The term cardiorenal syndrome (CRS) refers to multiple possible 
clinicopathological correlations between heart and kidney failure. The most 
recent classification recognizes five types of CRS: types I and II originate 
from heart failure (acute and chronic, respectively), type III and IV from 
kidney failure (again acute and chronic), while type V originates from a range 
of systemic diseases. Echocardiography and renal ultrasound are important means 
to arrive at a correct diagnosis. Basic echocardiography (defined by some as 
"echocardioscopy") allows the assessment of the left and right ventricles 
(diastolic and systolic function), atrial size, pulmonary circulation markers 
such as systolic pulmonary arterial pressure (PAPs) and tricuspid annular plane 
excursion (TAPSE), pericardial effusions, valve dysfunctions, and volume 
repletion. Renal ultrasound is of help in distinguishing between chronic and 
acute renal failure (kidney volume, parenchymal thickness, echogenicity) and 
excluding obstructive kidney disease.