What are the most common causes of ascites?

Most Common Causes of Ascites

Cirrhosis is the most common cause of ascites, accounting for approximately 75-85% of cases in Western countries, with the remaining 15-25% caused by malignancy, heart failure, tuberculosis, pancreatic disease, and other conditions. 1

Cirrhosis-Related Ascites (75-85% of cases)

• Cirrhosis leads to portal hypertension and splanchnic arterial vasodilation, causing decreased effective arterial blood volume with activation of sodium-retaining systems (sympathetic nervous system and renin-angiotensin-aldosterone system) 1
• The resulting renal sodium retention leads to expansion of extracellular fluid volume and formation of ascites 1
• Development of ascites in cirrhosis is associated with poor prognosis, reducing 5-year survival from 80% to 30% 1
• Approximately 50% of patients with compensated cirrhosis develop ascites within 10 years of diagnosis 2
• Alcohol-induced liver injury is one of the most reversible causes of liver disease that leads to ascites 2

Non-Cirrhotic Causes of Ascites (15-25% of cases)

Malignancy-Related (10%)

• Peritoneal carcinomatosis and massive liver metastases 1
• Most commonly from primary breast, colon, gastric, or pancreatic carcinomas 2
• Ascitic fluid cytology has 96.7% sensitivity for detecting peritoneal carcinomatosis if three samples are processed promptly 2

Cardiac Causes (3%)

• Heart failure leads to increased central venous pressure and fluid accumulation 1
• Distinguishable by elevated jugular venous distention and pro-brain natriuretic peptide levels 1

Tuberculosis (2%)

• Tuberculous peritonitis, more common in endemic areas and immunocompromised patients 2, 1
• Diagnosis often requires laparoscopy with biopsy and mycobacterial culture of tubercles 2

Other Causes (5%)

• Pancreatic disease (pancreatitis with associated ascites) 1
• Nephrotic syndrome 1
• Budd-Chiari syndrome and sinusoidal obstruction syndrome (vascular causes) 1
• Myxedema 1
• Postoperative lymphatic leak 1

Mixed Ascites (5%)

• Approximately 5% of patients have two or more causes of ascites formation 2
• Usually, these patients have cirrhosis plus one other cause (e.g., peritoneal carcinomatosis or tuberculosis) 2
• Some patients may have multiple predisposing factors (e.g., heart failure, diabetic nephropathy, and cirrhosis) that together lead to fluid retention 2

Diagnostic Approach

• Serum-ascites albumin gradient (SAAG) is the most useful test to differentiate causes of ascites 2
  • SAAG ≥1.1 g/dL indicates portal hypertension (cirrhosis, heart failure, Budd-Chiari syndrome)
  • SAAG <1.1 g/dL suggests non-portal hypertension causes (malignancy, tuberculosis, pancreatitis)
• Diagnostic paracentesis is recommended for all patients with new-onset grade 2 or 3 ascites 2
• Neutrophil count >250 cells/μL indicates spontaneous bacterial peritonitis 2
• Ascitic fluid culture, total protein, and albumin concentration should always be assessed 2
• Additional tests may include cytology, amylase, and tuberculosis testing based on clinical suspicion 2

Clinical Implications and Pitfalls

• Development of ascites marks significant decline in prognosis for cirrhosis patients (15% die within 1 year, 44% within 5 years) 1
• CA125 testing should be avoided in patients with ascites as it is elevated in all types of ascites and can lead to unnecessary procedures 2
• Patients with ascites should be considered for liver transplantation evaluation 1
• Alcohol cessation is critical for patients with alcoholic liver disease, with 75% 3-year survival in those who stop drinking versus 0% in those who continue 3