4  Leukocoria

4.1 Approach

What is the radiological approach to Ddx of Leukocoria in children?

The primary imaging modality is ultrasound (US) due to its accessibility, safety, and ability to characterize intraocular lesions. MRI is then performed for more detailed evaluation, particularly when malignancy (e.g., retinoblastoma) is suspected or to assess intracranial/intraorbital extension.

4.1.1 Step-by-Step Radiological Approach:

  1. Clinical Correlation and Initial Screening:
    • Ultrasound (US): First-line imaging. Look for mass lesions, calcifications, retinal detachment, and associated vitreous or subretinal hemorrhage.
  2. Advanced Imaging (MRI):
    • T1-Weighted (T1W): Assess anatomy, hemorrhage, melanin content.
    • T2-Weighted (T2W): Characterize lesions, evaluate retinal detachment.
    • Diffusion-weighted imaging (DWI): Helpful in differentiating malignant from benign lesions.
    • Contrast-Enhanced Imaging: Evaluate lesion enhancement and extraocular or intracranial spread.
  3. CT Scan (less preferred):
    • Limited role due to radiation exposure, though excellent for detecting calcifications (common in retinoblastoma). MRI is usually preferred.

4.1.2 Differential Diagnoses & Radiological Features:

Diagnosis Age of Onset Radiological features Key Imaging Findings
Retinoblastoma (Most Common) Typically <5 yrs Calcified intraocular mass, high density/calcifications on CT, hyperintense on T1, hypointense on T2 due to calcifications; MRI shows restricted diffusion. Calcification, solid mass lesion, restricted diffusion.
Persistent Fetal Vasculature (PFV) Neonatal, congenital Small globe (microphthalmia), elongated ciliary processes, central retrolental fibrovascular stalk. Small globe, vascular stalk.
Coats Disease Typically boys, preschool to adolescence Retinal telangiectasia, subretinal exudation, retinal detachment without calcifications. MRI: high T1 (lipid exudates), high T2 signal retinal detachment. Retinal detachment, lipid-rich exudates, no calcifications.
Congenital Cataract Neonatal, infancy Echogenic lens opacity seen on US; lens opacity easily identified clinically. Isolated lens opacity.
Retinopathy of Prematurity (ROP) Premature infants Fibrovascular proliferation, retinal detachment, bilateral, symmetric retinal abnormalities. Bilateral, peripheral retinal detachment, history of prematurity.
Toxocariasis (Ocular Larva Migrans) Older children, history of contact with animals Subretinal granuloma or retinal mass, vitreous bands, tractional retinal detachment, calcifications rare. Vitreous strands, subretinal mass/granuloma, no calcifications.
Vitreous Hemorrhage Trauma, abuse, bleeding disorders Echoic vitreous contents on US, absence of mass lesion. MRI signal varies with age of blood products. Echoic vitreous debris, no distinct mass lesion.

4.1.3 Summary of Radiological Strategy:

  • Start with ultrasound (highly sensitive, safe, quick) for initial evaluation.
  • Follow-up with MRI to confirm diagnosis, assess lesion extent, exclude malignancy, and plan treatment.
  • CT scan only if MRI unavailable or calcification confirmation needed urgently.

4.1.4 Practical Clinical-Radiological Tips:

  • Calcifications strongly suggest retinoblastoma until proven otherwise.
  • Microphthalmia and vascular stalk strongly suggest persistent fetal vasculature.
  • Absence of calcification with lipid exudates and retinal detachment favors Coats disease.
  • Always correlate clinically (e.g., prematurity history, family history, clinical exam).

4.1.5 References:

  • Dahnert, Wolfgang. Radiology Review Manual. 9th ed. Wolters Kluwer, 2017.
  • Pediatric Imaging: The Fundamentals. Lane F. Donnelly, 3rd Edition, Elsevier, 2021.
  • Agarwal A, et al. Differential diagnosis of leukocoria and imaging algorithms. Indian J Radiol Imaging. 2012;22(4):248–257. doi:10.4103/0971-3026.111476