36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis

Spectrum of Gallbladder & Biliary Tract Diseases

Gallstone disease (cholelithiasis) affects over 20 million adults in the United States, representing one of the leading causes of ambulatory gastrointestinal visits and hospital admissions. The clinical spectrum spans from benign, silent gallstones to life-threatening ascending biliary sepsis.

Gallstone Pathogenesis & Classification

• Cholesterol Gallstones (75% to 80% of Cases): Formed when hepatic secretion of cholesterol exceeds the solubilizing capacity of bile salts and phospholipids (lecithin), leading to cholesterol supersaturation, accelerated crystal nucleation, and gallbladder hypomotility. Major risk factors are summarized by the classic mnemonic: Female, Forty, Fertile, and Fat (multiparity/estrogen exposure, obesity, rapid weight loss/bariatric surgery, and fibrate therapy).
• Black Pigment Gallstones (10% to 15% of Cases): Composed of calcium bilirubinate polymers. Driven by high concentrations of unconjugated bilirubin resulting from chronic hemolysis (sickle cell anemia, hereditary spherocytosis, beta-thalassemia major, malaria) and advanced cirrhosis (impaired bilirubin glucuronidation).
• Brown Pigment Gallstones (<5% of Cases): Form de novo within the intrahepatic or extrahepatic bile ducts in the presence of chronic biliary stasis and bacterial/parasitic infection (Escherichia coli, Klebsiella, Clonorchis sinensis). Bacterial beta-glucuronidase hydrolyzes conjugated bilirubin into insoluble unconjugated bilirubin precipitates.

Asymptomatic Cholelithiasis: Management & High-Risk Exceptions

• Natural History: Gallstones are discovered incidentally during routine abdominal imaging in 10% to 20% of adults. Approximately 60% to 80% remain completely asymptomatic throughout life, with only 1% to 2% per year progressing to symptomatic biliary colic.
• Management: Expectant observation (watchful waiting) is the universal standard of care. Prophylactic cholecystectomy is NOT recommended because the risks of general anesthesia and surgical bile duct injury outweigh the lifetime risk of developing symptomatic disease.
• Specific High-Risk Exceptions Mandating Prophylactic Cholecystectomy:
  1. Porcelain Gallbladder: Extensive transmural calcification of the gallbladder wall secondary to chronic inflammation; historically associated with a high incidence (up to 2% to 15%) of aggressive gallbladder adenocarcinoma.
  2. Large Gallstones (>3 cm in Diameter): Carry a tenfold increased risk of gallbladder carcinoma and a markedly increased risk of erosion into adjacent duodenum, causing cholecystoenteric fistula and mechanical gallstone ileus.
  3. Hemolytic Hemoglobinopathies: Sickle cell disease and hereditary spherocytosis, where rapid pigment stone formation and recurrent biliary colic confound the diagnosis of acute vaso-occlusive abdominal crises.
  4. Anomalous Pancreaticobiliary Duct Junction or gallbladder polyps >10 mm.

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Biliary Colic vs. Acute Cholecystitis

Differentiating uncomplicated biliary colic from acute cholecystitis is one of the most critical clinical decision points in ambulatory practice.

Comparison Table: Biliary Colic vs. Acute Cholecystitis

Diagnostic Evaluation of Acute Cholecystitis

• First-Line Imaging: Transabdominal Ultrasound:
  • Sensitivity ~88%, specificity ~80%. Cardinal diagnostic findings include: 1) Gallstones with acoustic shadowing; 2) Gallbladder wall thickening >3 mm; 3) Pericholecystic fluid halo; 4) Gallbladder hydrops (transverse diameter >4 cm); and 5) Sonographic Murphy sign (exquisite tenderness localized precisely when the ultrasound transducer compresses the visualized gallbladder; positive predictive value >90%).
• Diagnostic Gold Standard: Cholescintigraphy (HIDA Scan):
  • Utilizes Technetium-99m labeled iminodiacetic acid derivatives (mebrofenin or disofenin). The radiotracer is extracted by hepatocytes, excreted into the biliary tree, and normally enters the gallbladder and duodenum within 1 hour.
  • Positive HIDA Scan Criteria: The liver, common bile duct, and small bowel are clearly visualized, but the gallbladder fails to visualize at 1 and 4 hours (or within 30 minutes following intravenous morphine administration to increase sphincter of Oddi tone). Non-visualization conclusively confirms cystic duct obstruction, establishing the diagnosis of acute cholecystitis with sensitivity and specificity >95%.
• Laboratory Red Flag: Elevated Total Bilirubin:
  • Uncomplicated acute cholecystitis causes at most mild hyperbilirubinemia (<2.0 to 3.0 mg/dL). If total bilirubin is >4.0 mg/dL or clinical jaundice is present, the clinician must urgently suspect coexisting choledocholithiasis (common bile duct stone) or Mirizzi syndrome (a large stone impacted in the cystic duct neck causing extrinsic mechanical compression of the adjacent common hepatic duct).

Tokyo Guidelines 2018 (TG18) & Surgical Timing

• Severity Classification:
  • Grade I (Mild): Acute cholecystitis in a healthy patient without organ dysfunction and mild inflammatory changes.
  • Grade II (Moderate): Accompanied by any of: marked leukocytosis (WBC >18,000/mcL), palpable tender RUQ mass, symptom duration >72 hours, or marked local inflammation (gangrenous cholecystitis, emphysematous cholecystitis, pericholecystic abscess).
  • Grade III (Severe): Complicated by organ dysfunction (cardiovascular hypotension requiring vasopressors, neurologic altered consciousness, respiratory PaO2/FiO2 <300, renal oliguria/Cr >2.0 mg/dL, hepatic INR >1.5, or thrombocytopenia <100,000/mcL).
• Timing of Cholecystectomy (Critical Board Concept):
  • Early laparoscopic cholecystectomy performed within 24 to 72 hours of hospital admission is the gold-standard treatment for Grade I and II cholecystitis.
  • Large multicenter randomized trials have proven that early cholecystectomy is vastly superior to traditional delayed interval cholecystectomy (waiting 6 to 8 weeks). Early surgery significantly reduces total hospital stay, eliminates interval gallstone complications (recurrent cholecystitis, gallstone pancreatitis), reduces overall medical costs, and carries equivalent bile duct injury and complication rates.

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Acute Acalculous Cholecystitis & Acute Cholangitis

Acute Acalculous Cholecystitis

• Pathophysiology: Severe necroinflammatory disease of the gallbladder occurring in the absence of gallstones. Typically develops in critically ill, hospitalized patients: severe thermal burns, polytrauma, major non-biliary surgery, septic shock, prolonged mechanical ventilation, and long-term total parenteral nutrition (TPN). Driven by profound microvascular ischemia (hypoperfusion, shock) combined with severe biliary stasis (lack of enteral CCK stimulation causing thick, inspissated, toxic bile).
• Clinical Presentation: High mortality rate (30% to 50%) due to rapid progression to gangrene, empyema, and perforation. Patients are frequently intubated or non-verbal; manifests as unexplained fever, escalating leukocytosis, sepsis, or jaundice without an obvious source.
• Diagnosis: Bedside ultrasound shows gallbladder wall thickening >3 mm, pericholecystic fluid, subserosal edema, and absence of cholelithiasis.
• Management: Emergent broad-spectrum IV antibiotics and bedside percutaneous transhepatic cholecystostomy (PTC) tube drainage. PTC provides immediate source control without requiring high-risk general anesthesia and emergent laparotomy.

Acute Cholangitis: Charcot Triad & Reynolds Pentad

• Pathophysiology: Ascending bacterial infection of the biliary ductal system in the setting of complete or partial biliary outflow obstruction. The leading etiology is choledocholithiasis (70%), followed by benign/malignant strictures (pancreatic cancer, cholangiocarcinoma) and occluded biliary stents.
• Biliary Pressure Dynamics: Biliary obstruction causes intrabiliary pressure to exceed 20 to 25 cm H2O. This high pressure disrupts the blood-biliary barrier (tight junctions between cholangiocytes and hepatocytes), permitting rapid translocation of colonized enteric bacteria (E. coli, Klebsiella pneumoniae, Enterobacter, Enterococcus) into hepatic sinusoids and the systemic circulation, causing bacteremia and septic shock.
• Clinical Features:
  • Charcot Triad: 1) High fever with rigors; 2) Jaundice; 3) RUQ abdominal pain. Present in 50% to 70% of patients.
  • Reynolds Pentad: Charcot triad PLUS 4) Hypotension (Septic Shock); 5) Altered Mental Status (Confusion / Delirium). Defines acute toxic suppurative cholangitis; without immediate decompression, mortality approaches 100%!
• Management Protocol:
  1. Immediate ICU admission and aggressive isotonic crystalloid resuscitation;
  2. Broad-spectrum IV antibiotics (piperacillin-tazobactam 3.375–4.5 g IV Q8H or meropenem 1 g IV Q8H);
  3. Emergency Biliary Decompression: Urgent Endoscopic Retrograde Cholangiopancreatography (ERCP) with endoscopic biliary sphincterotomy and stone extraction / stent placement within 24 hours (or percutaneous transhepatic biliary drainage / PTBD if ERCP is unavailable). Emergent open surgical common bile duct exploration carries prohibitive mortality and is avoided.

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Acute Pancreatitis: Revised Atlanta Classification & Diagnostic Principles

Acute pancreatitis is an acute inflammatory process of the pancreatic parenchyma characterized by premature intracellular activation of digestive zymogens, resulting in autodigestion, microvascular thrombosis, and local and systemic inflammation.

The Revised Atlanta Diagnostic Criteria

Diagnosis requires fulfilling at least two of the following three criteria:

1. Characteristic Abdominal Pain: Acute onset of severe, persistent, steady epigastric pain that frequently radiates straight through to the back (described as boring or band-like, worsened by lying supine and partially relieved by sitting forward with knees flexed);
2. Serum Lipase or Amylase Elevation >=3 Times the Upper Limit of Normal (ULN);
3. Characteristic Findings on Cross-Sectional Imaging: Contrast-enhanced computed tomography (CECT), magnetic resonance imaging (MRI), or transabdominal ultrasound.

Lipase vs. Amylase: Clinical Pearls

• Serum Lipase is Markedly Superior: Lipase is secreted almost exclusively by pancreatic acinar cells, whereas amylase is produced by salivary glands, ovaries, fallopian tubes, and adipose tissue. Lipase rises within 4 to 8 hours of onset, peaks at 24 hours, and remains elevated for 8 to 14 days (due to renal tubular reabsorption), whereas amylase normalizes rapidly within 3 to 5 days. Lipase sensitivity is 95% to 100% and specificity is 99%.
• Diagnostic Pitfall: Serum amylase can be falsely normal in alcohol-induced pancreatitis and in severe hypertriglyceridemic pancreatitis (due to an uncharacterized circulating inhibitor that interferes with calorimetric amylase assays). Macroamylasemia causes chronic hyperamylasemia with completely normal lipase and no pancreatic disease.
• Serial Enzyme Monitoring: Once acute pancreatitis is diagnosed, serial monitoring of lipase or amylase is of zero clinical utility! Lipase concentrations do not correlate with disease severity, clinical progression, complication development, or readiness for discharge.

Indications & Timing of Abdominal CT Imaging

• Routine Early CT is NOT Indicated: In a patient presenting with classic epigastric pain and lipase >=3x ULN, contrast-enhanced abdominal CT on admission is NOT indicated! Early CT (<48 to 72 hours) does not alter clinical management, exposes the patient to radiation and nephrotoxic contrast, and underestimates the true extent of pancreatic necrosis, which takes 72 to 96 hours to demarcate fully.
• Valid Indications for Contrast-Enhanced CT:
  1. Diagnostic ambiguity (e.g., atypical pain, lipase not meeting 3x ULN, or need to exclude mesenteric ischemia or perforated viscous);
  2. Clinical deterioration or lack of clinical improvement after 48 to 72 hours of aggressive medical therapy;
  3. Sepsis or multi-organ failure developing after 72 hours, to detect local complications: acute peripancreatic fluid collections (APFC), acute necrotic collection (ANC), walled-off necrosis (WON), or pseudocysts.

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Etiologies: The 'I GET SMASHED' Framework

                         ACUTE PANCREATITIS ETIOLOGIES

     I ──> Idiopathic (10-20%; often occult biliary microlithiasis/sludge)
     G ──> Gallstones (40-50%; leading cause; stones <5mm traverse cystic duct)
     E ──> Ethanol (30%; requires chronic heavy use >50 g/day for >=5 years)
     T ──> Trauma (blunt abdominal, steering wheel, bicycle handlebars)
     S ──> Steroids & Autoimmune (Autoimmune pancreatitis: IgG4-related AIP)
     M ──> Mumps & Viruses (Coxsackie B, CMV, EBV, HAV/HBV, HIV)
     A ──> Autoimmune / Anatomical (Pancreas divisum, annular pancreas)
     S ──> Scorpion venom (Tityus trinitatis sting)
     H ──> Hypertriglyceridemia (>1,000 mg/dL) & Hypercalcemia (hyperparathyroidism)
     E ──> ERCP (post-ERCP pancreatitis in 3-10%; prevent with rectal indomethacin)
     D ──> Drugs (Azathioprine, 6-MP, valproate, thiazides, estrogens, DPP-4/GLP-1)

• Gallstone Pancreatitis (40% to 50%): Small gallstones (<5 mm) slip through the cystic duct into the common bile duct, lodging transiently at the ampulla of Vater. This creates transient common channel reflux of bile into the pancreatic duct or raises pancreatic ductal hypertension, initiating zymogen activation.
• Hypertriglyceridemia-Induced Pancreatitis (1% to 4%): Occurs when fasting serum triglycerides exceed 1,000 mg/dL (11.3 mmol/L). Pancreatic lipase hydrolyzes triglycerides into toxic, unbound free fatty acids that induce acinar cell lysis, microvascular thrombosis, and capillary ischemia. Serum appears lactescent/milky. Management involves continuous intravenous regular insulin infusion (0.1 units/kg/h) with 5% or 10% dextrose to activate endothelial lipoprotein lipase, and therapeutic plasma exchange (plasmapheresis) in severe cases.
• Post-ERCP Pancreatitis (PEP): Occurs in 3% to 10% of cases. Proven prevention: prophylactic rectal indomethacin (100 mg PR) administered immediately before or after the procedure, combined with temporary pancreatic duct stenting.

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Severity Stratification & Comprehensive Inpatient Management

Severity Classification (Revised Atlanta)

• Mild Acute Pancreatitis: Absence of organ failure and absence of local or systemic complications. Resolves in 3 to 5 days; mortality <1%.
• Moderately Severe Acute Pancreatitis: Transient organ failure that resolves within 48 hours, OR local/systemic complications without persistent organ failure.
• Severe Acute Pancreatitis: Persistent organ failure lasting >48 hours involving one or more systems: respiratory (PaO2/FiO2 <=300), renal (serum creatinine >=2.0 mg/dL or doubling), or cardiovascular (systolic BP <90 mmHg unresponsive to fluids). Mortality rate is 15% to 30%.

The BISAP Score (Bedside Index for Severity in Acute Pancreatitis)

Calculated within the first 24 hours of admission (1 point each; score 0 to 5):

• B - BUN >25 mg/dL (8.9 mmol/L);
• I - Impaired mental status (Glasgow Coma Scale <15 or confusion);
• S - SIRS (>=2 of: temp >38°C or <36°C, HR >90 bpm, RR >20, WBC >12k or <4k or >10% bands);
• A - Age >60 years;
• P - Pleural effusion present on imaging.
• Interpretation: BISAP 0-2 = low mortality (<1-2%); BISAP 3-5 = high risk of persistent organ failure and mortality (>15-20%).

Evidence-Based Inpatient Management Protocol

1. Aggressive Goal-Directed Crystalloid Hydration:
   • Fluid of Choice: Lactated Ringer's (LR) is superior to 0.9% Normal Saline. Normal saline induces hyperchloremic metabolic acidosis and worsens pancreatic inflammation, whereas LR reduces systemic inflammation (SIRS) and lower CRP at 24 hours.
   • Infusion Rates: Initial infusion of 200 to 500 mL/hour (or an initial bolus of 10 to 20 mL/kg followed by 200-250 mL/h) during the first 12 to 24 hours.
   • Goal-Directed Targets (Re-evaluated every 6-12 hours): Urine output >0.5 to 1.0 mL/kg/hour, Mean Arterial Pressure (MAP) 65 to 85 mmHg, reduction in BUN, and normalization of hematocrit toward 35% to 40%.
   • Hemoconcentration Pearl: Admission hematocrit >44% or failure of hematocrit to fall at 24 hours indicates severe intravascular volume depletion and correlates with pancreatic necrosis.
   • Caution: Avoid over-hydration in patients with underlying congestive heart failure or end-stage renal disease.
2. Multimodal Analgesia:
   • Intravenous opioids (hydromorphone or fentanyl) are first-line for severe pain. The historic dogma that morphine causes sphincter of Oddi spasm is a laboratory artifact with zero proven clinical detriment; morphine is fully acceptable.
3. Nutritional Support: Early Oral Refeeding Paradigm:
   • The historical dogma of prolonged 'bowel rest / NPO' until pain and labs resolve is obsolete and harmful.
   • In mild acute pancreatitis, early oral refeeding with a low-fat solid or liquid diet should be initiated as soon as severe pain improves, nausea/vomiting resolves, and ileus clears (usually within 24 to 48 hours of admission).
   • There is NO requirement to wait for lipase or amylase levels to normalize before feeding!
   • Early enteral feeding maintains gut mucosal barrier integrity, prevents bacterial translocation from the colon into the bloodstream, and significantly reduces infected necrosis, multi-organ failure, and death.
   • If oral intake is not tolerated after several days, enteral tube feeding (nasogastric or nasojejunal) is vastly superior to Total Parenteral Nutrition (TPN). TPN is associated with gut mucosal atrophy, central line infections, and increased mortality.
4. Antibiotic Stewardship: Strictly NO Prophylactic Antibiotics:
   • Routine prophylactic antibiotics are NOT recommended in acute pancreatitis, regardless of disease severity or whether CT demonstrates sterile necrotizing pancreatitis!
   • Prophylactic antibiotics do not decrease infected necrosis or mortality, but significantly increase the risk of multi-drug-resistant bacterial and opportunistic fungal superinfections (Candida).
   • Therapeutic antibiotics (carbapenems [meropenem 1 g IV Q8H], which penetrate pancreatic tissue) are indicated ONLY for confirmed or strongly suspected infected pancreatic necrosis (extraluminal gas on CT or CT-guided aspirate demonstrating bacteria) or extrapancreatic infections (cholangitis, bacteremia, pneumonia, UTI).
5. Surgical Timing: Same Index Admission Cholecystectomy:
   • In all patients with mild gallstone pancreatitis, laparoscopic cholecystectomy MUST be performed during the SAME index hospital admission once acute pancreatitis symptoms have resolved.
   • Discharging patients for 'delayed elective cholecystectomy' results in a disastrous 25% to 30% recurrence rate of recurrent pancreatitis, acute cholecystitis, or cholangitis within 30 to 60 days!
   • In severe necrotizing pancreatitis, cholecystectomy is deferred until systemic inflammation subsides and necrotic collections stabilize.