Diagnostic ultrasound ( PDFDrive )

228 PART II Abdominal and Pelvic Sonography
Acute Fluid Collections
Pancreatitis-associated luid collections represent a spectrum of
disease and thus can be problematic to classify (Figs. 7.38 and
7.39; see also Fig. 7.29). Fluid collections, when they contain
debris or necrosis or may be infected, cannot always be categorized.
Approximately 40% of patients with acute pancreatitis
develop acute luid collections. 69,70 About half of these appear to
resolve spontaneously, 69 with almost 70% resolving in patients
with nonnecrotizing pancreatitis. 70 hus drainage or other
intervention in acute collections is inappropriate, unless a rare
superinfection occurs. he Atlanta Classiication suggests that
the diferentiation between acute luid collection and pseudocyst
should be made ater 4 weeks from the onset of disease. 27,34 Others
suggest that a luid collection that persists for 6 weeks can be
considered a pseudocyst. he 6-week deinition is based on classic
surgical management; the pseudocyst wall requires 6 weeks to
“mature” to the point where it can be drained surgically. 71
Pseudocysts
Pancreatic pseudocysts are a well-known complication of acute
and chronic pancreatitis. Pseudocysts comprise 75% 72 to 90% 73
of all cystic lesions of the pancreas. he “wall” of pancreatic
pseudocysts consists of ibrous and granulation tissue. hus unlike
true cysts or cystic neoplasms, pseudocysts do not have an
epithelial lining. Pseudocysts are more common in patients with
chronic than acute pancreatitis. Pseudocyst prevalence ranges
from 5% to 16% in patients with acute pancreatitis. In chronic
pancreatitis, prevalence varies from 20% to 40%, with the highest
rates in alcohol-related chronic pancreatitis. 74 On occasion,
pseudocysts can be caused by trauma (Fig. 7.40).
GB
Liver
S
FIG. 7.37 Left Portal Vein Clot. Transverse sonogram shows clot
in the left portal vein (arrows) caused by pancreatitis. GB, Gallbladder.
FIG. 7.38 Acute Fluid Collection. Longitudinal image shows inlammation
and an acute luid collection (arrow) in the transverse mesocolon.
S, Stomach.
Inflammation
Acute fluid
A
B
FIG. 7.39 Pancreatitis-Associated Fluid Collection. (A) Transverse sonogram and (B) CT image show enlarged and heterogeneous pancreas,
with prominent peripancreatic inlammation (arrow) and an acute luid collection that later resolved spontaneously.