Ascites

Etiology

Ascites represents the pathological accumulation of fluid within the peritoneal cavity and reflects a complex interplay of hepatic, cardiac, renal, infectious, and malignant processes. The condition often signifies advanced disease and contributes to substantial morbidity and mortality. Understanding its diverse etiologies is essential for accurate diagnosis, effective management, and prevention of complications.

Cirrhosis

Ascites develops as a consequence of multiple underlying conditions, with cirrhosis representing the predominant cause in the United States and accounting for approximately 80% of cases. Among patients with cirrhosis, ascites represents the most frequent complication and affects nearly 50% of those who have experienced decompensated cirrhosis for more than 10 years.[1][2][3] The onset of ascites often marks the transition from compensated to decompensated cirrhosis. Mortality associated with cirrhotic ascites rises due to complications, eg, spontaneous bacterial peritonitis and hepatorenal syndrome, reaching 15% at 1 year and 44% at 5 years.

Alcohol-related liver disease, metabolic dysfunction-associated steatotic liver disease (MASLD), and chronic viral hepatitis contribute most often to cirrhosis complicated by ascites. Cirrhotic ascites occurs more frequently in individuals younger than 65 years, in those with alcohol-related cirrhosis, or with hepatic encephalopathy and varices.[4] The risk increases among patients taking nonselective beta-blockers but decreases with atorvastatin use or antiviral therapy for hepatitis C.[5] Up to 19% of cirrhotic patients develop hemorrhagic ascites, most often spontaneously, with 72% attributed to bloody lymph and 13% to hepatocellular carcinoma, though paracentesis may also trigger its development.[6][5]

Chylous Ascites

Chylous ascites, a rare variant characterized by its milky appearance and high triglyceride content, results from lymphatic fluid leakage into the peritoneal cavity. In children, lymphatic malformations represent the most frequent cause, while in adults, the condition is more commonly associated with cirrhosis and intra-abdominal malignancy in developed nations.[7]

Infections, eg, tuberculosis and filariasis, predominate as causes in developing and Eastern countries. Chylous ascites often arises from trauma, rupture of lymphatic channels secondary to obstruction, or elevated peritoneal lymphatic pressure from inflammation. Postoperative cases, as well as congenital or acquired forms, frequently accompany portal hypertension or traumatic injury.

Pancreatic Ascites

Pancreatic ascites may develop through iatrogenic mechanisms following procedures, eg, endoscopic retrograde cholangiopancreatography, renal or adrenal surgery, colectomy with splenic flexure mobilization, partial pancreatic resection, or splenectomy. External pancreatic fistulas, typically after surgery, may arise from anterior ductal disruptions leading to peripancreatic fluid collections in the lesser sac or from posterior ductal disruptions resulting in pancreatic-pleural fistula formation and pleural effusions. Noniatrogenic causes include chronic pancreatitis, persistent pancreatic fistulas to the peritoneum, pseudocysts, or walled-off necrosis.[8][9]

Additional Etiologies

Peritoneal cancer accounts for approximately 10% of ascites cases, most often resulting from breast, ovarian, bronchial, gastric, colon, or pancreatic malignancies, while 20% originate from cancers of unknown primary sites.[10] Congestive heart failure, usually linked to pulmonary hypertension, and constrictive pericarditis cause about 3% of cases. Tuberculosis accounts for 2%, nephrotic syndrome or dialysis for 1%, and pancreatic ascites for another 1%.

Other etiologies, accounting for approximately 2% of cases, include noncirrhotic alcohol-related liver disease, portal vein thrombosis, Budd-Chiari syndrome, lymphoma, other peritoneal malignancies, intravenous drug use, obesity, inferior vena cava obstruction or web formation, hypercholesterolemia, type 2 diabetes, severe malnutrition, infections, and ovarian lesions.

Epidemiology

Ascites affects approximately 60,000 per 100,000 individuals worldwide and occurs across all ages, sexes, and races. However, cirrhotic ascites demonstrates distinct epidemiologic trends. The male-to-female ratio reaches 2.5:1, reflecting a higher prevalence among men.

Mexican-Americans and Black populations experience a greater incidence, primarily due to the underlying distribution of cirrhosis. Individuals with lower education levels and those living below the poverty line also face a higher risk, highlighting socioeconomic influences on disease development and access to preventive care.[11]

Pathophysiology

The first stage in the development of cirrhotic ascites is portal hypertension. Portal pressure increases above a critical threshold, and circulating nitric oxide levels increase, leading to splanchnic arterial vasodilatation. As vasodilatation progresses, reduced effective arterial blood volume, increased permeability, and elevated pressure in splanchnic capillaries cause sodium retention through the induction of the renin-angiotensin-aldosterone system, arginine vasopressin secretion, and the sympathetic nervous system.[12] Increased lymph production, exceeding lymph reabsorption, also contributes to the accumulation of ascitic fluid. Portal hypertension also permits bacterial translocation, leading to increased pathogen-associated molecular patterns (PAMPs) and a consequent increased risk of infection, particularly spontaneous bacterial peritonitis.[13]

Additionally, by producing proteinaceous fluid, tumor cells lining the peritoneum can also cause ascites. In high-output or low-output heart failure or nephrotic syndrome, effective arterial blood volume is decreased, and the vasopressin, renin-angiotensin-aldosterone, and sympathetic nervous systems are activated, leading to renal vasoconstriction and, ultimately, sodium and water retention.[14]

Pancreatic ascites results from leakage from a pseudocyst or walled-off necrosis into the peritoneum through pancreatic duct disruption.[14] Alternatively, pancreatic duct disruption without a pseudocyst leads to the formation of a fistulous tract. Fistulas from an anterior pancreatic duct disruption cause secretions to empty directly into the peritoneum. Posterior pancreatic duct ruptures cause fistula formation through the aortic or esophageal hiatus and, possibly, through the diaphragmatic dome, leading to pleural effusions.[15]

In cases of chylous ascites, traumatic rupture of lymphatic vessels or excessive peritoneal lymphatic pressure due to obstruction can cause lymph to collect in the peritoneal space. In portal hypertension, endothelial compromise can occur due to elevated lymphatic pressure, leading to dilation of lymphatic channels, which can rupture and cause chylous ascites. In nonportal instances, lymph passes through a retroperitoneal fistula due to congenital or acquired megalymphatics. When the amount of fluid exceeds the intestinal mucosa's capacity to reabsorb it, chylous ascites and a protein-losing enteropathy can develop, manifested by malabsorption, malnutrition, and steatorrhea.[15]

History and Physical

Clinical History

Patients typically report progressive abdominal distension, which may be painless or associated with abdominal discomfort, weight gain, early satiety, shortness of breath, and dyspnea, resulting from fluid accumulation and increased abdominal pressure. Symptoms, eg, fever, abdominal tenderness, and confusion, can be seen in spontaneous bacterial peritonitis.

Patients with malignant ascites can have symptoms related to malignancy, which may include weight loss. On the other hand, patients with ascites due to heart failure may report dyspnea, orthopnea, and peripheral edema, and those with chylous ascites report diarrhea, steatorrhea, malnutrition, edema, nausea, enlarged lymph nodes, early satiety, fevers, and night sweats.

Physical Examination Findings

Typical physical findings include abdominal distention, flank dullness to percussion, shifting dullness, a fluid wave, and evidence of pleural effusions. Other findings are related to the underlying cause of the ascites, eg, stigmata of cirrhosis, including spider angiomas, palmar erythema, abdominal wall collaterals, muscle wasting, gynecomastia, leukonychia, and jaundice. In heart failure, physical examination findings may include jugular venous distension, pulmonary congestion, or peripheral edema. A palpable umbilical nodule, eg, a Sister Mary Joseph nodule, is a metastatic lesion most often from a gastrointestinal, pancreatic, or genitourinary cancer as the cause of ascites. Other symptoms and physical findings are related to the underlying cause of ascites formation.

Evaluation

Initial Evaluation

Diagnostic abdominal paracentesis with the appropriate ascitic fluid analysis is the most rapid and cost-effective method of diagnosing the underlying cause of ascites in affected patients.[16][17] The initial tests that should be performed on the ascitic fluid include:

• Complete blood cell count: A complete blood cell count with total nucleated cell and polymorphonuclear neutrophil (PMN) count. A PMN count ≥250/mm³ indicates spontaneous bacterial peritonitis, although similar findings may occur in pancreatic ascites.
• Bacterial culture: Bacterial culture may be performed through bedside inoculation of blood culture bottles.
• Cytology: This study is performed to identify evidence of malignancy.
• Serum-ascites albumin gradient (SAAG): SAAG equals the serum albumin level minus the ascitic albumin level (g/dL) and predicts the presence or absence of portal hypertension with 97% accuracy. The traditional method of classifying ascitic fluid as transudative or exudative based on protein concentration has been largely abandoned due to its limited accuracy of 56%.[18]
  • SAAG ≥1.1 g/dL: Indicative of portal hypertension and is seen in cirrhosis, alcoholic hepatitis, diffuse hepatic cancer obstructing portal vessels, Budd-Chiari syndrome (hepatic vein thrombosis), portal vein thrombosis, idiopathic portal fibrosis, congestive heart failure, and pericarditis.
  • SAAG <1.1 g/dL: Indicates the patient does not have portal hypertension and occurs in peritoneal carcinomatosis, pancreatitis, serositis, nephrotic syndrome, and peritoneal tuberculosis.

Additional Evaluation Studies

Additional tests should target specific clinical suspicions. A serum amylase level greater than 1000 U/L or more than 3 times the upper limit of normal supports a diagnosis of pancreatic ascites. Mycobacterial culture is appropriate when tuberculosis is strongly suspected. Ascitic fluid lactate dehydrogenase (LDH) and glucose levels assist in identifying secondary peritonitis.

Milky-appearing ascitic fluid suggests chylous ascites. Lipoprotein electrophoresis serves as the gold standard for detecting chylomicrons, but limited laboratory availability often necessitates triglyceride testing instead. A triglyceride level greater than 200 mg/dL typically confirms chylous ascites, while recent data support a diagnostic threshold of 187 mg/dL, yielding up to 95% sensitivity and specificity.[19] SAAG values in chylous ascites vary depending on etiology. The tumor marker CA-125 in ascitic fluid is frequently elevated in cirrhotic and chylous ascites. Increased adenosine deaminase is associated with tuberculous ascites. Other indices, including lactate and pH, add minimal diagnostic value.

Imaging Studies

Ultrasound offers the highest sensitivity for detecting ascites, revealing homogenous, freely mobile anechoic fluid within the peritoneal cavity, most prominently in the Morrison pouch (see Image. Abdominal Ascites). Computed tomography (CT) can detect fluid accumulation and identify mass lesions. In pancreatic ascites, CT demonstrates intraperitoneal fluid with a density greater than 15 Hounsfield units, reflecting high protein content, and often reveals collapsed pseudocysts, parenchymal atrophy, dilated main pancreatic duct, or pancreatic calcifications. Magnetic resonance or endoscopic cholangiopancreatography can further delineate ductal disruptions.[20]

Lymphangiography and nuclear lymphoscintigraphy using ⁹⁹Tc antimony sulfide colloid and dextran or albumin assist in diagnosing chylous ascites and locating lymphatic leaks or fistulas.[7] Single-photon emission computed tomography (SPECT) provides additional localization information, particularly when surgical intervention is required.[21]

Treatment / Management

Targeted Medical Therapies

Appropriate management of ascites depends on identifying and addressing the underlying cause of fluid retention. The primary therapeutic goals include reducing ascitic fluid accumulation and peripheral edema while maintaining adequate intravascular volume.[22][23][24] Sodium restriction and diuretics represent the first-line approach. In cases of high-SAAG ascites, treatment involves alcohol abstinence, dietary sodium restriction to 88 mEq (2000 mg) daily, and diuretic therapy with once-daily spironolactone and furosemide in a 100:40 mg ratio.

Patients with treatable liver diseases, eg, autoimmune hepatitis, chronic hepatitis B with reactivation, hemochromatosis, or Wilson disease, should receive targeted therapies. Although certain nonalcoholic or nonhepatitis B causes of cirrhosis may show partial reversibility, most remain progressive. By the time ascites develops, patients often benefit more from liver transplantation than from prolonged medical therapy. Low-SAAG ascites commonly results from nonovarian peritoneal carcinomatosis, where diuretics provide minimal benefit and repeated therapeutic paracentesis becomes necessary. Ovarian malignancy-associated ascites may improve with surgical debulking and chemotherapy, while lupus serositis-related ascites often responds to glucocorticoids.

Tuberculous peritonitis requires anti-tuberculous treatment, and infections caused by chlamydia or other bacteria demand appropriate antibiotic therapy. Postoperative lymphatic leaks following distal splenorenal shunt or radical lymphadenectomy may resolve spontaneously. Pancreatic ascites can often be managed medically; however, endoscopic pancreatic duct stenting may be needed to close ductal disruptions. Supportive measures, eg, nil per os status and parenteral nutrition, may suffice.

However, persistent ascites may require intermittent therapeutic paracentesis combined with diuretics and somatostatin or octreotide to reduce pancreatic exocrine secretion and promote ductal healing.[25] Please see StatPearls' companion resource, "Octreotide," for further information.  

Invasive Therapies

When conservative measures fail, endoscopic retrograde cholangiopancreatography (ERCP) with transpapillary pancreatic stent placement can be performed.[25] Surgical options depend on ductal caliber and leak location and may include pseudocyst-jejunal anastomosis, distal pancreatectomy with ductal ligation, or Roux-en-Y pancreaticojejunostomy.[26]

Patients with chylous ascites unresponsive to underlying etiologic therapy may undergo therapeutic paracentesis or transjugular intrahepatic portosystemic shunt (TIPS) placement. When these approaches fail, a peritoneovenous shunt may provide symptomatic relief by diverting lymph into the venous circulation. However, such shunts carry significant risks, including electrolyte imbalance, septic shock, small-bowel obstruction, disseminated intravascular coagulation, air embolism, and shunt occlusion due to lymph viscosity.[27](B3)

Therapeutic paracentesis offers symptomatic relief for tense ascites refractory to diuretics (see Images. Paracentesis and Ascites Pocket). Albumin administration following large-volume paracentesis helps prevent hypotension and postparacentesis circulatory dysfunction (PPCD), defined as a more than 50% increase in renin activity above baseline. PPCD may lead to hyponatremia, renal impairment, or hepatorenal syndrome.[28] The American Association for the Study of Liver Diseases (AASLD) recommends albumin replacement after removal of 5 or more liters of fluid; typically, 6 to 8 grams of albumin should be replaced per liter of fluid removed.[29] However, data to confirm whether albumin should be given after removing 3 to 5 L are lacking.[30] Updated studies suggest dosing albumin based on total volume removed: 25 g for 5 to 6 L, 50 g for 7 to 10 L, and 75 g for more than 10 L.[30]

TIPS, a side-to-side portacaval shunt inserted via the internal jugular vein, is an effective treatment for carefully selected patients with refractory ascites who are intolerant of frequent paracenteses. This procedure reduces portal pressure directly. Patients with Child C liver disease, a MELD score of 18 or greater, sarcopenia, congestive heart failure, or unexplained hepatic encephalopathy face higher risks of post-TIPS complications and generally do not qualify for the procedure.[31] Individuals with Child A or B liver disease and those receiving a covered stent less than 10 mm have better outcomes.[32] Earlier TIPS placement during ascites development improves long-term results, and patients unresponsive to TIPS should be evaluated for liver transplantation.

Differential Diagnosis

Other diagnoses that should be considered when evaluating patients with ascites include:

• Acute liver failure
• Chronic liver failure/cirrhosis
• Alcoholic hepatitis
• Portal hypertension
• Hepatitis B, C, D, and E
• Advanced metabolic dysfunction-associated steathepatitis (MASH)
• Liver cancer
• Hepatic adenomas
• Biliary tract disease
• Budd-Chiari syndrome, ie, hepatic vein thrombosis (Please see StatPearls' companion resource, "Budd-Chiari Syndrome," for further information.)
• Dilated cardiomyopathy
• Nephrotic syndrome
• Hepatorenal syndrome (Please see StatPearls' companion resource, "Hepatorenal Syndrome," for further information.)
• Dilated or restrictive cardiomyopathy
• Pancreatitis (pancreatic ascites)
• Protein-losing enteropathy
• Familial Mediterranean Fever
• Tuberculosis
• Pregnancy (associated with preeclampsia and HELLP syndrome of hemolysis, elevated liver enzymes, and low platelets)
• Ovarian cysts
• Hypoalbuminemia
• Chylous ascites

Prognosis

The prognosis of patients with ascites depends on the cause and chronicity. Acute underlying disorders that respond to treatment have a more favorable prognosis than those that do not. Overall, the prognosis is much worse for patients who have decompensated cirrhosis compared to those with compensated cirrhosis. Patients with cirrhotic ascites have a 1-year mortality rate of 40% that increases to 50% at 2 years.[33] Mortality is higher in patients with hepatic encephalopathy, sarcopenia, renal dysfunction, low urinary sodium levels, and hyponatremia.[34] Patients with refractory ascites have a 1-year survival of less than 50%.

Mortality was 27.6 times greater in otherwise similar individuals, and survival in people with people was 1.08 years (interquartile range [IQR] of 0.26 to 1.75 years) and 0.38 years (IQR of 0.1 to 1.3 years) in those who required therapeutic paracentesis.[35]

Complications

Complications of Ascites

Complications of ascites include:

• Spontaneous bacterial peritonitis
• Hepatic hydrothorax
• Pleural effusion
• Acute kidney injury due to hepatorenal syndrome
• Kidney failure
• Hyponatremia
• Sarcopenia
• Cellulitis
• Abdominal wall hernias
• Refractory/tense ascites

Complications related to paracentesis treatment include:

• Infection
• Electrolyte imbalance
• Bowel perforation
• Bleeding
• Leakage of fluid through the abdominal wall
• Injury to the kidneys