Acute Pancreatitis

Some important definitions

   Diagnosis of Acute Pancreatitis:

¤Two of the following three features

1. Characteristic Abdominal pain

-Acuteonset,severe,persistent,epigastric

2. Serum lipase(or amylase) activity 3 times normal

3.Characteristic findings on CECT (MRI  or US)

¤If (1) and (2) are present, CT is not required for diagnosis in in ER or admission

 

Definition of types of Acute Pancreatitis

♦ Atlanta 92

– Interstitial Pancreatitis

-Sterile Necrotizing Pancreatitis

-Infected Necrotizing Pancreatitis

♦Revised Atlanta 2012

– Interstitial edematous Pancreatitis

-Necrotizing Pancreatitis

• Both types are either sterile or infected

Interstitial edematous Pancreatitis:

♦ Diffuse or focal enlargement

-inflammatory edema

♦ Resolves in the first week

Necrotizing Pancreatitis:

♦ Necrosis of pancreatic parenchyma,peripancreatic tissue or both

◊ impairment of pancreatic perfusion

– Evolves for several days

-Early CECT may underestimate extent of disease

Pancreatic necrosis:

• – Focal/diffuse nonviable pancreatic parenchyma
• – Accompanied by peripancreatic fat necrosis
• -Necrosis can be sterile/infected
• -There is no absolute correlation between extent of necrosis and risk of infection
• -Infected necrosis is rare during the first week

Course and pathophysiology of Acute Pancreatitis

•     Two overlapping phases
• ♦ Early Phase: first week
• -SIRS and organ failure is characteristic.
• – Local complications usually not present: Extent of morphological changes is not proportionate to the severity of organ failure
• – No need to evaluate morphological changes in early phase (in 72 hour)
• ♦ Late phase: after the first week
• -Severity related to persistent organ failure and local complications
• – Local complications:Need for morphological evaluation

                  Definitions of Local Complications

Pancreatic and Peripancreatic collections:

-♦ Collections composed of fluid alone

•Acute peripancreatic Fluid Collections (APFC)- first 4 weeks

• Pancreatic pseudocyst(after 4 weeks)

-♦ Collections in part with solid components

• Acute necrotic collections- first 4 weeks

• Walled-off necrosis (WON)- after 4 weeks

 

– Acute fluid collection occur in 30-50% of acute pancreatitis

-On CT: Low attenuation mass with poor margin and no capsule

– Most resolves spontaneously

-Suspected if:

1.Recurrence of abdominal pain

2.Secondary increase in serum amylase level

3.Increased organ dysfunction or sepsis: increase in CRP,fever,leucocytosis

 

Grades of severity of Acute Pancreatitis:

1.Mild AP:

– No organ failure

– No Local/systemic complications

2. Moderately severe AP:

– Transient organ failure (resolves >48 hours) and/or

-Local or systemic complications without persistent organ failure

3. Severe AP:

-Persistent organ failure(>48 hours): single or multiple

 

Peripancreatic necrosis:

• – Necrotic fatty tissue debris around the pancreas
• – Not appreciated on imaging, so important for surgeons

Pseudocyst:

• – Fluid collection that persists for 4-6 weeks and becomes encapsulated by a fibrous wall or granulation tissue
• – Located adjacent to or body of the pancreas

Walled-off necrosis:

• – Walled-off fluid appearing pseudocyst-like structure involving the pancreas
• – Should be drained after 5-6 weeks later
• Previously termed Organized pancreatic necrosis.

Pancreatic abscess:

• – Circumscribed intra-abdominal collection of pus occurring after an episode of pancreatitis or pancreatic trauma
• – It is not infected necrosis

Hemorrhagic pancreatitis:

• – Not synonymous for necrotizing pancreatitis
• – Hemorrhage is more commonly associated with pseudoaneurysm formation, erosion of peripancreatic blood vessels

Ranson Criteria:

• – Uses 11 signs
• – Disease is mild if score <2
• – Disease is severe if score >
• Drawback of Ranson’s criteria:
• – List is cumbersome
• – Takes 48 hours to complete
• – Not validated beyond 48 hours

 

Glasgow criteria:

• – Slightly simplified list is used
• – Uses 8 criteria
• – Similar drawback as Ranson’s criteria

APACHEII:

• – Uses 12 variables of the patient
• – Most patients survive if APACHEII score ≤9 during the first 48 hours
• – APACHE score ³13 are more likely to die

BISAP Score (Bed Side Index in Acute Pancreatitis):

• – B- BUN>25 mg/dl
• – I- Impaired mental status
• – S-SIRS
• – A-Age >60 years
• – P- Pleural effusion
• – BISAP 4 or 5 is associated with 7-12 fold increased risk of developing organ failure
•  SIRS: 2 or more of the following criteria if present
•                         • Pulse: >90 beats/min
•                         • Respiratory rate: >20/min
•                         • Temp: <36°c or >38°c
•                         • WBC: <4,000/mm³ or >12,000/mm³

                                                   

Diagnostic laboratory parameters:

Amylase:

– Rises within few hours after the symptom onset

– Returns to normal within 3-5 days

– S. Amylase may be in alcohol and triglyceride induced AP

Causes of raised amylase in the absence of AP

• – Macro-amylasemia: Syndrome characterized by formation of large molecular complex between amylase and abnormal immunoglobulin
• – ↓GFR
• – Disease of salivary gland
• – Extrapancreatic abdominal inflammatory disease
•                                     • Acute appendicitis
•                                     • Cholecystitis
•                                     • Intestinal obstruction
•                                     •Intestinal ischemia
•                                     •PUD
•                                     •Gynecological disease

 

 

Walled-off Pancreatic Necrosis (WON)

Pancreatic Necrosis

• – Nonviable pancreas
• – Usually associated with peri-pancreatic fat necrosis
• – Frequently associated with major pancreatic duct disruption
• – Over the course of several weeks
• – Area of necrosis continue to evolve and expand
• – Contain both liquid and solid

 

Indications for drainage of sterile WON

• – Refractory abdominal pain
• – Gastric outlet obstruction
• – Failure to thrive at 4 or more weeks after the onset of AP

*Endoscopic drainage of pancreatic necrosis is technically difficult than drainage of pseudocyst

 

Alternative management of pancreatic necrosis

• – Nutritional support with parenteral/ enteral (jejunal feeding)
• – Non endoscopic drainage
•                 • Percutaneous drainage
•                 • Surgical drainage
•                 • Minimally invasive surgical drainage
• – Because of the need to evacuate solid material,the endoscopic approach to drain WON differs from pseudocyst drainage
• – Endoscopic endoscopic transmural drainage is prefereable to endoscopic transpapillary draingae as transpapillary route is not adequate for drainage of solid debris.