Renal failure complicates congestive heart failure so often that many have suggested a ‘cardio–renal’ syndrome, which influences survival, duration of hospitalisation and re-admission ratio.2 A sub-study of PRIDE15 showed a reduction in the sensitivity and specificity of NT-pro-BNP in the diagnosis of heart failure for persons with renal failure, and also showed that its concentration tends to be more affected by renal dysfunction than BNP levels.2 The levels of BNP are known to be significantly increased for patients on haemodialysis, and they are known to decrease after dialysis.2 This evidence concerns the gene NPPB and acute kidney injury.