Introduction

Pancreatic arteriovenous malformation (AVM) is rare and can cause progressive gastrointestinal hemorrhage from varices associated with portal hypertension [1]. Treatment by surgical resection, transcatheter arterial embolization (TAE), and radiotherapy are reported [2–4]. However, surgical resection carries the risk of perioperative hemorrhage with high mortality and postoperative insulin dependence, especially in cases with total pancreatectomy [5]. Very few reports describe successful treatment with TAE [6], which is associated with short-term recurrence [3]. We performed external beam radiotherapy for an angiographically diagnosed massive pancreatic AVM involving the entire pancreas.

Case report

A 66-year-old man with type 2 diabetes mellitus of 2 years’ duration complained of abdominal discomfort. Ultrasonography detected abnormality of the pancreas, and color doppler ultrasonography demonstrated dilated and tortuous arteries and nidi (Fig. 1). Multiphase contrast-enhanced computed tomography (CT) revealed multiple dilated arteries in the swelled pancreas and early enhancement of the portal vein (Fig. 2). These findings led to suspicion of pancreatic AVM, and diagnostic angiography was performed. Celiac angiography revealed the feeding arteries to include the dorsal pancreatic, anterior and posterior superior pancreaticoduodenal, right and left gastric, and splenic arteries. Superior mesenteric angiography revealed the middle colic artery as the feeding artery (Fig. 3). We chose conservative therapy rather than TAE or surgical resection because the patient’s only symptom was abdominal discomfort, and he demonstrated no portal hypertension or gastrointestinal varices.

Fig. 1
figure 1

Doppler ultrasonography of the abdomen shows swelling of the entire pancreas and confirms dilated venous and arterial blood signals. a Pancreas body to tail, b pancreas head

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Fig. 2
figure 2

a Arterial phase of contrast-enhanced computed tomography (CT) of the abdomen shows the entire pancreas enhancing and confirms large numbers of dilated and tortuous arteries in the pancreas, b volume-rendered 3-dimensional (3D) CT of arterial phase demonstrates large numbers of dilated and tortuous arteries involving the pancreas head to tail

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Fig. 3
figure 3

Celiac and superior mesenteric angiography by digital subtraction technique. a Selective angiogram of the common hepatic artery confirms feeding arteries from the anterior and posterior superior pancreaticoduodenal artery in the pancreas head. b Selective angiogram of the splenic artery demonstrates large numbers of dilated pancreatic branches as feeding arteries. c, d Angiograms of the superior mesenteric artery show the middle colic artery as a feeding artery. e Selective angiogram of the right gastric artery. f Selective angiogram of the left gastric artery

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One month after diagnostic angiography, the patient came to our institution’s emergency room with severe abdominal pain. Hemorrhage into the main pancreatic duct was suspected on CT (Fig. 4), and we observed slight elevation in levels of serum amylase (254 IU/mL) and C-reactive protein (CRP) (2.6 mg/dL). The patient received external radiotherapy from a 10-MV linear accelerator (PRIMUS KD2; Siemens, Erlangen, Germany) with total dose of 44 Gy following a conventional fractionation schedule of 2 Gy daily for 22 days administered 5 days a week using three-dimensional conformal treatment planning (Fig. 5). Contrast-enhanced CT 1 month after irradiation confirmed disappearance of many dilated and tortuous arteries and nidi (Fig. 6). We observed no complication of adjacent organs caused by irradiation, such as liver dysfunction, intestinal obstruction, or gastric ulcer. The level of glycated hemoglobin (HbA1c) was 6.2 % before irradiation and 5.4 % 2 months after. Evidence of recurrence was not detected on contrast-enhanced CT 6 months after irradiation (Fig. 6).

Fig. 4
figure 4

High density fluid collection in the dilated main pancreatic duct is suspected hematoma and hemorrhage from pancreatic arteriovenous malformation (AVM)

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Fig. 5
figure 5

a Dose distribution. Entire pancreas treated with 44 Gy. b Dose volume histogram (Red: Pancreas, Green: Liver, Blue: Right kidney, Cyan: Left kidney, Yellow: Duodenum)

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Fig. 6
figure 6

Arterial phase of contrast-enhanced computed tomography (CT) of the abdomen. a Before external radiotherapy. b One month after radiotherapy, swelling of the pancreas is improved, and dilated arteries and nidi have disappeared. c Six months after radiotherapy, no detectable recurrence of pancreas AVM. d Volume-rendered 3-dimensional (3D) CT of arterial phase before external radiotherapy. e One month after radiotherapy, dilated and tortuous arteries have disappeared and normal structures, such as the celiac and splenic arteries and portal vein, remain

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Discussion

Pancreatic AVM is rare, accounting for only a reported 0.9 % of all AVMs in digestive organs [1]. Ninety percent are congenital, and 10 % are acquired and arise secondary to inflammation, trauma, or tumor. Ten to 30 % of congenital pancreatic AVMs have associated hereditary hemorrhagic telangiectasia (HHT) [2]. Our case was probably congenital because his history included only diabetes mellitus. HHT was clinically excluded because he had not symptoms such as family history, nose bleed or telangiectasia of skin or mucosa. The most common clinical manifestations of pancreatic AVM are gastrointestinal bleeding, epigastralgia, and portal hypertension [2]. Of these, our patient had only epigastralgia, and its relationship to diabetes mellitus is unknown. Two of 12 patients in Song’s group [7] had diabetes mellitus. Bleeding into the main pancreatic duct is also reported [8].

Several reports describe diagnosis of pancreatic AVM by angiography, CT, ultrasound, color doppler sonography, and magnetic resonance (MR) imaging; ultrasound and color doppler sonography are reported as powerful diagnostic modalities [9]. However, in our case, difficulty confirming the tail of the pancreas on ultrasound made evaluation of the distribution of the AVM challenging. Multiphase contrast-enhanced CT aids evaluation of distribution but does not rule out other hypervascular pancreatic lesions. Overall, angiography was effective in diagnosing and evaluating AVM distribution, and angiographic findings were almost the same as previously reported [10]. Our angiography demonstrated involvement of the entire pancreas, a very rare condition. Only 8 of 81 cases of pancreatic AVM reviewed by Song’s group involved the organ head to tail [7].

Transcatheter arterial embolization, surgical resection, and radiotherapy have been used to treat pancreatic AVMs [2–4, 6]. Gomes and associates described the utility of TAE, but embolization of large numbers of feeding arteries is difficult without infarction of other organs [6]. Sato and colleagues reported AVM recurrence after a short follow-up period after TAE [3]. Our case required total pancreatectomy and resection of adjacent organs including the colon. The Mayo Clinic recently reported 5 % perioperative mortality with total pancreatectomy and postoperative problems that included insulin dependence, hypoglycemia, and chronic diarrhea [5]. To our knowledge, only 2 cases of radiotherapy of pancreatic AVMs are reported—one used irradiation during surgical laparotomy and external beam irradiation for a massive pancreatic AVM, and the other employed external beam irradiation for early-stage pancreatic AVM involving mainly the head of the pancreas in a patient with Child Class B liver cirrhosis and hepatocellular carcinoma [3, 4]. In 8 cases of pancreatic AVM involving head to tail reviewed by Song’s group, 4 patients underwent total pancreatectomy and a fifth, palliative therapy for portal hypertension; 3 cases received no treatment. No patient received radiotherapy in their series [7].

Ours is rare report of successful treatment of a massive pancreatic AVM involving the entire pancreas using only external beam radiotherapy. We treated the patient with a total dose of 44 Gy following a conventional fractionation schedule of 2 Gy daily for 22 days administered 5 days a week using three-dimensional conformal treatment planning. Kishi and colleagues successfully treated early-stage AVM involving mainly the head of the pancreas in a patient with Child Class B liver cirrhosis and hepatocellular carcinoma using a total dose of 40 Gy administered following a conventional fractionation schedule of 2 Gy daily for 20 consecutive days. This dose involves little risk of liver failure in patients with Child Class B cirrhosis and no other risk of dysfunction of adjacent organs, such as nephritis, intestinal obstruction, or gastric ulcer. Liver function was normal in our patient; we did not confirm abnormality in adjacent organs, including liver dysfunction.

Follow-up in the 2 cases previously reported was 18 months and 6 years. Our case has been followed for 6 months and requires long-term follow-up.

Radiotherapy as the treatment for pancreas AVM has not established yet, because there are only a few reports. Radiotherapy might not be always effective for all pancreas AVM. More experience is needed and most suitable treatment should be selected by cases.

In conclusion, accurate angiography is a powerful tool for the interventional radiologist to diagnose and evaluate the distribution of pancreatic AVMs. However, TAE is associated with a high incidence of early AVM recurrence and infarction of adjacent organs. External beam radiotherapy is effective, safe and minimally invasive, especially in cases involving the entire pancreas.