How to rule out the cause of itching with abdominal pain?

Diagnostic Approach to Itching with Abdominal Pain

The most effective diagnostic approach for evaluating itching with abdominal pain is to start with laboratory tests for hepatobiliary disease, followed by targeted imaging based on pain location, as hepatic disorders are the most common cause of systemic pruritus with abdominal symptoms. 1

Initial Laboratory Evaluation

When a patient presents with both itching and abdominal pain, the following laboratory tests should be ordered:

• First-line tests:

  • Complete blood count with differential
  • Comprehensive metabolic panel (with liver function tests)
  • Renal function tests (BUN, creatinine)
  • Thyroid function tests
  • Urinalysis
  • Lipase level 1

• Additional tests to consider:

  • Pregnancy test for women of reproductive age 1
  • Blood glucose for diabetes screening 2
  • Eosinophil count (may serve as a biomarker for chronic pruritus) 2

Imaging Based on Pain Location

After laboratory testing, imaging should be selected based on the location of abdominal pain:

• Right upper quadrant pain:

  • Ultrasonography is the initial imaging test of choice 3, 1
  • Consider CT if ultrasonography is inconclusive 3

• Right or left lower quadrant pain:

  • CT scan with IV contrast is recommended 3
  • Ultrasonography may be considered first in younger patients to reduce radiation exposure 3

• Nonlocalized abdominal pain:

  • CT abdomen and pelvis with IV contrast is the imaging modality of choice 3, 1
  • Conventional radiography has limited diagnostic value for most abdominal pain 3, 1

Key Differential Diagnoses

Hepatobiliary Causes

• Cholestatic liver disease - most common systemic cause of pruritus with abdominal pain 4, 2
  • Primary biliary cholangitis
  • Primary sclerosing cholangitis
  • Obstructive biliary disease
  • Drug-induced cholestasis

Other Systemic Causes

• Endocrine disorders:

  • Thyroid disease (particularly hyperthyroidism) 4
  • Diabetes mellitus 2

• Hematologic disorders:

  • Polycythemia vera 4
  • Lymphoma (particularly Hodgkin's disease) 4

• Renal disease:

  • Chronic kidney disease with uremia 4, 2

• Inflammatory conditions:

  • Inflammatory bowel disease 5
  • Hereditary angioedema (can present with recurrent abdominal pain and pruritus) 6

Special Considerations

Elderly Patients

• May present with atypical symptoms
• Only 17% of elderly patients with acute diverticulitis present with fever
• 43% do not have leukocytosis 1
• Higher risk of malignancy with new-onset pruritus (especially if >60 years with liver disease and diffuse itch <12 months duration) 2

Medication-Related Causes

• Consider medication side effects:
  • Dicyclomine can cause allergic dermatitis, erythema, and rash 7
  • Ursodeoxycholic acid can cause abdominal pain (6.2% of patients) 8

Diagnostic Algorithm

1. Rule out dermatological causes - examine skin for primary lesions
2. Laboratory testing - focus on hepatic, renal, thyroid, and hematologic parameters
3. Imaging based on pain location - ultrasound for RUQ, CT for other quadrants or nonlocalized pain
4. Consider specialized testing if initial workup is inconclusive:
   • MRCP for suspected biliary disorders
   • Endoscopy for suspected GI disorders
   • C1 esterase inhibitor levels if hereditary angioedema is suspected

Common Pitfalls to Avoid

• Overlooking hepatobiliary disease - the most common cause of systemic pruritus
• Failing to obtain pregnancy testing in women of reproductive age 1
• Relying solely on conventional radiography - has limited diagnostic value for most causes of abdominal pain 3, 1
• Ignoring medication side effects as potential causes
• Delaying imaging in elderly patients - can result in higher morbidity and mortality 1
• Missing hereditary angioedema - can present with recurrent abdominal pain for years without cutaneous symptoms 6

By following this systematic approach, clinicians can effectively rule out the various causes of itching with abdominal pain, prioritizing conditions that affect morbidity, mortality, and quality of life.