© SciePro – stock.adobe.com The pathological accumulation of fluid in the abdominal cavity (peritoneum) is called abdominal fluid or ascites; if it occurs in the context of cancer, it is called malignant ascites. This develops in 20 to 50% of all patients with an advanced stage of a tumor in the abdomen, such as ovarian cancer and gastrointestinal tumors, but also in tumors of the breast, lung and lymphoma. The prognosis is usually extremely unfavorable and, depending on the underlying cancer, patients have a significantly shortened life expectancy. The occurrence of malignant ascites is associated with some cancers, such as ovarian carcinoma often even the first indication of malignant disease. In addition to purely palliative treatment, ascites puncture (paracentesis) procedures are combined with treatment of the underlying cancer using chemotherapy or new therapeutic approaches.
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The organs of the abdominal cavity (peritoneal space) are enveloped by what is known as the peritoneum. Its surface is covered with a clear film of liquid, which allows the organs to be moved against each other. This abdominal fluid is constantly replenished and the used fluid is removed via the lymphatic vessels. In this way there is a balance between production and disposal in a healthy person. In some patients, this balance is disturbed and pathological accumulation of abdominal fluid occurs, which is also called ascites.
Causes of this may include heart failure or decreased kidney function, peritonitis, or liver disease such as cirrhosis (1, 2). In about 10% of ascites patients, abdominal fluid accumulates as a result of malignant cancer, which is why the term ascites is used malignant ascites is spoken. (2)
If malignant tumor cells appear on the peritoneum, this is referred to as malignant ascites Peritoneal carcinomatosis. The cause is usually metastases of an advanced tumor in another abdominal organ, such as the ovaries, pancreas or gastrointestinal tract. Peritoneal carcinomatosis with the appearance of malignant ascites is considered a late-stage cancer and leads to a significantly reduced life expectancy. But malignant ascites can also occur in tumors outside the abdominal cavity, such as breast cancer (mammary carcinoma), lung cancer and lymphoma. In one fifth of all patients with malignant ascites, however, no tumor of origin can be identified, so that this is then referred to as malignant ascites in cancer with unknown primary tumor (Cancer of Unknown Primary, CUP) (2,3)
Although not every patient with one of the aforementioned tumors suffers from malignant ascites, malignant ascites is almost always a sign of advanced cancer. For example, ovarian cancer is often first detected due to an increase in abdominal girth along with a feeling of fullness at the bottom of malignant ascites. By then, the cancer is often well advanced and often already has an unfavorable prognosis (4).
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Symptoms and diagnosis of malignant ascites
Symptoms such as nausea, vomiting, heartburn, loss of appetite, hiccups or shortness of breath coupled with an increase in abdominal girth and weight gain occur because the tumor cell mass impairs the function of the organs.
If ascites is suspected, a physical examination and medical history, a laboratory test of liver values, kidney function, serum and urine electrolytes, and an ultrasound examination (sonography) are performed as part of the primary diagnostic procedure. For a more accurate diagnosis of ascites, an ascites puncture (Peritoneal puncture), in which fluid is removed from the abdominal cavity with the aid of a puncture cannula and examined.
The Cytological diagnostics provides information about the presence of tumor cells and thus allows the direct detection of malignant ascites. The cells may still be affected by so-called. Tumor marker (such as AFP, CEA, CA 19-9, or CA-15-3) are more accurately characterized, which helps determine the tumor of origin (2, 5). In addition, color, odor, cholesterol content, total protein content, and serum ascites albumin gradient (SAAG) are determined in the collected abdominal fluid. For example, the total protein content is a measure of the ability of the innate immune system to fight off bacteria and indicates the risk of spontaneous bacterial peritonitis (SBP). In this dangerous inflammation of the peritoneum, intestinal bacteria multiply in the abdominal fluid and pain, fever and chills occur. Because of the life-threatening nature of this case, rapid antibiotic therapy is necessary (2, 5).
Development of malignant ascites
Treatment of malignant ascites
Treatment of malignant ascites is divided into symptomatic therapies to relieve symptoms and improve quality of life and tumor-specific therapies to limit tumor cell growth.
The main symptomatic treatments include ascites puncture or paracentesis, d. h. piercing the wall of the abdomen with a cannula, as is already done for diagnosis. Draining of abdominal fluid leads to pressure relief. But because fluid is always replenished, this procedure must be performed again and again, so that permanent drainage systems with pump systems, indwelling catheters and shunts for artificial connection of the abdominal cavity with the venous system are also available. Because of the risk of the tubes becoming clogged with tumor cells, there are increasing systems that are transplanted under the skin and pump water from the abdomen through a tube directly into the urinary bladder, from which the fluid can be excreted through the toilet. Field reports on this can be found online (7). In addition to these pumping systems, classic diuretics (so-called "water tablets") are available that can increase the excretion of fluid through the kidney (2, 3).
The tumor-specific therapies by means of chemotherapy aim at slowing down the growth of cancer cells, because this also reduces the production of ascites.
New therapy approaches also include so-called targeted therapies, with the help of which specific structures of the tumor are targeted. VEGF, for example, plays an important role as a messenger substance in the vascularization of a tumor and has been found to be 40 times more concentrated in malignant ascites than in the abdominal fluid of healthy individuals.