Chronic Pancreatitis

Even repeat bouts of acute pancreatitis do not necessarily lead to chronic pancreatitis. In fact, clinical evidence suggests that chronic pancreatitis is a de novo condition and that acute and chronic pancreatitis should be considered separate diseases. The most common cause of chronic pancreatitis in North America and Europe is alcohol related.
Classification
No universally acceptable classification of chronic pancreatitis exists. The diagnostic criteria of chronic pancreatitis using ERCP criteria were proposed by the Japan Pancreas Society in 1995 and are used by some. The Marseilles classification defines chronic pancreatitis as continued inflammation of the pancreas associated with irreversible damage. The pancreas may be involved focally or diffusely, and there is loss of both exocrine and endocrine function. Abdominal pain is a constant feature in the vast majority of patients.
Etiology
Many of the etiologies causing acute pancreatitis are also responsible for chronic pancreatitis. Aside from cystic fibrosis and hereditary pancreatitis (see Congenital Abnormalities), chronic pancreatitis is rare in children and adolescents. Some families with familial hyperlipidemia, cystic fibrosis, and hyperparathyroidism have a higher than normal prevalence of chronic pancreatitis. a1- Antitrypsin deficiency is typically associated with pulmonary disease; in rare instances it may be associated with chronic pancreatitis. Chronic pancreatitis has been associated with ulcerative colitis; the several reported patients suggest a possible nonfortuitous relationship between these two entities. The prevalence of chronic pancreatitis is low in primary sclerosing cholangitis, and the occasional synchronous finding is probably by chance. Some cirrhotic patients have ERCP findings consistent with chronic pancreatitis. These changes are found even in nonalcoholic cirrhotic patients.
Clinical
Idiopathic Fibrosing (Autoimmune)
A syndrome of idiopathic fibrosing pancreatitis, also called chronic relapsing pancreatitis of childhood, is a rare form of chronic pancreatitis, often developing in children and young adults. Etiology is unknown, although an autoimmune basis is postulated. Its relationship to autoimmune hepatitis, a well-established entity, is not clear. Pain is a common feature. These patients have developed obstructive jaundice, but pancreatic insufficiency is not a prominent feature in this entity.
A curious form of chronic pancreatitis is centered on the pancreatic ducts, called autoimmune pancreatitis, sclerotic pancreatitis and lymphoplasmacytic pancreatitis.Whether these represent the same entity is conjecture. Imaging reveals either a focal pancreatic tumor or the entire pancreas is enlarged and is hypoechoic with US. Pancreatography in patients with autoimmune pancreatitis reveals an irregular and narrowed main pancreatic duct; some patients develop pancreatic duct obstruction. Neither pancreatic duct dilation nor calcifications develop. A focal pancreatic tumor, often with pancreatic duct obstruction, is not an uncommon presentation, and surgery for suspected pancreatic cancer is performed. Retroperitoneal fibrosis develops in an occasional patient. Resection, often for suspected pancreatic cancer, reveals pancreatic fibrosis and, at times, an eosinophilic infiltrate. Fibrosis, of course, is not limited to this condition and is common in chronic calcifying pancreatitis. Disease often recurs in the remnant pancreas. Their pancreatitis tends to respond to steroid therapy.
Chronic Obstructive
Duct obstruction with little or no evidence of stones is classified an a separate etiology for chronic pancreatitis. Yet this term is also a descriptive one representing a stage in evolution of chronic pancreatitis due to a number of
etiologies, including secondary to inflammation of sphincter of Oddi, acute pancreatitis, or even a malignant tumor. Some patients diagnosed with chronic obstructive pancreatitis do develop ductal stones and, similarly, of those with chronic calcifying pancreatitis not allhave calcifications throughout their disease course.
Chronic Calcifying Chronic calcifying pancreatitis is most often associated with chronic alcohol consumption; gallstone pancreatitis rarely progresses to calcifying pancreatitis. An exception to this is a young patient with gallstone pancreatitis and pseudocysts who eventually develops pancreatic calcification; superimposed hereditary pancreatitis may play a role in some of these patients. The presence of pancreas divisum does not change the course of chronic calcifying pancreatitis; in these patients pancreatitis may involve only the ventral segment, only the dorsal segment, or occur throughout the pancreas; in about half of these patients detected abnormalities are segmental.
Tropical Calcific
Tropical calcific pancreatitis generally starts in childhood. The etiology is not known, although these patients tend to have underlying nutritional deficiencies.
Tuberculous Isolated tuberculous pancreatitis or a pancreatic abscess are rare. This entity is more often seen in association with lung tuberculosis. Peripancreatic and mesenteric lymph nodes are often also enlarged, bowel wall is thickened, and ascites is present. Some patients have hepatosplenic involvement and splenic vein thrombosis. Tuberculous pancreatitis presents as a pancreatic tumor, at times containing cystic components, and tends to mimic a primary pancreatic neoplasm, including an appearance of vascular invasion. Some patients undergo laparotomy for suspected cancer. Attempted resection risks formation of a pancreatic fistula and miliary peritoneal dissemination. Focal tuberculomas are hypodense on CT.US shows inhomogeneous hypoechoic tumors within the pancreas. A cystic component may be evident. Endoscopic US is often compatible with a cystic pancreatic neoplasm. Even ERCP reveals a stricture, and pancreatic duct displacement can mimic a neoplasm.
Other Etiologies Eosinophilic pancreatitis is a rare entity of unknown etiology. It mimics a pancreatic neoplasm. An 18-year-old man presented with obstructive jaundice, epigastric pain, and weight loss, endoscopic US detected a small round, hypoechoic tumor in the head of the pancreas, an endocrine tumor was suspected, and a duodenopancreatectomy performed. An ERP in another man with weight loss and obstructive jaundice identified a narrow, smooth main pancreatic duct and a tight common bile duct stenosis. Both patients were eventually diagnosed with eosinophilic pancreatitis. Hydatid disease of the liver as a cause of pancreatitis has been mentioned above (see Acute Pancreatitis). Direct pancreatic involvement is rare. These cystic lesions tend to be misdiagnosed as pseudocysts and ascribed to pancreatitis
or trauma.About half of the cysts occur in the head of the pancreas, a somewhat uncommon location for pseudocysts. Calcifications may develop.
Pancreatic inflammation and fibrosis develop in congenital syphilis. In the Middle East, schistosomiasis (due to Schistosoma mansoni and Schistosoma haematobium) leads not only to hepatobiliary but also to pancreatic calcifications. A hydatid cyst in the head of the pancreas can result in obstructive jaundice.

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