What are the key findings to look for when assessing abdominal girth for ascites?

Key Findings When Assessing Abdominal Girth for Ascites

When assessing abdominal girth for ascites, the most reliable physical examination findings include shifting dullness, flank dullness, and bulging flanks, which should be systematically evaluated to determine the presence and severity of fluid accumulation. 1

Initial Assessment

• Shifting dullness is the most sensitive physical examination technique with 83% sensitivity and 56% specificity in detecting ascites 1
• Flank dullness has 84% sensitivity for detecting ascites and indicates approximately 1,500 mL of fluid must be present before it can be detected 1
• Bulging flanks has 81% sensitivity for ascites detection 2
• Fluid wave test is more specific but less sensitive and more cumbersome to perform than shifting dullness 1

Proper Technique for Physical Examination

• When abdominal swelling is observed, percussion of the flanks should be performed first 1
• To test for shifting dullness: percuss the abdomen to identify the tympany-dullness interface, then have the patient roll to one side and observe if the dullness shifts to the dependent side 1
• If there is no flank dullness, the patient has less than a 10% chance of having ascites 1

Grading Ascites Severity

Ascites is classified into three grades according to amount 1:

• Grade 1: Detected only by imaging techniques (ultrasonography); not clinically evident
• Grade 2: Easily identified by visual inspection and palpation; moderate symmetrical distension
• Grade 3: Profound distension of the abdomen (massive or tense ascites) 1

Additional Findings to Consider

• Patient history of increased abdominal girth (87% sensitivity) and recent weight gain significantly increase the likelihood of ascites 2, 3
• Ankle edema has 93% sensitivity for ascites detection and its absence decreases the likelihood of ascites (negative likelihood ratio = 0.17) 2, 3
• In obese patients, physical examination for ascites is more difficult and may require abdominal ultrasound for confirmation 1
• Jugular venous distension should be assessed, as its presence suggests heart failure rather than cirrhosis as the cause of ascites 1

Confirmatory Testing

• Abdominal ultrasound can detect ascites when volume exceeds 100 mL and is the preferred confirmatory test when physical examination is inconclusive 1
• Abdominal paracentesis is the most rapid and efficient test to diagnose the cause of ascites and should be performed in all patients with new-onset Grade 2 or 3 ascites 1
• Paracentesis is generally safe with bleeding complications occurring in only about 1% of patients 1

Differentiating Causes of Ascites

• Approximately 75-85% of ascites cases are due to liver cirrhosis 1
• Other causes include malignancy, tuberculosis, heart failure, pancreatic disease, and nephrotic syndrome 1
• For patients with suspected cardiac ascites, measurement of brain natriuretic peptide (BNP) can help distinguish heart failure (median pro-BNP: 6100 pg/mL) from cirrhosis (median pro-BNP: 166 pg/mL) 1

Pitfalls and Caveats

• Physical examination alone may miss small amounts of ascites (less than 1,500 mL) 1
• Giant cysts or pseudocysts can rarely mimic ascites; imaging usually provides the correct diagnosis 1
• A slowly enlarging abdomen over months to years is more likely due to obesity than ascites 1
• The serum-ascites albumin gradient (SAAG) from paracentesis fluid is the most useful test to identify portal hypertension-related ascites 1, 2