination. Working  at the Necker  Hospital  and  the Charite´,  Lae¨nnec  adopted  the goals and methods of the Paris school of hospital medicine. Eventually,  his inven- tion of the stethoscope  would make him one of the most famous exem- plars  of this  school,  and  a symbol  of French  science, but  during  his rather  brief lifetime, his peers generally  treated  him with  indifference and hostility.

Proponents of early nineteenth-century ‘‘hospital medicine’’ tended to see themselves as disciples of Hippocrates, because of their emphasis on clinical observation, but the context in which they worked, as well as their  methods  were very different  from  those  of the ancients.  Leaders of the French  Revolution had  imagined  a new era in which hospitals, medical schools, and doctors would disappear.  Instead,  in the aftermath of  the  Revolution, new  hospitals,  medical  schools,  and  professional standards emerged.  In  the  major  hospitals  of  Paris,  clinicians  could see thousands of  cases  and  carry  out  many  hundreds   of  autopsies. American  students  flocked  to  the  great  hospitals  of  France  to  sup- plement their limited education  and gain clinical experience. Becoming disciples of French  masters,  they translated their writings into English. A note of envy for the extensive opportunities for the observation of dis- ease found  only in Europe  often crept into their introductory remarks. Somewhat  later in the century,  schools and hospitals  in Germany  and Great  Britain  overtook  those  of France  as centers  of clinical studies and laboratory research.

The large scale of nineteenth-century hospital  medicine provided the ‘‘clinical material’’ for more active and intrusive methods of physical examination  and diagnosis, statistical  evaluation  of various therapeutic interventions  (sometimes  known  as  the  numerical  method  of  Pierre Charles Alexandre  Louis, 1787–1872), and confirmation of correlations among symptoms, lesions, and remedies by means of investigations con- ducted  in  the  autopsy   room.  Although   immediate  auscultation and chest percussion were becoming valuable aids to diagnosis and research into  what  Corvisart  called ‘‘internal medicine,’’ many  physicians  were reluctant  to practice these methods.  Given the great abundance of fleas and lice on many patients, and the general neglect of personal hygiene, a certain  reluctance  to  put  one’s ear  on  the  patient’s  chest  was under- standable.  The  stethoscope  not  only  provided  some distance  between physicians and patients, it improved the quality of the sounds that could be heard  within the chest. The name stethoscope  was coined from the Greek  for ‘‘chest’’ (stethos) and ‘‘to view’’ (skopein). It was the first of many ‘‘scopes’’ that  gave researchers  access to the interior  of the body and  allowed them to ‘‘anatomize’’ the living before  they dissected the deceased.

In On Mediate Auscultation (1819), Lae¨nnec described the difficul- ties he encountered  when examining a young woman with signs of heart disease. Discreet percussion with a gloved hand did not reveal anything about  the state  of the inside of her chest, because  of the rather  stout state of the outside of her chest. Considerations of propriety  precluded immediate  auscultation, but  in a flash of inspiration, Lae¨nnec  took  a sheaf of paper  and  rolled it into a cylinder. When he applied  one end of the cylinder to her chest and the other  to his ear, he could hear the heartbeat with remarkably clarity.  Improvements in the basic cylinder

Stethoscopes

Stethoscopes for sale in 1869.

of Lae¨nnec  made it possible to listen to many sounds  and movements within the chest. Through  changes in materials  and configuration, and the introduction of stethoscopes  that  transmitted sound  to  both  ears, doctors  tried to improve the stethoscope.  The instrument  has remained fairly consistent in appearance since the 1920s. The classical stethoscope has been relegated  to the status  of a ‘‘triage tool’’ to detect obviously suspicious sounds  that  lead to more sophisticated and  expensive tests, such as the echocardiogram.

Lae¨nnec warned physicians not to neglect Auenbrugger’s  methods

when using the stethoscope,  because the physician should use as many aids to diagnosis as possible. More important, it was essential to realize

that a great deal of practice was required before the instrument  could be used  effectively. To  learn  the  technique,  the  young  physician  should work in a hospital  where he had access to many kinds of patients  and expert guidance. Moreover,  large numbers of postmortems were needed to confirm  diagnostic  accuracy.  Like many  of his colleagues, Lae¨nnec succumbed  to tuberculosis,  the disease that  was so often  the object of his research.  France,  which had  contributed so much  to  the study  of tuberculosis,  had the highest mortality  rate from consumption in west- ern Europe  well into the twentieth  century,  perhaps  largely due to lin- gering  beliefs that  heredity  was more  significant  than  contagion  and general indifference to public health measures.

Sir John Forbes  (1787–1861), who translated excepts of Lae¨nnec’s nine  hundred-page treatise  on  auscultation and  diseases  of  the  chest into English in 1821, noted that the stethoscope  was extremely valuable, but he doubted  that mediate auscultation would ever come into general use among English doctors,  because its use required too much time and trouble.  His most serious objection  was that  the instrument  was totally foreign  in character  and  incompatible  with  British  traditions. Its  use could be imposed  on patients  in the army  and  navy, and  in hospitals, but  not  on private  patients.  Like many  of his colleagues, Forbes  saw something   ludicrous   about   a   dignified   physician   listening   to   the patient’s  chest through  a long tube.  In other  words,  instruments  were associated  with surgeons  and manual  labor,  not with the philosophical habits of English physicians. Many physicians believed that  the advan- tages of objective aids to diagnosis were small and uncertain  compared to  the  threat  that  instruments  might  disrupt  the  bond  that  was sup- posed to exist between physician  and  patient.

Obviously, Dr. Forbes proved to be a very poor prophet.  The stethoscope  soon became the very symbol of medicine and a necessary part of the doctor’s wardrobe. Few doctors were able to match Lae¨nnec’s extraordinary skill at auscultation, but many learned that it was possible to use the instrument  to gain objective information about the nature of a patient’s condition  and to distinguish between different diseases, such as tuberculosis  and  pleurisy. The stethoscope  made  it possible for physi- cians to  ‘‘anatomize’’ the living body,  but  it was only in the autopsy room  that  the  diagnosis  could  be  confirmed.  Even  the  most  selfless patient  was unlikely  to  sympathize  with  a physician  who  referred  to the  postmortem as the  best  ways to  diagnose  disease,  because  a few autopsies  shed more light on pathology  than  20 years spent observing symptoms.

It is interesting  that  the thermometer was not accepted  into diag-

nostics as quickly as the stethoscope,  although  Santorio  Santorio  had introduced   the  clinical  thermometer in  the  seventeenth  century.  The concept  of localized pathology  is generally given credit for the accept- ance of physical aids to diagnosis,  as well as advances  in surgery,  but

the thermometer, which reflected a general condition  of bodily heat, did not fit the pattern of a pathology  of solids.

The stethoscope was, of course, only the first of the many ‘‘scopes’’

that allowed physicians to view every nook and cranny of the interior of the body. It is obviously a long way from Lae¨nnec’s cylinder to comput- erized  axial  tomography  (CAT  scans),  nuclear   magnetic  resonance imaging  (MRI),  and  positron  emission  tomography (PET  scans),  but it  is a  brief  interval  compared  to  the  many  centuries  that  separated Hippocrates from Lae¨nnec. From  the patient’s point of view, advances in diagnostics  that  were not  associated  with  progress  in therapeutics were of dubious  value. Although  increasingly sophisticated and expen- sive new instruments  have  contributed to  the  power  and  prestige  of medicine, and may have saved many patients from the burden of uncer- tainty,  they do not necessarily improve  the treatment of disease or the healing of wounds.

One of the persistent complaints  issued against  the great hospitals of  Paris  and  Vienna  was  that   their  physicians  were  too  interested in  diagnosis  and  pathology,   but  too  little  interested  in  therapy.   A nineteenth-century cynic assessing the battle between practitioners who favored  active  interventions and  researchers  who  relied  on  a  passive or expectative approach could conclude that  Viennese hospital  doctors no longer killed their patients, they just let them die. In the Parisian hos- pitals, a variety of approaches to therapy  competed for attention. Some physicians favored bleeding, others relied on antimony  or other chemi- cal remedies,  while some remained  loyal to  complex ancient  remedies derived from plants, animals, and minerals. Even the standard definition of therapeutics  as the art of curing diseases was called into question  by those who claimed that the term referred to the most convenient  means of  treating   disease.  Oliver  Wendell  Holmes  suggested  that   patients might  be  better  off  if the  entire  materia  medica,  except  for  quinine and  opium,  was thrown  into  the  sea. Most  doctors,  however,  agreed that it was better to try something doubtful  than do nothing. Moreover, advances  in chemistry  were providing  new drugs—such  as morphine, emetine, strychnine, codeine, and iodine—that  were unquestionably powerful,  even if their safety and efficacy remained  in doubt.

An accurate  diagnosis  at an early stage of a disease like tubercu- losis, which was made  possible by tuberculin  and  chest X-rays,  could be  interpreted as  simply  increasing  the  length  of  time  in  which  the patient  brooded  on the inevitability of death. Nevertheless, the develop- ment of sophisticated diagnostic  instruments  has become fundamental to the health-care  enterprise and is often blamed for the escalating costs of medical  care.  Although  the  stethoscope  and  similar  devices intro- duced the fundamental concept  of studying  the interior  structures  and functions  of the living body,  the trend  to ever more sophisticated and expensive  diagnostic   techniques   can  be  traced   to  Wilhelm  Konrad

Roentgen’s  (1845–1923) discovery  of  X-rays  in  1895. Roentgen   was investigating  the  properties  of cathode  rays  when he observed  a new kind  of ray  that  was able  to  pass  through  opaque  objects,  including clothing,  hair,  and  flesh. Bones, however,  stopped  the rays,  leaving a picture  of their  shadow  on a photographic plate.  Roentgen’s  prelimi- nary  report  to the Physico-Medical  Society of Wurzburg, ‘‘On a New Kind  of Ray,’’ included several radiographs, including the well-known picture  of  Frau   Roentgen’s  skeletal  hand.   When  the  popular   press published  stories about  X-rays,  Roentgen’s  findings caused worldwide speculation  about  their potential  role in medicine. In 1901, Roentgen, already  a  universal  celebrity,  was  awarded   the  first  Nobel  Prize  in Physics.

X-rays gave physicians a new diagnostic tool, as well as a means of

investigating  the interior  of the body.  Just as the microscope  and tele- scope  made  it possible  to  look  at  the  microcosm  and  macrocosm  in new ways, by making the flesh that  clothed the bones essentially trans- parent  X-rays created  a new way of looking at the human  body. After the initial period of enthusiastic  and uncritical  use, researchers realized that  prolonged   exposure  to  X-rays  might  cause  tissue  damage  and cancer, in addition  to the burns  that  were more quickly noted.

By the  late  1960s, new medical  instruments  made  it possible  to

visualize interior aspects of the body that had been impossible to see with ordinary  X-rays. The methods called the ‘‘second wave of imaging tech- nology’’ included  computerized  tomography, MRI,  ultrasound, mam- mography, and  PET.  Sir  Godfrey  Hounsfield  (1919–2004), a  British electrical engineer, and Allan Macleod  Cormack  (1924–1998), a South African physicist, shared the 1979 Nobel Prize in Physiology or Medicine for  their  independent  contributions to  the  development  of computer- assisted  tomography.  (The  brightness  of  images  that  appear   on  the CAT  scanner  is measured  in  Hounsfield   units.)  Neither  man  had  a background in  medicine  or  a  doctoral   degree,  but,  according  to  the Nobel  Prize  Committee,  their  revolutionary work  ‘‘ushered medicine into the space age.’’

Computed axial tomography allows computers to analyze and pro-

duce a series of cross-sectional images from X-rays that  are taken from many  different  angles. Although  the original  scanner  was designed to examine the head, the instrument  was adapted  to study every organ sys- tem in the body. Despite the enormous  cost of the device, about  seven thousand CAT  scanners  were in use in American  hospitals  by 2000. Magnetic  resonance  imaging  (originally  called nuclear  magnetic  reso- nance or NMR)  can create thin-section  images of any part  of the body from  any  angle,  generating  biomedical  and  anatomical information. MRI   has  been  particularly  valuable  for  diagnosing   diseases  of  the brain  and  central  nervous  system. Physicists and  chemists used NMR

technology  in the 1940s, but it became a diagnostic  tool, referred to as

MRI,  in the 1980s.

In less than two hundred years, diagnostic and therapeutic technol- ogies have  become  central  and  enormously  expensive components  of medicine.  Technological  success  has  created  an  avalanche  of  expec- tations and questions about the actual risks and benefits associated with this transformation of medical practice.  Faith  in the diagnostic  power of medical instruments  led to decreased  interest  in the procedure  that the pioneers  in this field thought so fundamental: confirmation at the postmortem.

Autopsies were once routinely  performed  in a majority of hospital deaths, but since the 1980s, the number of such procedures in the United States and several other countries has dropped  sharply. Before 1970, the Joint  Commission  on Accreditation of Healthcare Organizations man- dated autopsies in at least 20 percent of all hospital deaths, but by 1995, the  National Center  for  Health  Statistics  stopped  collecting  national autopsy  statistics.  In  most  wrongful-death cases against  hospitals  or physicians,  an  autopsy  is critical  to  establishing  negligence.  Doctors and  hospital  administrators, afraid  of being sued over mistaken  diag- noses, increasingly avoid autopsies.  Attempts  to quantify  the incidence of medical  errors  suggest  that  autopsies  uncover  missed  or  incorrect diagnoses in up to 25 percent of hospital deaths. In many cases, the cor- rect diagnoses might have led to changes in therapy or other procedures. Autopsies   revealed  that   many  systemic  bacterial,   viral,  and  fungal infections had not been diagnosed prior to death. Whatever the cause of death  in a particular case, such infections  might have been a threat  to those  who  had  been  in  contact  with  the  patient.   Similar  studies  of patients who died in intensive-care units found many instances of incor- rect  diagnoses,  as  well as  evidence  of  infections,  cancers,  and  other undiagnosed diseases. Researchers suggested that over-reliance on soph- isticated  diagnostic  imaging techniques  sometimes contributed directly to major  diagnostic  errors.

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