Acute pancreatitis or acute pancreatic necrosis is a sudden inflammation of the pancreas. It can have severe complications and high mortality despite treatment. While mild cases are often successfully treated with conservative measures, such as NPO (nil per os, fasting) and aggressive intravenous fluid rehydration, severe cases may require admission to the intensive care unit or even surgery to deal with complications of the disease process.
Mayo-Robson's point - a point on border of inner 2/3 with the external 1/3 of the line that represents the bisection of the left upper abdominal quadrant, where tenderness on pressure exists in disease of the pancreas. At this point the tail of pancreas is projected on the abdominal wall.
The most common causes of pancreatitis, are as follows:
Western countries: In the United States alcohol represents the primary etiology in 65% of acute pancreatitis cases (Sweden (20%), United Kingdom (5%))
Eastern countries: gallstones
Adolescents and young adults: mumps
Obesity in developed countries
The two types of pancreatitis are mild pancreatitis and severe pancreatitis, which are separated based on whether their predominant response to cell injury is inflammation or necrosis, respectively. In mild pancreatitis there is inflammation and edema of the pancreas. In severe pancreatitis there are additional features of necrosis and secondary injury to extrapancreatic organs. Both types share a common mechanism of abnormal inhibition of secretion of zymogens and inappropriate activation of pancreatic zymogens inside the pancreas, most notably trypsinogen. Normally, trypsinogen is activated to trypsin in the duodenum where it assists in the digestion of proteins. During an acute pancreatitis episode there is colocalization of lysosomal enzymes, specifically cathepsin, with trypsinogen. Cathepsin activates trypsinogen to trypsin leading to further activation of other molecules of trypsinogen and immediate pancreatic cell death according to either the necrosis or apoptosis mechanism (or a mix between the two). The balance between these two processes is mediated by caspases which regulate apoptosis and have important anti-necrosis functions during pancreatitis: preventing trypsinogen activation, preventing ATP depletion through inhibiting polyADP-ribose polymerase, and by inhibiting the inhibitors of apoptosis (IAPs). If, however, the caspases are depleted due to either chronic ethanol exposure or through a severe insult then necrosis can predominate.
As part of the initial injury there is an extensive inflammatory response due to pancreatic cells synthesizing and secreting inflammatory mediators: primarily TNF-alpha and IL-1. A hallmark of acute pancreatitis is a manifestation of the inflammatory response, namely the recruitment of neutrophils to the pancreas. The inflammatory response leads to the secondary manifestations of pancreatitis: hypovolemia from capillary permeability, acute respiratory distress syndrome, disseminated intravascular coagulations, renal failure, cardiovascular failure, and gastrointestinal hemorrhage.
The acute pancreatitis (acute hemorrhagic pancreatic necrosis) is characterized by acute inflammation and necrosis of pancreas parenchyma, focal enzymic necrosis of pancreatic fat and vessel necrosis (hemorrhage). These are produced by intrapancreatic activation of pancreatic enzymes. Lipase activation produces the necrosis of fat tissue in pancreatic interstitium and peripancreatic spaces as well as vessel damage. Necrotic fat cells appear as shadows, contours of cells, lacking the nucleus, pink, finely granular cytoplasm. It is possible to find calcium precipitates (hematoxylinophilic). Digestion of vascular walls results in thrombosis and hemorrhage. Inflammatory infiltrate is rich in neutrophils. Due to the pancreas lacking a capsule, the inflammation and necrosis can extend to include fascial layers in the immediate vicinity of the pancreas.
Acute pancreatitis is diagnosed clinically but requires CT evaluation to differentiate mild acute pancreatitis from severe necrotic pancreatitis. Experienced clinicians were able to detect severe pancreatitis in approximately 34-39% of patients who later had imaging confirmed severe necrotic pancreatitis. Blood studies are used to identify organ failure, offer prognostic information, determine if fluid resuscitation is adequate, and if antibiotics are indicated.
Imaging - A triple phase abdominal CT and abdominal ultrasound are together considered the gold standard for the evaluation of acute pancreatitis. Other modalities including the abdominal xray lack sensitivity and are not recommended. An important caveat is that imaging during the first 12 hours may be falsely reassuring as the inflammatory and necrotic process usually requires 48 hours to fully manifest.
Elevated serum amylase and lipase levels, in combination with severe abdominal pain, often trigger the initial diagnosis of acute pancreatitis. However, they have no role in assessing disease severity.
Serum lipase rises 4 to 8 hours from the onset of symptoms and normalizes within 7 to 14 days after treatment.
Serum amylase may be normal (in 10% of cases) for cases of acute or chronic pancreatitis (depleted acinar cell mass) and hypertriglyceridemia.
Reasons for false positive elevated serum amylase include salivary gland disease (elevated salivary amylase), bowel obstruction, infarction, cholecystitis, and a perforated ulcer.
If the lipase level is about 2.5 to 3 times that of amylase, it is an indication of pancreatitis due to alcohol.
Decreased serum calcium
Regarding selection on these tests, two practice guidelines state:
"It is usually not necessary to measure both serum amylase and lipase. Serum lipase may be preferable because it remains normal in some nonpancreatic conditions that increase serum amylase including macroamylasemia, parotitis, and some carcinomas. In general, serum lipase is thought to be more sensitive and specific than serum amylase in the diagnosis of acute pancreatitis"
"Although amylase is widely available and provides acceptable accuracy of diagnosis, where lipase is available it is preferred for the diagnosis of acute pancreatitis (recommendation grade A)"
CT is an important common initial assessment tool for acute pancreatitis. Imaging is indicated during the initial presentation if:
the diagnosis of acute pancreatitis is uncertain
there is abdominal distension and tenderness, fever>102, or leukocytosis
there is a Ranson score > 3 or APACHE score > 8
there is no improvement after 72 hours of conservative medical therapy
there has been an acute change in status: fever, pain, or shock
CT is recommended as a delayed assessment tool in the following situations:
acute change in status
to determine therapeutic response after surgery or interventional radiologic procedure
before discharge in patients with severe acute pancreatitis
CT abdomen should not be performed before the 1st 12 hours of onset of symptoms as early CT (<12 h) may result in equivocal or normal findings.
CT Findings can be classified into the following categories for easy recall :
Intrapancreatic - diffuse or segmental enlargement, edema, gas bubbles, pancreatic pseudocysts and phlegmons/abscesses (which present 4 to 6 wks after initial onset)
Peripancreatic / extrapancreatic - irregular pancreatic outline, obliterated peripancreatic fat, retroperitoneal edema, fluid in the lessar sac, fluid in the left anterior pararenal space
Locoregional - Gerota's fascia sign (thickening of inflamed Gerota's fascia, which becomes visible), pancreatic ascites, pleural effusion (seen on basal cuts of the pleural cavity), adynamic ileus, etc.
Magnetic resonance imaging
While computed tomography is considered the gold standard in diagnostic imaging for acute pancreatitis,magnetic resonance imaging (MRI) has become increasingly valuable as a tool for the visualization of the pancreas, particularly of pancreatic fluid collections and necrotized debris. Additional utility of MRI includes its indication for imaging of patients with an allergy to CT's contrast material, and an overall greater sensitivity to hemorrhage, vascular complications, pseudoaneurysms, and venous thrombosis.
Acute pancreatitis patients recover in majority of cases. Some may develop abscess, pseudocyst or duodenal obstruction. In 5 percent cases, it may result in ARDS (acute respiratory distress syndrome), DIC (disseminated intravascular coagulation), etc. Acute pancreatitis can be further divided into mild and severe pancreatitis. Mostly the Ranson Criteria are used to determine severity of acute pancreatitis. In severe pancreatitis serious amount of necrosis determine the further clinical outcome. About 20% of the acute pancreatitis are severe with a mortality of about 20%. This is an important classification as severe pancreatitis will need intensive care therapy whereas mild pancreatitis can be treated on the common ward.
Necrosis will be followed by a systemic inflammatory response syndrome (SIRS) and will determine the immediate clinical course. The further clinical course is then determined by bacterial infection. SIRS is the cause of bacterial (Gram negative) translocation from the patients colon.
There are several ways to help distinguish between these two forms. One is the above mentioned Ranson Score.
In predicting the prognosis, there are several scoring indices that have been used as predictors of survival. Two such scoring systems are the Ranson criteria and APACHE II (Acute Physiology and Chronic Health Evaluation) indices. Most, but not all studies report that the Apache score may be more accurate. In the negative study of the Apache II, the Apache II 24 hr score was used rather than the 48 hour score. In addition, all patients in the study received an ultrasound twice which may have influenced allocation of co-interventions. Regardless, only the Apache II can be fully calculated upon admission. As the Apache II is more cumbersome to calculate, presumably patients whose only laboratory abnormality is an elevated lipase or amylase do not need prognostication with the Apache II; however, this approach is not studied. The Apache II score can be calculated at www.sfar.org.
Practice guidelines state:
2006: "The two tests that are most helpful at admission in distinguishing mild from severe acute pancreatitis are APACHE-II score and serum hematocrit. It is recommended that APACHE-II scores be generated during the first 3 days of hospitalization and thereafter as needed to help in this distinction. It is also recommended that serum hematocrit be obtained at admission, 12 h after admission, and 24 h after admission to help gauge adequacy of fluid resuscitation."
2005: "Immediate assessment should include clinical evaluation, particularly of any cardiovascular, respiratory, and renal compromise, body mass index, chest x ray, and APACHE II score"
Ranson criteria is a clinical prediction rule for predicting the severity of acute pancreatitis. It was introduced in 1974.
age in years > 55 years
white blood cell count > 16000 cells/mm3
blood glucose > 10 mmol/L (> 200 mg/dL)
serum AST > 250 IU/L
serum LDH > 350 IU/L
At 48 hours
Calcium (serum calcium < 2.0 mmol/L (< 8.0 mg/dL)
Hematocrit fall >10 mmol/l
Oxygen (hypoxemia PO2 < 60 mmHg)
BUN increased by 1.8 or more mmol/L (5 or more mg/dL) after IV fluid hydration
Base deficit (negative base excess) > 4 mEq/L
Sequestration of fluids > 6 L
The criteria for point assignment is that a certain breakpoint be met at anytime during that 48 hour period, so that in some situations it can be calculated shortly after admission. It is applicable to both gallstone and alcoholic pancreatitis.
Alternatively, pancreatitis can be diagnosed by meeting any of the following:
Ranson's score of ≥ 8 Organ failure Substantial pancreatic necrosis (at least 30% glandular necrosis according to contrast-enhanced CT)
Interpretation If the score ≥ 3, severe pancreatitis likely. If the score < 3, severe pancreatitis is unlikely Or
Score 0 to 2 : 2% mortality Score 3 to 4 : 15% mortality Score 5 to 6 : 40% mortality Score 7 to 8 : 100% mortality
Serum calcium < 1.90 mmol/L (<8.0 mg/dL) or serum albumin <33 g/L (<3.2.g/dL)>
Developed in the early 1990s by Emil J. Balthazar et al., the Computed Tomography Severity Index (CTSI) is a grading system used to determine the severity of acute pancreatitis. The numerical CTSI has a maximum of ten points, and is the sum of the Balthazar grade points and pancreatic necrosis grade points:
Appearance on CT
CT Grade Points
Focal or diffuse enlargement of the pancreas
Pancreatic gland abnormalities and peripancreatic inflammation
Fluid collection in a single location
Two or more fluid collections and / or gas bubbles in or adjacent to pancreas
0 to 30% necrosis
30 to 50% necrosis
Over 50% necrosis
CTSI's staging of acute pancreatitis severity has been shown by a number of studies to provide more accurate assessment than APACHE II, Ranson, and C-reactive protein (CRP) level. However, a few studies indicate that CTSI is not significantly associated with the prognosis of hospitalization in patients with pancreatic necrosis, nor is it an accurate predictor of AP severity.
The Glasgow criteria is valid for both gallstone and alcohol induced pancreatitis, whereas the Ranson score is only for alcohol induced pancreatitis. If a patient scores 3 or more it indicates severe pancreatitis and the patient should be transferred to ITU. It is scored through the mnemonic, PANCREAS:
P - PaO2 <8kPa
A - Age >55 years old
N - Neutrophilia - WCC >15x10(9)/L
C - Calcium <2 mmol/L
R - Renal function, Urea >16 mmol/L
E - Enzymes: LDH >600iu/L; AST >200iu/L
A - Albumin <32g/L (serum)
S - Sugar: blood glucose >10 mmol/L
Originally it was thought that analgesia should not be provided by morphine because it may cause spasm of the sphincter of Oddi and worsen the pain, so the drug of choice was meperidine. However, due to lack of efficacy and risk of toxicity of meperidine, more recent studies have found morphine the analgesic of choice.Meperidine may still be used by some practitioners in more minor cases, or where morphine is contraindicated.
In the management of acute pancreatitis, the treatment is to stop feeding the patient, giving him or her nothing by mouth, giving intravenous fluids to prevent dehydration, and sufficient pain control. As the pancreas is stimulated to secrete enzymes by the presence of food in the stomach, having no food pass through the system allows the pancreas to rest. Approximately 20% of patients have a relapse of pain during acute pancreatitis. Approximately 75% of relapses occur within 48 hours of oral refeeding.
The incidence of relapse after oral refeeding may be reduced by post-pyloric enteral rather than parenteral feeding prior to oral refeeding. IMRIE scoring is also useful.
Recently, there has been a shift in the management paradigm from TPN (total parenteral nutrition) to early, post-pyloric enteral feeding (in which a feeding tube is endoscopically or radiographically introduced to the third portion of the duodenum). The advantage of enteral feeding is that it is more physiological, prevents gut mucosal atrophy, and is free from the side effects of TPN (such as fungemia). The additional advantages of post-pyloric feeding are the inverse relationship of pancreatic exocrine secretions and distance of nutrient delivery from the pylorus, as well as reduced risk of aspiration.
Disadvantages of a naso-enteric feeding tube include increased risk of sinusitis (especially if the tube remains in place greater than two weeks) and a still-present risk of accidentally intubating the trachea even in intubated patients (contrary to popular belief, the endotracheal tube cuff alone is not always sufficient to prevent NG tube entry into the trachea). Oxygen may be provided in some patients (about 30%) if Pao2 levels fall below 70mm of Hg.
A subsequent randomized controlled trial that used meropenem 1 gram intravenously every 8 hours for 7 to 21 days stated no benefit; however, 28% of patients in the group subsequently required open antibiotic treatment vs. 46% in the placebo group. In addition, the control group had only 18% incidence of peripancreatic infections and less biliary pancreatitis that the treatment group (44% versus 24%).
In summary, the role of antibiotics is controversial. One recent expert opinion (prior to the last negative trial of meropenem) suggested the use of imipenem if CT scan showed more than 30% necrosis of the pancreas. In mild cases, antibiotics may be avoided since administering virtually any antibiotic does carry some risk in itself.
Clinical deterioration or lack of improvement after 24 hours
Detection of common bile duct stones or dilated intrahepatic or extrahepatic ducts on CT abdomen
The disadvantages of ERCP are as follows :
ERCP precipitates pancreatitis, and can introduce infection to sterile pancreatitis
The inherent risks of ERCP i.e. bleeding
It is worth noting that ERCP itself can be a cause of pancreatitis.
Surgery is indicated for (i) infected pancreatic necrosis and (ii) diagnostic uncertainty and (iii) complications. The most common cause of death in acute pancreatitis is secondary infection. Infection is diagnosed based on 2 criteria
Gas bubbles on CT scan (present in 20 to 50% of infected necrosis)
Positive bacterial culture on FNA (fine needle aspiration, usually CT or US guided) of the pancreas.
Surgical options for infected necrosis include:
Minimally invasive management - necrosectomy through small incision in skin (left flank) or stomach
Conventional management - necrosectomy with simple drainage
Closed management - necrosectomy with closed continuous postoperative lavage
Open management - necrosectomy with planned staged reoperations at definite intervals (up to 20+ reoperations in some cases)
Pancreatic enzyme inhibitors are not proven to work.
Locoregional complications include pancreatic pseudocyst (Most common, occurring in up to 25% of all cases) and phlegmon / abscess formation, splenic artery pseudoaneurysms, hemorrhage from erosions into splenic artery and vein, thrombosis of the splenic vein, superior mesenteric vein and portal veins (in descending order of frequency), duodenal obstruction, common bile duct obstruction, progression to chronic pancreatitis
Annual incidence in the U.S. is 18 per 100,000 population. In a European cross-sectional study, incidence of acute pancreatits increased from 12.4 to 15.9 per 100,000 annually from 1985 to 1995; however, mortality remained stable as a result of better outcomes. Another study showed a lower incidence of 9.8 per 100,000 but a similar worsening trend (increasing from 4.9 in 1963-74) over time.
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