Sir,

Metastatic choroidal abscess is a rare subset of metastatic endophthalmitis. Septic emboli usually arise from focal pyogenic infection, spread through the blood-ocular barrier, and proliferate within the eye. Here, we describe a diabetic patient with Staphylococcus aureus kidney abscess who developed a metastatic choroidal abscess in the macula. Early ophthalmic evaluation and continued systemic antibiotic treatment resulted in a localized choroidal abscess without progression to fulminant endophthalmitis. However, late complication of choroidal neovascularization (CNV) led to vitreous haemorrhage and profound visual loss. To our knowledge, the occurrence of CNV secondary to metastatic choroidal abscess in a patient with S. aureus renal abscess has never been reported before.

Case report

A 48-year-old male with irregularly controlled diabetes mellitus was admitted via the Emergency Room due to persistent fever and chills for 3 days. Right renal abscess was diagnosed after abdominal sonography, computed tomography (CT) abdominal scan (Figure 1), and systemic evaluation. The fasting blood sugar level was 210 mg/dl. The patient was treated with tight diabetic blood sugar control, intravenous antibiotics, and ultrasonography-guided renal abscess aspiration. The cultures from blood and the pus of abscess showed S. aureus, which was sensitive to cefazolin. His medical condition became stable a few days after the intervention and systemic antibiotics; the follow-up CT scan showed gradual resolution of the renal abscess.

Figure 1
figure 1

Computed tomography abdominal scan showed several small low-attenuation lesions (size about 1–3 cm) with irregular shape and septa noted in right kidney (arrow), compatible with the formation of renal abscess. Simple renal cyst (arrowhead) was also noted in left kidney.

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After 1 month, he complained of progressive blurring in his left eye. On examination, his best-corrected visual acuity was 20/30 in the right and 20/100 in the left. Both eyes had a quiet anterior segment and vitreous, while the fundus examination showed retinal heamorrhages, lipid exudates, and cotton-wool spots in both eyes, which were compatible with nonproliferative diabetic retinopathy. A well-demarcated, round, grey, and slightly elevated mass approximately 1 disc diameter (DD) in size was noted 1 DD temporal to the fovea in the left eye (Figure 2). Fluorescent angiography displayed a hypofluorescent lesion. Systemic examination was unremarkable except the renal abscess mentioned above. An initial diagnosis of presumed metastatic choroidal abscess was made, and the patient was kept on continued systemic cefazolin treatment. Gradual consolidation of the choroidal abscess had the appearance of a solitary choroidal granulomatous lesion during the follow-up examination. Intravitreal antibiotics were not given because the lesion remained localized and improved without progression to vitreous after systemic antibiotic treatment. Unfortunately, 2 month later, the patient's left eye vision deteriorated to 20/400 because of vitreous haemorrhage and preretinal haemorrhage. Fundus examination showed a CNV in a sea fan-like pattern just beneath the previous site of active choroidal abscess (Figure 2). It was well-delineated and hyperfluorescent in the early phase of fluorescent angiography, and there was marked leakage of fluorescein dye into the vitreous from the neovascularization in the late phase. Transpupillary thermotherapy (TTT) hyperthermic procedure (setting as following: spot size 1.2 mm, power 200 mW, exposure 60 s) was performed to treat the CNV tuft in the left eye. After 3 weeks, the CNV resolved, leaving a gliotic scar just temporal to the left fovea. Subsequent pars plana vitrectomy was carried out to clear the vitreous haemorrhage and preretinal haemorrhage in the same eye. The vision of the left eye remained 20/100, 6 months after operation.

Figure 2
figure 2

Fundus photography showed a well-defined, slightly elevated, localized choroidal abscess in the macula of left eye (a) and ordinary findings of nonproliferative diabetic retinopathy. After 2 months, a choroidal neovascularization (CNV) tuft (b) developed just beneath the previous choroidal abscess, complicated with vitreous haemorrhage and preretinal haemorrhage along the posterior hyaloid face. Fluorescent angiography showed a well-delineated and hyperfluorescent CNV in the early phase (c), and marked, fluffy fluorescein dye leakage from CNV in the late phase (d).

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Comments

Haematogenous spreading of infectious agents, mostly bacteria, is the aetiology of metastatic infectious choroiditis or endophthalmitis.1 The underlying medical conditions of susceptible hosts include diabetes mellitus, intravenous drug abuse, cardiac valvular abnormality,2 malignancy, and immune-compromised patients. Mowat et al3 suggested the defect in the chemotaxis function of leukocytes in poorly controlled diabetic patients, as this case, probably makes such patients more susceptible to bacterial infection. Besides due to bacteria, metastatic choroidal abscess caused by mycotic organisms, such as Nocardia, Aspergillus, and atypical mycobacterium, had been reported by the opportunistic infection occurring in patients of AIDS, immunosuppressed status, or after organ transplant.4, 5, 6

The case reported here represents a presumed metastatic septic embolus to the choroid from a renal abscess. The diagnosis of metastatic S. aureus choroidal abscess was based on the identification of the organism in blood cultures and on isolation of the organism from the ultrasonography-guided renal abscess aspiration. In a recent literature review, S. aureus is among one of the most common Gram positive causing organisms in endogenous bacterial endophthalmitis.7 In cases of diagnostic dilemma, transvitreal fine needle aspiration of a choroids abscess may be used to establish the diagnosis.8

Treatment with intravenous antibiotic is essential for patients with metastatic choroidal abscess. Although penetration of the antibiotics into the eye is often poor and may be inadequate, systemic antibiotics are mandatory as these are life-threatening events. Most cases of metastatic choroidal abscess progress to endophthalmitis as a result of a delay in treatment. This case presented with a partially treated metastatic infection, that is why it was not a fulminant endophthalmitis but did emphasize that continued systemic antibiotics were required. Intravitreal antibiotic injection and surgical drainage are the other therapeutic options of choroidal abscess. Frequent ophthalmologic examinations are required to determine the optimal management in individual patient.

The complication of CNV secondary to bacterial infectious choroiditis/abscess is not well recognized by most physicians, mainly because it is rare. The temporal events make it an obvious and unsurprising result given the chronicity of this presentation. Munier et al described two cases of acute bacterial endocarditis with multiple metastatic septic emboli in the choroids; subsequent CNV occurred after 10 months and 5 years, respectively, at the choroidal scars.2 Coll and Lewis reported a patient of S. aureus endocarditis in a heroin user. Metastatic choroidal abscess was also found, and subsequent CNV with retinochoroidal vascular anastomosis developed 1 week later.9 Our case resembles the one reported by Coll et al, whose CNV developed in the early stage of metastatic choroidal abscess. It appeared that the inflammation was still active, and every chorioretinal process affecting Bruch's membrane kept the capability for the development of CNV. We recommend that patients with metastatic choroidal abscess should be carefully followed up, because these patients are at risk of developing secondary CNV.

In conclusion, metastatic choroidal abscess can arise from renal abscess in a diabetic patient. Prompt diagnosis and early systemic antibiotic treatment are mandatory to prevent its progression to fulminant endophthalmitis. The subsequent occurrence of CNV is a rare, but potentially devastating complication.