Radiological Imaging in Nail Unit Disorders (Part I) - Modalities Used.

The nail unit is a unique skin appendage, capable of mounting only a limited number of reaction patterns to a variety of insults. This makes it difficult to diagnose many nail conditions based on clinical features alone. Thus, diagnostic modalities have an important role to play in nail disorders. Emphasis is placed on non-invasive diagnostic methods, of which, radiological imaging forms an important part; however, it is a field largely under-explored with very few studies and reports available in the literature. This could be due to the problems encountered in nail unit radiology including its small size, complex anatomy, requirement for special high-frequency probes to reliably evaluate superficial structures, and non-familiarity with nail unit radiological features even amongst trained radiologists. Nevertheless, it plays a useful role in diagnosing nail disorders (especially tumors), localizing the changes, exploring differential diagnoses, estimating prognosis, and planning management. This article is aimed at collating scientific data pertaining to various radiological modalities used in the diagnosis of nail diseases. The advantages and limitations of various imaging techniques used for evaluating the nail unit, including digital radiographs, high-frequency ultrasound, ultrasound doppler (USD), computed tomography (CT), and magnetic resonance imaging (MRI), are discussed in the first part. The second part will discuss the features of common and uncommon nail diseases.