Complete Blood Count
bloodimmediate
Normal Range: WBC 4,500-11,000/mm³
Abnormal: Leukocytosis > 11,000; > 18,000 suggests moderate-severe disease
Confirms inflammation; high WBC suggests complications
Acute CholecystitisAcute PancreatitisPeptic Ulcer DiseaseIrritable Bowel Syndrome (IBS)Small Bowel ObstructionFunctional DyspepsiaAbdominal Aortic Aneurysm (AAA) RuptureAcute Mesenteric IschemiaDyspepsia — Approach to the PatientAcute Abdominal Pain — General Approach
C-Reactive Protein
bloodimmediate
Normal Range: < 5 mg/L
Abnormal: Elevated CRP
Acute phase reactant; correlates with severity
Acute Cholecystitis
Liver Function Tests
bloodimmediate
Normal Range: ALT 7-56 U/L, AST 10-40 U/L, ALP 44-147 U/L
Abnormal: Elevated bilirubin (up to 4 mg/dL), elevated ALP/GGT
Elevation suggests choledocholithiasis
Acute CholecystitisAcute PancreatitisAcute Abdominal Pain — General Approach
Normal Range: 0-160 U/L
Abnormal: Elevated > 3x upper limit
If elevated, consider gallstone pancreatitis
Acute CholecystitisAcute Abdominal Pain — General Approach
RUQ Ultrasound
imagingimmediate
Abnormal: Gallstones, gallbladder wall thickening > 3mm, pericholecystic fluid, sonographic Murphy's sign
First-line imaging — sensitivity 81%, specificity 83%
Acute CholecystitisAcute Pancreatitis
HIDA Scan (Cholescintigraphy)
imagingurgent
Abnormal: Non-visualization of gallbladder at 4 hours
Gold standard if ultrasound equivocal — sensitivity 97%, specificity 90%
Acute Cholecystitis
Serum Lipase
bloodimmediate
Normal Range: 0-160 U/L
Abnormal: > 3x upper limit of normal (> 480 U/L)
Diagnostic criterion — sensitivity 85-100%
Acute Pancreatitis
Serum Amylase
bloodimmediate
Normal Range: 30-110 U/L
Abnormal: > 3x upper limit of normal
Less specific than lipase; normalizes faster
Acute Pancreatitis
Basic Metabolic Panel
bloodimmediate
Normal Range: BUN 7-20 mg/dL, Cr 0.7-1.3 mg/dL
Abnormal: Elevated BUN, elevated glucose, low calcium
BUN > 20 at admission predicts mortality
Acute PancreatitisSmall Bowel ObstructionAcute Abdominal Pain — General Approach
CT Abdomen with Contrast
imagingurgent
Abnormal: Pancreatic enlargement, peripancreatic fluid, necrosis, pseudocyst
Not needed for diagnosis if clinical + lipase clear. Obtain at 72-96 hours if no improvement
Acute PancreatitisSmall Bowel Obstruction
H. pylori Testing
bloodroutine
Normal Range: Negative
Abnormal: Positive urea breath test, stool antigen, or serology
Identifies treatable cause; urea breath test preferred
Peptic Ulcer DiseaseDyspepsia — Approach to the Patient
Upper GI Endoscopy (EGD)
procedureurgent
Abnormal: Mucosal defect, active bleeding, malignant features
Gold standard for diagnosis; allows biopsy and treatment
Peptic Ulcer Disease
Gastric Biopsy
procedureurgent
Abnormal: H. pylori organisms, dysplasia, malignancy
All gastric ulcers should be biopsied to exclude malignancy
Peptic Ulcer Disease
Normal Range: CRP < 5 mg/L
Abnormal: Elevated suggests IBD, not IBS
Helps distinguish IBS from IBD
Irritable Bowel Syndrome (IBS)
Celiac Serology (TTG-IgA)
bloodroutine
Normal Range: Negative
Abnormal: Positive TTG antibodies
Celiac disease mimics IBS — must exclude
Irritable Bowel Syndrome (IBS)
Fecal Calprotectin
bloodroutine
Normal Range: < 50 µg/g
Abnormal: > 50 µg/g suggests inflammation (IBD)
Best non-invasive test to distinguish IBS from IBD in patients < 45
Irritable Bowel Syndrome (IBS)
Thyroid Function Tests
bloodroutine
Normal Range: TSH 0.4-4.0 mIU/L
Abnormal: Hyper/hypothyroidism
Thyroid disease can mimic IBS symptoms
Irritable Bowel Syndrome (IBS)
Abdominal X-ray (Erect + Supine)
imagingimmediate
Abnormal: Dilated small bowel loops (> 3 cm), air-fluid levels, absence of colonic gas
Sensitivity 70-80%; multiple air-fluid levels diagnostic
Small Bowel ObstructionAcute Abdominal Pain — General Approach
Serum Lactate
bloodimmediate
Normal Range: < 2 mmol/L
Abnormal: Elevated > 2 mmol/L
Elevated lactate suggests bowel ischemia/strangulation
Small Bowel ObstructionAcute Mesenteric Ischemia
H. pylori Test
bloodroutine
Normal Range: Negative
Abnormal: Positive
Test and treat strategy for uninvestigated dyspepsia in patients < 60
Functional Dyspepsia
Upper GI Endoscopy
procedureroutine
Abnormal: Normal (required for diagnosis)
Indicated if age > 60, alarm features, or treatment failure
Functional DyspepsiaGastroparesisDyspepsia — Approach to the Patient
Gastric Emptying Scintigraphy
imagingroutine
Normal Range: < 10% retention at 4 hours
Abnormal: > 10% retention at 4 hours (> 60% at 2 hours)
Gold standard diagnostic test
Gastroparesis
Normal Range: < 6.5%
Abnormal: Elevated (poor glycemic control)
Hyperglycemia worsens gastric emptying
Gastroparesis
CT Angiography
imagingimmediate
Abnormal: Aneurysm with retroperitoneal hemorrhage, contrast extravasation
Definitive diagnosis in hemodynamically STABLE patients only
Abdominal Aortic Aneurysm (AAA) Rupture
Bedside Ultrasound (FAST)
imagingimmediate
Abnormal: Aortic diameter > 3 cm, free fluid
Rapid bedside assessment; can confirm AAA presence
Abdominal Aortic Aneurysm (AAA) Rupture
Type and Crossmatch
bloodimmediate
Abnormal: N/A — preparation for transfusion
Prepare 6-10 units pRBC, activate massive transfusion protocol
Abdominal Aortic Aneurysm (AAA) Rupture
CT Angiography (Mesenteric)
imagingimmediate
Abnormal: Arterial occlusion, venous thrombosis, bowel wall thickening, pneumatosis, portal venous gas
Gold standard — sensitivity > 95% for arterial occlusion
Acute Mesenteric Ischemia
Arterial Blood Gas
bloodimmediate
Normal Range: pH 7.35-7.45
Abnormal: Metabolic acidosis (low pH, low bicarbonate, elevated lactate)
Metabolic acidosis indicates tissue ischemia
Acute Mesenteric Ischemia
Normal Range: < 500 ng/mL
Abnormal: Elevated
Sensitive but not specific; normal D-dimer has high negative predictive value
Acute Mesenteric Ischemia
Urea Breath Test (UBT)
procedureroutine
Normal Range: Negative
Abnormal: Positive (labeled CO2 detected)
Preferred non-invasive test — sensitivity/specificity > 95%. Must stop PPI 2 weeks before.
Helicobacter pylori Infection
Stool Antigen Test
bloodroutine
Normal Range: Negative
Abnormal: Positive
Alternative to UBT — sensitivity/specificity > 90%. Must stop PPI 2 weeks before.
Helicobacter pylori Infection
Gastric Biopsy (at endoscopy)
procedureroutine
Abnormal: H. pylori organisms on histology or rapid urease test
Gold standard if endoscopy performed
Helicobacter pylori Infection
H. pylori Serology (IgG)
bloodroutine
Normal Range: Negative
Abnormal: Positive IgG antibodies
Cannot distinguish active from past infection; NOT for eradication confirmation
Helicobacter pylori Infection
Normal Range: No blood, WBC, nitrites
Abnormal: Hematuria, pyuria, nitrites
UTI, nephrolithiasis
Acute Abdominal Pain — General Approach
Urine Pregnancy Test
urineimmediate
Normal Range: Negative
Abnormal: Positive
MUST exclude ectopic pregnancy in reproductive-age women
Acute Abdominal Pain — General Approach
CT Abdomen/Pelvis with Contrast
imagingimmediate
Abnormal: Varies by condition
Most useful single imaging study for acute abdomen in adults
Acute Abdominal Pain — General Approach