Acute Pancreatitis

Acute pancreatitis refers to inflammation of the pancreas.

It can be distinguished from chronic pancreatitis by its limited damage to the secretory function of the gland, with no gross structural damage developing.

Acute pancreatitis has an increasing incidence in the UK, described in the literature at around 152 per million each year, with a regional variation. Mortality figures can range between 5-30%, depending on severity.

In this article, we shall look at the causes, clinical features and management of acute pancreatitis.


Aetiology

The majority of acute pancreatitis cases occur secondary to gallstone disease or excess alcohol consumption. However, causes are wide ranging and a popular mnemonic is ‘GET SMASHED’:

  • Fig 1 - The biliary tree. A gallstone in the ampulla of Vater is a common cause of acute pancreatitis.

    Fig 1 – The biliary tree. A gallstone in the ampulla of Vater is a common cause of acute pancreatitis.

    Gallstones

  • Ethanol (Alcohol)
  • Trauma
  • Steroids
  • Mumps
  • Autoimmune disease, such as SLE
  • Scorpion venom (a rare and unlikely cause in the UK)
  • Hypercalcaemia
  • Endoscopic retrograde cholangio-pancreatography (ERCP)
  • Drugs, such as Azathioprine, NSAIDs, or Diuretics

Pathogenesis

Each cause described above will trigger a premature and exaggerated activation of the digestive enzymes within the pancreas. The resulting pancreatic inflammatory response causes an increase in vascular permeability and subsequent fluid loss into the third space (transcellular space, e.g. peritoneal cavity).

Enzymes are also released from the pancreas into the systemic circulation, causing the autodigestion of fats (resulting in a ‘fat necrosis’) and blood vessels (sometimes leading to haemorrhage in the retroperitoneal space). Fat necrosis can cause the release of free fatty acids, reacting with serum calcium to form chalky deposits in fatty tissue, resulting in hypocalcaemia.

Severe end-stage pancreatitis will eventually result in partial or complete necrosis of the pancreas.


Clinical Features

Patients will classically present with a sudden onset of severe epigastric pain, which can radiate through to the back, with nausea and vomiting.

On examination, there may be epigastric tenderness, but often a soft abdomen with normal bowel sounds. However, severe acute pancreatitis can present with signs of guarding and a rigid abdomen, with potential circulatory instability (including hypovolaemic shock).

Rarer signs that are often described are Grey Turner’s Sign (bruising in the flanks) and Cullen’s Sign (bruising around the umbilicus), representing retroperitoneal haemorrhage. Tetany may occur from hypocalcaemia secondary to fat necrosis, and any gallstone pathology may also result in a concurrent jaundice or cholangitis clinical picture.

Fig 1 - Clinical Signs of Retroperitoneal Haemorhhage, as seen in acute pancreatitis (A) Cullen's Sign (B) Grey-Turner's Sign

Fig 1 – Clinical Signs of Retroperitoneal Haemorhhage, as seen in acute pancreatitis (A) Cullen’s Sign (B) Grey-Turner’s Sign


Differential Diagnosis

There are a wide variety of causes of an acutely painful abdomen, as discussed elsewhere on the site.

However causes specifically resulting in abdominal pain that radiates through to the back include symptomatic or ruptured AAA, chronic pancreatitis, aortic dissection, and a duodenal ulcer.


Investigations

Laboratory Tests

Routine bloods, as per investigation of any acute abdomen, are required. Specifically for acute pancreatitis, it is important to consider:

  • Serum amylase – diagnostic of acute pancreatitis if 3x the upper limit of normal*
    • Also raised in bowel perforation, ectopic pregnancy, mesenteric ischaemia, and DKA.
  • LFTs – assess for any concurrent cholestatic element to the clinical picture (e.g. gallstones causing post-hepatic jaundice).

A raised serum lipase is more accurate for acute pancreatitis (as it remains elevated longer than amylase), yet it is not available or routinely performed at every hospital.

*Serum amylase levels do not directly correlate with disease severity

Imaging

An abdominal ultrasound scan may be requested if the underlying cause is unknown. It is typically used to identify a possible gallstone, by demonstrating dilation of the bile ducts.

Whilst not routinely performed for acute pancreatitis, an AXR taken can show a ‘sentinal loop sign’. This is a dilated proximal bowel loop adjacent to the pancreas, which occurs secondary to localised inflammation.

A contrast-enhanced CT scan can be performed if the clinical assessment and blood tests prove inconclusive. If performed after 48hrs from initial presentation, it will often show areas of pancreatic oedema and swelling, as well as any potential complications that may have developed.

Fig 2 - Pancreatitis on Axial CT Scan (A) Localised oedema around the pancreas (B) Extensive fluid collections around the pancreas

Fig 2 – Pancreatitis on Axial CT Scan (A) Localised oedema around the pancreas (B) Extensive fluid collections around the pancreas

Risk Scoring

The modified Glasgow criteria is used to assess the severity of acute pancreatitis within the first 48hrs of admission. Any patient scoring with ≥3 positive factors within the first 48hrs should be considered to have a ‘severe’ pancreatitis and a high-dependency care referral is warranted.

Helpfully, the mneumonic to remember the score is PANCREAS:
pO2 <8kPa
Age >55yrs
Neutrophils (/WCC) >15×109/L
Calcium <2mmol/L
Renal function (Urea) >16mmol/L
Enzymes LDH>600U/L or AST>200U/L
Albumin <32g/L
Sugar (blood glucose) >10mmol/L

Other risk scores that can be used scoring severity of acute pancreatitis include the APACHE II score (a severity of disease classification used for any disease on admission to ICU) and the Ranson Criteria

Management

There is no curative management for acute pancreatitis, so supportive measures are the mainstay of treatment. Treat any underlying cause as necessary (e.g. urgent ERCP and sphincterotomy if gallstones are demonstrated within the common bile duct).

Supportive treatment includes:

  • High-flow oxygen 
  • IV fluid resuscitation
    • ACG guidelines recommend 250-500ml/hr of crystalloid solution to be given to all patients (unless CVS or renal co-morbidites) in the initial period, with Hartmann’s solution as the preferred choice of fluid.
    • Due to the potential for rapid third space losses, close fluid monitoring is essential. Start a fluid balance chart.
  • Nasogastric tube – if the patient is vomiting profusely.
    • Make the patient nil-by-mouth.
  • Catheterisation – to accurately monitor urine output.
    • Aim for a urine output of at least >0.5ml/kg/hr and check U&Es regularly.
  • Opioid analgesia
    • A recent Cochrane review stated there is no current evidence that suggests opioid analgesia should be avoided due to increased risk of pancreatitis complications or other adverse events when compared to other analgesia.

Current UK guidelines state that all patients with severe acute pancreatitis should be managed in a high dependency unit or intensive therapy unit (although this is often impractical). A broad-spectrum antibiotic, such as Imipenem, should be considered for prophylaxis against infection in cases of confirmed pancreatic necrosis, as studies have shown a decreased mortality with their use.


Complications

Systemic Complications

The systemic complications of acute pancreatitis tend to occur within days of the initial onset:

Fig 4 - Pulmonary oedema in acute respiratory distress syndrome, which can occur as a complication of acute pancreatitis.

Fig 4 – Pulmonary oedema in acute respiratory distress syndrome, which can occur as a complication of acute pancreatitis.

  • DIC
  • Acute Respiratory Distress Syndrome (ARDS)
  • Hypocalcaemia
  • Hyperglycaemia
    • Secondary to disturbances of insulin metabolism
  • Hypovolemic shock and multiorgan failure

Local Complications

Pancreatic Necrosis

Ongoing inflammation eventually leads to ischaemic infarction of the pancreatic tissue. This presents in a patient with an ongoing acute pancreatitis and rising CRP, confirmed by CT scan. Pancreatic necrosis is prone to becoming infected and may require a pancreatic necrosectomy (open or endoscopic).

Any infected pancreatic necrosis should be suspected if a positive blood culture, changes of low density within the pancreas, or patient’s condition deteriorates with a high WCC. Definitive diagnosis of infected pancreatic necrosis can be confirmed by a fine needle aspiration of the necrosis, yet it can associated with a risk of seeding infection therefore it must be performed with care.

Pancreatic Pseudocyst

A pancreatic pseudocyst is a collection of fluid within the pancreatic tissue. It is typically formed weeks after the initial acute pancreatitis episode, whereby the inflammatory reaction produces a necrotic space in the pancreas that fills with pancreatic fluid, surrounded by fibrous tissue.

As it lacks epithelial or endothelial cells surrounding the collection, it is termed a pseudocyst.  Pseudocysts may be found incidentally on imaging or can present with symptoms of mass effect, such as biliary obstruction or gastric outlet obstruction. They are prone to haemorrhage or rupture, and can become infected.

Cysts which have been present for longer than 6 weeks are unlikely to resolve spontaneously. Treatment options include surgical debridement or endoscopic drainage (into the stomach)

Further Reading

Opioids for acute pancreatitis pain
Basurto Ona X et al., Cochrane Review

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