Acute pancreatic

Acute pancreatic inflammation does not lend itself to an easy classification. ince 1963, at least four international symposia have debated this subject and proposed classifications. Among the changes adopted has been a shift in emphasis from pancreatic necrosis to presence of organ failure and inclusion of information obtained from various imaging examinations (incidentally, the terms pancreatic necrosis and necrotizing pancreatitis are used synonymously). Some of the terminology has also been redefined. There now is a distinction between an acute fluid collection that occurs early in acute pancreatitis and often regresses spontaneously and a pseudocyst that requires several weeks to form and has a distinct wall. A pancreatic abscess is
defined as an intraabdominal collection of pus near the pancreas that contains little if any necrotic tissue. The term infected pseudocyst has been deleted and this entity is now considered a pancreatic abscess.
The terms hemorrhagic pancreatitis and phlegmon have also been deleted, although the wisdom in deleting the term phlegmon has been questioned. The primary reason for deleting phlegmon was its past imprecise usage. For instance, some physicians interpret phlegmon to mean a sterile process while others place it in the infectious category.Nevertheless, the vagueness of this term is useful during initial evaluation of acute pancreatitis prior to imaging
studies; contrast-enhanced CT can then subdivide a phlegmon into interstitial versus necrotizing pancreatitis, while percutaneous aspiration can establish a sterile versus infected collection of fluid. It remains to be seen whether phlegmon will continue to be used in a setting of acute pancreatitis.
Etiology
Congenital Anomaly

Aberrant pancreaticobiliary duct insertions are associated with recurrent pancreatitis. Thus a pancreatic duct inserting into a communicating duodenal duplication or diverticulum and cystic duct insertion close to the ampulla have resulted in pancreatitis. Even a communicating duplication results in stasis, and, in time, calculi form within a duplication. The rare intraluminal duodenal diverticulum is also associated with acute pancreatitis.
Some patients with pancreas divisum develop pancreatitis; therapeutic options in this clinical setting are discussed in the Congenital Abnormalities section. In the absence of more common etiologies for pancreatitis, especially in a younger patient, aberrant pancreaticobiliary duct communica
tions and termination should be sought. An MRCP should detect any major duct anomalies and related fluid-filled structures suggesting a duplication. The inability to cannulate the main papilla during ERCP should prompt efforts to cannulate the duct of Santorini.
Bile Duct Related Acute biliary pancreatitis appears to be more severe; more complications develop and mortality is greater in patients who have an intact gallbladder compared to those who had a previous cholecystectomy. Choledocholithiasis is a common cause of acute pancreatitis. Although not common, gallstone pancreatitis does occur during pregnancy. Presumably a stone impacts at the ampulla of Vater, but most of these obstructions are transient and the stone passes into the duodenum. About 40% of gallstone pancreatitis recurs within 6 months, with recurrence often associated with stones in the gallbladder, and thus the rationale for performing cholecystectomy once pancreatitis is quiescent. Clinically it is difficult to differentiate between gallstone- and non–gallstoneassociated acute pancreatitis. One useful laboratory test is alanine aminotransferase (ALT) level; a greater than threefold elevation above normal has a strong positive predictive value for acute gallstone pancreatitis. Admission plasma cholecystokinin levels in patients with gallstone pancreatitis are significantly higher than in patients with other causes of acute pancreatitis, although cholecystokinin levels do not correlate with serum bilirubin or pancreatic enzyme levels or severity of acute pancreatitis. Plasma cholecystokinin elevation in gallstone pancreatitis appears to be a result of a transient bile flow disturbance by stones or duct wall edema. Hemobilia, regardless of cause, is associated with acute pancreatitis. Anecdotal etiologies of acute pancreatitis include a bile duct suture or clip acting as a nidus, debris from a hepatocellular carcinoma rupturing into the bile ducts, and associations with primary sclerosing cholangitis and duodenal Crohn’s disease. A patient with familial adenomatous polyposis with adenomas in the common bile duct developed relapsing acute pancreatitis.
Endoscopic Retrograde Cholangiopancreatography Induced Endoscopic retrograde cholangiopancreatography is a not uncommon cause of subclinical or mild pancreatitis. Of more importance is that ERCP is an occasional precursor to acute necrotizing pancreatitis, especially if a sphincterotomy is performed. Among 72 consecutive patients with acute necrotizing pancreatitis requiring surgery at the Mayo Clinic, ERCP was implicated in 8%; of note is that on admission these post-ERCP patients had higher Acute Physiology and Chronic Health Evaluation (APACHE II) scores, more extensive pancreatic necrosis, and a higher rate of infected necrosis, and they required earlier necrosectomy and developed more enteric fistulas than similar non–ERCP-induced acute necrotizing pancreatitis patients. These post-ERCP patients had a lower mortality rate, but they were significantly younger; nevertheless, all survivors suffered long-term morbidity. The authors postulated that infection introduced during ERCP may account for some of the increased severity of pancreatitis in these patients. A relationship appears to exist between common bile duct diameter and the subsequent risk of sphincterotomy-induced pancreatitis, with pancreatitis developing more often in patients with a nondilated bile duct.
Infection
Infectious organisms linked to pancreatitis include viral (mumps, measles, Coxsackie, hepatitis B, cytomegalovirus, varicella-zoster virus, herpes simplex virus), bacterial (mycoplasma, legionella, leptospira, salmonella), fungal (aspergillosis), and occasional parasitic infestations (toxoplasmosis, cryptosporidiosis, ascariasis). Even a scorpion bite has been implicated. Acute fatal necrotizing pancreatitis has developed after liver transplantation for fulminant hepatitis B virus infection, presumably due to the hepatitis B virus.
An ascaris roundworm migrating into the pancreatic duct after sphincterotomy and pan
creatic stent placement led to acute pancreatitis. These worms can be removed with a Dormia basket. Intrabiliary rupture of a hydatid cyst and the subsequent spill of cyst contents into the bile ducts is a cause of acute pancreatitis; CT and US identify both the liver infection and bile duct debris.
Neoplasm
Pancreatic carcinomas are commonly associated with surrounding pancreatitis, although symptoms related to the cancer tend to predominate. An occasional papilla of Vater carcinoid or a pancreatic islet cell tumor produces a pancreatic duct stricture and a clinical picture consistent with acute pancreatitis.
Drug Related Steroids, diuretics, some antibiotics, and even cimetidine are some of the medications implicated in acute pancreatitis. Yet drug-associated pancreatitis is uncommon. Organophosphate insecticide toxicity is a rare cause of pancreatitis. Intranasal snorted heroin is associated with pancreatitis.
Vascular Pancreatic ischemia is not common but does result in pancreatitis. Thus patients undergoing thoracoabdominal aortic aneurysm repair and descending thoracic aorta cross-clamping are subject to pancreatic ischemia and pancreatitis. Cholesterol crystal embolization to the pancreas
has led to necrotizing pancreatitis. Such embolization probably is more common than reported in patients with atherosclerotic vascular disease.
Other Etiologies Rarer conditions associated with pancreatitis include the vasculitides, hyperlipidemia, ulcerative colitis, chronic renal failure, a peri-Vaterian diverticulum or neoplasm, and even a choledochal cyst. Acute pancreatitis in long-distance runners is more common in women. A rare cause of acute pancreatitis is pancreatic volvulus associated with a hiatal hernia. A patient
with duodenal obstruction distal to the papilla occasionally presents with acute pancreatitis; more distal small bowel obstruction is not associated with pancreatitis. Thus an obstructing duodenal carcinoma distal to the papilla of
Vater or even an afferent loop obstruction after a gastrectomy and Billroth II gastrojejunostomy has led to acute pancreatitis. Hypercalcemia due to hyperparathyroidism is a known cause of acute pancreatitis. Hypercalcemia secondary to  malignancy, on the other hand, seldom causes acute pancreatitis.
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