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Ascites is the accumulation of fluid in the peritoneal space. It is a common problem in cirrhosis (due to portal hypertension) and when there is malignant spread into the peritoneum (which is common in ovarian and gastrointestinal cancers). It can cause significant swelling and discomfort and peritoneal drainage often brings relief.
Epidemiology and pathogenesis
Ascites is a common problem in patients with palliative illnesses.
The majority of Most patients with end-stage liver disease from cirrhosis develop ascites.
About 10% of cancer patients develop ascites, with the most common malignant causes including:
- Ovarian cancer
- Breast cancer
- Lung cancer
- Gastric cancer
- Pancreas cancer
- Cancer of unknown primary (accounts for around 20% of case of malignant ascites)
As ascites develops, the abdomen becomes increasingly swollen. This can cause tightness and discomfort and eventually the resultant mass effect of the fluid causes poor appetite, early satiety and nausea (through compression the gastrointestinal tract) and dyspnoea (through upwards pressure on the diaphragm and lungs).
On abdominal examination:
- On inspection, abdominal distension is obvious with significant ascites
- On percussion, dullness at the flanks that moves when the patient rolls on his side tends to become apparent once at least a litre of fluid has accumulated (shifting dullness)
On general inspection there may be signs of the underlying cause of the ascites. In cirrhosis, for example, a hepatic flap, jaundice and spider naevi are often present. In malignancy on the other hand, the patient may appeared frail and cachectic.
Point of care ultrasound is very useful in confirming ascites. The cheapest and most basic of hand-held ultrasounds can be used to immediately confirm or exclude the presence of a significant volume of ascites.
Ascites can be confirmed radiologically via a formal ultrasound or CT imaging, although this usually isn't necessary in the palliative care context in a patient who has had recurrent ascites previously diagnosed.
Where the cause of the ascites isn't known, a diagnostic tap is helpful to confirm the aetiology and fluid can be sent for:
- Cell count and differential
- Gram stain and culture
Ascites with a high amount of albumin is an exudate which is what would be expected in malignant infiltration. When the albumin level is low this is a transudate consistent with portal hypertension (e.g. from cirrhosis). However most patients already have a low serum albumin which means that what is considered a high or low albumin in the peritoneal fluid is relative to the absolute serum albumin level. Thus to determine if the fluid looks like an exudate or a transudate, the serum-ascites albumin gradient (SAAG) should be calculated as follows:
Serum-ascites albumin gradient = Serum albumin - ascites albumin
Low gradient ascites (exudate)