When cancer breaks through the wall of an organ such as the stomach or bowel and spreads to the thin membrane lining the abdominal cavity, called the peritoneum, this is known as peritoneal metastasis. Because the peritoneum covers the organs across the whole abdomen, cancer cells settling there can affect the entire belly.
A common companion of peritoneal metastasis is ascites, the buildup of fluid inside the abdominal cavity. Normally the peritoneum makes a small amount of fluid and reabsorbs it, keeping a balance. When cancer cells irritate the peritoneum, more fluid leaks out, and at the same time drainage through the lymphatic vessels can become blocked, so the fluid cannot leave and collects in the belly.
As ascites builds, the abdomen swells and feels taut. It can be hard to stand up straight, a person may feel full after only a few bites, and there may be bloating or shortness of breath. Lying down and sitting become uncomfortable, and some people notice leg swelling or reduced urine output. Because these symptoms lower quality of life, reducing ascites is one important goal of treatment.
When chemotherapy responds well, the amount of cancer in the peritoneum can decrease, and with it the amount of fluid leaking out. As a result the tightness may ease, walking can feel easier, and appetite may slowly improve. Because the pace and degree of these changes differ from person to person, doctors do not rely on how the body feels alone; imaging such as CT is used to compare the volume of ascites and the size of the peritoneal lesions.
A fever that rises and falls can have several overlapping causes, including infection, inflammation, or the tumor itself, so a lower fever does not by itself prove that treatment is working. That is why the medical team weighs symptoms, blood tests, and imaging together.
It is safer to contact your care team without waiting for the next appointment if the belly swells rapidly, if it becomes so tight that breathing is difficult, if you have a fever of 38°C or higher or chills, if the abdomen is severely painful or feels hard, or if urine output drops sharply or your weight rises a lot within a few days.
This article is general information and does not replace an individual diagnosis or treatment. Please discuss your symptoms, the meaning of your test results, and your treatment plan with your own medical team.