A Closer Look at Clubbing

Feb 12 2020

I saw a patient in clinic today referred from the emergency department for worsening dyspnea. This elderly gentleman had been experiencing shortness of breath on exertion for several months (and likely longer) which had become progressively worse. He did have a significant smoking history and potential history of workplace exposure to paints. In terms of associated symptoms, he denied any symptoms of cough or sputum production, had no symptoms of heart failure, and no infectious symptoms. He did note some unintentional weight loss in the past few months despite no changes in his diet or appetite. My initial physical exam for him was relatively unremarkable, although his respiratory exam showed slightly decreased air entry at the bases but no adventitious sounds. His investigations were notable for a venous blood gas showing a pattern consistent with chronic respiratory acidosis with a compensatory metabolic alkalosis. Given his presentation, smoking history and VBG, we were quite suspicious for COPD. After presenting the case to my preceptor and discussing our plan, she asked if I had examined him for clubbing, which I had forgotten to do.

When we returned to the room, we went over his respiratory exam and took some time to look at his nails. Indeed, the patient did have many features consistent with clubbing! Surprisingly, this was the first time I had seen features of clubbing in a patient. My preceptor carefully showed me the various ways to assess for clubbing. We examined the distal curvature of his nail, the nail-fold angle, the phalangeal depth ratio (comparing the distal phalangeal depth with the interphalangeal depth) and felt the pulp of his distal finger. I really appreciated the time my preceptor took to go over these details of the physical exam. As medical students we often just use the Schamroth sign to assess for digital clubbing, since it is a relatively quick way to qualitatively assess for clubbing. Although a study did show Schamroth sign was a reasonable way to assess for clubbing, having good concordance with other methods (Pallares-Sanmartin A et al., 2010), there are many other more quantitative measures to assess for clubbing. I also realized how going back to the basics of pre-clerkship and following the order of careful inspection, percussion, palpation and auscultation in the physical exam allows us to capture details which can be so telling!

After noting the findings of clubbing, we also reviewed which conditions are associated with this finding and built our differential. Although I remember being taught to look for clubbing in COPD patients, COPD itself is actually not a cause of clubbing. I use the mnemonic "CLUBBING", which I find helpful, to remember some of the diseases associated with clubbing:

• C: cyanotic heart disease, cystic fibrosis
• L: lung cancer, lung abscess
• U: ulcerative colitis
• B: bronchiectasis
• B: benign mesothelioma
• I: infective endocarditis, idiopathic pulmonary fibrosis
• N: neurogenic tumors
• G: gastrointestinal disease (biliary cirrhosis, celiac)

In this patient, it is possible he has underlying bronchiectasis or perhaps a malignancy contributing to his clubbing, in addition to a diagnosis of COPD. We have ordered PFTs and a CT chest to help elucidate the etiology of his dyspnea (and clubbing) and will see him again in clinic afterwards. This experience taught me the various ways to assess for clubbing and to not overlook the value of a head-to-toe inspection in patients!

-MB-

References:

1. Pallares-Sanmartin A, et al. Validity and Reliability of the Schamroth Sign for the Diagnosis of Clubbing. JAMA. 2010; 304(2):159–161. doi:10.1001/jama.2010.935.