What is the differential diagnosis for a general adult patient presenting with right-sided abdominal pain?

Differential Diagnosis for Right-Sided Abdominal Pain

Appendicitis is the most common surgical cause of right-sided abdominal pain, accounting for the majority of cases requiring emergency intervention, but you must systematically consider right colonic diverticulitis, ureteral stones, colitis, intestinal obstruction, and gynecologic pathology in your differential. 1

Most Common Etiologies by Frequency

Right Lower Quadrant Pain

• Appendicitis: Most common surgical pathology in the United States, representing the primary diagnosis requiring operative management 1
• Right colonic diverticulitis: Accounts for approximately 8% of right lower quadrant pain cases 1
• Intestinal obstruction: Present in approximately 3% of cases 1
• Ureteral stone/nephrolithiasis: Common cause requiring differentiation from appendicitis 1
• Infectious enterocolitis: Including typhlitis and inflammatory terminal ileitis 1
• Colitis: Including inflammatory bowel disease 1

Right Upper Quadrant Pain

• Cholecystitis: One of the most common causes (9-11% of acute abdominal presentations) 2
• Hepatobiliary pathology: Including biliary colic and cholangitis 3, 4
• Pancreatitis: Can present with right-sided predominance 3, 4

Additional Diagnoses in Women of Reproductive Age

• Gynecologic pathology: Including ectopic pregnancy (mandatory to exclude), ovarian torsion, tubo-ovarian abscess, and pelvic inflammatory disease 1, 3, 4
• Benign adnexal masses: Frequently identified on imaging 1
• Pelvic congestion syndrome: Identified in patients without other clear diagnosis 1

Critical Diagnostic Considerations

High-Risk Diagnoses Requiring Immediate Recognition

• Perforated appendicitis: Delays in diagnosis increase morbidity and mortality; imaging does not increase perforation rates 1
• Mesenteric ischemia: Consider lactate and D-dimer if suspected, though these lack specificity 3, 4
• Ectopic pregnancy: Beta-hCG testing is mandatory in all women of reproductive age before imaging 3, 4

Special Population Considerations

• Elderly patients: May present with atypical symptoms and have higher mortality (2-12% for acute abdomen, increasing hourly without treatment) 2
• Asian descent patients: Right-sided diverticulitis is significantly more common and mimics appendicitis clinically 5
• Patients with intestinal malrotation: Appendicitis can present in atypical locations, including left upper quadrant 6

Diagnostic Approach Algorithm

Initial Clinical Assessment

• Location specificity: Right lower quadrant pain strongly suggests appendicitis, though clinical determination alone has unacceptably high negative appendectomy rates (up to 25%) 1
• Clinical scoring tools: Alvarado score has not improved diagnostic accuracy and shows mixed results for guiding CT use 1

Mandatory Laboratory Workup

• Complete blood count: Assess for leukocytosis indicating infection or inflammation 3, 4
• Comprehensive metabolic panel: Including liver function tests for hepatobiliary pathology 3, 4
• Urinalysis: Evaluate for urinary tract infection or nephrolithiasis 3, 4
• Serum lipase: More specific than amylase for pancreatitis 3, 4
• Beta-hCG: Mandatory in all women of reproductive age to exclude pregnancy-related conditions 3, 4
• Blood cultures: If fever present and sepsis suspected 3, 4

Imaging Strategy

• CT abdomen/pelvis with IV contrast: Imaging modality of choice for right lower quadrant pain with 95% sensitivity and 94% specificity for appendicitis; also identifies alternative diagnoses in 94.3% concordance with clinical diagnosis [1, @28@]
• Ultrasonography: Preferred initial study for right upper quadrant pain and in women of reproductive age to minimize radiation 7, 8
• Plain radiography: Has limited diagnostic value and should not be routinely ordered 4, 9

Common Diagnostic Pitfalls

Critical Errors to Avoid

• Failing to obtain pregnancy testing: Before any imaging in women of reproductive age leads to delayed diagnosis of ectopic pregnancy and unnecessary radiation exposure 3, 4, 7
• Over-reliance on clinical examination alone: Results in negative appendectomy rates as high as 25% without imaging 1
• Dismissing right-sided diverticulitis in young patients: Particularly in Asian populations where it commonly mimics appendicitis and can be managed medically, avoiding unnecessary surgery 5
• Delaying imaging in equivocal cases: CT use has increased from 3.9% (1997) to 37.8% (2016) for abdominal pain, reflecting improved diagnostic accuracy without increasing perforation rates 1

Non-Appendiceal Diagnoses Requiring Intervention

41% of patients with non-appendiceal CT diagnoses require hospitalization, and 22% undergo surgical or image-guided intervention, compared to only 14% hospitalization and 4% intervention in patients without CT diagnosis [1, @27@]