MR imaging findings of endophthalmitis

Abstract

Endophthalmitis is a sight-threatening ophthalmologic emergency. The clinical diagnosis is often challenging, and delayed diagnosis may exacerbate the poor visual prognosis. B-scan ultrasonography or spectral domain optical coherence tomography are imaging aids at the clinician's office. Cross-sectional imaging such as CT and particularly MRI can also help in the assessment of disease extent or complications. MR imaging findings are rarely described in the literature. Here, we discuss the spectrum of imaging findings of endophthalmitis and correlate them with key anatomic and pathophysiologic details of the globe. Early disease is often subtle on MR imaging with thick uveal enhancement, while advanced disease demonstrates retinal/choroidal detachment, vitreal exudates and peribulbar inflammation. Other noninfectious inflammatory diseases of the globe can show similar findings; however, MR diffusion-weighted images help identify infectious exudates and evaluate response to therapy. Knowledge of the spectrum of imaging findings of this disease is important for radiologists and help in the management decision process.

Keywords: Endophthalmitis; computed tomography; diffusion-weighted images; globe infection; magnetic resonance imaging; ocular infection.

Figure 1.

Normal cross-sectional anatomy and MR imaging of the globe. (a) Diagrammatic representation of the eye. Key: 1, cornea; 2, anterior chamber; 3, sclera; 4, iris; 5, ciliary body; 6, choroid; 7, retina; 8, posterior chamber (vitreous); 9, lens; 10, Tenon’s capsule; 11, optic nerve; 12, extraocular muscle. Note the uvea is composed of the iris, ciliary body, and choroid. (b) Axial T2-weighted MR image of the eye demonstrates the normal hyperintense vitreous and aqueous chambers. The sclera demonstrates low signal (arrow) and is difficult to separate from the uvea. (c) Contrast-enhanced axial fat-sat T1-weighted MR image demonstrates the normal thin layer of uveal enhancement (arrow). The sclera can be seen as hypointense outer layer (asterisk). MR: magnetic resonance; fat-sat: fat saturation.

Figure 2.

Clinical image of the eye in a patient with endophthalmitis. There is marked conjunctival injection, mild corneal haziness, and a layered collection (arrow) of white (hypopyon) and red (hyphema) blood cells in the inferior anterior chamber.

Figure 3.

Pathophysiologic evolution of endophthalmitis (compare with normal representation on Figure 1(a)). (a) Early disease. Key: 1, uveal involvement with thickening and inflammatory changes (thick enhancement is seen on imaging); 2, infection extends to the vitreous (abnormal density or signal is depicted on CT or MRI). (b) Fulminant/advanced disease. Key: 3, scleral involvement; 4, inflammatory changes to Tenon’s capsule; 5, retinal detachment (subhyaloid, subretinal and suprachorodial effusions with detachment are seen as the disease progress); 6, hypopyon. (c) Late stage. Shrunken globe with calcifications (phthisis bulbi) and vision loss is seen in some cases. CT: computed tomography; MRI: magnetic resonance imaging.

Figure 4.

Pseudomonas endophthalmitis. A 45-year-old diabetic female with endogenous left eye endophthalmitis. (a) Non-contrast CT shows thickening of the preseptal soft tissues (asterisk). However, there is no obvious bulbar inflammatory change. (b) Non-contrast CT from one year prior (when patient had no infection) shows similar appearance of the left globe (elongation is due to degenerative myopia). There was significant visual deterioration on current presentation resulting in enucleation of the left globe and subsequent diagnosis of endophthalmitis. CT: computed tomography.

Figure 5.

Staphylococcus aureus endophthalmitis. A 25-year-old female IV drug abuser with endogenous MRSA endophthalmitis. (a) Axial non-contrast CT image shows thickening of the uve-oscleral layer and subtle increased density in the lateral and posterior aspect of the vitreous chamber of the right globe (arrow). (b) Axial fat-sat T2-WI better defines crescentic areas of abnormal mixed hypointensity in the vitreous chamber. There is episcleral inflammation that corresponds to Tenon’s capsule (arrow). (c) Axial FLAIR image demonstrates hyperintensity of a crescentic area, suspicious for focal exudate or abscess in the subretinal or suprachoroidal space. (d) DWI and (e) ADC maps demonstrate diffusion restriction (arrows) corresponding to signal abnormality noted on (c). Note normal DWI and ADC maps in the left globe. The patient underwent surgery with vitrectomy and debridement. The crescentic areas of abnormal signal on MRI correspond to retinal detachment with subretinal abscess. IV: intravenous; MRSA: methicillin-resistant Staphylococcus aureus; CT: computed tomography; T2-WI: T2-weighted imaging; fat-sat: fat saturation; FLAIR: fluid-attenuated inversion recovery; DWI: diffusion-weighted imaging; ADC: apparent diffusion coefficient; MRI: magnetic resonance imaging.

Figure 6.

Bilateral endophthalmitis. (a) Axial T2-WI shows bilateral diffuse peribulbar edema. Subtle areas of intermediate to low signal intensity are present in the vitreous chamber of the right globe, particularly in the anterior portion (arrow), suspicious for focal exudates. There is also thickening of the ciliary bodies bilaterally. (b) Non-contrast T1-WI shows subtle hyperintensity layering posteriorly within the vitreous chamber (arrow). Abnormality in the anterior portion of the vitreous chamber is difficult to define. (c) Contrast enhanced T1-WI shows diffuse smooth thickening and enhancement of the uvea bilaterally (finding difficult to visualize with bilateral involvement; compare with thin normal uveal enhancement on Figure 1(c)). There is no enhancement within the vitreous chamber. (d) Diffusion-weighted MR image and (e) ADC map show diffusion restriction in the anterior portion of the vitreal chamber of the right globe (arrow) consistent with focal exudate or abscess. There is also rim-like diffusion restriction, likely involving the sub-hyaloid space or uveal coat bilaterally. T2-WI: T2-weighted imaging; MR: magnetic resonance; ADC: apparent diffusion coefficient.

Figure 7.

Endogenous endophthalmitis. A 63-year-old diabetic female with pancreatic cancer and endogenous left endophthalmitis. (a) On fat-sat T2-WI, the left globe is enlarged and deformed with irregular rim-like intermediate to low signal intensity in the vitreous chamber (arrow). (b) Axial fat-sat post-contrast T1-WI shows thick irregular uveal enhancement (compare with normal thin uveal enhancement in the right globe). The globe is proptotic and there is extensive peribulbar stranding and enhancement; abnormal enhancement of the extraocular muscles is also noted. Findings are consistent with associated orbital cellulitis. (c) DWI shows well-defined rim-like diffusion restriction in the vitreous chamber consistent with exudate/abscess, most likely in the subhyaloid space or uveal coat. fat-sat: fat saturation; T2-WI: T2-weighted imaging; DWI: diffusion-weighted imaging.

Figure 8.

Late-stage endophthalmitis. Bilateral shrunken deformed globes (phthisis bulbi) in a patient nine months after bilateral acute endophthalmitis.

Figure 9.

Ocular neoplastic processes. Choroidal melanoma ((a), (b)) and retinoblastoma ((c), (d)). (a) Axial fat-sat T2-WI shows focal area of hypo intensity in the posterior aspect of the globe. (b) Axial fat-sat post-contrast T1-WI demonstrate focal homogeneous enhancement in the posterior uveal region. (c) Axial T2-WI and (d) axial fat-sat post-contrast T1-WI show significant mass-like enhancement in the temporal aspect of the posterior globe with retinal detachment (better visualized on T2-WI). Note the focal nature of both lesions described here and the relative absence of exudates within the globe or inflammatory orbital findings. fat-sat: fat saturation; T2-WI: T2-weighted imaging.

Figure 10.

Ocular inflammatory process. A 16-year-old with atypical Cogen’s syndrome and bilateral posterior scleritis. Axial contrast-enhanced fat-sat T1-WI shows abnormal enhancement superficial to the posterior sclera bilaterally (arrows). Compare to normal enhancement of the globe in Figure 1(c). fat-sat: fat saturation; T2-WI: T2-weighted imaging.