The term cardiorenal syndrome (CRS) describes a broad spectrum of clinical 
conditions with four combinations of acute and chronic heart and kidney failure. 
Based on the pathophysiological primum movens, the actual classification 
recognizes five CRS types: in type I and II CRS, the initiating event is heart 
failure (acute or chronic), while it is kidney failure in type III and IV CRS; 
type V is linked to systemic diseases. Ultrasound techniques (echocardiography 
and ultrasonography of the kidney, inferior vena cava and chest) can be 
extremely helpful in establishing a prompt diagnosis and a correct CRS 
classification. Basic echocardiography allows evaluation of ventricular 
diastolic and systolic functions, investigates pulmonary congestion and 
pericardial effusion, and describes volume overload. On the other hand, renal 
ultrasound helps clinicians to distinguish between acute and chronic renal 
failure, excludes urinary tract dilation or pathological bladder repletion, and 
provides crucial information regarding kidney volume or echogenicity. Applying 
basic knowledge of echocardiography and renal ultrasound, nephrologists may be 
in a better position for patient treatment and management, bearing in mind that 
doctors can properly use a stethoscope although not being a cardiologist.