What is the workup for a patient with a history of appendectomy (removal of the appendix) and poor adherence to thyroid medication, presenting with right upper quadrant (RUQ) pain?

Workup for Right Upper Quadrant Pain in a Patient with History of Appendectomy and Poor Thyroid Medication Adherence

For a patient with right upper quadrant pain who has had an appendectomy and demonstrates poor thyroid medication adherence, a CT scan of the abdomen and pelvis with IV contrast is the most appropriate initial diagnostic test. 1

Initial Evaluation Considerations

• CT abdomen and pelvis is the preferred initial imaging modality due to its high diagnostic yield for detecting various causes of right upper quadrant pain, with sensitivity of 95% and specificity of 94% 1
• The history of appendectomy eliminates appendicitis from the differential diagnosis, but many other conditions can cause RUQ pain 2
• Poor thyroid medication adherence may contribute to gastrointestinal symptoms but is unlikely to be the sole cause of acute RUQ pain 3

Diagnostic Algorithm

Step 1: Laboratory Testing

• Complete blood count to assess for leukocytosis suggesting inflammation 1
• Liver function tests to evaluate for hepatobiliary disease 2
• Lipase to rule out pancreatitis 4
• Thyroid function tests (TSH, free T4) to assess the degree of hypothyroidism due to medication non-adherence 3

Step 2: Imaging

• CT abdomen and pelvis with IV contrast is the first-line imaging study 1

  • Provides excellent visualization of hepatobiliary structures, pancreas, and other abdominal organs
  • Can detect alternative diagnoses such as cholecystitis, hepatitis, pancreatitis, and other causes of RUQ pain
  • Contrast-enhanced CT without enteral contrast has sensitivities ranging from 90% to 100% and specificities from 94.8% to 100% 1

• Ultrasound may be considered as an alternative or complementary test:

  • Particularly useful for evaluating gallbladder pathology 2, 5
  • Less sensitive than CT for non-biliary causes of RUQ pain 3
  • May be preferred as initial test if gallstone disease is strongly suspected 2

Common Causes of RUQ Pain to Consider

• Biliary disease (cholecystitis, choledocholithiasis, biliary colic) 2, 3
• Hepatic disorders (hepatitis, abscess, mass) 4
• Pancreatic disease (pancreatitis) 3
• Gastrointestinal causes (peptic ulcer disease, gastritis) 6
• Non-abdominal causes (lower lobe pneumonia, musculoskeletal pain) 6

Special Considerations

• Hypothyroidism from poor medication adherence can cause:

  • Decreased intestinal motility potentially contributing to biliary stasis 3
  • Constipation which may present with abdominal pain 4
  • Myalgias that could mimic abdominal pain 6

• Pitfalls to avoid:

  • Don't assume RUQ pain is related to the previous appendectomy 1
  • Don't attribute symptoms solely to thyroid dysfunction without appropriate imaging 3
  • Don't delay imaging in patients with significant RUQ pain, as conditions like acute cholecystitis require prompt diagnosis 2

Follow-up Recommendations

• Based on CT findings, additional targeted studies may be necessary:

  • MRCP (Magnetic Resonance Cholangiopancreatography) for detailed evaluation of biliary tract if initial imaging suggests biliary disease 2
  • HIDA scan if cholecystitis is suspected but ultrasound is equivocal 3
  • Endoscopy if upper GI pathology is suspected 4

• Address thyroid medication non-adherence concurrently with the acute RUQ pain workup to prevent complications of untreated hypothyroidism 3