Peritoneal effusion is the medical term for the abnormal buildup of fluid within the peritoneal cavity, the space located between the abdominal organs and the abdominal wall lining. This condition is most commonly known as ascites. While a small amount of fluid naturally lubricates the organs, an accumulation exceeding 25 milliliters is considered an effusion. This fluid collection causes abdominal distention and is a frequent complication of advanced liver disease.
Why Fluid Accumulates in the Abdomen
The most frequent underlying cause for this fluid accumulation is advanced liver disease, specifically cirrhosis, accounting for over 80% of cases. Cirrhosis causes scarring that obstructs blood flow through the liver, leading to high blood pressure in the portal vein system, a condition known as portal hypertension. This increased pressure forces fluid out of the blood vessels and into the peritoneal space. The resulting pressure imbalance and decreased production of the protein albumin by the damaged liver combine to promote fluid leakage.
The accumulation is primarily driven by an imbalance of hydrostatic and oncotic pressures within the circulatory system. As the condition progresses, the body attempts to compensate for the perceived low blood volume by activating neurohormonal systems. This activation leads to the kidneys retaining excessive amounts of sodium and water, which expands the plasma volume and exacerbates the effusion.
Other conditions can also lead to peritoneal effusion, although less frequently than liver disease. Congestive heart failure, for example, causes fluid buildup due to increased pressure in the veins, slowing the return of blood to the heart. Various cancers, such as ovarian, breast, and colon cancer, can cause malignant ascites. Tumors may irritate the peritoneal lining, causing leakage, or obstruct the lymphatic system, preventing proper fluid drainage.
Identifying the Symptoms
Symptoms of peritoneal effusion often develop gradually, but they can appear quickly depending on the underlying cause and the rate of fluid accumulation. The most common physical sign is a noticeable increase in abdominal size, often described as distention or bloating. Patients may also experience rapid weight gain as the fluid collects.
As the volume of fluid increases, it creates pressure within the abdomen, leading to a feeling of fullness and discomfort. This pressure can push upward on the diaphragm, which in turn compresses the lungs and causes shortness of breath. Other digestive issues, such as indigestion, constipation, and a general loss of appetite, may also occur due to the physical compression of the stomach and intestines.
How Doctors Confirm the Diagnosis
Diagnosis of peritoneal effusion typically begins with a physical examination, where a doctor may observe abdominal distention and test for a fluid wave. Confirmation and precise quantification of the fluid are usually achieved using imaging techniques. An abdominal ultrasound or CT scan can visualize the fluid collection and provide information about the size and condition of the abdominal organs, such as the liver.
A procedure called diagnostic paracentesis is often necessary to determine the underlying cause of the fluid accumulation. This involves inserting a thin needle into the abdomen to withdraw a sample of the fluid for laboratory analysis. Analyzing the fluid helps classify the effusion as either a transudate, which is low in protein and caused by pressure imbalances, or an exudate, which is high in protein and often caused by inflammation or malignancy.
The Serum-Ascites Albumin Gradient (SAAG) is used to differentiate between causes by comparing the albumin concentration in the blood serum to that in the ascitic fluid. A high SAAG value (≥ 1.1 g/dL) strongly suggests the effusion is due to portal hypertension, a common feature of cirrhosis. Conversely, a low SAAG value suggests causes not related to portal hypertension, such as peritoneal cancer or infection.
Approaches to Managing the Condition
Management of peritoneal effusion involves a two-pronged approach: treating the underlying condition and controlling the fluid buildup. For patients where the cause is liver disease, dietary changes are often the first step. This typically involves a strict restriction of sodium intake to help reduce the body’s tendency to retain water.
Medications known as diuretics are commonly prescribed to increase the excretion of sodium and water by the kidneys. A combination of diuretics, such as spironolactone and furosemide, is frequently used to maximize fluid removal while maintaining a balance of electrolytes. Diuretic-induced weight loss is carefully monitored, generally not exceeding 0.5 kg per day in patients without swollen limbs.
If the fluid accumulation is severe or does not respond to diuretics, a procedure called therapeutic paracentesis may be performed. This involves draining a large volume of the fluid using a needle inserted into the abdomen. When large amounts of fluid are removed, an infusion of albumin may be administered to prevent circulatory dysfunction and maintain blood volume.
For cases where the effusion is refractory to maximum medical therapy, more advanced interventions may be considered. A transjugular intrahepatic portosystemic shunt (TIPS) is a specialized procedure that creates a new pathway within the liver to relieve portal hypertension. While effective in reducing the need for repeated draining, the ultimate curative option for end-stage liver disease remains liver transplantation.