Assessment and Management of Adult Abdominal Pain
Initial Red-Flag Assessment
Begin by immediately checking for life-threatening conditions: hemodynamic instability (tachycardia or hypotension), peritoneal signs (rigid abdomen, rebound tenderness), pain out of proportion to exam findings (mesenteric ischemia), abdominal distension with vomiting (bowel obstruction), or fever with severe pain (perforation/abscess). 1, 2
Critical Vital Sign Interpretation
- Tachycardia is the single most sensitive early warning sign of surgical complications and demands urgent investigation even before other symptoms develop 2
- The triad of fever, tachycardia, and tachypnea predicts serious complications including anastomotic leak, perforation, or sepsis 2
- Hypotension suggests bleeding or sepsis requiring immediate resuscitation 1
High-Risk Pain Characteristics
- Abrupt or instantaneous onset of severe pain indicates vascular catastrophe—assume aortic dissection or mesenteric ischemia until proven otherwise 2
- Pain out of proportion to physical findings must be assumed to be acute mesenteric ischemia until disproven 2
- Ripping, tearing, or stabbing quality suggests aortic dissection 2
Mandatory Laboratory Testing
Order a complete blood count, comprehensive metabolic panel including liver function tests, urinalysis, serum lipase, and β-hCG in all women of reproductive age before any imaging. 3
Essential Labs by Clinical Scenario
- Elevated lactate suggests ischemia or sepsis, though normal levels do not exclude early ischemia or internal herniation 2
- High C-reactive protein has superior sensitivity and specificity compared to white blood cell count for ruling in surgical disease 2
- Serum lipase is more specific than amylase for pancreatitis 3
- Blood cultures if fever is present and sepsis suspected 3
- D-dimer and lactate if mesenteric ischemia suspected 2, 3
Critical Pitfall to Avoid
Failing to obtain β-hCG testing in all women of reproductive age before imaging delays diagnosis of ectopic pregnancy—this is mandatory regardless of patient history. 1, 3
Imaging Strategy by Pain Location
Right Upper Quadrant Pain
Ultrasonography is the initial imaging modality of choice for right upper quadrant pain to evaluate acute cholecystitis and hepatobiliary pathology. 4, 1, 2
- Ultrasound has 81% sensitivity and 83% specificity for acute cholecystitis and identifies alternative diagnoses without radiation exposure 4
- CT may be considered if ultrasound is inconclusive or to guide surgical planning 4
- MRI has similar performance to ultrasound (85% sensitivity, 81% specificity) and can be used for equivocal cases 4
Right Lower Quadrant Pain
CT of the abdomen and pelvis with IV contrast is the initial imaging of choice for right lower quadrant pain, with 95% sensitivity and 94% specificity for appendicitis. 4, 1, 2
- CT identifies non-appendiceal diagnoses in 94% of cases, changing management decisions in 25% of patients 1
- Ultrasound with graded compression is an alternative in select patients to avoid radiation, though it is operator-dependent 4
- In women of reproductive age, transvaginal ultrasound is first-line when gynecologic pathology (ectopic pregnancy, ovarian torsion, pelvic inflammatory disease) is suspected 1, 2
Left Lower Quadrant Pain
CT of the abdomen and pelvis with IV contrast has 98% diagnostic accuracy for diverticulitis and is recommended for detecting complications (abscess, perforation, fistula, obstruction). 4, 1, 2
- CT has greater than 95% sensitivity for detecting diverticulitis and provides information about disease extent 4
- Ultrasonography shows variable sensitivity compared to CT due to operator-dependence 4
Nonlocalized or Diffuse Abdominal Pain
CT of the abdomen and pelvis with IV contrast is the imaging modality of choice for diffuse or nonlocalized pain, changing the primary diagnosis in 51% of cases and altering admission decisions in 25% of patients. 4, 1, 2
- CT is particularly beneficial in marked obesity, unclear ultrasound findings, bowel obstruction, and when multiple lesions are suspected 5
- If mesenteric ischemia is suspected based on pain out of proportion to exam, order CT angiography of the abdomen immediately 2
Epigastric Pain
- Consider upper GI series with fluoroscopy if gastritis, peptic ulcer disease, or GERD is suspected 2
- Serum lipase for pancreatitis evaluation 3
Role of Conventional Radiography
Conventional radiography has limited diagnostic value in most patients with abdominal pain and should not be routinely ordered. 4, 2, 3
- Plain films are appropriate only for suspected bowel obstruction, perforated viscus (free air), urinary tract calculi, or foreign bodies 4
- Studies show conventional radiography rarely changes patient treatment 4
Special Population Considerations
Elderly Patients
Elderly patients commonly present with atypical symptoms and require more thorough evaluation even when laboratory tests are normal—maintain high suspicion for malignancy, diverticulitis, and vascular causes (especially mesenteric ischemia). 1, 2
- Do not over-rely on normal laboratory values early in disease, as many tests are nonspecific in elderly patients 2
Women of Reproductive Age
Mandatory β-hCG testing before imaging and transvaginal ultrasound as first-line when gynecologic pathology is suspected (ectopic pregnancy, ovarian torsion, pelvic inflammatory disease). 1, 2, 3
Immunocompromised Patients
Typical signs of abdominal sepsis may be masked in immunocompromised patients—a more extensive workup is necessary to avoid delayed diagnosis and high mortality. 1, 2
Post-Bariatric Surgery Patients
Tachycardia is the most critical warning sign in post-bariatric surgery patients, as classic peritoneal signs are often absent—consider internal herniation even with normal lactate. 2
Differential Diagnosis by Location
Right Upper Quadrant
- Acute cholecystitis (primary consideration) 1
- Choledocholithiasis, cholangitis 1
- Hepatitis or hepatic abscess 1
- Peptic ulcer disease 1
Right Lower Quadrant
- Appendicitis (most critical to exclude) 4, 1
- Ectopic pregnancy in women of reproductive age 1
- Nephrolithiasis (renal colic) 1
- Ovarian torsion, pelvic inflammatory disease 1
- Colitis, inflammatory bowel disease 1
Left Lower Quadrant
- Diverticulitis (leading consideration in older adults) 1
- Sigmoid volvulus (especially with chronic constipation history) 1
- Colorectal cancer 1
Diffuse or Epigastric
- Bowel obstruction (adhesions 55-75%, hernias 15-25% of small bowel obstruction) 1
- Acute pancreatitis 1
- Perforated viscus 1
- Mesenteric ischemia 1, 2
- Peptic ulcer disease or gastritis 1
Initial Treatment Approach
Immediate Interventions for Red Flags
- Hemodynamic instability: initiate IV fluid resuscitation, obtain surgical consultation immediately 1
- Peritoneal signs or suspected perforation: NPO status, IV antibiotics, urgent surgical consultation 1
- Suspected mesenteric ischemia: immediate CT angiography, surgical consultation, anticoagulation if no contraindications 2
- Bowel obstruction: NPO status, nasogastric decompression, IV fluids, surgical consultation 1
Pain Management Considerations
- Analgesics should not be withheld pending surgical evaluation, as pain control does not mask peritoneal signs 6
- Avoid opioids if functional pain or chronic pain is suspected after acute pathology is excluded 4
Common Pitfalls to Avoid
- Overlooking hernia orifices and surgical scars during examination can miss incarcerated hernias 1
- Dismissing atypical presentations in elderly patients leads to missed diagnoses 1
- Over-relying on normal laboratory values early in disease, especially in elderly or immunocompromised patients 2
- Failing to document the last bowel movement and passage of gas in patients with prior abdominal surgery (85% sensitivity for adhesive small bowel obstruction) 2
- Not considering extra-abdominal causes such as pneumonia, which can cause referred abdominal pain 1