Update on the role of color Doppler ultrasound in hidradenitis suppurativa: a game-changer.

Hidradenitis suppurativa has greatly benefited from the insights of color Doppler ultrasound. Thus, ultrasonography has helped prove the follicular link of this disease and has ruled out the primary involvement of the apocrine glands, which, in the old days, was supposedly the cause of the disease. Importantly, ultrasound can detect subclinical anatomical information in HS that cannot be deducted from the clinical examination. Moreover, high-frequency (≥15 MHz) and ultra-high-frequency (≥50 MHz) ultrasound present a much higher axial spatial resolution compared to magnetic resonance imaging. Ultrasound allows us to detect better subclinical cutaneous anatomical abnormalities and, therefore, arrive earlier and more accurately at diagnosis and staging. Ultrasonographic diagnostic criteria can discriminate HS from other clinical simulators, which is also critical in diagnosing mild and moderate stages and is relevant for the severe stages. This imaging technique supports the severity (mSOS-HS) and activity (US-HSA) scorings more accurately, which can help assess the actual stage of the disease. This is important to decide the type of treatment and to perform a more objective follow-up of the patients. Magnetic resonance imaging has been reported as helpful in diagnosing deep perianal tunnels; however, it presents a lower axial spatial resolution compared with high and ultra-high frequency ultrasound. Nowadays, there is solid evidence of the usefulness of ultrasound in HS, which implies that it is a game-changer and should be recommended as the first-choice imaging technique and a standard of care tool for HS patients.