What are the causes, symptoms, and management of acute pancreatitis, mesenteric arterial thrombosis, aortic dissection, and perforated peptic ulcer for the Canadian NAC OSCE?

NAC OSCE Canada: Acute Abdominal Emergencies

1. ACUTE PANCREATITIS

Causes

The two main culprits are gallstones (biliary pancreatitis) and alcohol abuse 1. Together these account for 75-80% of cases, leaving only 20-25% as "idiopathic" 2. Other causes include:

• Hypertriglyceridemia
• Medications
• Post-ERCP
• Trauma
• Hypercalcemia
• Pancreatic tumors (especially in elderly patients) 2

Symptoms

Look for the classic presentation: sudden onset severe epigastric pain radiating to the back, accompanied by nausea and vomiting 1. The pain is typically:

• Constant and boring in nature
• Worse when lying flat, better when leaning forward
• Associated with anorexia

Physical exam reveals:

• Epigastric tenderness
• Abdominal distension
• Tachycardia
• Fever
• In severe cases: signs of shock (hypotension, tachypnea)
• Rarely: Grey Turner's sign (flank ecchymosis) or Cullen's sign (periumbilical ecchymosis)

Diagnosis requires 2 of 3 criteria: (1) characteristic abdominal pain, (2) lipase/amylase >3x upper limit of normal, (3) imaging findings 1, 3.

Management

Severity stratification within 48 hours is mandatory 2. This determines your entire management pathway:

MILD Pancreatitis (80% of cases, <5% mortality):

• General ward management with basic monitoring (vitals, urine output) 2
• Aggressive IV fluid resuscitation - most beneficial in first 12-24 hours 3
• Early oral feeding - start immediately if no nausea/vomiting 3
• NO routine antibiotics - only give for specific infections (pneumonia, UTI, line sepsis) 2
• NO routine CT scanning - only if diagnosis unclear or clinical deterioration 2
• IV line and possibly NG tube; urinary catheter rarely needed 2

SEVERE Pancreatitis (20% of cases, up to 35% mortality):

Severe disease = persistent organ failure >48 hours (cardiovascular, respiratory, renal) 1.

• Immediate ICU/HDU admission 2, 1
• Full resuscitation with multidisciplinary approach:
  • Central venous line for CVP monitoring and fluid administration
  • Urinary catheter for strict output monitoring
  • NG tube
  • Arterial line for blood gas monitoring if needed
  • Swan-Ganz catheter if cardiovascular compromise or failed initial resuscitation 2
• Prophylactic antibiotics - IV cefuroxime is reasonable for severe cases 2
• Dynamic CT scan with IV contrast between days 3-10 to assess for necrosis 2
• Enteral nutrition preferred over parenteral to prevent infectious complications 3
• Infected necrosis requires antibiotics that penetrate pancreatic tissue and delayed intervention (preferably ≥4 weeks) 1, 3

Gallstone Pancreatitis Specific:

• ERCP within 24 hours if concurrent cholangitis 3
• Definitive cholecystectomy within 2-4 weeks for mild cases 2

Common Pitfall: Don't use aprotinin, glucagon, somatostatin, fresh frozen plasma, or peritoneal lavage - none have proven benefit 2.

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2. MESENTERIC ARTERY THROMBOSIS (Acute Mesenteric Ischemia)

Causes

Acute mesenteric ischemia has four main mechanisms 4:

• Arterial embolism (35%) - usually from atrial fibrillation, lodges in superior mesenteric artery (SMA)
• Arterial thrombosis in situ (35%) - occurs on pre-existing atherosclerotic disease
• Non-occlusive mesenteric ischemia - SMA vasoconstriction in low-flow states
• Venous thrombosis - hypercoagulable states

Symptoms

The hallmark is "pain out of proportion to physical findings" 4:

Embolic presentation:

• Sudden onset intense abdominal pain
• Minimal abdominal tenderness initially
• Bowel emptying (vomiting, diarrhea)
• History of atrial fibrillation or other embolic source
• May have emboli in other locations 4

Thrombotic presentation:

• Less dramatic onset
• May have prior symptoms of chronic mesenteric ischemia (postprandial pain, food fear, weight loss)
• Other atherosclerotic disease manifestations 4

Late findings (indicate bowel infarction):

• Peritonitis
• Bloody diarrhea
• Shock
• Metabolic acidosis

Lab findings: Elevated lactate, leukocytosis, elevated D-dimer (but these are unreliable for early diagnosis) 4.

Management

CTA is the gold standard diagnostic test - shows thrombus/embolus in SMA and signs of intestinal ischemia 4.

Immediate revascularization is required for survival 4:

Treatment Algorithm:

1. Resuscitation:

   • Aggressive IV fluids
   • Broad-spectrum antibiotics
   • NG decompression
   • Correct acidosis and electrolytes

2. Revascularization (choose based on available expertise):

   • Endovascular intervention is preferred - superior outcomes for in-hospital mortality and bowel resection rates compared to surgery 4
   • Open surgical approach - indicated if:
     • Peritonitis present
     • Endovascular expertise unavailable
     • Retrograde open mesenteric stenting (ROMS) is an alternative 4

3. Bowel assessment:

   • May require laparotomy to assess bowel viability
   • Resect non-viable bowel
   • Consider second-look laparotomy in 24-48 hours

Critical Pitfall: Plain abdominal X-ray lacks specificity and normal results don't rule out diagnosis 4. Don't delay CTA.

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3. AORTIC DISSECTION (Dissecting Aortic Aneurysm)

Causes

Hypertension is the most important risk factor, present in 70-90% of cases. Other causes:

• Connective tissue disorders (Marfan syndrome, Ehlers-Danlos)
• Bicuspid aortic valve
• Coarctation of aorta
• Trauma
• Iatrogenic (cardiac surgery, catheterization)
• Cocaine use
• Pregnancy (third trimester)

Symptoms

Sudden onset "tearing" or "ripping" chest pain radiating to the back is classic:

Type A (ascending aorta - 60% of cases):

• Anterior chest pain
• May have aortic regurgitation murmur
• Signs of cardiac tamponade (Beck's triad: hypotension, muffled heart sounds, JVD)
• Stroke symptoms if carotid involvement
• Pulse deficits or blood pressure differentials between arms

Type B (descending aorta - 40% of cases):

• Interscapular back pain
• Abdominal pain if extends to abdominal aorta
• Lower extremity ischemia

Physical exam findings:

• Hypertension or hypotension (if rupture/tamponade)
• Pulse deficits (>20 mmHg BP difference between arms)
• Aortic regurgitation murmur
• Neurological deficits
• Signs of end-organ malperfusion

Rare presentation: Can mimic acute pancreatitis if celiac/SMA involvement causes pancreatic ischemia 5, 6.

Management

CTA is the diagnostic test of choice - shows intimal flap, true and false lumens 4.

Type A Dissection:

IMMEDIATE surgical emergency - requires:

• Emergency cardiothoracic surgery consultation
• Surgical repair with graft replacement of ascending aorta ± aortic valve replacement 6
• Blood pressure control while awaiting surgery (target SBP 100-120 mmHg):
  • IV beta-blocker first (esmolol, labetalol)
  • Then vasodilator if needed (nitroprusside)
• Mortality without surgery approaches 100%

Type B Dissection:

Medical management unless complicated:

• Aggressive blood pressure control (target SBP 100-120 mmHg, HR <60 bpm):
  • IV beta-blocker (esmolol, labetalol)
  • Add vasodilator if needed
• Endovascular repair (TEVAR) indicated for:
  • Rupture or impending rupture
  • Malperfusion syndromes
  • Refractory pain
  • Uncontrolled hypertension
  • Progression of dissection

Critical Pitfall: Never give vasodilators before beta-blockade - this causes reflex tachycardia and increased shear stress, worsening the dissection.

Post-operative complications: Watch for ARDS, systemic inflammatory response, and abdominal complications including pancreatitis if celiac/SMA involved 6.

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4. PERFORATED PEPTIC ULCER

Causes

The main causes have shifted over time 7:

• H. pylori infection - still common but decreasing
• NSAIDs/aspirin use - increasingly important
• Smoking
• Corticosteroids
• Stress ulcers (ICU patients, burns, trauma)
• Malignancy (gastric cancer can present as perforation)

Symptoms

The classic triad: sudden onset severe abdominal pain + tachycardia + abdominal rigidity 8:

Acute presentation:

• Sudden, severe epigastric pain - "like being stabbed"
• Pain rapidly becomes generalized peritonitis
• Patient lies still (movement worsens pain)
• Shoulder tip pain (referred from diaphragmatic irritation)

Physical exam:

• Board-like rigidity of abdomen
• Absent bowel sounds
• Percussion tenderness
• Rebound tenderness
• Tachycardia
• Fever (develops later)
• Signs of shock if delayed presentation

Imaging:

• Erect chest X-ray - pneumoperitoneum (air under diaphragm) in 85% of cases
• 15% may have normal X-ray - don't rely on this alone 8
• CT abdomen - more sensitive, shows free air and can identify perforation site

Management

Early diagnosis, prompt resuscitation, and urgent surgical intervention are essential 8.

Initial Resuscitation:

• Aggressive IV fluid resuscitation
• Broad-spectrum IV antibiotics immediately (cover gram-negatives and anaerobes)
• NG tube decompression
• Urinary catheter
• NPO
• Analgesia
• Correct electrolyte abnormalities

Surgical Management:

Exploratory laparotomy with omental patch repair is the gold standard 8:

1. Laparoscopic repair - preferred if expertise available and patient stable 8

   • Lower wound infection rates
   • Faster recovery
   • Less postoperative pain

2. Open repair - if:

   • Hemodynamically unstable
   • Delayed presentation (>24 hours)
   • Large perforation
   • Laparoscopic expertise unavailable

3. Definitive surgery (gastrectomy):

   • Indicated for large perforations (>2 cm)
   • Malignant ulcers 8
   • Chronic ulcers with scarring

Operative steps:

• Peritoneal lavage
• Omental patch (Graham patch) closure
• Drain placement (controversial)
• Biopsy edges if malignancy suspected

Non-operative Management:

May be considered ONLY if ALL criteria met 7:

• Hemodynamically stable
• No signs of generalized peritonitis
• Contained perforation on imaging
• Presentation within 12 hours
• Close monitoring in ICU setting

This is rarely appropriate and requires:

• IV antibiotics
• IV PPI (proton pump inhibitor)
• NG decompression
• Serial abdominal exams
• Low threshold for conversion to surgery

Post-operative Management:

• Continue IV antibiotics 3-5 days
• H. pylori eradication therapy if positive
• PPI therapy for 8 weeks minimum
• Stop NSAIDs permanently if possible
• Biopsy results to rule out malignancy

Critical Pitfall: Don't delay surgery for extensive imaging if diagnosis is clear clinically. Time to surgery directly correlates with mortality - mortality increases from 1.3% if operated within 6 hours to 20% if delayed >24 hours 8.

Scoring systems (Boey score, Mannheim Peritonitis Index) help predict mortality but shouldn't delay treatment 7.