Keywords
chronic pancreatitis - pseudoaneurysm - embolization
Introduction
Bleeding pseudoaneurysm in chronic pancreatitis is a rare vascular complication but
potentially lethal. It is associated with a high mortality rate and poses a diagnostic
challenge to the attending physicians. Imaging plays a significant role in the diagnosis
of this serious condition.
Case Presentation
A 33-year-old male presented to our emergency department with acute onset of epigastric
pain for 3 days. The patient had been diagnosed with chronic alcoholic pancreatitis
for 5 years and diabetes mellitus for 1.5 years. The patient suffered from the last
acute attack 7 months prior to this presentation. Magnetic resonance imaging performed
at that time revealed a large pancreatic pseudocyst in the pancreatic body and tail
with a maximal diameter of 6.7 cm ([Fig. 1]). The patient was treated conservatively and had been doing well since. Three days
before admission, the patient had acute onset of epigastric pain and one episode of
emesis. The patient also reported anorexia and was unable to eat.
Fig. 1 Axial T2-weighted magnetic resonance image obtained 7 months prior to this presentation
shows a T2-hyperintense pseudocyst (pc) at the pancreatic body and tail. The pseudocyst
is clear without content.
On admission, he had a blood pressure of 150/79 mm Hg, a regular heart rate of 60
bpm, and a body temperature of 36.3°C. Clinical examination revealed moderate tenderness
in the epigastric area. No rebound tenderness or signs of peritonitis were observed.
The pain score was 6 out of 10. The laboratory investigation revealed an elevated
white blood cell count (13.4 × 109/L) as well as elevated serum lipase level (1,466 U/L). His hemoglobin level was 113
g/L. The electrolyte panel and liver function tests were within normal limits. The
international normalized ratio was 1.0.
An emergency contrast-enhanced computed tomography (CT) scan was obtained at the emergency
department that showed multiple pancreatic calcifications as signs of chronic pancreatitis.
No signs of acute pancreatitis were evident on the CT scan. However, there was an
increase in size of the pancreatic pseudocyst to a maximum diameter of 8.6 cm. The
pseudocyst content appeared heterogeneously hyperdense (~65–70 Hounsfield unit), which
represented internal hemorrhage. A 16-mm pseudoaneurysm was visualized at the anterior
aspect of the pseudocyst and was thought to originate from the left gastric or splenic
artery at the time of interpretation ([Fig. 2]). Interventional radiology consultation was made after a discussion with the patient
and a multidisciplinary care team. We decided to proceed with transcatheter embolization
via the right femoral artery approach. Several angiograms in the different projections
of the celiac artery, left gastric artery, superior mesenteric artery, splenic artery,
and common hepatic artery failed to demonstrate active contrast extravasation or pseudoaneurysm.
The dorsal pancreatic artery and transverse pancreatic artery were not demonstrated
from the superselective angiograms. After a careful review of the vascular anatomy,
superselective catheterization using a microcatheter into the gastroduodenal artery
(GDA) was performed. This superselective angiogram revealed that there was a very
short segment of GDA before giving off superior and inferior pancreaticoduodenal arteries.
We advanced the microcatheter into the superior pancreaticoduodenal artery and eventually
into the pancreaticoduodenal arcade. The pancreaticoduodenal arcade appears to end
blindly with two small terminal vessels branched at its terminus. There was a communication
from the blind end to the pseudoaneurysm ([Fig. 3A]). Two 2 × 3 cm Nester coils (Cook Medical, Indiana, United States) were used for
embolization, which resulted in complete occlusion of the feeding artery and no further
opacification of the pseudoaneurysm ([Fig. 3B]). After the coils were deployed, the microcatheter and the catheter system became
dislodged proximally and ultimately we lost the vascular access. Because the patient’s
vital signs were stable during the procedure and the final angiograms demonstrated
no further opacification of the pseudoaneurysm, we decided not to recannulate to deploy
more coils. The follow-up CT angiography on the following day confirmed complete occlusion
of the pseudoaneurysm. The patient tolerated the procedure well and was discharged
from the hospital on the following day.
Fig. 2 Axial portovenous phase computed tomography image shows heterogeneous hyperattenuation
of the pseudocyst (pc) and a pseudoaneurysm (arrow) at the anterior aspect.
Fig. 3 Pre-embolization digital-subtraction angiogram of the pancreaticoduodenal arcade
(A) shows blind-ended terminal vessel with a small communication (white arrow) to the
pseudoaneurysm sac (arrowhead). Post-embolization image (B) shows coil embolization (arrow) and no opacification of the pseudoaneurysm sac.
ASPDA, anterior superior pancreaticoduodenal artery; PSPDA, posterior superior pancreaticoduodenal
artery.
He had been doing well after 4 weeks of outpatient follow-up. He denied any vomiting,
abdominal pain, melena, hematemesis, or anemic symptoms. Outpatient CT angiography
had been scheduled. Unfortunately, the patient did not show up and lost to follow-up.
Discussion
We herein described a rare complication of ruptured pancreaticoduodenal artery pseudoaneurysm
in an unusual location in a patient who has chronic pancreatitis. He had been successfully
treated with transcatheter coil embolization.
Chronic pancreatitis is an inflammatory condition that is usually irreversible and
progressive. The vascular complications of chronic pancreatitis are the main causes
of morbidity and mortality. Pseudoaneurysm formation after chronic pancreatitis is
an uncommon complication with an estimated incidence of 10 to 17%.[1]
[2] The formation of pancreatic pseudoaneurysm is thought to be secondary to long-standing
erosion of the vessel wall by the pancreatic enzyme or due to the persistent extrinsic
compression from the pseudocyst that eventually leads to ischemia and elastolytic
degradation of the vessel wall.[3] Splenic artery is the most common artery to be involved in almost half of the cases
(30–50%) due to close anatomical relationship to the pancreas as the splenic artery
runs along posterior margin of the pancreas toward the splenic hilum. GDA and pancreaticoduodenal
artery are the next commonly involved arteries (~10–15% and 10% of the cases, respectively).[4]
[5] The GDA typically arises from common hepatic artery and gives off anterior superior
pancreaticoduodenal artery and posterior superior pancreaticoduodenal artery, forming
pancreaticoduodenal arcades. These arteries and arcades serve as a major blood supply
to the second part of duodenum and the pancreatic head. The GDA and pancreaticoduodenal
artery pseudoaneurysm are usually found in the pancreatic head region as the GDA and
the pancreaticoduodenal arcade lie in close proximity with the duodenal bulb and the
pancreaticoduodenal groove. In this report, we described an unusual location of the
pancreaticoduodenal artery pseudoaneurysm that originates from terminal branch of
the pancreaticoduodenal arcade and locates in the pancreatic body.
Most of the patients who have pancreatic pseudoaneurysm usually remain asymptomatic.
Unfortunately, when the pseudoaneurysm becomes symptomatic, the clinical presentation
cannot be easily distinguished from an episode of acute pancreatitis, thus making
a diagnosis very challenging. The pseudoaneurysm can rupture, and causes hemorrhage
into the pancreatic pseudocyst, adjacent bowel lumen, or frankly into the intraperitoneal
cavity, which can result in hemodynamic instability. About 3% of the patients with
pseudoaneurysm develop hemorrhage and the mortality rate is as high as 30 to 50% if
bleeding occurs.[2]
[3]
[6]
[7] The risk of rupture is independent of the pseudoaneurysm size.[8]
Clinically, the possibility of bleeding pancreatic pseudoaneurysm should be considered
if there are any of the following conditions: (1) sudden enlargement of a known pancreatic
pseudocyst; (2) audible bruit over a pancreatic pseudocyst regardless of symptoms;
(3) upper gastrointestinal bleeding in a patient with known pancreatic pseudocyst
and absence of other cause seen on endoscopy; or (4) sudden drop in the hemoglobin
level in a patient with known pancreatic pseudocyst, without other apparent cause.[9] Unfortunately, the clinical presentation of acute abdominal pain in our patient
is vague and cannot be distinguished from an episode of acute pancreatitis.
Imaging plays a significant role in the diagnosis of bleeding pancreatic pseudoaneurysm.
Doppler ultrasound (US) can establish the diagnosis of pseudoaneurysm by demonstrating
a classic “yin-yang sign” and “to-and-fro” spectral waveform.[3]
[7]
[9] However, US is operator dependent and has low sensitivity in detection of the pancreatic
pseudoaneurysm due to its deep retroperitoneal location.[10] CT angiography has higher sensitivity and specificity in diagnosis of pancreatic
pseudoaneurysm. The main advantages of CT angiography are wide availability, relatively
fast acquisition, and less operator dependency. CT angiography also provides accurate
size measurement, location of the pseudoaneurysm, and can evaluate pressure effect
to the adjacent organs as well as the presence of active contrast extravasation. In
addition, postprocessing with a three-dimensional reconstruction and maximum intensity
projections can give important information for the treatment decision and preprocedural
planning. However, the major drawbacks of CT are the radiation exposure, the need
of intravenous contrast injection, and that concurrent interventional treatment is
not possible.
Catheter angiography is accepted to be the most accurate investigation for diagnosis
and treatment, but it is an invasive procedure and may not be available in all institutions.
The major advantage of angiography is the ability to detect small pseudoaneurysm and
the vessel of origin. Angiography can better define the location and character of
the pseudoaneurysm and can serve both diagnostic and therapeutic purposes.[11] Angiography is reported to have 100% sensitivity for the detection of arterial bleeding
in patients with pancreatic pseudoaneurysms.[3] The lesion that can mimic pancreatic pseudoaneurysm on other imaging modalities
such as true aneurysm, arteriovenous fistula, or vascular malformation can be accurately
diagnosed with angiography.[3]
The management of ruptured pancreatic pseudoaneurysm remains a challenging clinical
problem. The treatment goal is to control the bleeding by either endovascular therapy
or surgery. The preferred choice of treatment has long been debated and some authors
suggested that the operation and endovascular therapy play complementary roles.[12] Multiple factors such as hemodynamic status, comorbidities, and character of the
bleeding pseudoaneurysm influence the treatment decision. Generally, a less invasive
endovascular therapy is preferred to open surgery as it allows precise localization
and characterization of the pseudoaneurysm, and assessment of the collateral vessels.[13] Endovascular therapy also offers advantages in terms of less postoperative pain,
shorter hospital length of stay, and early return to daily life activity.[5] Embolization may also be a second option following unsuccessful surgery, complication
of surgical procedure, or in patients with rebleeding after surgery. The currently
available options for endovascular therapy include transcatheter embolization using
coils, liquid embolic agents, or plugs; placement of a stent-graft; percutaneous thrombin
injection; and combined or multimodal approach.[13] The selection of the endovascular technique mainly depends on the morphological
appearance and location of the pseudoaneurysm. The success rate of endovascular therapy
is very high (79–100%) with a low recurrent bleeding rate (11–37%).[14]
[15]
[16] It is important to use Sandwich technique and to do both proximal and distal embolization
for the GDA and pancreaticoduodenal artery pseudoaneurysm as well as most of the pseudoaneurysms
of the gastrointestinal tract to prevent retrograde filling of the pseudoaneurysm
sac from the rich collateral vessels.[3] Unfortunately, in our case, the catheter system became dislodged proximally after
we deployed the coils and ultimately the vascular access was lost. We decided not
to recannulate and deploy more coils because of the fact that the pseudoaneurysm was
communicated to blind end terminal vessel of pancreaticoduodenal artery and the final
angiograms demonstrated no further opacification of the aneurysm.
Surgical treatment of pancreatic pseudoaneurysm can be challenging and is associated
with higher morbidity and mortality. The surgery is usually performed either by pancreatectomy
along with the ruptured pseudoaneurysm or direct ligation of the bleeding vessel.[13]
[17] Surgery is usually reserved for hemodynamically unstable patients, unavailable or
unsuccessful embolization, recurrent pseudoaneurysm after successful embolization,
patients with infected pancreatic necrosis, or patients with the pseudoaneurysm located
in the pancreatic head.[18]
[19] Distal pancreatectomy and splenectomy may be an appropriate treatment for the bleeding
pseudoaneurysm in the pancreatic tail because the endovascular treatment can be technically
difficult and these surgical procedures are associated with low morbidity and mortality
rates.[14]
Conclusion
Pseudoaneurysm formation with a contained hematoma in chronic pancreatitis is a rare
but potentially fatal complication. Here we reported an unusual location of a ruptured
pancreaticoduodenal artery pseudoaneurysm in the pancreatic body. Pseudoaneurysm rupture
can occur at any time and can lead to hemodynamic instability. Early recognition of
this complication is essential to prevent catastrophic consequences. Multidisciplinary
team approach among the emergency radiologists, interventional radiologists, gastroenterologists,
and surgical colleagues is ideal so that the optimum treatment strategy can be delivered
to the patient.
