The role of imaging in immunoglobulin G4-related disease of the upper urinary tract.

Background: Immunoglobulin G4-related disease remains a modern, relatively unknown field in the urological world. An increasing number of cases require urological input, often with invasive diagnostics and aggressive medical treatment first-line. Given this, we sought to evaluate modern radiological options of disease affecting the upper urinary tract, to provide clarity and reduce diagnostic burden and delay in this poorly understood yet potentially debilitating disease process.

Summary: We conducted a systematic literature search including PubMed and Medline, focusing on immunoglobulin G4-related disease affecting the upper urinary tract, before reviewing articles assessing different radiological modalities in diagnosis. Consistent computed tomography findings have been demonstrated in the literature and contributed to recent breakthroughs in classification criteria, however invasive biopsy remains a mainstay in work-up, given the difficulties in comparing against malignancy. Early work in positron-emission tomography and magnetic resonance imaging has shown promise in radiologically distinguishing from other differentials, especially diffusion-weighted imaging showing high sensitivity levels, but not yet enough to formulate protocols and cause histological investigation to be redundant.

Key Messages: Our article has highlighted repeated findings in the literature of computed tomography appearances of IgG4-RD in the upper urinary tract, however invasive work-up remains a mainstay given the overlap with malignancy. Prospective, comparative studies into magnetic resonance imaging and positron-emission tomography are now required, given their early results, to improve consistency in reporting and reduce patient burden when investigating this benign, yet debilitating disease process.