What are the steps in a physical exam for ascites?

Physical Examination for Ascites

The physical examination for ascites should include percussion of the flanks, shifting dullness test, and fluid wave test, with the shifting dullness test being more reliable than the fluid wave test. 1

Initial Assessment

• Visual inspection: Look for abdominal distension, which may indicate Grade 2 or 3 ascites
• Palpation: Assess for abdominal distension and fluid presence
• Percussion of the flanks: Essential first step when abdominal swelling is present
  • Flank dullness indicates potential ascites
  • Note: Generally 1,500 mL of fluid must be present before flank dullness is detectable 1
  • If no flank dullness is present, the patient has less than a 10% chance of having ascites 1

Specific Maneuvers

1. Shifting dullness test:

   • Position patient supine
   • Percuss from midline toward flank until dullness is detected
   • Mark the border between tympany and dullness
   • Have patient turn to lateral decubitus position
   • Re-percuss to detect if the area of dullness "shifts" with gravity
   • Sensitivity: 83%, Specificity: 56% 1

2. Fluid wave test:

   • Place one hand on one side of abdomen
   • Tap opposite side of abdomen
   • Feel for transmitted wave of fluid
   • Note: This test is less reliable and more inconvenient than shifting dullness 1

Grading Ascites

Ascites is classified into three grades 1, 2:

• Grade 1: Detectable only by imaging techniques (ultrasound)
• Grade 2: Moderate ascites, easily identified by visual inspection and palpation
• Grade 3: Profound distension of abdomen (massive or tense ascites)

Important Considerations

• Obese patients: Physical examination is less reliable; abdominal ultrasound is recommended 1, 2
• Minimal ascites: May not be detectable by physical examination; ultrasound can detect as little as 100 mL of fluid 2
• Differential diagnosis: Look for signs of underlying causes:
  • Cirrhosis: Spider angiomata, palmar erythema, jaundice
  • Heart failure: Jugular venous distension (JVD), peripheral edema 1

When to Consider Diagnostic Paracentesis

Paracentesis should be performed in the following scenarios 1:

• All patients with new-onset Grade 2 or 3 ascites
• All patients hospitalized for worsening ascites
• Any patient with complications of cirrhosis (fever, abdominal pain, GI bleeding, hepatic encephalopathy, hypotension, renal insufficiency)

Preferred Paracentesis Site

• Left lower quadrant is preferred due to:
  • Greater depth of ascites
  • Thinner abdominal wall 1
• Right lower quadrant is an alternative site

Pitfalls to Avoid

• Relying solely on physical examination in obese patients
• Performing paracentesis without appropriate indications
• Delaying diagnostic paracentesis in suspected spontaneous bacterial peritonitis (each hour of delay increases mortality by 3.3%) 1
• Failing to recognize that absence of flank dullness makes ascites unlikely (less than 10% chance) 1

When physical examination findings are equivocal or in obese patients, abdominal ultrasound should be used to confirm the presence of ascites, as it can detect as little as 100 mL of fluid 1, 2.