Chapter 20: Clinical Thinking: From Data to Plan

You should then be ready to establish a working definition of the problem. Make this at the highest level of explicitness and certainty that the data allow. You may be limited here to a symptom, such as "pleuritic chest pain, cause unknown." At other times you can define a problem explicitly in terms of structure, process, and cause. Examples include "pneumococcal pneumonia, right lower lobe," and "hypertensive cardiovascular disease with left ventricular enlargement, congestive heart failure, and sinus tachycardia."

Difficulties and Variations

Limitations of the Medical Model. Although medical diagnosis is based rimarily on identifying abnormal structures, disturbed processes, and specific causes, you will frequently see patients whose complaints do of fall neatly into these categories. Some symptoms defy analysis, and you may never be able to move beyond simple descriptive categories such as "fatigue" or "anorexia." Other problems relate to the patient's ' e rather than to the body. Events such as loss of a job or loved one eaten a person and may increase the risk of subsequent illness. Iden- ing such life events, evaluating a person's responses to them, and or king out a plan to help the person cope with them are just as apropriate as dealing with the pharyngitis or duodenal ulcer. Health maintenance has become an increasingly important and legitimate item problem lists for patients. Plans may include, for example, updating immunizations, advice on nutrition, exploring feelings about an import life event, and recommendations for seat belts or exercise.

Single Versus Multiple Problems. One of the greatestdifficulties faced y the student is deciding whether to cluster the patient's symptoms d signs into one or into several problems. The patient's age may help, ' ce young people are more likely to have single diseases while older people tend to have multiple ones. The timing of symptoms is often use1. An episode of pharyngitis 6 weeks ago is probably unrelated to ver, chills, chest pain, and cough today. To use timing effectively, you need to know the natural history of various diseases. A yellowish disarge from the penis followed in 3 weeks by a painless penile ulcer, for ample, suggests two problems, gonorrhea and primary syphilis. A pee ulcer followed in 6 weeks by a maculopapular skin rash and generalized lymphadenopathy, on the other hand, suggests two stages of the me problem: primary and secondary syphilis.

Involvement of different body systems may help you to cluster the items of data. While symptoms and signs within a single system can often be exlpained by one disease, manifestations in different, apparently unrelated stems often require more than one explanation. Again, a knowledge of 's ease patterns is necessary. You might decide, for example, to group a tient's high blood pressure and sustained thrusting apical impulse tother with the flame-shaped retinal hemorrhages, place them in the cardiovascular system, and label the constellation "hypertensive cardiovascular disease with hypertensive retinopathy" You will probably develop another explanation for the diarrhea and left lower quadrant tenderness.

Some diseases affect more than one body system. As you gain in knowledge and experience, you will become increasingly adept at recognizing such multisystem conditions and at building plausible explanations that link together their seemingly unrelated manifestations. In trying to explain the productive cough, hemoptysis, and weight loss reported by a 60-year-old man who has smoked cigarettes for 40 years, you probably even now would postulate lung cancer as a likely cause. You might even support this hypothesis by your observation of clubbed fingernails. With time you will also recognize that his other symptoms and signs can be linked to the same diagnosis. The dysphagia is caused by extension of the cancer to his esophagus; the pupillary inequality is a Horner's syndrome caused by pressure on the cervical sympathetic chain; and the jaundice results from metastases to the liver.

In another case of multisystem disease, a man's fever, weight loss, chronic diarrhea, dysphagia, white-coated tongue, generalized lymphadenopathy, and purplish skin nodules can all be explained by AIDS. The clinician who has not already explored the patient's risk factors for this disease should do so.

An Unmanageable Array of Data. In trying to understand a patient's problems, the clinician often is confronted with a relatively long list of symptoms and signs and an equally long list of potential explanations or labels. As already suggested, you can tease out separate clusters of observations and deal with them one cluster at a time.

You can also analyze a given group of observations by asking key questions, the answers to which steer your thinking in one direction and allow you to ignore others temporarily. For example, you may ask what produces and relieves a person's chest pain. If the answer is exercise and rest, respectively, you can concentrate on the cardiovascular system (and possibly the musculoskeletal system as well) and put aside the gastrointestinal tract. If the pain results from eating quickly and is relieved by regurgitating the food, you logically concentrate on the upper gastrointestinal tract. A series of such discriminating questions forms a branching logic tree or algorithm and is helpful in collecting data, analyzing them, and reaching conclusions that probably explain them.

Quality of the Data. Virtually all the information with which the clinician works is subject to error. Patients forget symptoms, misremember the sequence in which they occurred, hide important but embarrassing facts, and shape their stories toward what interviewers seem to want to hear. Clinicians misunderstand their patients, overlook some relevant information, fail to ask the one key question, jump to premature diagnostic conclusions, or forget to examine the genitals of a patient with asymptomatic testicular carcinoma. You can avoid some of these errors by being thorough, by keeping an open mind as you gather data, and by analyzing any mistakes that you might make...