Ascites is the abnormal collection of fluid in the abdomen, causing distension and discomfort. This fluid accumulates within the peritoneal cavity, the space containing the digestive organs. Ascites cannot be “sucked in” or held back by muscle contraction because it is a free-floating liquid, unlike fat or muscle tissue. It is a medical complication requiring diagnosis and management of the underlying cause, not an issue of muscle tone.
Understanding Ascites: Fluid Accumulation vs. Fat
Ascites fluid collects in the peritoneal cavity, the space between the abdominal organs and the lining of the abdominal wall. This location is distinct from subcutaneous fat, which sits beneath the skin, or visceral fat, which is packed around the organs. The fluid is not contained by muscle or connective tissue, preventing voluntary compression.
The fluid’s mobility differentiates it from fat or bloating. When a person with a large volume of ascites changes position, the fluid shifts due to gravity, a phenomenon doctors detect during a physical exam. This “shifting dullness” or “fluid wave” is impossible with solid tissue. The abdominal wall is stretched and feels tense, making it physically impossible to contract muscles enough to reduce the distension significantly.
Primary Medical Causes of Ascites
The most frequent cause of ascites is advanced liver disease, specifically cirrhosis, accounting for about 80% of cases. Cirrhosis involves extensive scarring that impedes the normal flow of blood through the liver. This restriction causes a buildup of pressure in the portal vein, known as portal hypertension.
The increased pressure forces fluid to leak out of the liver and intestines into the peritoneal cavity. Portal hypertension also triggers a response in the kidneys, leading to the retention of sodium and water, which exacerbates fluid accumulation. This resulting ascites fluid is often classified as a transudate, meaning it has a low protein content typical of leakage due to pressure imbalances.
Ascites can also be caused by conditions other than liver disease, though these are less common. Identifying the specific cause is necessary because it dictates the management and treatment strategy.
Other Causes
Other causes include severe heart failure, where the heart cannot pump blood effectively, leading to back pressure and fluid leakage. Kidney failure, certain cancers that spread to the lining of the abdomen (peritoneal carcinomatosis), and infections like tuberculosis can also cause fluid to accumulate.
Diagnosis and Treatment Options
Diagnosis typically begins with a physical examination, where a doctor looks for abdominal distension and tests for a fluid wave. Imaging tests, such as an abdominal ultrasound or CT scan, confirm the fluid’s presence and estimate the volume, often detecting quantities as small as 100 to 200 milliliters. A critical diagnostic step is paracentesis, using a thin needle to withdraw a fluid sample for laboratory analysis.
Analyzing the fluid helps determine the underlying cause by measuring protein levels and calculating the serum-ascites albumin gradient (SAAG). Standard medical management focuses on reducing fluid volume through conservative measures and medication. Lifestyle changes include strict dietary sodium restriction, typically aiming for less than 2,000 milligrams per day, to encourage water excretion.
Pharmacological treatment involves diuretics, often a combination of spironolactone and furosemide, which help the kidneys eliminate excess sodium and water. For patients with a large volume of fluid causing significant discomfort or breathing difficulty, therapeutic paracentesis may be performed. This procedure involves draining several liters of fluid through a needle for immediate relief, and it may need to be repeated if the fluid reaccumulates.