• Clinical science

Ascites

Summary

Ascites is the abnormal accumulation of fluid in the peritoneal cavity and a common complication of diseases presenting with portal hypertension (e.g., liver cirrhosis, acute liver failure) and/or hypoalbuminemia (e.g., nephrotic syndrome). Other conditions resulting in ascites include chronic heart failure, visceral inflammation (e.g., pancreatitis), and malignant tumors. Clinical features include progressive abdominal distension, shifting dullness, and a positive fluid wave test. Ascites may be associated with abdominal pain in rare cases. An adequate clinical assessment should be followed by imaging (e.g., ultrasound), which helps to identify even very small quantities of ascitic fluid in the peritoneal cavity. If the onset of ascites is spontaneous or the origin is unclear, an abdominal paracentesis and ascitic fluid assessment may be performed (i.e., to determine the appearance, composition). Management involves treating the underlying condition in addition to sodium restriction and diuretic therapy. Severe or refractory ascites may require therapeutic abdominal paracentesis. A severe complication is spontaneous bacterial peritonitis.

Etiology

Etiology Pathophysiology

High SAAG ascites

≥ 1.1 g/dL (obsolete term: transudate)

  • All result in ↑ pressure in portal vein↑ hydrostatic pressure in the hepatic vessels → pushing of fluid out from the intravascular space to the peritoneal cavity

Low SAAG ascites

< 1.1 g/dL (obsolete term: exudate)

  • All result in ↓ intravascular osmotic gradient → secondary influx of water from the intravascular space to the peritoneal cavity
  • Production of protein-rich fluid from tubercles
  • Accumulation of pancreatic fluid in the peritoneal cavity

References:[1][2][3][4][5][6][7]

Clinical features

References:[3][8][9]

Subtypes and variants

References:[10]

Diagnostics

  • Clinical chemistry
    • Dilutional hyponatremia as a result of overhydration despite normal or increased sodium concentration (see electrolyte imbalance of sodium)
    • Hypoalbuminemia
  • Imaging
    • Ultrasound (best initial test): Reliable detection even of smaller quantities of ascitic fluid: lower limit of detection approx. 30 mL
    • CT scan

Criteria for analyzing ascitic fluid

Ascites due to portal hypertension (SAAG ≥ 1.1 g/dL)

(Previously referred to as transudate)

Ascites due to other causes (SAAG < 1.1 g/dL)

(Previously referred to as exudate)

Color
  • Clear, sometimes opalescent
  • Cloudy
  • Bloody
  • Milky
  • Dark brown
Cell count and differentiation
  • ↓ Cell count
Protein concentration

Remember, eggs, like“EGGsudates” (exudates) are high in protein.

References:[1][2]

Treatment

General measures

  • Treatment of the underlying disease (e.g., using anticoagulation in case of a thrombosis or tuberculostatics in case of a tubercular peritonitis)
  • Sodium restriction
  • Regular weight control
  • Water restriction or avoiding overhydration

Diuretic therapy

  • Indications
    • Portal hypertensive ascites: usually responsive; may be treated in the same way as ascites caused by liver cirrhosis (see treatment of cirrhosis).
    • Non-portal hypertensive ascites (exudate): usually not effective; therefore it is essential to focus on treating the underlying disease!
  • Approach
  • Regular control of potassium and creatinine during diuretic therapy

Diuretics should be used with precaution in cases of severe hyponatremia, hepatic encephalopathy, or deterioration of renal function!

Treatment of refractory ascites

References:[1][2]

Complications

  • Spontaneous bacterial peritonitis (ascitic fluid infection): abdominal tenderness, fever, altered mental status (see peritonitis for more information)

We list the most important complications. The selection is not exhaustive.