Intracystic arteries in a chronic pancreatic pseudocyst

Abstract

Background

An enlarging pancreatic pseudocyst can incorporate adjacent vessels into its wall, leading to pseudoaneurysm formation in the presence of proteolytic enzymes. Intact arteries running through the cyst cavity are very rare, however.

Case outline

A 54-year-old man with a chronic pancreatic pseudocyst (15 cm diameter) underwent internal drainage by means of cystjejunostomy Roux-en-Y. Two large pulsating arteries running through the cyst cavity were identified as the middle colic artery and one of its branches. Temporary clamping of the transcystic arteries revealed no signs of ischaemia in the transverse colon, so the vessels were ligated and the cystjejunostomy completed. The patient remains well one year later.

Discussion

Bleeding following internal drainage procedures carries a higher mortality rate than spontaneous bleeding in chronic pancreatic pseudocysts but is easier to prevent.This case highlights the importance of thorough exploration of the pseudocyst to identify any vessels in its cavity or wall.

Introduction

Pseudocysts representing encapsulated collections of pancreatic juice commonly develop in both acute and chronic pancreatitis. Chronic pancreatic pseudocysts are generally contained within the gland and undergo complications in 42% of cases ¹. A diameter greater than 4 cm and extrapancreatic involvement are independent predictive factors of persistent symptoms or complications ². Bleeding is the most rapidly lethal complication of established pseudocysts related to chronic pancreatitis, with an incidence of 5–10% ¹,³. As the pseudocyst enlarges it can incorporate adjacent arteries into its wall, and weakening of the vessel wall will lead to pseudoaneurysm formation. Such an aneurysm can rupture into the pseudocyst and then into an adjacent organ such as the stomach, duodenum or colon; rupture seems to be commoner in alcohol-related pancreatitis ⁴. The splenic artery is most commonly involved, followed by the gastroduodenal, pancreaticoduodenal, gastric and hepatic arteries ⁵. Mortality rates from bleeding pseudoaneurysms within pseudocysts vary from 13 to 49% depending on the patient's clinical state, the site and nature of the bleeding lesion and the type of surgical management ⁵,⁶. Haemorrhage is generally thought to occur from erosion of an artery in the wall of the cyst, but the present case suggests that sometimes the bleeding vessel might actually traverse the cyst cavity.

Case report

A 54-year-old man presented to another hospital in January 1999 with severe upper abdominal pain radiating to the back and an epigastric mass. Alcohol intake was moderately heavy. Serum amylase was normal, but CT scan revealed a swollen head of pancreas consistent with chronic pancreatitis. Although his symptoms subsided at first, repeat abdominal CT scans 4 and 8 months later revealed an enlarging pseudocyst in the head of pancreas which was causing persistent abdominal discomfort. The patient was referred to this unit for internal drainage of the pseudocyst in November 1999.

Preoperative investigations included a Pancreolauryl (exocrine function) test, which was grossly abnormal (4.6%: normal ≥30%) and a coeliac angiogram, which demonstrated compression of the portal vein but no obvious arterial abnormalities. Laparotomy revealed a huge pseudocyst, 15 cm in diameter, replacing the head of pancreas and bulging through the transverse mesocolon to the right of the middle colic vessels. The body and tail of pancreas were relatively normal, and there was no other intra-abdominal pathology. On-table cystography revealed no ductal communication. On opening the cyst, 500 ml yellow/brown fluid was evacuated together with a moderate quantity of necrotic debris. Running through the cyst cavity were two large pulsating arteries. These were identified as the middle colic artery and one of its branches (Figure 1). The vessels were occluded with vascular clamps and since no signs of ischaemia were seen in the transverse colon, they were ligated and excised. A Roux-en-Y cystojejunostomy was fashioned. The patient tolerated the procedure well and made an uneventful postoperative recovery. He remains asymptomatic one year later.

Figure 1. .

Middle colic vessels (white arrow) running within the pseudocyst cavity. (Incised margins of pseudocyst wall are outlined by grey arrow heads.)

Discussion

Visceral vessel involvement by pancreatic pseudocysts is commonest in men, usually in the fourth-to-sixth decade, with alcohol-induced chronic pancreatitis ³,⁵,⁶,⁷,⁸,⁹. Duration of disease, pseudocyst diameter and the presence of splenic vein thrombosis are significant predictors of the formation of pseudoaneurysms ¹⁰.

Incorporation of one of the visceral vessels into a pancreatic pseudocyst such that it runs through the cavity without any connection to the pseudocyst wall (except at the points of entry and exit) has never been previously described to the best of our knowledge. Perhaps the usual process of tissue destruction entailed when a pseudocyst enlarges and incorporates a vessel in its edge may occasionally be incomplete, depending on the concentration of enzymes within its cavity. The cyst could then extend right around the vessel without eroding it completely. In the present case, enzyme concentrations within the pseudocyst cavity are likely to have been low, since there was no communication with the pancreatic duct.

Involvement of the middle colic artery by a pseudocyst is extremely rare. In a review of the literature by Stabile and colleagues, only one of 131 cases of bleeding associated with pancreatic pseudocysts was found to arise from the middle colic artery ⁵. In this series, 19% of pseudocyst-associated bleeding followed internal or external drainage procedures, and this situation carried a higher mortality rate than spontaneous haemorrhage (60 vs 34%). In a collective review of internal drainage procedures reported by Nielsen, there was an 11% incidence of bleeding after cystgastrostomy and a 7% incidence after cystjejunostomy ¹¹. The risk of postoperative haemorrhage from a leaking pseudoaneurysm may be sufficient to justify routine angiography before an internal drainage procedure.

This case report highlights the importance of adequate exploration of the inside of a chronic pseudocyst during surgical drainage procedures, even if a recent angiogram has been ostensibly normal. This manoeuvre will allow ligation or under-running of any obvious vessel within the cyst wall or cavity and should thus prevent rupture and internal bleeding after decompression of the pseudocyst.