S4 XRay Examination

5.5 Discussion

The use of imaging techniques is not widely developed in dermatology, most likely because the skin is immediately available for inspection and clinical examination. Imaging techniques, however, do have a role to play in the examination of skin diseases, in particular in diseases that may spread to deeper tissues. HS is an excellent example of such a disease.

Different techniques are available (see Table 5.1) and each method has different advantages, although traditional x-ray examination appears to be less useful than the more modern methods. The use of either high-frequency ultrasound or MRI may be helpful, and the two differ mainly in that high-frequency ultrasound is more readily available and that ultrasound is capable of distinguishing the involvement of superficial skin layers, meaning that ultrasound may be able to detect early changes, even sub-clinical ones, of the disease leading to earlier diagnosis and treatment.

Ultrasound may be of particular use in the management of HS. The fluid collections found by ultrasound examination are mostly bigger in size and depth than the clinical lesions, and the changes in echogenicity and thickness of the skin layers are also more extensive when compared to the clinical lesions. In addition, ultrasound will often identify nodular hypoechoic (inflammatory) lesions in the skin that are not perceptible to the clinician. In this way the ultrasound examination may give valuable information about the size and severity of the disease in a given patient.

The ultrasound examination is also capable of determining the real magnitude of the dis

Table 5.1. Imaging of HS. If high-frequency ultrasounda is used excellent imaging is possible of primary lesions and sinus tracts as well, whereas more widely available ultrasound equipment is less well adapted to skin imaging

Ultrasounda

MRI

X-ray

Primary lesions

++(+)

+

-

Sinus tracts I fistulas

++(+)

++

+

Abscesses

+++

+++

?+

Traditional x-ray examination may occasionally be useful if combined with contrast media. Nad-gir and co-workers [5] thus were able to identify perirectal sinus tracts and fistulas caused by HS using a traditional barium enema technique. The use of radiography for the identification of skin lesions or abscesses does not appear fruitful in view of the other techniques available.

ease and measures the extent and sometimes volume of the fluid collections. Monitoring this disease with ultrasound can therefore show, in an objective way, treatment effects and thereby help guide subsequent steps in medication or surgery. In some cases the fluid collections can also be punctured and drained under ultrasound guidance.

Finally ultrasound may add to our understanding of this disease process. Enlargement of the hair follicles is often seen in areas of the involved zones that are not generally scarred or oedematous, suggesting that it may be an early event in the development of the disease. These observations are in good accordance with earlier studies.

Imaging may also be used in cases where other complications are suspected, and may help to distinguish internal disease such as Crohn's disease from HS. Crohn's disease tracts are different from HS fistulas because they tend to connect with the bowel or anorectal area. In HS the tracts are mostly superficial in location. In patients where Crohn's disease is suspected a computed tomography examination may help to determine inflammatory changes to the bowel. Tuberculosis can also produce sinus tracts and fistulas and they also tend to be deeper in location, near to the bowel or ano-genital area. In this case laboratory tests and chest radiographs could be helpful.

Contrast media ultrasound and molecular imaging using MRI may be a future tool for early identification of inflammatory activity in the skin in asymptomatic or mild cases, since the goal of the imaging methods is to make an earlier diagnosis and improve treatment.

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