Ascites

Introduction

Ascites in Greek language means “bag”, “bladder” or “sack”.¹ Ascites is defined as collection of fluid in the peritoneum.^1,2 Ascitic fluid could be transudative or exudative. This is based upon the total protein concentration in the ascitic fluid; the ratio of total protein in ascitic fluid and serum, or ratio of lactic dehydrogenase in ascitic fluid and serum.³

ETIOLOGY

There are various etiologies of ascites and they differ in infants and children.¹

Causes of fetal ascites¹

• Gastrointestinal diseases: Malrotation of intestines, intussception, atresia of the small or large intestines, volvulus, biliary atresia.
• Genitourinary diseases: Hydronephrosis, polycystic kidney disease, urinary obstruction.
• Cardiac diseases: Heart failure, arrhythmias
• Metabolic disease: Niemann pick type C, lysosomal storage disease
• Chylous ascites: Intestinal lymphangiectasia
• Infections: syphilis, cytomegalovirus, toxoplasmosis
• Hematologic: Hemolytic anemia, haemochromatosis
• Chromosomal abnormalities: Turner’s syndrome; trisomy 13,18, 21
• Neoplasms
• Idiopathic

Causes of neonatal ascites¹

• Hepatobiliary diseases: biliary atresia, viral hepatitis, Budd Chiari syndrome, congenital hepatic fibrosis
• Genitourinary disorders: posterior urethral valve, ureterocele, rupture of bladder, nephrotic syndrome
• Gastrointestinal disorders: Intestinal atresia, malrotation, intestinal perforation
• Cardiac diseases: Heart failures, arrhythmias
• Hematologic diseases: Neonatal hematochromatosis
• Metabolic diseases: Mucopolysaccharidosis VIII
• Idiopathic

Causes of ascites in infants and children¹

• Hepatobiliary disorders: cirrhosis due to any chronic liver disease, acute hepatitis, budd chiari syndrome, congenital hepatic fibrosis
• Gastrointestinal diseases: Intestinal atresia, pancreatitis, appendicitis
• Serositis: Eosinophilic enteritis, inflammatory bowel disease
• Neoplasms: Wilm’s tumor, mesothelioma, lymphoma, germ cell malignancies, ovarian tumors
• Cardiac diseases: Heart failure
• Pseudo-ascites: Ovarian cyst, celiac disease, mesothelioma
• Genitourinary disorders: Nephrotic syndrome.
• Chylous ascites: Lymphatic duct trauma or obstruction, intestinal lymphangiectasia
• Toxins: Ethanol, methotrexate, 6-mercaptopurine
• Idiopathic

Pathophysiology

Various theories have been proposed for the formation of ascites. These include the following:

• Underfilling theory: Portal hypertension causes decreased sequestration of fluid in splanchnic circulation which causes hypotension and activates renin angiotensinogen aldosterone and sympathetic systems resulting in renal sodium and water retention.
• Overflow theory: There are renal sodium and water retention in the absence of volume depletion.
• Peripheral arterial vasodilation: Due to portal hypertension underfilling occurs leading to renal sodium and water retention. Overfilling theory operates later in the natural history of cirrhosis.³

Clinical Features

Presenting features include abdominal distension, increasing weight, respiratory distress, associated pedal edema. Ascites associated with malignancies are usually painful while cirrhotic patients have painless ascites.¹ Ascites needs to be differentiated from other causes of abdominal distension like gaseous distension, bowel obstruction, obesity, or abdominal mass. The examination should also focus on signs of chronic liver disease and portal hypertension. Flank dullness is present in about 90% of patients and is the most sensitive physical sign.

Clinical grading of ascites:

• Mild: Puddle sign+
• Moderate: Shifting dullness +, no fluid thrill
• Severe: Fluid thrill+

Using a modified criterion of the European Association for the Liver Study, ascites grades were defined as follows:⁴

• Grade 1: ascites detected by only radiological tests such as ultrasound of the abdomen.
• Grade 2: there is moderate abdominal distension detected on physical examination and/or by radiologic tests.
• Grade 3: there is gross ascites with marked abdominal distension.

Investigations

• Blood investigations: Complete blood count, liver function tests, renal functional tests, plasma proteins
• Ascitic fluid examination-
  • White cell count: Ascitic fluid normally contains <500 leukocytes/ml and <250 polymorphonuclear leukocytes/ml. A neutrophil count of >250 cells/ml is highly suggestive of bacterial peritonitis. In tuberculous peritonitis and peritoneal carcinomatosis, there is predominance of lymphocytes.
  • Red blood count: RBC Count >50,000/µl denotes hemorrhagic ascites, usually seen in malignancies, trauma or tuberculosis.
  • Total protein: Ascitic fluid is considered as an exudate if the protein level is more than or equal to 2.5 g/dl.
  • Triglycerides: A high level is suggestive of chylous ascites
  • Serum Ascites Albumin Gradient (SAAG): It is calculated as serum albumin - ascitic fluid albumin. SAAG >1.1 g/dl is suggestive of portal hypertension and SAAG <1.1 g/dl as non-portal hypertensive causes of ascites
• Imaging Studies
  • Chest and Plain Abdominal Films: Elevation of the diaphragm is seen in massive ascites. To be diagnosed on the basis of radiographic films, >500 ml of fluid is usually required.
  • Ultrasound: Abdominal ultrasound can be used to detect ascites even in morbidly obese patients. It is also useful in indicating the appropriate sites for paracentesis. It can detect as little as 100 ml of fluid in the peritoneal cavity.
  • CT and MRI: Small amounts of ascitic fluid such as in the perihepatic space, Morison's pouch, can be detected easily. Malignancies arising from abdominal organs can also be detected.

Management

The use of diuretics and salt-restricted diet form the mainstay of treatment in children with mild to moderate ascites.^1,2 Fluid restriction is helpful when serum sodium is less than 120 mEq/liter

Diuretics¹

• Spironolactone: 2 to 3 mg/kg/day. Contraindicated in hyperkalemia, renal failure.
• Frusemide: 1 to 2 mg/kg/dose; maximum: 6 mg/kg/dose. Contraindicated in dyselectrolytemia, anuria, hypersensitivity.
• Metolazone: useful in congestive heart failure. Dose: 5 to 20 mg/dose once a day. Contraindicated if hypersensitivity or anuria

Drugs contraindicated in ascites:

• NSAIDS - considering the risk of further sodium retention, renal failure
• ACE inhibitors, angiotensin II antagonist or alpha1-adrenergic receptor blocker - they decrease arterial pressure, renal blood flow and are at increased risk to cause renal failure.

Diuretic-Resistant Ascites ^1,2

In children with large ascites or not responding to medical treatment following options can be considered:

• Therapeutic large-volume paracentesis with albumin infusion
• LeVeen or Denver (peritoneovenous) shunt
• Transjugular intrahepatic portosystemic stent shunt (TIPS)
• Liver transplantation if ascites due to chronic liver disease (tomar).

Complications

• Umbilical Hernia: There may be an increase in the size of an already existing umbilical hernia or development of a new hernia.
• Spontaneous Bacterial Peritonitis: It is defined when ascitic fluid polymorphonuclear leucocyte (PMN) count is more than 250 cells/cumm. It occurs due to increased intestinal wall permeability which leads to bacterial translocation from the intestinal lumen into the mesentery. Patients present with fever, abdominal pain, malaise, vomiting.
• Pleural effusion: It occurs usually on the right side due to the passage of fluid through the diaphragmatic small holes into the pleural space.