Ilkka Pörsti

Background Screening for primary aldosteronism is based on measuring aldosterone-to-renin ratio. Non-suppressed renin may cause false negative screening results, and such patients may miss focused, potentially curable treatment. We investigated the association between renal cysts and non-suppressed plasma renin. Methods Altogether, 114 consecutive patients with confirmed primary aldosteronism undergoing adrenal vein sampling were prospectively recruited between October 7, 2020 and December 30, 2021. During the procedure, plasma samples for renin analyses were collected from the right and left renal veins and the inferior vena cava. Renal cysts were identified using contrast-enhanced computed tomography. Results Renal cysts were found in 58.2% of the 114 patients. Neither screening nor renal vein renin concentrations were significantly different in patients with and without cysts, or when the kidneys with and without cysts were evaluated. However, cysts were significantly more prevalent in the “high-normal renin” group (cut point 23.0 mU/L) than in the “low to low-normal renin” group (90.9%, n = 11 vs. 56.0%, n = 102, P = .027, respectively). All patients ≤50 years of age in the “high-normal renin” group had renal cysts. Strong correlations were found between renin concentrations in the right and left renal veins (r = .984), and between renin concentration and renin activity in the inferior vena cava (r = .817). Conclusion Renal cysts are found in the majority of patients with primary aldosteronism, and they may interfere with diagnostics, especially in patients aged 50 years or less. In patients with non-suppressed renin due to renal cysts, aldosterone-to-renin ratio below the diagnostic threshold does not always exclude the diagnosis of primary aldosteronism.