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PSEUDOPANCREATIC CYSTS
(PSEUDOCYSTS)

Definition:
Pancreatic pseudocysts are localized collection of fluids with high concentration of pancreatic enzymes. They are called psuedocyst because unlike congenital cysts or cystic neoplasm, they lack a true epithelium and they do not originate in the substance of the pancreas but is located in close proximity to it and attached to it. The relationship between the pancreas and the cyst is so intimate that, on exploration, it is almost impossible to decide whether the cyst is in the gland or outside it, and it is equally impossible to dissect the cyst from the pancreas.

Origin
A pseudocyst is actually a collection of fluid in the peripancreatic cellular tissue or the lesser sac, the collection having been so encapsulated as to give it the shape of a cyst. Such collection of fluid, with subsequent encapsulation, may result under the following circumstances:
  • Injury to the pancreas, together with laceration of the posterior wall of the lesser sac that covers the pancreas. Blood and pancreatic secretions accumulate in the peripancreatic cellular tissue and the lesser sac. The epiploic foramen is sealed and so the collection gets localized. The cyst increases in size by the drawing in of the fluid into the cyst because of the high osmotic tension of its contents. The surrounding peritoneum (i.e. the peritoneum of the lesser sac) becomes so condensed as to make a capsule for the cyst
  • Acute haemorrhagic pancreatitis may be followed by the formation of the pseudocyst because of the outpour of the blood and pancreatic ferments around the pancreas and into the lesser sac
  • Perforation of the posterior wall of the stomach by the ulcer, the epiploic foramen having been previously sealed, and the gastric contents escape into the lesser sac and may form a cyst there
  • Healed tubercular peritonitis, localized in the lesser sac
Sites of presentation:
There being the tough posterior wall on the back, the cyst projects anteriorly and, in order of frequency, this may be as follows:
  • Between the stomach and the transverse colon
  • Between the liver and the stomach
  • Between the layers of the transverse mesocolon, with the colon stretched on the surface of the cyst
Clinical features:
Pseudocysts are not common occurrence. Their importance lies in that they have to be taken into consideration while making a differential diagnosis of an upper abdominal swelling. The main clinical presentations are as follows:
  • There is either a history of trauma or an acute abdominal pain (suggestive of pancreatitis, rarely of peptic perforation) in the majority of the cases.
  • At the variable intervals usually about two weeks, a swelling appears in the epigastrium. The swelling gradually increases in size.
  • To start with, there is pain, but this is usually replaced by an epigastric discomfort, often associated with severe anorexia, nausea and vomiting cue to pressure on the stomach. Because of inanition, the patient often losses weight quickly
  • The swelling is localized and its surface is smooth (c.f. retroperitoneal sarcoma, which is nodular)
  • The swelling can not be moved (c.f. mesenteric cyst, ovarian cyst, cyst of the greater omentum). It does not move with respiration (c.f. liver, gall bladder, spleen, kidney) and it is not ballotable (c.f. hydronephrosis)
  • As the cyst is usually tense, it has often a firm rather than a cystic feel and fluctuation is often absent
  • There is often a transmitted pulsation of the abdominal aorta (c.f. aneurysm of the abdominal aorta, where the pulsation is expansile, much diminished in the knee-elbow position and there is presence of bruit on the auscultation)
Diagnosis:
  • US and CT scans are the most useful test to diagnose pseudocysts. However, CT scans are more sensitive and specific than US and have the additional advantages of superior resolution and more precise location. Moreover, bowel gas, obesity and displacement of the intra-abdominal structures, from the prior surgery may impair US images
  • Endoscopic Retrograde Cholangiopancreatography (ERCP) has also been used before surgery to provide anatomical information about pseudocysts but it should be done routinely. ERCP is indicated in jaundiced patients to differentiate between common bile duct compression by the cysts and strictures of the intrapancreatic portion of the common duct caused by fibrotic pancreas. In the former case, cyst drainage alone would relieve the jaundice while in the latter instance; a biliary bypass procedure to relieve the biliary obstruction would be required, because it may introduce bacteria into the previous sterile cyst. ERCP should be performed only when the cyst drainage is to be done with in the 24 hours
  • Barium meal X-ray I done and the lateral views are more important. The stomach is pushed anteriorly i.e. the vertebro-gastric interval in increased
  • An I.V.P. may necessary to exclude the possibility of the Hydronephrosis
Complications:
  • Infection (commonest)
  • Haemorrhage
  • Rupture
Treatment:
Operation is the only available treatment and this should be done early. Excision of the cyst is impracticable because of the intimate relationship of the cyst wall to the stomach, mesocolon, pancreas and liver, from which structures it can not be separated. The available operations are:
  • Internal drainage: This means anastomosing the cyst to the stomach (cysto-gastrostomy) or to the jejunum (cysto-jejunostomy). Cysto-gastrostomy is the most common procedure. The posterior wall of the stomach and the anterior wall of the cyst, which are closely adherent to each other, are now incised (5cm) and the contents of the cysts are sucked out. Then several stitches are applied between the anterior cyst wall and the posterior gastric wall, around the stoma. The opening made on the anterior gastric wall is closed
  • External drainage: This is also known as marsupialisation. The cyst is exposed, part of its wall is removed, and the cut edges of the wall are sutured to the skin and the cyst is packed. The track usually closes in a month but this procedure is rare done because of the delay in wound healing and secondary infection
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This article has been written by Dr. M. Javed Abbas.
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21:52 09/02/2003