From the Guidelines
Ascites is most commonly caused by liver cirrhosis, which accounts for about 75% of cases, and other major causes include heart failure, kidney disease, and cancer. The underlying mechanism typically involves either increased hydrostatic pressure, decreased oncotic pressure from hypoalbuminemia, increased vascular permeability, or lymphatic obstruction 1. According to the guidelines on the management of ascites in cirrhosis, liver cirrhosis is the most common cause of ascites, and portal hypertension leads to increased hydrostatic pressure and decreased albumin production, creating an imbalance that allows fluid to leak into the abdominal cavity 1.
Other causes of ascites include:
- Heart failure, where poor cardiac output leads to increased venous pressure
- Kidney disease, particularly nephrotic syndrome which causes protein loss
- Cancer, especially ovarian, pancreatic, and liver cancers that can obstruct lymphatic drainage or directly produce fluid
- Infections like tuberculosis peritonitis can trigger inflammatory responses leading to fluid accumulation
- Pancreatic disorders such as pancreatitis or pancreatic duct leakage can cause ascites with high amylase content
- Less common causes include thyroid disease, severe malnutrition, and certain medications 1.
Diagnosis usually requires identifying the underlying cause through physical examination, blood tests, imaging, and sometimes paracentesis to analyze the fluid 1. The serum-ascites albumin gradient (SAAG) can help differentiate between portal hypertension and other causes of ascites, with a SAAG greater than or equal to 1.1 g/dL indicating portal hypertension with an approximate 97% accuracy 1.
In terms of management, the guidelines recommend a diagnostic paracentesis in all patients with new onset grade 2 or 3 ascites, and in all patients hospitalized for worsening of ascites or any complication of cirrhosis 1. The initial treatment for patients with ascites involves taking medication, commonly known as 'water tablets' (diuretics), and dietary sodium restriction 1.
Overall, the management of ascites requires a comprehensive approach that takes into account the underlying cause, the severity of the ascites, and the patient's overall health status, with the goal of improving morbidity, mortality, and quality of life 1.
From the Research
Causes of Ascites
The causes of ascites are multifactorial, but principally involve significant volume and hormonal dysregulation in the setting of portal hypertension 2. The main factors that lead to the development of ascites in cirrhosis are:
- Severe sinusoidal portal hypertension and hepatic insufficiency 3
- Circulatory dysfunction characterized by arterial vasodilation, arterial hypotension, high cardiac output, and hypervolemia 3
- Renal sodium and water retention 3
- Splanchnic arterial vasodilation, which impairs systemic hemodynamics and renal function, and alters hemodynamics in the splanchnic microcirculation 3
- Lymph leakage from the liver and other splanchnic organs, which is the mechanism of fluid accumulation in the abdominal cavity 3
Differential Diagnosis of Ascites
The differential diagnosis of ascites is complex and includes various causes, such as:
- Chronic liver disease (roughly 80-85% of cases) 4
- Cardiac failure 4
- Tuberculosis 4
- Malignancy-related ascites 4
- Other less common causes 4
To determine the cause of ascites, careful evaluation of the patient, including a clinical history, physical examination, and diagnostic paracentesis, should be performed 4. The serum-ascites albumin gradient can be used to classify the cause of ascites into portal hypertension-related and non-related with a diagnostic accuracy of > or = 97% 4.