The fluid wave test is a relatively simple test that is used to aid in the diagnosis of ascites. It is often used in conjunction with the test for shifting dullness.

Performing the Test

  1. Have the patient lie in the supine position.
  2. Have the patient use the ulnar surface of one of their hands to push along the midline of the abdomen.
  3. Place your hand flat against the patients flank on one side, use your other hand to tap the contralateral flank sharply.
  4. The test is positive if the tap generated on flank of the abdomen can be felt clearly on the other side.


  • The fluid wave test has been criticized as being insensitive and unfortunately only moderately specific. One group, for example, has reported a sensitivity of only 0.50 and a specificity of 0.82.


  1. Bickley LS, Szilagyi PG. Bates’ Guide to Physical Examination and History Taking. 10th ed. Philadelphia, PA: Wolter Kluwer Health; 2009.
  2. Catau EL, Benjamin SB, Knuff TE, Castell DO. The Accuracy of the Physical Examination in the Diagnosis of Suspected Ascites. JAMA. 1982; 247: 1164-1166.