Ascites

Ascites refers to the abnormal build-up of fluid in the abdominal cavity or peritoneum, which is the lining of the abdomen and abdominal organs.  

The fluid is generally serous, meaning that it’s a watery, protein-poor fluid that is normally present in the body to help reduce friction between organs. However, in the case of ascites, the amount of fluid is excessive.  

Ascites becomes clinically detectable when approximately 500 mL or more of fluid has accumulated in the abdominal cavity. The presentation varies based on severity. In mild cases, the abdomen may appear normal, and fluid may only be detected through imaging or physical exam maneuvers. In moderate to severe ascites, individuals may develop a distended abdomen, and the skin may appear stretched and shiny with a protruding or everted umbilicus as the pressure increases. 

As fluid accumulates, this pressure causes the abdomen to feel tense, full, and tight. The expanding fluid can compress nearby organs, leading to abdominal discomfort or pain, early satiety, nausea, and, in some cases, shortness of breath due to upward pressure on the diaphragm. This respiratory discomfort is often worse when lying flat, a condition known as orthopnea. 

Ascites itself can be diagnosed clinically using a physical assessment. However, to determine the cause of ascites, additional testing is required, such as a liver ultrasound and diagnostic paracentesis. A paracentesis uses a large needle to remove fluid from the peritoneal cavity, which is then sent for testing.  

One important test is the serum-to-ascites albumin gradient (SAAG). A SAAG of 1.1 g/dL or higher usually means ascites is due to portal hypertension, most often from cirrhosis. Additional blood work is needed in order to perform this calculation, such as serum albumin. The fluid may also be checked for cells such as mesothelial cells and white blood cells. A few mesothelial cells and white blood cells are normal, but a high number of neutrophils suggests an infection like spontaneous bacterial peritonitis (SBP), which can be life-threatening. 

Ascites can lead to serious, life-threatening complications. One of the most critical is SBP, which is an infection of the ascitic fluid. If not recognized and treated quickly, the infection can spread to the bloodstream, causing bacteremia and potentially sepsis, a dangerous condition where the immune system overreacts and begins damaging the body’s own organs. This can lead to organ failure and death, if not managed promptly. 

Other complications, especially in the setting of portal hypertension, include hepatorenal syndrome, malnutrition, pleural effusion, and severe gastrointestinal bleeding.