Diagnostic Ultrasound - Abdomen and Pelvis

Ascites
Diagnoses: Abdominal Wall/Peritoneal Cavity
TERMINOLOGY
• Abnormal accumulation of fluid within peritoneal cavity
IMAGING
• Fluid collects in most dependent locations unless there are
loculations
• Pelvis: In pouch of Douglas
• Free-flowing: Fluid insinuates itself between organs and is
shaped by surrounding structures
• US accurate at detecting, localizing, and characterizing
ascites; quantification more subjective
• Simple: Anechoic; homogeneous, freely mobile, deep
acoustic enhancement
• Complicated: Echogenic fluid with coarse or fine internal
echoes, layering debris or particulate material, septa
• Small free fluid in cul-de-sac; physiologic in women
• Look for associated hepatic disease, peritoneal masses, or
adherent bowel
KEY FACTS
TOP DIFFERENTIAL DIAGNOSES
• Hemoperitoneum
• Infectious ascites
• Malignant ascites
• Pseudomyxoma peritonei
PATHOLOGY
• Traditionally classified as transudative or exudative ascites
based on protein content
• Serum Albumin Ascites Gradient (SAAG) is difference
between serum and ascites albumin, now widely used to
differentiate causes of ascites
DIAGNOSTIC CHECKLIST
• Imaging alone cannot characterize nature or cause of
peritoneal fluid collections; sampling is required
(Left) Longitudinal ultrasound
shows the right upper
quadrant in a patient with
cirrhosis and ascites. The liver
contour is nodular ſt. Ascites
surrounds the liver and fills
Morison pouch st. The right
kidney appears echogenic
secondary to acoustic
enhancement. (Right)
Transverse ultrasound shows
the left lower quadrant in a
patient with end-stage liver
disease. There is free fluid
surrounding the bowel st
with no mass effect.
(Left) Longitudinal ultrasound
of the pelvis in a patient with
cirrhosis shows a large volume
of complex ascites ſt
containing low-level echoes.
Paracentesis showed
hemorrhage. Ascites extends
into the cul-de-sac . The
uterus st is normal. (Right)
Longitudinal transvaginal
ultrasound shows the pelvis in
a ruptured ectopic pregnancy.
There is free anechoic fluid in
the upper pelvis st with
clotted blood in the
dependent pouch of Douglas.
Endometrial thickening is
noted in the uterus with no
intrauterine sac ſt.
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