Acute pancreatitis essay

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Acute Pancreatitis

Introduction

Acute pancreatitis (AP) is a sudden inflammatory condition of the pancreas that represents one of the most common gastrointestinal causes of hospital admission. Its incidence in the USA has been rising over recent decades. The disease spans a wide clinical spectrum: approximately 80% of cases are mild and self-limiting, resolving within a few days, while up to 20% develop severe disease with life-threatening local and systemic complications. Mortality from severe AP can approach 30-50% when multiple organ failure supervenes.

Aetiology

The two dominant causes globally are gallstones (~40-50%) and alcohol (~25-35%), together accounting for the vast majority of cases. The mnemonic "I GET SMASHED" captures the full differential: Idiopathic, Gallstones, Ethanol, Trauma, Steroids, Mumps (and other viruses), Autoimmune, Scorpion venom, Hyperlipidaemia/Hypercalcaemia, ERCP, Drugs.

Gallstone pancreatitis arises from transient or sustained impaction of a stone or sludge within the ampulla of Vater, obstructing the common channel and triggering ductal hypertension. Alcohol causes AP by promoting premature activation of digestive enzymes within acinar cells. Hypertriglyceridaemia (types I and V hyperlipoproteinaemia) is thought to liberate toxic free fatty acids into the pancreatic microcirculation, causing ischaemia. Drug-induced AP is relatively uncommon and has been associated with thiazide diuretics, furosemide, oestrogens, steroids, azathioprine, valproate, and L-asparaginase among others. Post-ERCP pancreatitis is an important iatrogenic cause, with an incidence of around 3-5% after the procedure. Hereditary pancreatitis is linked to gain-of-function mutations in PRSS1 (cationic trypsinogen) and loss-of-function mutations in SPINK1 and CFTR, collectively predisposing to premature trypsinogen activation.

Pathophysiology

The central event in AP is the premature, intrapancreatic activation of digestive zymogens - a concept first proposed by Chiari in 1896. Under normal physiology, multiple protective mechanisms prevent autodigestion: enzymes are synthesised as inactive precursors, their site of production is separated from their site of activation, and trypsin inhibitors (e.g. SPINK1) are present within the gland. When these defences are overwhelmed, intra-acinar trypsinogen is converted to active trypsin, which in turn activates a cascade of other enzymes (elastase, phospholipase A2, chymotrypsin), producing pancreatic autodigestion.

The severity of the attack is not solely determined by this initial precipitating event but by the systemic inflammatory response that follows. Acinar cell damage triggers inflammatory cell recruitment, with release of pro-inflammatory cytokines - notably TNF-α, IL-1, IL-6, and IL-8 - into the systemic circulation. This causes the systemic inflammatory response syndrome (SIRS). Early systemic complications (shock, ARDS, AKI) are driven by this hyperinflammatory state. In the later phase, immune paralysis and compensatory anti-inflammatory response syndrome (CARS) predisposes to septic complications such as infected pancreatic necrosis.

The intestine plays a pivotal role: mucosal barrier breakdown allows translocation of gut bacteria, further fuelling systemic sepsis. Pancreatic necrosis results from occlusion of the small vessels supplying the gland; infection of necrotic tissue, typically with enteric gram-negative organisms, is the single most important determinant of mortality in severe AP.

Clinical Features

AP classically presents with severe, constant epigastric pain, often radiating to the back or left scapular region, reaching maximum intensity within 30-60 minutes. The pain is characteristically relieved by sitting forward (leaning position). Nausea, vomiting, fever, anorexia, and abdominal distension from an associated ileus are typical accompanying features.

On examination, patients appear acutely unwell and are tachycardic, tachypnoeic, and febrile. Abdominal tenderness is maximal in the epigastrium with guarding. Bowel sounds are reduced. Two rare but important signs reflect haemorrhagic pancreatitis with dissection of blood along fascial planes:

Cullen's sign: periumbilical bruising
Grey-Turner's sign: flank bruising

Peripheral signs of shock (cool, cyanotic extremities, hypotension) indicate severe disease with significant third-space fluid losses.

Investigations

Serum amylase rises within 2-12 hours and is typically elevated more than 3 times the upper limit of normal; however, it is neither highly sensitive nor specific (can be elevated in other abdominal emergencies such as perforated peptic ulcer or mesenteric ischaemia). Serum lipase is more sensitive and specific, remains elevated longer, and is the preferred diagnostic enzyme.

Additional bloods include FBC (leucocytosis 12,000-20,000/mm³ is common), U&E, LFTs (elevated bilirubin and transaminases suggest biliary aetiology), calcium (hypocalcaemia from saponification), glucose (hyperglycaemia from loss of islet function), CRP (a CRP >150 mg/L at 48 hours predicts severity), and ABG (hypoxaemia in ARDS).

Ultrasound is the first-line imaging investigation - it identifies gallstones in the gallbladder and can detect biliary dilatation. Its sensitivity for pancreatic oedema is limited by overlying bowel gas.

CT with IV contrast (contrast-enhanced CT - CECT) is the gold standard for assessment of pancreatic necrosis and local complications. It should be reserved for patients with severe or complicated disease, or diagnostic uncertainty, and is ideally performed 48-72 hours after onset to accurately delineate necrosis. The CT Severity Index (CTSI, or Balthazar score) grades inflammation and necrosis and correlates with morbidity.

MRCP or endoscopic ultrasound (EUS) can identify bile duct stones in suspected biliary pancreatitis without the risks of ERCP.

Severity Assessment

Accurate severity stratification guides management decisions around triage to HDU/ITU, fluid resuscitation, and the need for intervention. The widely used tools include:

Atlanta Classification (revised 2012): Mild - no organ failure, no complications; Moderately severe - transient organ failure (<48 hours) or local complications; Severe - persistent organ failure (>48 hours), single or multi-organ.
Ranson's Criteria: 11 clinical and biochemical parameters scored over 48 hours (5 at admission, 6 at 48 hours). <3 predicts mild disease; >6 carries 50% mortality risk.
BISAP score: BUN >25 mg/dL, impaired mental status (GCS <15), SIRS, age >60, pleural effusion - all assessable within 24 hours of admission.
APACHE II: A score ≥8 at 24 hours predicts severe disease.
CRP: >150 mg/L at 48 hours is a reliable marker of severity.

Management

Initial Resuscitation

The cornerstone of early management is aggressive IV fluid resuscitation with crystalloids (lactated Ringer's solution is preferred over normal saline based on evidence of reduced SIRS and organ failure). Large volumes are required to compensate for third-space losses, vomiting, and insensible losses. Fluid balance and haemodynamic parameters must be closely monitored.

Analgesia

Adequate pain control is essential. IV opioids (e.g. morphine or tramadol) are used; the old teaching that morphine causes sphincter of Oddi spasm has largely been abandoned in clinical practice.

Nutritional Support

Patients should be kept nil by mouth only in the immediate period. Early enteral nutrition (within 24-48 hours) via nasogastric or nasojejunal tube is now strongly preferred over parenteral nutrition in severe AP. Enteral feeding preserves the gut mucosal barrier, reduces bacterial translocation, and is associated with fewer infectious complications and lower cost. Nasogastric feeding is as effective as post-ligament of Treitz placement in most patients.

Antibiotics

Prophylactic antibiotics are not recommended in AP - multiple randomised trials have failed to show a mortality benefit and they may promote fungal superinfection. Antibiotics are reserved for proven or strongly suspected infected necrosis, ideally guided by fine-needle aspiration (FNA) culture.

Biliary Pancreatitis

In gallstone pancreatitis with concurrent cholangitis or biliary obstruction, early ERCP (within 24-72 hours) is indicated. Early laparoscopic cholecystectomy (within 3 days) in mild biliary pancreatitis improves outcomes and is the standard of care. In patients unfit for surgery, endoscopic biliary sphincterotomy reduces the risk of recurrent episodes.

Management of Local Complications

Local complications include peri-pancreatic fluid collections, acute pancreatic pseudocysts, pancreatic necrosis (sterile or infected), and walled-off necrosis (WON). Most acute fluid collections resolve spontaneously. Pseudocysts require at least 4 weeks to encapsulate and should only be drained if symptomatic or enlarging. Infected pancreatic necrosis requires drainage, now typically via minimally invasive approaches: endoscopic ultrasound-guided transmural drainage, percutaneous CT-guided drainage, or video-assisted retroperitoneal debridement (VARD). Open necrosectomy carries higher morbidity and is avoided where possible. The "step-up" approach (percutaneous/endoscopic drainage first, proceeding to surgery only if needed) has become the standard of care.

Complications

Local complications include pseudocyst, infected necrosis, and splenic/portal vein thrombosis. Systemic complications include ARDS (from phospholipase A2-mediated surfactant destruction and cytokine-driven lung injury), AKI, DIC, hyperglycaemia, and hypocalcaemia. Colonic infarction from thrombosis of the middle or right colic artery is a rare but catastrophic complication requiring immediate laparotomy.

Conclusion

Acute pancreatitis is a dynamic disease with outcomes ranging from full recovery to death from multi-organ failure. Early recognition, aggressive fluid resuscitation, prompt severity stratification, and early enteral nutrition are the key pillars of management. Cause-directed therapy - particularly early cholecystectomy in biliary pancreatitis - reduces recurrence. Infected necrosis remains the main driver of late mortality and is now managed via minimally invasive step-up approaches. A thorough understanding of its pathophysiology and the rational use of severity scores remains essential for the clinical management of this condition.

Sources: Sleisenger & Fordtran's Gastrointestinal and Liver Disease; Harrison's Principles of Internal Medicine 20e; Clinical Gastrointestinal Endoscopy 3e; Pye's Surgical Handicraft 22e

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Here is the same essay rewritten in structured bullet-point format, suitable for a clinical medical student exam answer:

Acute Pancreatitis

Definition

Acute inflammatory condition of the pancreas caused by premature activation of pancreatic digestive enzymes
Incidence is rising; one of the most common GI causes of hospital admission
~80% mild and self-limiting; ~20% severe with significant morbidity and mortality

Aetiology

Common causes (mnemonic: I GET SMASHED):

I - Idiopathic
G - Gallstones (40-50%) - most common cause; impaction at ampulla of Vater
E - Ethanol (25-35%) - promotes intra-acinar enzyme activation
T - Trauma - blunt abdominal injury, post-surgical
S - Steroids
M - Mumps and other viruses (coxsackievirus, EBV)
A - Autoimmune (IgG4-related disease)
S - Scorpion venom / Sepsis
H - Hyperlipidaemia (types I and V) / Hypercalcaemia
E - ERCP (iatrogenic; ~3-5% incidence post-procedure)
D - Drugs: thiazides, furosemide, oestrogens, azathioprine, valproate, L-asparaginase

Pathophysiology

Initiating event:

Premature intra-acinar activation of trypsinogen → active trypsin
Trypsin activates downstream enzymes: elastase, phospholipase A2, chymotrypsin
Results in autodigestion of the gland ("Chiari's hypothesis," 1896)
Normally prevented by: synthesis of enzymes as inactive zymogens, physical separation of production and activation sites, trypsin inhibitors (SPINK1)

Local consequences:

Acinar cell injury → inflammatory cell recruitment → cytokine release (TNF-α, IL-1, IL-6, IL-8)
Oedema, haemorrhage, fat necrosis, and vascular occlusion → pancreatic necrosis in severe disease
Gut mucosal barrier breakdown → bacterial translocation → infected necrosis

Systemic consequences:

Cytokines enter circulation → SIRS (Systemic Inflammatory Response Syndrome)
Early phase: SIRS-driven organ failure (shock, ARDS, AKI)
Late phase: immune paralysis (CARS) → septic complications from infected necrosis
ARDS caused by phospholipase A2-mediated surfactant destruction and cytokine-driven lung injury

Clinical Features

Symptoms:

Severe, constant epigastric pain - reaches maximum intensity within 30-60 minutes
Radiates to the back or left scapular region (boring/penetrating character)
Relieved by sitting forward (leaning position)
Nausea, vomiting, fever, anorexia
Abdominal distension from paralytic ileus

Signs:

Acutely unwell; tachycardia, tachypnoea, fever
Epigastric tenderness with guarding; reduced bowel sounds
Cullen's sign - periumbilical bruising (haemorrhagic pancreatitis)
Grey-Turner's sign - flank bruising (haemorrhagic pancreatitis)
Cool, cyanotic extremities / hypotension - indicate shock and severe disease

Investigations

Bloods:

Serum lipase - preferred; more sensitive and specific than amylase, remains elevated longer
Serum amylase - rises within 2-12 hours; >3x upper limit of normal is diagnostic; less specific
FBC: leucocytosis (12,000-20,000/mm³)
U&E: raised BUN (severity marker), electrolyte disturbance
LFTs: elevated bilirubin/transaminases suggest biliary cause
Serum calcium: hypocalcaemia from saponification of fat
Blood glucose: hyperglycaemia from islet dysfunction
ABG: hypoxaemia suggests ARDS
CRP: >150 mg/L at 48 hours predicts severity

Imaging:

Ultrasound (first-line): identifies gallstones, biliary dilatation; limited pancreatic visualisation
Contrast-enhanced CT (CECT) (gold standard): assesses necrosis and local complications; reserved for severe/complicated disease; ideally performed at 48-72 hours
CT Severity Index (CTSI/Balthazar score): grades inflammation and necrosis; correlates with morbidity
MRCP/EUS: identifies bile duct stones without ERCP risk; preferred in suspected biliary pancreatitis

Severity Assessment

Revised Atlanta Classification (2012):

Mild - no organ failure, no local/systemic complications
Moderately severe - transient organ failure (<48 hours) OR local complications
Severe - persistent organ failure (>48 hours), single or multi-organ

Scoring systems:

Ranson's Criteria - 11 parameters over 48 hours (5 at admission, 6 at 48h); <3 = mild; >6 = 50% mortality
BISAP score - BUN >25, impaired mental status, SIRS, age >60, pleural effusion; assessable within 24 hours
APACHE II - score ≥8 at 24 hours predicts severe disease
CRP - >150 mg/L at 48 hours; simple and reliable
Modified Glasgow (Imrie) criteria - 8 parameters at 48 hours; ≥3 = severe

Ranson's Criteria (non-gallstone) - key parameters:

At Admission	At 48 Hours
Age >55	Haematocrit fall >10%
WBC >16,000/mm³	BUN rise >5 mg/dL
Glucose >200 mg/dL	Calcium <8 mg/dL
LDH >350 IU/L	PO₂ <60 mmHg
AST >250 U/dL	Base deficit >4 mEq/L
	Fluid sequestration >6 L

Management

Immediate resuscitation:

Aggressive IV fluid resuscitation - lactated Ringer's preferred over normal saline (reduced SIRS, organ failure)
Close monitoring of haematodynamics, urine output, fluid balance
NBM initially; supplement with IV fluids

Analgesia:

IV opioids (morphine, tramadol) - old concern about sphincter of Oddi spasm is largely discarded

Nutritional support:

Early enteral nutrition within 24-48 hours - strongly preferred over parenteral nutrition in severe AP
Nasogastric feeding is as effective as nasojejunal (post-Treitz) feeding in most patients
Benefits: preserves gut mucosal barrier, reduces bacterial translocation, fewer infectious complications, lower cost

Antibiotics:

Prophylactic antibiotics are NOT recommended - multiple RCTs show no mortality benefit; risk of fungal superinfection
Antibiotics indicated only for proven/strongly suspected infected pancreatic necrosis

Biliary pancreatitis - specific management:

ERCP within 24-72 hours if concurrent cholangitis or biliary obstruction (hyperbilirubinaemia + clinical cholangitis)
Early laparoscopic cholecystectomy (within 3 days) in mild biliary pancreatitis - standard of care; reduces recurrence
If unfit for surgery: endoscopic biliary sphincterotomy reduces recurrent AP

Local complications:

Acute peripancreatic fluid collections - usually resolve spontaneously
Pseudocyst (≥4 weeks to encapsulate) - drain only if symptomatic/enlarging; endoscopic ultrasound-guided or percutaneous drainage
Infected pancreatic necrosis - drainage required; step-up approach preferred:
1. Percutaneous CT-guided or endoscopic transmural drainage
2. Video-assisted retroperitoneal debridement (VARD) if step 1 fails
3. Open necrosectomy - last resort; high morbidity

Complications

Local	Systemic
Infected pancreatic necrosis	ARDS
Pseudocyst	AKI
Walled-off necrosis (WON)	Septic shock
Splenic/portal vein thrombosis	DIC
Colonic infarction (rare, catastrophic - needs laparotomy)	Hypocalcaemia, Hyperglycaemia

Prognosis

Mild AP: full recovery in days; very low mortality
Severe AP: mortality 20-30%; up to 50% if >6 Ranson criteria met
Main cause of late mortality: infected pancreatic necrosis
Main cause of early mortality: multi-organ failure from SIRS

Sources: Sleisenger & Fordtran's Gastrointestinal and Liver Disease; Harrison's Principles of Internal Medicine; Clinical Gastrointestinal Endoscopy 3e

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