Chronic Pancreatitis is caused by alcohol abuse in the majority of patients. Other etiologies include idiopathic or metabolic (hypercalcemia, hypertriglyceridemia, hypercholesterolemia, hyperparathyroidism, cystic fibrosis) factors, drugs, trauma, and congenital abnormalities (sphincter of Oddi dysfunction or pancreas divisum). A history of recurrent acute pancreatitis is present in some but not all patients with chronic pancreatitis.
A. Pathophysiology
Chronic pancreatitis is characterized by diffuse scarring and strictures in the pancreatic duct and often leads to endocrine or exocrine insufficiency, although substantial glandular destruction must occur before secretory function is lost. The islets of Langerhans have a greater resistance to injury than do the exocrine tissues; most patients who develop diabetes already have pancreatic exocrine insufficiency and steatorrhea. Based on ductal involvement and morphology, the disease is subclassified as either large-duct or small-duct disease.
B. Diagnosis
Diagnosis is based on a complete history and examination, complemented by the appropriate investigative studies. Upper midepigastric pain radiating to the back is the cardinal symptom and is present in 95% of cases. Early episodes mimic acute pancreatitis and may last for several hours to days. As the disease progresses, the attacks tend to be more frequent and prolonged. Physical findings include weight loss proportional to the severity of anorexia, as well as steatorrhea. Tenderness of the upper abdomen is common.
Laboratory tests
A 72-hour fecal collection for estimation of daily fecal fat is the most sensitive and specific stool test for exocrine insufficiency. Fat absorption has the most clinical significance, although fewer problems are associated with protein malabsorption.
Radiologic studies
Plain films of the abdomen show diffuse calcification of the pancreas in approximately 30% of patients with relatively early stages of chronic pancreatitis and in 50% to 60% of cases of advanced disease.
CT is 75% sensitive for the diagnosis of parenchymal or ductal disease. It is also useful for detecting complications or associated findings in patients presenting with epigastric abdominal pain, such as splenic aneurysms, pancreatic pseudocyst, or pancreatic cancer.
ERCP is essential to define the extent of disease and optimize surgical management through evaluation of ductal anatomy. Brushings and biopsies of suspicious lesions can be performed as well as therapeutic interventions, including stenting and sphincterotomy.
MRI is less sensitive than CT for detection of calcification. Falsely positive studies for filling defects can be caused by air in the duct, clips, and artifacts. MR pancreatography is more sensitive in visualizing a dilated duct and strictures but loses sensitivity relative to ERCP in evaluating side branch disease (i.e., small-duct disease).
Ultrasonography- or CT-guided fine-needle biopsies may be useful in cases in which chronic pancreatitis cannot be distinguished from pancreatic cancer. By itself, however, a single biopsy finding of inflammatory changes is not sufficient to rule out carcinoma. A normal biopsy may also result from sampling error.
C. Complications
Common bile duct obstruction may result from transient obstruction from pancreatic inflammation and edema or from stricture of the intrapancreatic common bile duct. When present, strictures are often long and smooth (2 to 4 cm in length) and must be distinguished from pancreatic carcinoma.
Duodenal obstruction can occur due to acute pancreatic inflammation, chronic fibrotic reaction, pancreatic pseudocyst, or neoplasm.
Pancreaticoenteric fistulas result from spontaneous drainage of a pancreatic abscess cavity or pseudocyst into the stomach, duodenum, transverse colon, or biliary tract. They are often asymptomatic but may become infected or result in hemorrhage.
Pseudocyst
Pancreatic carcinoma. Chronic pancreatitis has been suggested in some studies to increase the risk of pancreatic carcinoma by two- to threefold.
D. Treatment
Medical management
Malabsorption or steatorrhea. There is some evidence that adequate oral pancreatic enzyme supplementation improves pain control.
Diabetes initially is responsive to careful attention to overall good nutrition and dietary control; however, use of oral hypoglycemic agents or insulin therapy often is required. eatic resections.
Narcotics usually are required for pain relief. Narcotic dependency is a frequent complication of therapy and correlates with higher mortality. In selected patients, tricyclic antidepressants and gabapentin may be effective.
Abstinence from alcohol and withdrawal prophylaxis are of paramount importance.
Endoscopic therapy. Endoscopic sphincterotomy, stenting, stone retrieval, and lithotripsy have all been used with moderate success in the management of patients with ductal complications from chronic pancreatitis.
Surgical principles
Indications for surgery include severe intractable pain, multiple relapses, inability to rule out neoplasm, and complications of pancreatitis (pseudocyst, obstruction, fistula, infections, portal hypertension).
Longitudinal side-to-side pancreaticojejunostomy (Partington-Rochelle) is indicated in patients with functionally significant strictures along the pancreatic duct (chain of lakes on pancreatograms) and with ducts at least 8 mm in diameter.
Puestow procedure includes a distal pancreatectomy with a distal pancreaticojejunostomy for drainage, with reported success in postoperative pain relief ranging between 61% and 90%
Combined duct drainage-resection
Pancreaticoduodenectomy (Whipple procedure) is indicated in cases in which the pancreatitis disproportionately involves the head of the pancreas, the pancreatic duct is of small diameter, or cancer cannot be ruled out in the head of the pancreas. For chronic pancreatitis, the pylorus-preserving technique is advocated. The use of vagotomy is controversial.
Celiac plexus block. Although transiently effective in some cases, nerve ablation procedures more recently have been shown to have a beneficial role in the management of pain in patients with chronic pancreatitis. Methods for ablating the celiac ganglion include image-guided ethanol injection and surgery (ganglionectomy).