Chapter 17: Differential Diagnosis

CLINICAL SCENARIO

Your patient is a 78-year-old man who, at today's routine visit for the follow-up of his longstanding hypertension, is surprised to be told that his weight has decreased 10 kg since his last visit 6 months ago. He reports eating less, with little appetite but no food-related symptoms. He takes a diuretic for his hypertension, with no change in dose for more than a year, and uses acetaminophen for occasional knee pain and stiffness. He stopped smoking 11 years ago, and he stopped drinking alcohol 4 decades ago. His examination reveals him to be extremely thin but provides no localizing clues. His initial blood and urine test results are normal.

You review the long list of the possible causes of involuntary weight loss, yet you realize that an immediate exhaustive search for all possibilities is not sensible. Instead, you will seek information about the causes of involuntary weight loss that are common and most plausible in this patient.

Using the Guide

You begin by framing your knowledge gap as a question: “In adults presenting with involuntary weight loss who undergo a diagnostic evaluation, how frequent are the important categories of underlying disease, such as neoplasms, gastrointestinal conditions, and psychiatric disorders?” As you sit at your computer to search for an answer, you notice your nearby files that store your article reprint collection. On a whim, you open the file for involuntary weight loss and find an article about the frequency of diseases in patients with involuntary weight loss that was published more than 30 years ago.¹ Hoping to find some newer evidence, you access PubMed and locate this older citation in the database. Clicking the “Related Articles” link yields 92 citations, of which the second listing, by Hernandez et al,² published in 2003, looks promising because it also explicitly addresses the frequency of underlying disorders in patients with weight loss.² Farther down the list, you find a similar, newer study that has fewer patients,³ as well as 2 narrative review articles on unintentional weight loss,^4,5 which cites the article by Hernandez et al² as the largest of the recent studies of causes of weight loss. To double check, you scan the chapter on weight loss in an electronic text and find that no newer large study is mentioned. With some confidence that you have found recent evidence, you decide to start with the larger of the 2 studies and retrieve its full text to appraise critically.