Ascites 

What are the options for imaging procedures for evaluating ascites?

• US
• CT
• Plain radiographs

Which is the imaging procedure of choice in a suspected case of ascites?

• Smaller amounts of ascites are best imaged with ultrasound and CT.

What are the radiological findings of ascites in plain radiographs?

Only large amounts of intra peritoneal fluid can be detected on the plain abdominal film. 

• The fluid causes a generalized haziness or "ground glass" appearance to the abdomen. 
• The bowel loops may be separated by interposed fluid and bowel loops assume a central location as they float to the highest point of the abdomen. 

Imaging findings of ascites in ultrasound and CT:

• Ascites is seen as an anechoic space on ultrasound.
• Ascites is seen as low density collection surrounding the bowel in CT.
• Bowel loops float anteriorly.
• Ascites is seen earliest in the pelvis due to its dependent position in the recto vescical or vagino vescical pouch..
• Next it accumulates in the sub hepatic region, in the Morrison's pouch.
• In infectious or malignant conditions the ascites may be loculated, with enhancement of the peritoneum on post-contrast study.
• The presence of soft tissue masses on CT, in association with ascites, may be a clue as to a malignant etiology.

	Ascites Findings: Ascites appears echo free (black).

Loculated Ascites Findings: Large loculated ascites low density collection, displacing bowel posteriorly

Ascites Finding: Free fluid in the posterior cul de sac

Loculated Ascites Finding: Multiple strands of adhesions are producing loculations.

Which imaging procedure is ideal to assist with paracentesis abdominis?

• US and CT are both useful.
• US can be done at bed side and involves no radiation and is the preferred procedure to assist with tapping loculated ascites or a small amount of ascites.