What are the causes and management of ascites?

Causes of Ascites

Cirrhosis accounts for approximately 75-85% of all ascites cases in Western countries, making it by far the most common cause, followed by malignancy (10-15%), heart failure (3-5%), tuberculosis, and pancreatic disease. 1, 2

Primary Etiologies

Cirrhotic Causes (Portal Hypertension-Related)

• Cirrhosis is responsible for 75-85% of ascites cases, with alcoholic cirrhosis being the most frequent cirrhotic etiology, followed by non-alcoholic steatohepatitis (NASH), chronic viral hepatitis, and autoimmune liver diseases. 3, 1, 2
• Portal hypertension is an absolute prerequisite for ascites development in cirrhosis—ascites only occurs when portal hypertension has developed. 2
• The pathophysiology involves splanchnic arterial vasodilation causing decreased effective arterial blood volume, which activates the sympathetic nervous system and renin-angiotensin-aldosterone system, leading to renal sodium retention and extracellular fluid expansion. 3, 1, 2

Malignancy-Related Causes

• Peritoneal carcinomatosis from primary breast, colon, gastric, or pancreatic carcinomas is the second most common cause overall, accounting for 10-15% of cases. 1, 2
• Massive liver metastases can also produce ascites. 1, 2
• Ascitic fluid cytology has 96.7% sensitivity for detecting peritoneal carcinomatosis if three samples are processed promptly. 1, 2

Cardiac Causes

• Heart failure produces ascites distinguishable by elevated jugular venous distension and markedly elevated pro-brain natriuretic peptide (median 6100 pg/mL versus 166 pg/mL in cirrhosis). 1, 2, 4
• Heart failure accounts for 3-5% of ascites cases. 2

Infectious Causes

• Tuberculous peritonitis is more common in endemic areas and immunocompromised patients, often requiring laparoscopy with biopsy and mycobacterial culture for diagnosis. 1, 2

Other Causes

• Pancreatic ascites from pancreatitis. 3, 1, 2
• Nephrotic syndrome (renal cause). 1, 2
• Budd-Chiari syndrome and sinusoidal obstruction syndrome (vascular causes). 1, 2
• Acute liver failure. 2
• Mixed ascites occurs in approximately 5% of patients who have two or more causes, usually cirrhosis plus peritoneal carcinomatosis or tuberculosis. 1, 2

Diagnostic Approach

Physical Examination

• Shifting dullness is the primary examination maneuver with 83% sensitivity and 56% specificity. 1, 2
• At least 1,500 mL of fluid must be present before flank dullness is detectable. 1, 2
• If no flank dullness is present, the patient has less than 10% chance of having ascites. 2
• Abdominal ultrasound is required in obese patients to confirm ascites presence. 1, 2, 4

Diagnostic Paracentesis

• Diagnostic paracentesis with appropriate ascitic fluid analysis is essential in all patients with new-onset grade 2 or 3 ascites and must be performed before initiating any therapy. 3, 1, 2
• This is the most rapid and cost-effective method for determining the cause of ascites. 2, 4

Laboratory Analysis

• The serum-ascites albumin gradient (SAAG) is the single most useful test to differentiate causes of ascites. 1, 2, 4
• SAAG ≥1.1 g/dL indicates portal hypertension (cirrhosis, heart failure, Budd-Chiari syndrome) with 97% accuracy. 3, 1, 2
• SAAG <1.1 g/dL suggests non-portal hypertension causes (malignancy, tuberculosis, pancreatitis, nephrotic syndrome). 1, 2
• Neutrophil count >250 cells/μL indicates spontaneous bacterial peritonitis requiring immediate antibiotic therapy. 1, 2
• Ascitic fluid culture (10 mL inoculated in blood culture bottles at bedside), total protein, and albumin concentration should always be assessed. 3, 1
• Additional tests such as cytology, amylase, and tuberculosis testing should be performed based on clinical suspicion. 3, 1

Prognostic Implications

• Development of ascites marks a critical turning point, reducing 5-year survival from 80% in compensated cirrhosis to 30% in decompensated cirrhosis with ascites. 1, 2, 4
• Approximately 15-20% of patients with ascites die within the first year after diagnosis. 1, 2, 4
• Patients with ascites should be evaluated for liver transplantation, which offers the most definitive curative treatment. 3, 1, 2, 4
• Patients with ascites are prone to additional complications including spontaneous bacterial peritonitis, electrolyte abnormalities, and hepatorenal syndrome. 1