Fluid in the abdomen, medically termed ascites, is an abnormal accumulation of fluid within the peritoneal cavity. While not always indicative of malignancy, it can be a notable sign of advanced cancer. Its presence often prompts investigation into underlying health conditions, including the potential involvement of cancer. Understanding ascites is important for recognizing its implications and how cancer can contribute to its development.
What is Fluid in the Stomach (Ascites)?
Ascites is a swelling of the belly due to fluid collecting in the abdominal space. This accumulation can cause discomfort, fullness, bloating, and sometimes shortness of breath as the fluid puts pressure on internal organs and the diaphragm. It is not a disease itself but a symptom signaling an underlying medical issue.
Many conditions unrelated to cancer, such as severe liver disease, heart failure, or kidney problems, can also lead to ascites. When cancer is the cause, it is specifically referred to as malignant ascites. The abdominal cavity contains a membrane called the peritoneum, which has two layers that normally produce a small amount of fluid to allow organs to move smoothly. Ascites occurs when too much fluid builds up between these layers.
Cancers Commonly Associated with Ascites
Ascites frequently accompanies several types of cancer, particularly in advanced stages, due to their tendency to affect the abdominal region. Ovarian cancer is often associated with ascites because it commonly spreads to the peritoneum, the abdominal lining. This spread, known as peritoneal carcinomatosis, can cause irritation and excess fluid production.
Gastrointestinal cancers, including stomach, colorectal, and pancreatic cancers, are also frequent causes of malignant ascites. These cancers can spread to the peritoneum or obstruct lymphatic drainage, leading to fluid accumulation. Liver cancer (hepatocellular carcinoma) and cancers that have metastasized to the liver can also result in ascites. This can happen if the liver’s function is impaired or if increased pressure develops in the portal vein system.
Breast cancer, though originating outside the abdomen, can cause ascites if it spreads to the peritoneum or liver. Lung cancer can also lead to ascites through metastasis to the peritoneal surfaces. Lymphoma, a lymphatic system cancer, can sometimes involve abdominal lymph nodes or the peritoneal surfaces, contributing to fluid buildup.
How Cancer Leads to Fluid Accumulation
Cancer can lead to fluid accumulation through several processes. One common mechanism is peritoneal carcinomatosis, where cancer cells spread to the peritoneum. These cells irritate the lining, prompting excessive fluid production that overwhelms the body’s reabsorption ability. About two-thirds of malignant ascites cases are due to this spread.
Another pathway involves the obstruction of lymphatic vessels. Cancer cells or tumors can block these drainage vessels, preventing fluid reabsorption from the peritoneal cavity. This blockage causes fluid to back up and accumulate.
Cancer can also affect the liver, leading to portal hypertension or impaired liver function. When cancer spreads to the liver, it can increase pressure in surrounding blood vessels, forcing fluid into the abdominal cavity. Advanced cancer or its treatments can also reduce the liver’s ability to produce albumin, a protein that helps maintain fluid balance. A decrease in albumin levels can cause fluid to leak from blood vessels and collect in spaces like the abdomen.
Identifying and Managing Cancer-Related Ascites
Identifying ascites typically begins with a physical examination, where a healthcare provider may observe abdominal swelling or feel for a “fluid wave.” Imaging techniques like ultrasound or CT scans confirm the presence and amount of fluid and evaluate abdominal organs for signs of cancer. Paracentesis involves inserting a thin needle into the abdomen to remove a fluid sample for analysis. This fluid is examined for cancer cells, protein levels, and other indicators to help determine the cause.
Managing cancer-related ascites focuses on alleviating symptoms and treating the underlying cancer. Therapeutic paracentesis, the removal of larger fluid volumes, can provide immediate relief from discomfort, pressure, and shortness of breath. This procedure can be repeated as needed, sometimes with a long-term drainage catheter for frequent fluid buildup. While diuretics (“water pills”) may be prescribed to help the body excrete excess fluid, they are often less effective for cancer-related ascites compared to other causes. The most effective long-term management involves treating the primary cancer. Chemotherapy, targeted therapies, or other cancer treatments can help shrink tumors and reduce their impact on fluid production and drainage, controlling the ascites.