Clubbing

Original Editor - Kalyani Yajnanarayan
Top Contributors - Kalyani Yajnanarayan and Rucha Gadgil

Definition/Description

Digital clubbing is the uniform, soft tissue swelling of the distal phalanx of a digit. This commonly occurs bilaterally, however, can be unilateral in presentation (e.g. brachial arteriovenous malformations, axillary artery aneurysm). Often distal clubbing is painless unless associated with underlying conditions such as pulmonary hypertrophic osteoarthropathy. While patients are often unaware of its presence, an understanding of its causation alerts healthcare professionals to the significance of this sign and the need for further investigation.

Pathophysiology and Etiology

Although there have been multiple hypothesis on the pathophysiology of digital clubbing, the primary pathogenic finding has been increased capillary density.

1. The increased production of vascular endothelial growth factor (VEGF) stimulated by hypoxia results in increased permeability, vascularity and eventually connective tissue changes.
2. Growth hormone has been implicated as a cause of clubbing in bronchogenic carcinoma.
3. Platelet derived growth factor (PDGF) released by platelets in the vasculature of the fingertips in conditions that involve chronic platelet excess (e.g., inflammatory bowel disease) leads to proliferation of vascular smooth muscle cells and fibroblasts, causing clubbing.
4. Local arteriovenous anastomoses provoked by neurocirculatory stimuli can also cause clubbing. Clubbing is often associated with numerous gastrointestinal and cardiorespiratory diseases.

Clinical Presentation

Stages of digital clubbing

Stage 1: peri-ungual erythema and softening of nail bed

Stage 2: increase in the normal 160° angle (lovibond angle) between the nail bed and the proximal nail fold occurs, resulting in convexity as the nails grow. Eventually, the depth of distal phalanx increases and distal inter-phalangeal joint may become hyper-extensible. At this stage, finger develops a clubbed appearance

Stage 3: Finally, the nail and peri-ungual skin appear shiny and nail develops longitudinal ridging. This whole process usually takes years but in certain conditions, clubbing may develop sub-acutely (e.g. lung abscess, empyema thorasis).

Clubbing can also be graded in 5 steps

Grade 1: fluctuation and softening of the nail bed,

Grade 2: increase of the hyponychial angle,

Grade 3: accentuated convexity of the nail,

Grade 4: clubbed appearance of the fingertip, and

Grade 5: development of a shiny or glossy change in nail and adjacent skin.

Diagnostic Procedures

As there's no "gold standard" for the evaluation of clubbing, healthcare professionals must rely on their clinical examination skills to verify the diagnosis.

• Palpation and visual examination are usually sufficient to diagnose advance clubbing, however, early stages are more difficult to detect.

The Schamroth sign: is the absence of the diamond shaped "window" that normally occurs when the dorsal surfaces of the distal phalanges on opposing fingers are placed together. With palpation, the nail may seem loose within the soft tissue and in advance stages the proximal edge of the nail can be felt through the skin.

The nail-fold angle: is one method of diagnosing clubbing. In asymptomatic fingers, the nail extends at approximately 160 degrees from the bed, however, in clubbed fingers the angle approaches 180 degrees.

The phalangeal-depth ratio: is also used to differentiate normal nails to clubbed nails. In distal clubbing, the interphalangeal depth is smaller than the distal phalangeal depth. Healthcare professionals usually estimate the phalangeal depth ratio as calipers are not readily available.

Palpation: the sides of the finger are griped between the thumb and middle finger of each hand and the examiner rocks the proximal and distal ends of the nail applying a downward pressure and using the nail bed as fulcrum. In patients with digital clubbing, the nail is perceived as "floating" within the soft tissue and in more advanced cases may even be able to feel the proximal edges of the nail.

• Diagnosing clubbing with a high frequency ultrasound allows for non-invasive diagnosis measuring the soft tissue depth under the nail (SDUN), interphalangeal depth (IPD), and distal phalangeal depth (DPD) and calculating the ratio of DPD and IPD (DPD/IPD) . Increased DPD/IPD (above 1) and increased SDUN and IPD were signs that clubbing was present.

Differential Diagnosis

Common differential diagnosis:

• Lung cancer
• Bronchiectasis
• Lung abscess
• Empyema
• Idiopathic pulmonary fibrosis
• Endocarditis
• Congenital heart disease
• Ulcerative colitis
• Crohn's disease
• Liver disease (primary biliary cirrhosis)
• Cystic fibrosis
• Interstitial pulmonary fibrosis
• Sarcoidosis
• Asbestosis

Management / Interventions

The primary focus of treatment of digital clubbing isn't on the clubbing itself but the underlying etiology if present. Therefore, the response to treatment provided is highly dependent on the underlying disease process. Observing clubbing in initial physical evaluation can prove to be essential for a positive health outcome. Although, clubbing itself cannot be treated, it can be a sign of prognosis of the disease.

Treatment of the underlying condition should be with a multidisciplinary team with physical therapist being a part of it.