Important Diseases Causing Abdominal Pain
3.1. Acute Pancreatitis
Definition
Acute pancreatitis is an acute inflammatory process of the pancreas with variable involvement of regional tissues or remote organ systems 1. The condition results from intrapancreatic activation of digestive enzymes leading to autodigestion and local inflammatory response 2.
Etiology and Pathogenesis
The two most common causes are gallstones (45-60% of cases) and alcohol (20-25% of cases) 3. Other important etiologies include:
- Hypertriglyceridemia (4-10% of cases, third most common cause) 3
- Drug-induced: Azathioprine/6-mercaptopurine (4% of IBD patients), mesalazine (lower risk) 1, 3
- Post-ERCP 1
- Idiopathic causes including microlithiasis 4
- Cholesterolosis (gallbladder polyps causing mechanical obstruction) 5
The pathogenesis involves premature activation of pancreatic enzymes within the gland, triggering autodigestion, local inflammation, and potentially systemic inflammatory response syndrome (SIRS) with organ failure 2.
Morphology and Classification
The 2012 revised Atlanta classification is the standard system, categorizing severity as mild, moderate, or severe based on organ failure duration and local complications 1:
- Mild: Interstitial edematous pancreatitis with no organ failure, local complications, or systemic complications; resolves within first week 1
- Moderate: Transient organ failure (<48 hours), local complications, or exacerbation of comorbidities 1
- Severe: Persistent organ failure (>48 hours) with mortality rate of approximately 15% 1
Morphologic complications include 1:
- Acute fluid collections: Early collections lacking fibrous wall 1
- Pancreatic necrosis: Diffuse or focal non-viable pancreatic parenchyma with peripancreatic fat necrosis 1
- Infected necrosis: Occurs in 20-40% of severe cases; mortality 35.2% with organ failure vs 1.4% without 1
- Acute pseudocyst: Pancreatic juice collection with fibrous wall, requires ≥4 weeks to form 1
- Pancreatic abscess: Circumscribed pus collection with little/no necrosis 1
Clinical Features
Classic presentation includes epigastric pain radiating to the back, worse with eating, accompanied by nausea and vomiting 6, 7. Pain characteristics vary by severity:
- Severe, sudden onset pain is typical 6
- Persistent severe pain with prolonged ileus indicates severe disease 6
- Periumbilical or flank ecchymoses may occur in severe cases 6
Diagnosis
Diagnosis requires meeting at least two of three criteria 8, 7:
- Epigastric abdominal pain consistent with pancreatitis 8, 7
- Serum lipase or amylase >3 times upper limit of normal 8, 7
- Imaging findings of pancreatic inflammation 8, 7
Critical diagnostic workup includes 1:
- Right upper quadrant ultrasound to identify gallstones 1
- Dynamic CT scan between 3-10 days for all severe cases to assess necrosis 1, 2
- Fine needle aspiration to confirm infected necrosis when suspected 9
Common pitfall: Asymptomatic elevated lipase occurs in 7% of IBD patients, making diagnosis challenging when abdominal pain is present 1.
Management
Initial management for mild cases includes moderate fluid resuscitation, pain control, and early oral feeding within 24 hours 1, 7. The "nothing by mouth" approach is no longer recommended 7.
For severe acute pancreatitis, management must occur in HDU/ITU setting with full systems support 1, 2:
- Fluid resuscitation: Aggressive but cautious approach in first 24 hours 8
- Pain control: Intravenous opiates used judiciously are safe 8
- Nutritional support: Enteral feeding (nasogastric or nasojejunal) if oral feeding not tolerated 9, 7
- Antibiotics: Only for radiologically confirmed infected necrosis or systemic infection, NOT prophylactically 9, 7
Etiology-specific interventions 1, 3, 2:
- Gallstone pancreatitis with cholangitis/jaundice: ERCP with sphincterotomy and stone extraction urgently 1, 2
- Mild gallstone pancreatitis: Definitive management (cholecystectomy) within 2-4 weeks 1
- Hypertriglyceridemia-associated: Insulin and/or heparin, plasmapheresis for severe cases 3
Patients with extensive necrotizing pancreatitis require referral to specialist units with multidisciplinary expertise including ICU, interventional radiology, emergency ERCP capability, and pancreatico-biliary surgical expertise 1.
Course and Prognosis
Overall mortality is 10-15% for diagnosed cases, with approximately one-third of deaths occurring early from multiple organ failure 1. Most deaths after the first week result from infected necrosis 1.
Mortality rates by complication 1:
- Infected necrosis with organ failure: 35.2%
- Sterile necrosis with organ failure: 19.8%
- Infected necrosis without organ failure: 1.4%
Recurrence risk is substantial: Nearly 50% for alcoholic pancreatitis, 32-61% for untreated gallstone pancreatitis 4. Long-term sequelae include diabetes mellitus (one-third to one-half of patients) and chronic pancreatitis (3-13%) 4.
3.2. Cholelithiasis
General Considerations
Cholelithiasis (gallstones) represents the formation of solid crystalline deposits within the gallbladder, serving as the leading cause of acute pancreatitis globally 3.
Prevalence and Risk Factors
Gallstones account for 45-60% of acute pancreatitis cases 3. Risk factors include:
- Female sex
- Obesity (emerging cofactor) 9
- Age >50 years (requires tumor exclusion with first presentation) 9
- Genetic susceptibility 9
- Microlithiasis (small stones often missed on standard imaging) 9, 4
Pathogenesis
Gallstones cause pancreatitis through mechanical obstruction of the ampulla of Vater and sphincter of Oddi, leading to reflux of bile into the pancreatic duct and subsequent enzyme activation 5. Even cholesterol polyps (cholesterolosis) without frank stones can cause mechanical obstruction and pancreatitis 5.
Clinical Features
Gallstone pancreatitis presents identically to other forms of acute pancreatitis with epigastric pain radiating to the back 6, 7. The presence of jaundice or cholangitis indicates biliary obstruction requiring urgent intervention 1, 2.
Natural History
Without treatment, recurrence risk ranges from 32-61% 4. After initial episode, the risk of developing chronic pancreatitis is 3-13% 4.
Diagnosis
Right upper quadrant ultrasound is mandatory in all acute pancreatitis cases to identify gallstones 1. For suspected microlithiasis, endoscopic ultrasound may be necessary 9.
Management
For mild gallstone pancreatitis without complications, definitive management (cholecystectomy) should occur within 2 weeks, no longer than 4 weeks 1.
For severe gallstone pancreatitis with jaundice or cholangitis, urgent ERCP with sphincterotomy and stone extraction or stenting is required 1, 2. This intervention directly impacts mortality by relieving biliary obstruction 2.
3.3. Acute Cholecystitis
Etiology and Pathogenesis
Acute cholecystitis results from inflammation of the gallbladder wall, most commonly (>90% of cases) due to cystic duct obstruction by gallstones. The obstruction leads to:
- Increased intraluminal pressure
- Gallbladder wall ischemia
- Chemical inflammation from concentrated bile
- Secondary bacterial infection (in 50-70% of cases)
Acalculous cholecystitis (5-10% of cases) occurs in critically ill patients, post-surgery, or with severe systemic illness.
Clinical Features
Classic presentation includes right upper quadrant pain, fever, and Murphy's sign (inspiratory arrest during right upper quadrant palpation). Additional features include:
- Nausea and vomiting
- Leukocytosis
- Pain may radiate to right shoulder or scapula
- Jaundice (suggests Mirizzi syndrome or choledocholithiasis)
Diagnosis
Diagnosis combines clinical features with imaging findings:
- Right upper quadrant ultrasound is first-line: shows gallbladder wall thickening (>4mm), pericholecystic fluid, gallstones, sonographic Murphy's sign 1
- HIDA scan when ultrasound equivocal: non-filling of gallbladder indicates cystic duct obstruction
- CT scan for complicated cases or alternative diagnoses
Management
Early cholecystectomy (within 72 hours of symptom onset) is the definitive treatment and reduces complications compared to delayed surgery. Management approach:
- Initial stabilization: IV fluids, antibiotics (covering gram-negative and anaerobic organisms), pain control
- Laparoscopic cholecystectomy is preferred approach
- Percutaneous cholecystostomy for high-risk surgical candidates
- ERCP if concurrent choledocholithiasis or cholangitis 1, 2
Antibiotics alone without source control lead to 20-30% failure rate and high recurrence risk, making surgical intervention essential for definitive management.