What is the approach to evaluating a patient with abdominal pain?

Systematic Approach to Evaluating Abdominal Pain

Begin by analyzing six critical features of the pain—onset (sudden, rapid, or gradual), progression, migration, character (cramping vs. constant), intensity, and localization—as these characteristics directly correlate with specific pathologic processes and can identify the source 80-90% of the time from history alone. 1, 2

Initial Clinical Assessment

Pain Characterization (Most Diagnostically Important)

Onset timing:

• Sudden onset (within seconds): Suspect perforated viscus (gastric/duodenal ulcer, diverticulum), ruptured ectopic pregnancy, mesenteric infarction, ruptured aortic aneurysm, or vascular embolism 2
• Rapid onset (over minutes): Consider cholecystitis, pancreatitis, intestinal obstruction, diverticulitis, appendicitis, ureteral stone, or penetrating ulcer 2
• Gradual onset (hours to days): Think neoplasms, chronic inflammatory processes, or large bowel obstruction 2

Pain character:

• Cramping with pain-free intervals: Pathognomonic for mechanical small bowel obstruction; shorter intervals indicate proximal obstruction, longer intervals suggest distal obstruction 2
• Constant dull aching: Results from distention or edema of hollow viscus walls or capsular stretch of liver/spleen 2

Pain migration:

• Periumbilical to right lower quadrant: Classic for appendicitis as visceral pain transitions to somatic when parietal peritoneum becomes involved 2
• Epigastric to lower quadrants: Suggests perforated duodenal ulcer with leaking contents tracking through peritoneal cavity 2

Physical Examination Maneuvers

Patient positioning reveals pain type:

• Lies completely still with knees/hips flexed: Indicates somatic (peritoneal) pain 2
• Constantly moving, unable to find comfortable position: Indicates visceral pain 2

Functional assessment without palpation:

• Have patient alternately push abdomen out to touch your hand, then suck in toward spine—this identifies somatic pain location through peritoneal stretching without examiner-induced anxiety, especially useful in children 2

Referred pain patterns:

• Supraclavicular pain (Kehr's sign): Diaphragmatic irritation from C3-C5 phrenic nerve 2
• Medial thigh to knee pain (Howship-Romberg sign): Obturator nerve irritation from incarcerated obturator hernia 2
• Testicular/labial pain: Genitofemoral nerve irritation from retroperitoneal processes (retrocecal appendicitis, retroperitoneal duodenal perforation) 2

Vital Signs and Red Flags

Immediately assess for:

• Tachycardia, fever, hypotension, respiratory distress, or decreased urine output—all require prompt intervention 1
• Hemodynamic instability mandates immediate resuscitation and surgical consultation 1

Laboratory Investigations

Essential initial tests:

• Complete blood count for leukocytosis (though normal WBC does not exclude appendicitis) 3, 1
• C-reactive protein as inflammation marker 1
• Liver function tests and hepatobiliary markers for right upper quadrant pain 1
• Serum electrolytes, creatinine, and blood urea nitrogen for renal function 1
• Lactate levels to assess bowel ischemia or severe sepsis 1
• Mandatory pregnancy test for all women of reproductive age before any imaging 1

Common pitfall: Do not rely solely on laboratory tests—many serious conditions require imaging for definitive diagnosis 1

Imaging Strategy Based on Pain Location

CT abdomen/pelvis with IV contrast is the preferred initial imaging for acute nonlocalized abdominal pain because it changes the leading diagnosis in 51% of patients, alters admission decisions in 25%, and modifies surgical plans in 25% of cases 3

Location-Specific Imaging Algorithms:

• Right upper quadrant pain: Ultrasonography first-line (81% sensitivity, 83% specificity for cholecystitis) 1
• Right lower quadrant pain (suspected appendicitis): CT with contrast (>95% sensitivity) 1
• Left lower quadrant pain (suspected diverticulitis): CT with contrast 1
• Diffuse or nonlocalized pain: CT abdomen/pelvis with IV contrast 3, 1
• Pelvic pain: CT abdomen/pelvis with contrast 1
• Suspected kidney stones: Non-contrast CT abdomen/pelvis 1

Oral contrast is not routinely necessary as it delays scan acquisition without clear diagnostic advantage 3

Plain radiographs have limited value except for suspected bowel obstruction (49% sensitivity) or foreign bodies (90% sensitivity); even low-dose CT is superior 3, 1

Special Population Imaging Considerations:

• Pregnant patients: Ultrasound first-line; if additional imaging needed, use MRI over CT 1
• Children with suspected appendicitis: Ultrasound before CT to avoid radiation 3
• Elderly patients: Lower threshold for imaging as they present with atypical symptoms and may have normal labs despite serious pathology 3, 1
• Immunocompromised patients: Early CT imaging as signs of abdominal sepsis may be masked with high mortality risk 3, 1

Management Decisions

Immediate Surgical Consultation Required:

• Signs of peritonitis, perforation, or septic shock 1
• Hemodynamic instability despite resuscitation 1
• Clinical suspicion high enough that imaging would not change surgical decision 3

Medical Management:

• Intra-abdominal abscesses >3cm: Percutaneous drainage with antimicrobial therapy 1
• Small abscesses (<3cm): IV antibiotics alone 1
• Do not routinely administer antibiotics unless infection or abscess suspected 1

Disposition:

• Admit: Severe pain, hemodynamic instability, peritoneal signs, or suspected surgical conditions 1
• Discharge with close follow-up: Very low clinical suspicion after appropriate workup 3
• Observation: Intermediate probability requiring serial examinations 3

Critical Pitfalls to Avoid

• Delaying surgical consultation in patients with peritonitis or septic shock 1
• Overlooking gynecological causes in women of reproductive age (ectopic pregnancy, ovarian torsion, pelvic inflammatory disease) 1
• Assuming elderly patients will present typically—they often have atypical symptoms with normal labs despite serious pathology 3, 1
• Overusing CT in young patients causing unnecessary radiation exposure 1
• Performing appendectomy for right lower lobe pneumonia that produces referred abdominal pain via shared intercostal nerve innervation 2
• Missing retrocecal or pelvic appendicitis because they lack classic right lower quadrant somatic pain due to retroperitoneal or pelvic location away from anterior parietal peritoneum 2