The "comet-tail" is an ultrasound sign detectable with ultrasound chest 
instruments; this sign consists of multiple comet-tails fanning out from the 
lung surface. They originate from water-thickened interlobular septa and would 
be ideal for nonradiologic bedside assessment of extravascular lung water. To 
assess the feasibility and value of ultrasonic comet signs, we studied 121 
consecutive hospitalized patients (43 women and 78 men; aged 67 +/- 12 years) 
admitted to our combined cardiology-pneumology department (including cardiac 
intensive care unit); the study was conducted with commercially available 
echocardiographic systems including a portable unit. Transducer frequencies 
(range 2.5 to 3.5 MHz) were used. In each patient, the right and left chest was 
scanned by examining predefined locations in multiple intercostal spaces. 
Examiners blinded to clinical diagnoses noted the presence and numbers of lung 
comets at each examining site. A patient lung comet score was obtained by 
summing the number of comets in each of the scanning spaces. Within a few 
minutes, patients underwent chest x-ray, with specific assessment of 
extravascular lung water score by 2 pneumologist-radiologists blinded to 
clinical and echo findings. The chest ultrasound scan was obtained in all 
patients (feasibility 100%). The imaging time per examination was always <3 
minutes. There was a linear correlation between echocardiographic comet score 
and radiologic lung water score (r = 0.78, p <0.01). Intrapatient variations (n 
= 15) showed an even stronger correlation between changes in echocardiographic 
lung comet and radiologic lung water scores (r = 0.89; p <0.01). In 121 
consecutive hospitalized patients, we found a linear correlation between 
echocardiographic comet scores and radiologic extravascular lung water scores. 
Thus, the comet-tail is a simple, non-time-consuming, and reasonably accurate 
chest ultrasound sign of extravascular lung water that can be obtained at 
bedside (also with portable echocardiographic equipment) and is not restricted 
by cardiac acoustic window limitations.