Imaging aids in the diagnosis of reninoma: a case series.

Background: Reninoma, a rare juxtaglomerular cell tumour, causes secondary hypertension due to renin hypersecretion. Despite characteristic biochemical features (hypertension, hypokalaemia, and elevated renin-angiotensin-aldosterone system activity), diagnostic challenges persist due to its rarity and phenotypic heterogeneity. Case summary: We reported two young males with surgically cured hypertension secondary to renin-secreting juxtaglomerular cell tumours. Both presented with refractory hypertension and hypokalaemia. They exhibited discordant renin levels but shared concordant imaging findings. Post-operative pathological immunohistochemistry definitive confirmed reninoma. Discussion: Our cases highlight the diagnostic challenges of reninoma. In hypertensive patients with hypokalaemia, reninoma should be considered despite its rarity. Normal plasma renin activity cannot definitively exclude reninoma. We recommend plasma renin concentration testing alongside multimodality imaging-contrast-enhanced computed tomography (CT), magnetic resonance imaging, and contrast-enhanced ultrasound to facilitate diagnosis. Both cases were ultimately confirmed by definitive immunohistochemical pathology.