Puddle Sign. Is it useful?

Does anyone use puddle sign? My professor asked me about that today and I am unable to find authentic information anywhere. He suggested that I refer some older editions of textbooks.

Puddle sign is a sign that is not often used in clinical medicine. It is a test to detect minimal ascites.

Technique:
Patient should lie prone for about five minutes and then assume a knee-elbow position. Examiner should then apply the diaphragm of stethoscope to the most dependent part of the abdomen at the bottom. With the stethoscope in that position, the examiner should repeatedly flick the flank with finger. As the stethoscope is then gradually moved away from the dependent position, if the loudness of the transmitted sound increases, it suggests that there is a puddle of fluid at the dependent region.

Interpretation:
If the percussion note becomes more resonant as the stethoscope is moved up the flank and away from the dependant part, it is interpreted that fluid indeed has puddled.

Use:
Puddle sign can detect as little as 120 ml of fluid in the peritoneal cavity. On the other hand, shifting dullness, the commonly used clinical test to detect ascites becomes positive only in the presence of at least 500 ml of fluid.

Obsolete because:
Puddle sign is not used commonly as it is not very comfortable for the patient as well as the examiner. With the advent of ultrasound, even lesser quantities of free fluid in the peritoneal cavity may be detected non-invasively, further obviating the need to use this not-so-comfortable method of clinical examination.

PubMed Resources on puddle sign.

Dictionary definition of the term "puddle": A small pool of water, especially rainwater.