Ascites is caused by malignancy in approximately 7% of patients. A number of mechanisms exist whereby cancer can cause ascites, and its development is not always synonymous with a diagnosis of peritoneal carcinomatosis. The two main causes observed in the Beatson West of Scotland Cancer Centre are:
- Peritoneal carcinomatosis secondary to malignancies of ovarian and urological origin. In these cases, accumulation of ascites results from blockage of the draining lymphatic channels and increased vascular permeability.
- Colonic, gastric, breast, pancreatic, and lung cancers may cause peritoneal carcinomatosis and/or massive liver metastases, which can lead to ascites either because they obstruct / compress portal veins or because they cause liver failure.
Assessment / Monitoring
- Patients often seek medical attention because of symptoms such as abdominal swelling / pain / discomfort, shortness of breath, early satiety, or nausea and vomiting.
- Weight loss will often be recounted prior to the development of ascites (when weight begins to increase again).
- The presence of bulging flanks, a distended / firm abdomen, or an everted umbilicus should lead to percussion for dullness and testing for shifting dullness.
- Positive ascitic fluid cytology to establish the diagnosis of malignancy-related ascites, if this is in doubt e.g. a patient with a history of cirrhosis. The overall sensitivity of cytology for the detection of malignancy-related ascites is 58–75%.
- CT or ultrasound can confirm clinical suspicion of ascites, with the latter often used for marking an appropriate site for paracentesis. CT is useful to confirm the mechanism of ascites formation, assessing the peritoneum, portal vein and liver.
- Blood tests include FBC, U&Es, LFTs, and coagulation screen. During paracentesis monitor U&Es daily.
- Send ascitic fluid for investigation to help confirm diagnosis and exclude infection. These include cell count and differential, bacterial culture, albumin (for serum-to-ascites albumin gradient), total protein, glucose, LDH, and cytology (described above). Bacterial culture is particularly important in those with fever or abdominal pain, although it should be noted that peritoneal carcinomatosis can sometimes mimic spontaneous bacterial peritonitis. Initially give antibiotics (see here) when an elevated fluid neutrophil count is detected, but discontinue when it becomes clear (by positive cytology and absence of growth on bacterial culture) that ascites is related to malignancy and not infection.
- Avoid serum CA125 testing as it is often falsely elevated in the presence of ascites. In fact, virtually all patients, including men, with ascites or pleural fluid of any cause have elevated serum level of CA125. In ovarian cancer, CA125 should not be used to monitor response for at least 28 days following a paracentesis.
- Ascites in women with epithelial ovarian / peritoneal cancer is not necessarily associated with a severely limited prognosis – such patients will often live for years (with resolution of their ascites) once treatment of the underlying cause is established.
- When a patient develops ascites in the setting of a non-ovarian / peritoneal cancer, the prognosis is usually poor and often less than three months. Paracentesis here is symptom-driven with the focus on improving quality of life.
Treatment of underlying cause
- For women with a new diagnosis of epithelial ovarian / peritoneal cancer, the initial treatment of choice is surgical debulking with chemotherapy. If surgical debulking is not feasible then primary chemotherapy can be given with delayed primary surgery after 3 cycles. More than one-half of these patients will have a complete remission from this treatment.
- For other solid tumours with malignant ascites, prognosis is poor and the role of surgery is not established. Palliative systemic therapy is sometimes appropriate, with the specific regimen chosen based upon the primary site of cancer.
- Abdominal paracentesis with appropriate ascitic fluid analysis is the most efficient way to diagnose its cause, and determine if ascitic fluid is infected.
- Repeated abdominal paracentesis is sometimes needed for women with ovarian / primary peritoneal cancer, while chemotherapy treatment is established, with the frequency of drainage again guided by the patient's symptoms. For patients where chemotherapy is unlikely to be effective and who require repeated drainage, an indwelling catheter should be considered
- Aim should be to drain 1 litre every 2–4 hours until dry, clamping the drain in between. Large volumes of fluid can usually be removed without fear of haemodynamic sequelae or circulatory failure. Available data suggests colloid / albumin replacement to prevent haemodynamic deterioration after paracentesis is not necessary. Drains should be removed after 48 hours.
- Patients often have a poor appetite and thus a diet should be considered to maximise caloric intake. Patient with co-existing bowel obstruction may require parenteral nutrition.
- Ascitic fluid will be bloody in about 20% of malignancy-related ascites.
- Consider if there is peripheral oedema or refractory ascites. They are more likely to be effective if portal hypertension is contributing to the pathophysiology of the ascites. Diuretics may cause hypotension and intravascular depletion so response must be monitored on an individual basis
- Spironolactone oral 100mg daily is the suggested initial dose, with titration upwards as necessary.
- U&Es must be closely monitored as necessary. Furosemide can be considered as an alternative if hyperkalaemia develops.