Pathophysiology

1. Vasodilation of nail-bed vessels secondary to an unidentified mediator (candidates - ferritin, bradykinin, prostaglandin, 5-HT) which is normally inactivated in the lung but may persist in those with digital clubbing where inactivation is defective or there is a right-to-left shunt
2. Increased growth hormone
3. Organs supplied by the vagus are affected by digital clubbing - vagotomy can reverse digital clubbing in bronchial carcinoma
4. Tumour necrosis factor
5. Increased PDGF and FGF

Causes of digital clubbing:

1. Idiopathic - by far the commonest
2. Secondary :
   

   Gastrointestinal	Respiratory	Cardiac	Rare
   Cirrhosis (esp PBC) IBD (esp Crohn's) Malabsorption (coeliac, tropical sprue) GI lymphoma	Bronchial carcinoma (most commonly squamous cell) Chronic suppurative lung disease (abscess, bronchiectasis, cystic fibrosis, empyema) Fibrosing alveolitis Mesothelioma	Congenital cyanotic heart diseases (Fallot's, transposition) Infective endocarditis Atrial myxoma (rare)	Familial Grave's disease - pseudoclubbing (thyroid acropachy) Unilateral - seen in axillary artery aneurysm and brachial AV malformation

    

Approach

• Spot diagnosis
• Expose hands to above the elbows
• Ask patient to place palms upwards on a pillow

1. Inspection
   • Exaggerated anteroposterior and longitudinal curvature of the nails
   • Loss of angle between nail and nail bed (demonstrated by "Lovidond's diamond sign")
   • "Drumstick" or "parrot beak" appearance of the nail - doigts hippocratique
2. Palpation
   • Bogginess / fluctuation of nail bed
   • Elicit by supporting patient's finger with two thumbs

Grading of Clubbing

Completion

1. Palpate wrist joint for tenderness
   • Seen in hypertrophic pulmonary osteoarthropathy - rapid painful digital clubbing nearly always due to bronchial carcinoma
2. Examine toes for digital clubbing
3. History and examine patient for causes of clubbing