There is much symptomatic similarity between acute kidney disease and acute 
heart disease. Both may present with shortness of breath and chest discomfort, 
and thus it is not surprising that biomarkers of acute myocardial and renal 
disease often coexist in many physicians' diagnostic work-up schedules. In this 
review we explore the similarities and differences between current and future 
tests of myocardial and renal injury and function, with particular emphasis on 
the diagnostic utility of currently available biomarkers to assist with the 
diagnosis of cardiorenal syndromes. Imaging studies have not traditionally been 
viewed as clinical biomarkers, but as tests of structure and function; they 
contribute to the diagnostic process, and we believe that they should be 
considered alongside more traditional biomarkers such as blood and urine 
measurements of circulating proteins and metabolites. We discuss the place of 
natriuretic peptides, novel tests of kidney damage as well as kidney function 
and conclude with a discussion of their place in guiding future research studies 
whose goals must include better characterization of the degree of dysfunction 
imposed on one organ system by failure of the other.