Discussion
Pancreatic AVM, first reported by Halpern et al. in
1968,1) is one of the abnormal blood flow diseases in
which the arteriovenous system is short-circuited and anastomosed in the
pancreas. The most common sites for gastrointestinal arteriovenous
malformations are the cecum, ascending colon, and jejunum and pancreatic
AVM accounts for only 0.9%.2) The causes of this
disease are classified into congenital due to the remnants of the
primitive vascular network,3) and acquired due to
excessive angiogenesis caused by inflammation such as pancreatitis and
trauma.4) In this case, it was considered to be
congenital because there was no particular history in the past.
According to 97 cases of pancreatic AVM reported by Hirai et al. in
Japan,5) pancreatic AVM is an overwhelmingly male
disease since there were 90 males opposed to 7 females, as shown in this
case. The average age is 54.4 years, which is relatively young. The most
common symptoms were abdominal pain (47.4%) and gastrointestinal
bleeding (38.1%). Repeated gastrointestinal bleeding was observed in
this case as well. The causes were esophagogastric varicose bleeding due
to portal hypertension associated with AVM, rupture of AVM itself into
the gastrointestinal tract, bleeding from an ulcer caused by an ischemic
change of the gastrointestinal mucosa due to progression of AVM,
bleeding of AVM into the pancreatic duct, and bleeding of AVM into the
bile duct. 6,-7, 8) In this case, no varicose veins
were observed, no ulceration was formed, and bleeding from the papilla
of Vater was not clear. Therefore, it is considered that the bleeding
was caused by the mechanism of rupture of AVM itself into the
gastrointestinal tract. Gastrointestinal ulcer (26.8%) was the most
common comorbidity of pancreatic AVM, but it is unclear whether the
history of this case treated for duodenal ulcer 20 years ago had
something related to the cause or not. The AVM is located in the
pancreatic head in more than half of the lesions in 56 cases (57.7%),
and in the whole pancreas (10.3%) as this case.
Contrast-enhanced CT and angiography are helpful for diagnosis.6) As a characterization of Contrast-enhanced CT
result, it is known that in the early stage of the arterial phase, there
is reticular deep stain of lesions and depiction of the portal vein,3, 9) as well as dilated and tortuous inflowing blood
vessels, reticular intra-pancreatic vascular plexus, and early venous
return to portal vein or splenic vein are characteristic findings in
Angiography. In addition, there are reports that angiography is not only
important for diagnosis, but also for obtaining detailed information
such as multiple lesions, localization of lesions, and their spread as
well. 10) In this case, CT showed spotty staining of
the pancreatic uncinate process, and angiography showed a reticulated
vascular plexus at the pancreatic head, which was similar in
characteristics.
For treatment, pancreatic resection was performed in 46 patients
(47.4%). Since there are many cases with lesions at the pancreatic
head, pancreatoduodenectomy is performed most often, and it was
performed in 30 cases (30.9%). Minimally invasive treatment with
interventional radiology may be selected due to poor general condition;
nevertheless, surgery is selected as the radical treatment if there are
many inflowing blood vessels and complicated collateral circulation
because it is difficult to embolize all of them. In this case, as well,
complete hemostasis was not achieved with coil embolization, therefore
pancreatoduodenectomy was selected.