Diagnostic ultrasound ( PDFDrive )

230 PART II Abdominal and Pelvic Sonography
Necrosis and Abscess
Signiicant pancreatic necrosis has been deined by the Atlanta
Classiication system as nonenhanced pancreatic parenchyma
greater than 3 cm or involving more than 30% of the area of the
pancreas on CECT. 27,28 hese patients are at greater risk than
patients without necrosis and are treated with prophylactic
antibiotics and observed closely. Necrosis cannot be deinitively
diagnosed by ultrasound, although ultrasound contrast agents
may change that situation.
he original Atlanta Classiication terminology describing
signiicant infection associated with pancreatitis was somewhat
confusing. Pancreatic abscess was reserved for infected luid
collections, essentially pseudocysts that become infected. Infected
pancreatic necrosis, a much more serious condition, can also
result in pus-illed collections, which might also be called abscesses
in other clinical settings. hus it is best to think of two distinct
types of acute pancreatitis–associated abscess, as follows:
1. he original Atlanta Classiication pancreatic abscess, an
infected luid collection/pseudocyst, which has minimal
necrosis. he revised Atlanta classiication has dropped
the term pancreatic abscess because of confusion over its
meaning. 34
2. Infected necrosis with a luid collection, which arises from
infection of necrotic pancreatic tissue.
Treatment
he major approaches to the treatment of pseudocysts include
surgery, percutaneous image-guided drainage and endoscopicguided
drainage. Andrén-Sandberg et al. 71 state:
here are no randomized studies for the management
protocols for pancreatic pseudocysts. … First of all, it is
important to diferentiate acute from chronic pseudocysts
for management, but at the same time not miss cystic
neoplasias. Conservative treatment should always be considered
the irst option (pseudocysts should not be treated
just because they are there).
It is diicult to determine the best method to treat pseudocysts.
he cause of pancreatitis, communication of the pancreatic duct
with the pseudocyst, and local technical expertise must be
considered when choosing a treatment method. Although the
data are unclear, percutaneous drainage of pseudocysts likely
is overall less successful than surgical or endoscopic drainage. 84
Nevertheless, percutaneous drainage can be used as a irst option
with other techniques reserved for percutaneous drainage failures.
In the large subset of patients with normal duct anatomy and
no communication of the pseudocyst with the pancreatic duct,
percutaneous drainage is successful in more than 80%. On the
other hand, percutaneous drainage failed in 77% to 91% of patients
who had duct obstruction or strictures. 80 herefore ERCP, 85 and
in some cases MRCP, 58,74 may be useful in the selection of treatment
technique.
Infected luid collections without signiicant necrosis may
oten be best treated by percutaneous drainage. 85 Percutaneous
drainage can also be used in infected necrosis, for which it is
curative in some patients 86 and is a useful temporizing technique
in others. 84 Although management of infection in pancreatitis
is evolving, 27 therapy for infected pancreatic necrosis remains
surgical debridement.
Vascular Complications
Vascular complications occur in both acute and chronic pancreatitis.
Pseudoaneurysms and venous thrombosis are the
most important vascular complications. Most cases of clinically
insigniicant hemorrhagic pancreatitis are related to venous and
small vessel disease, whereas potentially fatal hemorrhage is
usually related to enzymatic digestion or pseudoaneurysm of
major vessels, including the splenic, gastroduodenal (Fig. 7.43),
and superior pancreaticoduodenal arteries. he prevalence of
hemorrhage in patients with a pseudocyst is 5%, but with an up
to 40% rate of mortality. 87 Vascular erosion can produce a sudden,
painful expansion of the cyst or gastrointestinal bleeding caused
by bleeding into the pancreatic duct (“hemosuccus pancreaticus”).
88 hrombosis of the portal venous system may occur in
both acute and chronic pancreatitis 68 ; splenic vein thrombosis
is most common (Fig. 7.44). Agarwal et al. 89 reported a 22%
prevalence of splenic vein thrombosis in patients with chronic
pancreatitis. Bernades et al. 90 reported the prevalence of portal
vein thrombosis as 5.6% (15/266). Splenic vein thrombosis may
result in upper gastrointestinal bleeding from gastric varices; this
condition is called “sinistral” (let-sided) portal hypertension.
CHRONIC PANCREATITIS
he prevalence of chronic pancreatitis ranges from 3.5 to 10 per
100,000 in the population. Chronic pancreatitis is characterized
by intermittent pancreatic inlammation with progressive, irreversible
damage to the gland. he key histologic features are ibrosis,
2
1 1
2
Feeder
FIG. 7.43 Pancreatic Pseudoaneurysm. Transverse color Doppler
sonogram shows acute pancreatitis–associated pseudoaneurysm arising
from the gastroduodenal artery. The clotted portion of the pseudoaneurysm
(arrowheads) is noted. Calipers denote the patent portion of
the pseudoaneurysm. Pseudoaneurysm is a rare complication of pancreatitis,
much less common than venous thrombosis. Notice the “yin
and yang” (red/blue) color Doppler appearance representing the blood
swirling in the lesion.