Does B-Scan Ultrasonography Assist in Evaluating a Patient With Uveitis?
Elisabetta
Miserocchi,
MD
Ultrasonography (US) is a noninvasive imaging technique that can help the uveitis specialist in the differential diagnosis of various types of intraocular and periocular inflammatory diseases. Ophthalmic US employs high-frequency sound waves that provide the high resolution required for ocular diagnosis. The main advantages of this method are that it is relatively inexpensive, rapid, produces images in real time, can obtain images in different planes (changing rapidly from one plane to another one), and does not produce biologic hazards. The disadvantages are the need for direct contact with the globe or eyelid (that make examination impossible in the case of acute pain) and the dependence on operator skills.
In the diagnosis of posterior scleritis, US is the most helpful ancillary test in detecting posterior inflammation of the sclera. The hallmark features of posterior scleritis seen with B-mode US are helpful in differentiating posterior scleritis from other conditions. Fluid can accumulate in the posterior episcleral space and extend around the optic nerve, forming the characteristic “T-sign” on B-scan (Figure 39-1). B-scan US may reveal the characteristic flattening of the posterior aspect of the globe due to retrobulbar edema. Abnormally increased thickening of the posterior ocular surface of the globe more than 2 mm, optic disc swelling, distension of the optic nerve sheath, retinal detachments, and choroidal detachments can be detected.1
Figure 39-1. Characteristic T-sign on B-scan US in case of posterior scleritis.
US may help in visualization of the posterior segment in patients with diffuse posterior synechia. This is particularly true for children with juvenile idiopathic arthritis-associated uveitis. Fundus examination in those young patients is already very difficult in the setting of an outpatient clinic, in particular when there are strong synechia between the iris and the lens that hamper an appropriate visualization of the posterior pole. Echography can be a quick and noninvasive tool to detect signs of posterior pole involvement (vitritis, retinal detachment, optic disc edema, presence of snow bank suggestive of pars planitis).
Echography may be of interest in the work-up of Vogt-Koyanagi-Harada when the media are opacified or pupillary dilatation is difficult. It can show thickening of the posterior choroid and serous retinal detachments. Echography is, however, not sufficient to detect subtle intrachoroidal inflammatory lesions.2
US may help in the differential diagnosis of masquerade syndromes. Choroidal melanoma (choroidal and ciliary body melanomas) may present with significant posterior uveitis. These cases may be very similar to the presentation of sarcoid, tuberculous uveitis, or posterior scleritis, and the choroidal mass may be misdiagnosed as a granuloma. B-scan US combined with A-scan has a more than 95% accuracy in the diagnosis of choroidal melanoma more than 3 mm thick. The characteristic features on B-scan are an acoustically silent zone within the melanoma, choroidal excavation, and the typical mushroom shape with low-medium internal reflectivity and lack of halo (Figure 39-2).3
Figure 39-2. Typical mushroom shape in choroidal melanoma.
Patients with retinal vasculitis may require US for diagnosis and follow-up of vitreous hemorrhages. The most common inflammatory retinal disease that complicates vitreous hemorrhages and secondary tractional retinal detachment is Eale disease. Eale disease is an idiopathic, usually peripheral, bilateral retinal vasculitis resulting in peripheral nonperfusion and neovascularization in young otherwise healthy males.4
Systemic autoimmune diseases, such as Wegener’s granulomatosis, can manifest with myositis. In myositis, there is usually a diffuse thickening of the involved muscle, including the inserting tendon to the globe with echolucency on B-scan and low reflectivity on A-scan. Comparative assessment with other muscles, especially the counterpart of the other orbit, is quite revealing for the condition.
B-scan US can help in the differential diagnosis of inflammatory optic disc edema, papillitis, or optic disc drusen.5
Retained intraocular foreign body can cause various degrees of inflammation leading to persistent anterior or posterior uveitis. The inflammatory feature secondary to an intraocular foreign body may masquerade as uveitis. B-scan US can give a general idea of the presence and relative position of an intraocular foreign body and will be especially useful in eyes with small particles, opaque media, poor patient cooperation, or hidden location.6
References
1. Foster CS, Sainz de la Maza M. The Sclera. New York, NY: Springer-Verlag; 1994.
2. Forster DJ, Cano MR, Green RL, Rao NA. Echographic features of the Vogt-Koyanagi-Harada syndrome. Arch Ophthalmol. 1990;108:1421-1426.
3. Read RW, Zamir E, Rao NA. Neoplastic masquerade syndromes. Surv Ophthalmol. 2002;47:81-124.
4. Biswas J, Sharma T, Gopal L, et al. Eales’ disease—an update. Surv Ophthalmol. 2002;47:197-214.
5. Kurz-Levin MM, Landau K. A comparison of imaging techniques for diagnosing drusen of the optic nerve head. Arch Ophthalmol. 1999;117:1045-1049.
6. Waheed NK, Young LH. Intraocular foreign body related endophthalmitis. Int Ophthalmol Clin. 2007;47:165-171.