The CRIB-2 trial The Effect of Spironolactone on Left Ventricular Mass and Aortic Stiffness in Early-Stage Chronic Kidney Disease; a Randomised Controlled Trial In a placebo controlled double blind trial, 112 patients (mean age 54 years) with stage 2 and 3 CKD with good blood pressure control on established treatment with ACE inhibitors or ARBs were treated in an active run-in phase with spironolactone 25 mg once daily for 4 weeks and then randomised to continue spironolactone or to receive a matching placebo for a total of 40 weeks. LV mass (cardiac magnetic resonance) and arterial stiffness (pulse wave velocity/analysis, aortic distensibility) were measured before run in and after 40 weeks of treatment. Compared with placebo, the use of spironolactone resulted in large reductions in LV mass and arterial stiffness (pulse wave velocity, augmentation index and aortic distensibility). This trial has been well received and widely publicised. In a recent review, Pitt stated that "we can be cautiously optimistic that use of an MRB in addition to an ACE inhibitor or an ARB will reduce the mortality and morbidity associated with CKD, as well as prevent its progression to end-stage renal disease with all of its health-care and health-cost consequences". Thus, this old and inexpensive drug has the potential to reduce adverse cardiovascular events and mortality in early stage CKD, a risk factor that is now screened for routinely in primary care by measurement of eGFR in the United Kingdom population. In the CRIB-2 trial, systolic blood pressure was significantly reduced; spironolactone is well recognised as an effective anti-hypertensive agent for patients with hypertension, even when this is resistant to other drugs. It is therefore necessary to determine whether the improvements in arterial stiffness and LV mass that occurred with spironolactone were mediated by this effect. Furthermore, before a large scale clinical trial of spironolactone can be contemplated, it is necessary to demonstrate that spironolactone can be used safely in a multi-centre trial design with local monitoring of renal function and serum potassium. This study will provide the pilot data on efficacy (independent of blood pressure) and safety that are necessary to undertake a definitive phase III trial of the role of spironolactone in reducing cardiovascular morbidity and mortality in patients with early stage CKD.