What are the appropriate evaluation and treatment approaches for abdominal pain in adults?

Evaluation and Management of Acute Abdominal Pain in Adults

For adults presenting with acute abdominal pain, begin with rapid assessment of hemodynamic stability and pain location, obtain mandatory β-hCG testing in all women of reproductive age, then proceed directly to CT abdomen/pelvis with IV contrast for nonlocalized pain or ultrasonography for right upper quadrant pain—conventional radiography should not be routinely ordered as it rarely changes management. 1, 2, 3

Immediate Assessment Priorities

Hemodynamic Stability

• Patients with hypotension, severe pain out of proportion to exam findings, or signs of peritonitis require immediate surgical consultation rather than extended diagnostic workup 2, 4
• Tachycardia is the most sensitive early warning sign of surgical complications and should trigger urgent investigation even before other symptoms develop 2, 3
• The combination of fever, tachycardia, and tachypnea predicts serious complications including anastomotic leak, perforation, or sepsis 2
• Begin rapid intravascular volume resuscitation immediately when hypotension is identified 1

Critical Red Flags Requiring Urgent Evaluation

• Severe pain out of proportion to physical findings should be assumed to be acute mesenteric ischemia until disproven 2
• Abrupt or instantaneous onset of severe pain suggests vascular catastrophe, particularly aortic dissection or mesenteric ischemia 2
• Syncope with abdominal pain warrants evaluation for pericardial tamponade or neurologic injury from aortic dissection 2
• Signs of peritonitis (rigid abdomen, rebound tenderness) require urgent evaluation 2

History Taking: Key Elements

Pain Characteristics

• Location specificity is the most valuable starting point: right upper quadrant suggests hepatobiliary disease, right lower quadrant indicates appendicitis, left lower quadrant points to diverticulitis, and diffuse pain requires broader evaluation 4, 3
• Ripping, tearing, stabbing, or sharp quality pain suggests aortic dissection 2
• Colicky pain indicates bowel obstruction as the bowel attempts to overcome occlusion 2

Associated Symptoms

• Asking about the last bowel movement and passage of gas has 85% sensitivity and 78% specificity for predicting adhesive small bowel obstruction in patients with prior abdominal surgery 2
• Vomiting occurs earlier and more prominently in small bowel obstruction versus large bowel obstruction 2
• The triad of abdominal pain, constipation, and vomiting suggests sigmoid volvulus 2
• Approximately 25% of acute mesenteric ischemia patients have occult blood in stool 2

Past Medical History

• Any prior laparotomy makes adhesive obstruction the leading diagnosis, accounting for 55-75% of small bowel obstructions 2
• Atrial fibrillation is present in nearly 50% of patients with embolic acute mesenteric ischemia 2
• Patients with cardiovascular disease presenting with acute abdominal pain should be suspected of having acute intestinal ischemia 2
• History of any chronic pain condition is the strongest predictor of transition from acute to chronic pain 4

Medications

• Oral contraceptives and estrogen use predispose to mesenteric venous thrombosis 2
• Psychotropic medications cause chronic constipation predisposing to volvulus, particularly in elderly institutionalized patients 2

Physical Examination: Specific Findings

• Asymmetric gaseous distention with emptiness of the left iliac fossa is pathognomonic for sigmoid volvulus 2
• Empty rectum on digital examination is classic for sigmoid volvulus 2
• Positive Murphy's sign (pain when pressing the right upper quadrant) suggests acute cholecystitis 2
• The absence of peritonitis on examination does not exclude bowel ischemia—patients with sigmoid volvulus often lack peritoneal signs despite having established ischemia 2
• Pelvic examination in women with lower abdominal pain is necessary to evaluate gynecologic causes 4

Laboratory Evaluation

Mandatory Tests

• β-hCG testing is mandatory in all women of reproductive age before proceeding with any imaging to rule out ectopic pregnancy 4, 3
• Complete blood count to assess for leukocytosis indicating infection or inflammation 4, 3
• Comprehensive metabolic panel including liver function tests to evaluate hepatobiliary pathology and organ function 4, 3

Additional Tests Based on Clinical Suspicion

• Serum lipase is specific for pancreatitis 4, 3
• Urinalysis for urinary tract infection or nephrolithiasis 4, 3
• High C-reactive protein has superior sensitivity and specificity compared to white blood cell count for ruling in surgical disease, though normal CRP does not exclude complications 2
• Elevated lactate suggests ischemia or sepsis, but normal levels do not exclude internal herniation or early ischemia 2
• Blood cultures if sepsis is suspected 4

Imaging Strategy by Pain Location

Right Upper Quadrant Pain

• Ultrasonography is the initial imaging test of choice for evaluating acute cholecystitis and hepatobiliary disease 1, 3
• Cholescintigraphy or CT may be considered if ultrasonography is equivocal 1

Right Lower Quadrant Pain

• CT of the abdomen and pelvis with contrast is the initial imaging study of choice for suspected appendicitis 1, 3
• Consider ultrasonography as an initial study before obtaining CT to reduce radiation exposure 1

Left Lower Quadrant Pain

• CT of the abdomen and pelvis with contrast is recommended, especially for suspected diverticulitis 2

Nonlocalized or Diffuse Abdominal Pain

• CT of the abdomen and pelvis with IV contrast is the preferred initial imaging study, as it changes the leading diagnosis in 51% of patients and alters admission decisions in 25% of cases 3

Patients Requiring Immediate Laparotomy

• Further diagnostic imaging is unnecessary in patients with obvious signs of diffuse peritonitis in whom immediate surgical intervention is to be performed 1

Imaging by Suspected Diagnosis

• Acute appendicitis: CT of abdomen and pelvis with contrast 1
• Acute cholecystitis: Ultrasonography of abdomen 1
• Diverticulitis: CT of abdomen and pelvis with contrast 1
• Bowel obstruction: CT of abdomen and pelvis with contrast 2
• Mesenteric ischemia: CT angiography of the abdomen 2
• Kidney stones: Non-contrast CT of abdomen and pelvis 2
• Acute pancreatitis: Ultrasonography of abdomen; consider CT if ultrasonography is nondiagnostic, presentation is atypical, or patient is critically ill 1

Antimicrobial Therapy

• Antimicrobial therapy should be initiated once intra-abdominal infection is diagnosed or considered likely 1
• For patients with septic shock, antibiotics should be administered as soon as possible 1
• For patients without septic shock, antimicrobial therapy should be started in the emergency department 1
• Satisfactory antimicrobial drug levels should be maintained during a source control intervention 1

Special Population Considerations

Women of Reproductive Age

• Always consider gynecologic conditions including ectopic pregnancy, ovarian torsion, or pelvic inflammatory disease 4, 3
• CT of the abdomen and pelvis with contrast is most appropriate for pelvic pain 2

Elderly Patients

• May have atypical symptoms and require more thorough evaluation, even if laboratory tests are normal 2, 3
• Have a higher likelihood of malignancy, diverticulitis, and vascular causes 2, 3

Immunocompromised Patients

• For selected patients with unreliable physical examination findings, such as those immunosuppressed by disease or therapy, intra-abdominal infection should be considered if the patient presents with evidence of infection from an undetermined source 1
• Maintain a lower threshold for extensive workup, as presentation may be atypical 4

Post-Bariatric Surgery Patients

• Often present with atypical symptoms, and tachycardia is the most critical warning sign 2
• Classic peritoneal signs are often absent, and internal herniation should be considered even with normal lactate 2

Critical Pitfalls to Avoid

• Never proceed with CT imaging in reproductive-age women without pregnancy testing, as this leads to delayed diagnosis of ectopic pregnancy and unnecessary fetal radiation exposure 4, 3
• Do not order conventional radiography routinely, as it has limited diagnostic value and rarely changes management 1, 4, 3
• Do not assume normal initial labs exclude serious pathology in patients with high clinical suspicion—proceed to appropriate imaging 4
• Do not delay imaging in clinically deteriorating patients while pursuing additional non-diagnostic tests 4
• Avoid overuse of CT scans to minimize ionizing radiation exposure, especially in young patients 1

Chronic Abdominal Pain Considerations

• The functional disorders should be considered after organic pathology has been confidently excluded 5
• Once a diagnosis of functional pain is established, repetitive testing is not recommended and the patient should be referred to receive psychological support associated with available pharmacological therapeutic options 5
• For chronic pain patients, recognize that peripheral initiating factors differ from central maintaining factors—address fear of pain and central sensitization rather than repeatedly investigating resolved inflammation 4