What is the initial approach to a patient presenting with ascites?

Initial Approach to Ascites Presentation

All patients presenting with new-onset grade 2 or 3 ascites require a diagnostic paracentesis with ascitic fluid analysis as the essential first step, combined with history, physical examination, abdominal ultrasound, and laboratory assessment of liver and renal function. 1

Clinical Presentation and Physical Examination

Key Physical Findings

• Shifting dullness test is the primary physical examination maneuver; at least 1,500 mL of fluid must be present before flank dullness is detected 1
• If no flank dullness is present, the patient has less than 10% chance of having ascites 1
• The fluid wave test is less reliable and more cumbersome than shifting dullness 1
• Physical examination is particularly difficult in obese patients, requiring ultrasound confirmation 1

Ascites Grading

• Grade 1: Detected only by imaging (ultrasound can detect as little as 100 mL) 1
• Grade 2: Easily identified by visual inspection and palpation 1
• Grade 3: Massive or tense ascites with profound abdominal distension 1

Essential Diagnostic Tests

Diagnostic Paracentesis - Mandatory Testing

A diagnostic paracentesis must be performed in all patients with new-onset grade 2 or 3 ascites, all hospitalized patients with worsening ascites, or any complication of cirrhosis (fever, abdominal pain, GI bleeding, encephalopathy, hypotension, renal insufficiency). 1

Required Ascitic Fluid Analysis

• Neutrophil count (manual or automated): Essential to rule out spontaneous bacterial peritonitis (SBP); >250 cells/µL indicates SBP 1
• Albumin concentration: Calculate serum-ascites albumin gradient (SAAG) 1
• Total protein concentration: Identifies patients at high risk for SBP (protein <1.5 g/dL or <15 g/L) 1
• Culture: Inoculate 10 mL into blood culture bottles at the bedside to enhance sensitivity 1

SAAG Calculation - The Key Diagnostic Test

• SAAG ≥1.1 g/dL (or 11 g/L) indicates portal hypertension with 97% accuracy 1
• Calculated by subtracting ascitic fluid albumin from serum albumin in simultaneously obtained samples 1
• This test differentiates portal hypertension-related ascites from other causes 1

Conditional Testing (Only When Clinically Indicated)

• Amylase: Only if pancreatic disease suspected 1
• Cytology: Only if malignancy suspected 1
• PCR and culture for mycobacteria: Only if tuberculosis suspected 1

Laboratory Assessment

• Liver function tests: AST, ALT, bilirubin, alkaline phosphatase 1
• Renal function: Creatinine, BUN 1
• Serum and urine electrolytes: Sodium, potassium 1
• Prothrombin time/INR 1
• Complete blood count 1
• Brain natriuretic peptide (BNP): Can help differentiate cardiac from hepatic ascites when heart failure is suspected 1

Imaging

• Abdominal ultrasound with Doppler: Evaluates liver appearance, splenomegaly (suggesting portal hypertension), pancreas, lymph nodes, and confirms ascites presence 1

Differential Diagnosis by Prevalence

Most Common Causes

• Cirrhosis: 75-85% of cases in Western countries, 60% in Korean data 1
• Malignancy: Second most common 1
• Heart failure: Third most common 1
• Tuberculosis: Particularly in endemic areas 1
• Pancreatic disease 1
• Nephrotic syndrome 1

Critical Pitfalls to Avoid

Paracentesis Safety

• Do NOT withhold paracentesis due to coagulopathy or thrombocytopenia - most patients with cirrhotic ascites have prolonged PT and thrombocytopenia, but serious complications are rare (<1/1000 procedures) 1
• Platelet transfusion only considered if platelets <40,000/µL 1
• Fresh frozen plasma is not routinely indicated before paracentesis 1
• Preferred site: Left lower quadrant (greater depth of ascites, thinner abdominal wall) 1
• Avoid inferior and superior epigastric arteries running lateral to umbilicus 1

Prognostic Implications

The development of ascites signals poor prognosis with 5-year survival dropping from 80% in compensated cirrhosis to 30% in decompensated cirrhosis with ascites; one and two-year mortality is approximately 40% and 50%, respectively. 1 Therefore, all patients with ascites should be considered for liver transplantation evaluation 1