Peritoneal cancer is usually very difficult to diagnose, but it may be discovered during the examination or the surgical treatment of the primary tumor or when a patient develops symptoms related to peritoneal cancer. There is no specific examination that is ideal for diagnosing peritoneal cancer. Most often, a combination of examinations is required.

These approaches usually include the following:

  • PHYSICAL EXAMINATION – Sometimes the peritoneal tumor nodules or ascites can be discovered by physical investigation of the belly, but this discovery typically occurs only in advanced cases.
  • TUMOR MARKER TESTS – These are blood tests that can indicate the presence of a malignant tumor in the body, but these tests are not very specific for most cancers, especially peritoneal cancer. The most commonly used tumor markers are Carcino Embryonal Antigen (CEA) for colon cancer, CA 19-9 for pancreatic cancer and CA-125 for ovarian cancer.
  • ULTRASOUND – This examination uses sound waves to create a detailed picture of the abdominal cavity on a computer screen. This examination is good for detecting ascites, but it is usually not sensitive enough to detect peritoneal cancer or the primary tumor.
  • COMPUTED TOMOGRAPHY (CT) – This detailed radiological examination can reveal the presence of peritoneal cancer or ascites in some cases. Unfortunately, a CT scan is not very good for detecting peritoneal cancer nodules, especially not in the early stages of the disease. In general, tumor nodules have to be as large as 1 cm, which is larger than the typical tumor nodules in peritoneal cancer, to be detected by a CT-scan.
  • PET-SCAN – This is an examination combining CT with nuclear radiology (positron emission tomography), and it is especially useful for detecting metastases outside the peritoneal cavity. Similar to the CT-scan, peritoneal cancer typically cannot be visualized by PET.
  • BIOPSY – If peritoneal cancer is suspected, a biopsy can be taken. In a biopsy, a small piece of tissue is removed from the body for investigation under a microscope. The biopsy can be taken after the patient has received local anesthesia through the skin or during a laparoscopy when the patient is under general anesthesia. A biopsy can confirm the presence of cancer cells in the peritoneal cavity. If the primary tumor is situated in the gastrointestinal tract, an endoscopy may be needed to take a biopsy from the primary tumor.
  • LAPAROSCOPY – When peritoneal cancer is suspected, a laparoscopy may be performed. This procedure is especially useful for collecting biopsies from tumor nodules and to determine the extent of the peritoneal cancer. An example can be seen here. Usually, the extent of the cancer is determined by calculating the peritoneal carcinomatosis index (PCI).
  • PATHOLOGY – Small parts of the tumor may be removed and examined under a microscope. Cancer can be confirmed and the aggressiveness of the tumor can be predicted based on these observations. Using specific techniques, the origin of the tumor can be determined, which is especially useful in cases in which the location of the primary tumor is not known yet.
  • ENDOSCOPY – When the primary tumor is potentially located in the gastrointestinal tract, an endoscope may be introduced by mouth to investigate the esophagus, stomach and duodenum (“esophagogastroduodenoscopy”) or through the anus to investigate the large intestine (“colonoscopy”). The inner layer of the gastrointestinal tract is visualized with the endoscope. Most gastrointestinal tumors originate from the inner layer and can be discovered by endoscopy. In addition to visualizing the tumor, biopsies from the tumor can be taken with the endoscope, which may be helpful to confirm the presence of cancer and to direct further treatment.