Glomerulonephritis through the lens of ultrasound and radiology.

Renal biopsy remains the diagnostic reference in glomerulonephritis, and no imaging modality has displaced its central role. The key question is whether imaging can complement histology by providing additional information on disease activity, prognosis, and treatment response. In clinical practice, conventional ultrasound is the first-line examination. Cortical thinning and elevated intrarenal resistive indices mainly reflect chronic structural damage and haemodynamic adaptation, without identifying the underlying pathological subtype. Techniques such as shear-wave elastography and contrast-enhanced ultrasound attempt to extend assessment beyond morphology by evaluating tissue stiffness and microvascular perfusion, with reported associations with fibrosis in immunoglobulin A nephropathy and microvascular changes in lupus nephritis and membranous nephropathy. Quantitative approaches integrating imaging features with clinical variables have also been explored for fibrosis staging, although broader validation remains limited. Computed tomography and magnetic resonance imaging continue to play a largely structural role, particularly in systemic diseases with renal involvement such as immunoglobulin G4-related nephropathy and vasculitis. Multiparametric magnetic resonance imaging can additionally assess perfusion and tissue microstructure through diffusion-weighted imaging, arterial spin labelling, and blood oxygenation level-dependent sequences. Nuclear medicine techniques may provide complementary molecular information, with exploratory applications in the assessment of inflammatory activity in antineutrophil cytoplasmic antibodies-associated vasculitis and in the evaluation of cortical or fibrotic involvement using newer tracers. Overall, evidence remains heterogeneous, and histological evaluation continues to determine diagnosis and guide treatment.