What is the best approach to manage a patient with abdominal swelling due to ascites, potentially caused by liver disease, heart failure, or malignancy?

Management of Abdominal Swelling Due to Ascites

Perform diagnostic paracentesis immediately in all patients with new-onset clinically detectable ascites (Grade 2 or 3) to determine the underlying cause and rule out spontaneous bacterial peritonitis before initiating any treatment. 1

Initial Diagnostic Approach

Physical Examination Technique

• Begin with percussion of the flanks when abdominal swelling is observed 1, 2
• Test for shifting dullness first (83% sensitivity, 56% specificity) as it is the most sensitive physical examination technique 2, 3
• Approximately 1,500 mL of fluid must accumulate before flank dullness becomes detectable 1, 2
• If no flank dullness is present, the patient has less than 10% probability of having ascites 1, 2, 3
• The fluid wave test is more cumbersome and less useful than shifting dullness 1

Confirmatory Imaging

• Order abdominal ultrasound when physical examination is inconclusive, particularly in obese patients 1, 2, 3
• Ultrasound can detect ascites volumes as small as 100 mL 1, 2, 3
• Ultrasound should also evaluate liver appearance, splenomegaly, portal vein patency, and lymph nodes 3

Ascites Grading

• Grade 1: Detected only by imaging; not clinically evident 1, 2
• Grade 2: Moderate symmetrical distension, easily identified by inspection and palpation 1, 2
• Grade 3: Massive or tense ascites with profound abdominal distension 1, 2

Mandatory Diagnostic Paracentesis

Indications (Perform in ALL of the following)

• All patients with new-onset Grade 2 or 3 ascites 1
• All patients hospitalized for worsening ascites 1
• Any patient with ascites who develops fever, abdominal pain, gastrointestinal bleeding, hepatic encephalopathy, hypotension, or renal insufficiency 1
• All cirrhotic patients with ascites on hospital admission (15% have spontaneous bacterial peritonitis) 1, 3

Paracentesis Technique

• Perform in the left or right lower quadrant, approximately 15 cm lateral to the umbilicus 1, 3
• The left lower quadrant is preferred due to greater ascites depth and thinner abdominal wall 1
• Avoid the inferior and superior epigastric arteries that run lateral to the umbilicus 1, 3
• Coagulopathy is NOT a contraindication to paracentesis 1, 3
• Serious bleeding complications occur in only 0.2-2.2% of procedures 1, 3
• Consider platelet transfusion only if platelet count is below 40,000/mm³ 1

Essential Ascitic Fluid Tests

• Serum-ascites albumin gradient (SAAG): SAAG ≥1.1 g/dL indicates portal hypertension with 97% accuracy 1, 3
• Ascitic fluid neutrophil count: >250 cells/mm³ is diagnostic of spontaneous bacterial peritonitis 1
• Ascitic fluid culture: Inoculate 10 mL into two blood culture bottles at bedside 1, 3
• Total ascitic fluid protein: Levels <15 g/L indicate increased risk of spontaneous bacterial peritonitis 1
• Additional tests only when indicated: Amylase (pancreatic disease), cytology (malignancy), PCR/culture for mycobacteria (tuberculosis) 1

Differential Diagnosis Framework

Portal Hypertension-Related (SAAG ≥1.1 g/dL)

• Liver cirrhosis accounts for 75-85% of all ascites cases 1
• Other causes: Alcoholic hepatitis, acute liver failure, Budd-Chiari syndrome, sinusoidal obstruction syndrome 3

Non-Portal Hypertension-Related (SAAG <1.1 g/dL)

• Peritoneal carcinomatosis, tuberculous peritonitis, pancreatic ascites, nephrotic syndrome 3

Distinguishing Cardiac from Cirrhotic Ascites

• Measure brain natriuretic peptide (BNP) or pro-BNP when cardiac ascites is suspected 1, 2, 3
• Median pro-BNP in cardiac ascites: 6,100 pg/mL vs. 166 pg/mL in cirrhotic ascites 2, 3
• Assess for jugular venous distension (suggests cardiac cause) 1, 2

Initial Management Based on Etiology

Cirrhotic Ascites (SAAG ≥1.1 g/dL)

• Refer all patients with new-onset ascites for liver transplantation evaluation as ascites indicates poor prognosis (85% one-year survival, 56% five-year survival without transplant) 1, 4
• Initiate sodium restriction and diuretic therapy for uncomplicated ascites 1
• Start spironolactone 100 mg daily (may range from 25-200 mg daily) in hospitalized cirrhotic patients with slow titration 5
• Administer for at least 5 days before increasing dose when used as sole diuretic 5
• Monitor for hyperkalemia (most common serious adverse effect) 5

Cardiac Ascites

• Treat underlying heart failure 1

Malignant Ascites

• Consider large-volume paracentesis for symptomatic relief 1
• Conventional saline diuretics are often ineffective 6

Tuberculous Ascites

• Initiate anti-tuberculous therapy when PCR or culture confirms diagnosis 1

Critical Pitfalls to Avoid

• Never assume the cause of ascites without paracentesis, even in patients with known liver disease or heart failure 1
• Do not delay paracentesis due to coagulopathy or thrombocytopenia unless platelet count is critically low (<40,000/mm³) 1, 3
• Physical examination alone will miss ascites volumes less than 1,500 mL 2, 3
• Always inoculate ascitic fluid into blood culture bottles at bedside to maximize bacterial recovery 1
• Screen all hospitalized cirrhotic patients for spontaneous bacterial peritonitis on admission regardless of symptoms 1, 3
• In cirrhotic patients, initiate diuretic therapy in a hospital setting with slow titration due to risk of hepatic encephalopathy and electrolyte disturbances 5