Chylous ascites is the accumulation of a milk-like peritoneal fluid rich in triglycerides, due to the presence of thoracic or intestinal lymph in the abdominal cavity[1]. Causes of chylous ascites (Table 1) relate to disruption of the lymphatic system due to traumatic injury or obstruction.

Chronic chylous ascites is usually asymptomatic, however, abdominal pain from chylous peritonitis, with sudden outpouring of chyle into the peritoneum, has been described in the literature. A review of 140 cases of all forms of chylous ascites showed that 21% of adults and 14% of children with chylous ascites have the acute form[2].

Pancreatitis is a recognised but rare cause of chylous effusion. In most published cases pancreatitis, usually chronic, results in the development of chronic chylous ascites without acute abdominal pain. Until 1984 only two cases of pancreatitis, both chronic, had been reported as causes of chylous effusions[3]. Goldfarb[4] described the first case of acute pancreatitis associated with acute chylous ascites, abdominal pain and peritonism in 1984.

In his review of the literature, Goldfarb discussed three other cases of chylous effusion which were likely secondary to pancreatitis. Acute abdominal pain and peritonism were not features of these presentations. Since 1984 few cases of pancreatitis associated chylous ascites have been described. In 1999, Ben-Ami ^{et al[5]} described acute chylous ascites secondary to acute pancreatitis. This was diagnosed during elective cholecystectomy and did not present with symptoms of peritonitis. In 2006, Chuang et al[6] described a case of hypertriglyceridemia-associated acute pancreatitis with chylous ascites in pregnancy. In this review there appeared to be a lack of correlation between the formation of chylous ascites and the severity of the pancreatitis.

Aalami proposed two mechanisms believed to play a role in the development of acute chylous ascites in the setting of pancreatitis. These are: the compression of lymphatic channels by an inflamed pancreas and the direct damage of channels by pancreatic enzymes[3].

Chronic chylous ascites frequently presents with progressive and painless abdominal distension. As with other types of ascites, respiratory embarrassment is a common feature secondary to diaphragmatic splinting. Constitutional symptoms such as anorexia, weakness and malaise are very common, but non-specific[1]. Other features include abdominal pain, weight loss, diarrhoea and steatorrhoea, malnutrition, oedema, enlarged lymph nodes, early satiety, fevers and night sweats[1].

In cases of acute chylous ascites symptoms of anorexia, nausea, vomiting and severe abdominal pain are reported. A high fat meal has been reported in the literature as a common precipitant in the development of symptoms. Examination findings of peritonism have been described in the literature. Interestingly, symptoms are often maximal in the right iliac fossa[7] and most likely a result of pooling of chylous fluid in the right paracolic gutter, mimicking acute appendicitis. Three cases have been reported in which acute chylous peritonitis presented clinically with acute appendicitis. In two cases, the patient underwent open appendicectomy, while, in the third patient a midline laparotomy was performed for what was suspected to be appendicitis complicated by appendiceal perforation. In all three cases a white milky fluid was found in the peritoneal cavity, biochemical assessment of this fluid confirmed chylous ascites. The appendix was normal and exploration of the abdomen could not find any cause for the acute chylous effusion in all of the three cases described[7-9].

Laboratory testing is rarely useful. The white cell count may be elevated, but other findings are non-specific[10]. Radiological investigations are of limited benefit although CT of the abdomen has been reported as being useful in identifying pathological lymph nodes and masses and in determining the extent and localisation of the fluid.

Paracentesis is the most useful diagnostic test. Typically chyle has a cloudy and turbid appearance. Table 2 shows the characteristics of ascitic fluid in chylous ascites.

Blood tests including a complete blood count, electrolytes, liver function tests, total protein, albumin, lactate dehydrogenase (LDH), triglycerides, cholesterol, amylase and lipase should be preformed but are by no means diagnostic.

The underlying cause should be addressed whenever feasible. In patients with an acute abdomen, immediate exploration should be performed[9]. Laparotomy usually allows a definitive diagnosis and provides an opportunity to address the underlying cause.

In chronic chylous ascites which cannot be managed surgically, the goals of treatment are (1) the maintenance of adequate nutrition, (2) decreasing the rate of chyle formation and (3) correcting the underlying disorder[3]. Considerable controversy exists regarding the effectiveness of a high-protein, low-fat diet with medium-chain triglycerides and diuretics, or total parenteral nutrition (TPN) alone as a means to reducing chyle formation. Guidelines for management published by Aalami in 2000 recommend the commencement of TPN only if no improvement is observed after three weeks on a low-fat, medium-chain triglyceride diet. Multiple case reports describe the use of octreotide in the management of chylous ascites. Somatostatin receptors have been described in the lymphatic vessels of the intestine and it may be that octreotide is effective in managing chylous ascites because it helps to decrease lymph flow through these vessels. The use of octreotide with TPN for the treatment of chylous ascites has been described with clinical improvement in the ascites and reduction in TPN requirements and paracentesis frequency[11].

In patients with a large amount of ascites a large volume paracentesis to relieve discomfort and dyspnoea can be performed and repeated as needed, however, the risk of infection and fat emboli should be noted[9]. Peritoneo-venous shunting may be an option, although this is controversial. Although there is some evidence of high initial success rates after insertion, as high as 75%[3], these shunts carry a high rate of complications which include fever, sepsis and DIC. The high viscosity of chyle has rendered shunt patency disappointing with an eventual occlusion rate approaching 100%.

In conclusion, acute chylous ascites can present with symptoms and signs of peritonism and can mimic acute appendicitis. Chylous effusions, both acute and chronic, are a complication of pancreatitis and may confuse clinical assessment and diagnosis.