What is the differential diagnosis and initial work‑up for a 60‑year‑old female with isolated right‑sided abdominal pain without nausea, vomiting or back pain?

Differential Diagnosis and Initial Work-Up for Right-Sided Abdominal Pain in a 60-Year-Old Female

In a 60-year-old woman with isolated right-sided abdominal pain without nausea, vomiting, or back pain, the differential diagnosis must prioritize life-threatening conditions including acute mesenteric ischemia, perforated viscus, complicated diverticulitis, and appendicitis, with CT abdomen and pelvis with IV contrast as the initial imaging study of choice. 1, 2

Critical "Can't Miss" Diagnoses in This Age Group

The absence of classic symptoms does not exclude serious pathology in elderly patients, who frequently present with atypical or minimal findings despite life-threatening conditions. 2, 3

Life-threatening conditions requiring immediate consideration:

• Acute mesenteric ischemia – Pain out of proportion to physical examination findings is the hallmark; mortality increases with every hour of delay, particularly in patients with cardiovascular disease or atrial fibrillation. 1, 2
• Perforated viscus – Abdominal rigidity indicates perforation requiring immediate surgical consultation; elderly patients with diverticulitis are more likely to present with complicated disease. 2
• Complicated appendicitis – Perforation occurs in 18-70% of elderly cases versus 3-29% in younger patients, with mortality reaching 8%; the classic triad of migrating right-lower-quadrant pain, fever, and leukocytosis is frequently absent in this age group. 2, 3
• Bowel obstruction with ischemia – Accounts for 15% of acute abdominal pain admissions in elderly patients with mortality up to 8%. 2

Differential Diagnosis by Location

Right Upper Quadrant Pain

• Acute cholecystitis – Most common surgical indication in elderly patients; gallbladder inflammation with fever and positive Murphy's sign. 1, 4
• Biliary colic – Episodic severe pain from gallstones causing transient cystic duct obstruction. 4
• Acute cholangitis – Triad of jaundice, fever/chills, and RUQ pain plus biliary dilatation on imaging. 4
• Hepatic abscess or ruptured tumor – Critical diagnosis requiring prompt attention. 4
• Pulmonary embolism – Can present with upper abdominal pain. 4

Right Lower Quadrant Pain

• Appendicitis – Pre-operative diagnostic accuracy is lower in elderly patients; complicated appendicitis with perforation is significantly more common. 2, 3
• Diverticulitis – Only 50% of elderly patients present with lower quadrant pain, 17% have fever, and 43% lack leukocytosis. 2
• Ovarian pathology – Ovarian cyst, torsion, or mass can cause referred RUQ pain in women. 4
• Ectopic pregnancy – Must be excluded in all women of reproductive age before imaging. 1, 4

Generalized Right-Sided Pain

• Colorectal cancer with obstruction – Accounts for 60% of large bowel obstructions. 2
• Sigmoid volvulus – Responsible for 15-20% of large bowel obstructions with sudden distension. 2
• Adhesive small bowel obstruction – Represents 55-75% of small bowel obstructions, particularly with prior abdominal surgery. 2

Initial Laboratory Work-Up

Mandatory initial laboratory tests:

• Complete blood count – Leukocytosis suggests bowel ischemia and is a predictor of transmural necrosis and mortality; however, normal values do not exclude serious pathology in elderly patients. 1, 2
• C-reactive protein – Normal CRP combined with normal leukocyte count has 100% negative predictive value for ruling out acute appendicitis in elderly patients. 2
• Serum lactate – Critical marker of poor tissue perfusion for bowel ischemia and septic shock. 2
• Hepatobiliary markers – Elevated liver enzymes suggest choledocholithiasis. 4, 5
• Lipase – Evaluate for pancreatitis. 5
• Urinalysis – Assess for urinary tract infection or urolithiasis. 5
• Beta-hCG – Mandatory in all women of reproductive age before imaging to exclude ectopic pregnancy. 1, 4
• Procalcitonin – Correlates with intestinal necrotic damage and mortality. 2

Initial Imaging Strategy

CT abdomen and pelvis with IV contrast is the initial imaging study of choice for right-sided abdominal pain in elderly patients. 1, 2

Rationale for CT as First-Line Imaging:

• Broad differential diagnosis – CT can evaluate for appendicitis, diverticulitis, bowel obstruction, perforation, peritonitis, ischemia, colorectal malignancy, and complications in a single study. 1, 2
• High diagnostic accuracy – Sensitivity 85.7-100% and specificity 94.8-100% for appendicitis; identifies alternative diagnoses in 23-45% of cases. 1
• Critical for elderly patients – Laboratory tests are often nonspecific and may be normal despite serious infection; imaging is especially helpful in this population. 1, 2
• Rapid acquisition – Fast imaging is essential given clinical acuity and broad differential. 1

Exception: Right Upper Quadrant-Predominant Pain

If pain is clearly localized to the right upper quadrant, ultrasound is the initial imaging study of choice. 1, 4

• Ultrasound has 96% accuracy for gallstones and provides rapid, cost-effective evaluation without radiation exposure. 1, 4
• The American College of Radiology rates ultrasound 9/9 (usually appropriate) for RUQ pain evaluation. 1, 4
• Escalate to CT with IV contrast if ultrasound is nondiagnostic, presentation is atypical, or patient is critically ill. 4

Critical Clinical Assessment Points

Mandatory physical examination elements:

• Digital rectal examination – Detect rectal mass, fecal impaction, blood, or rectal prolapse. 2
• Examination of all hernia orifices – Detect incarcerated hernias. 2
• Vital signs monitoring – Assess for shock or hemodynamic instability. 2
• Peritoneal signs – Pain with coughing and movement indicates parietal peritoneal irritation requiring urgent imaging. 6

Immediate Surgical Consultation Indications

Consult surgery immediately if:

• Hemodynamic instability despite resuscitation. 2
• CT evidence of perforation, closed-loop obstruction, or bowel ischemia. 2
• Abdominal rigidity indicating perforated viscus. 2
• Strangulated hernia or rectal prolapse. 2
• Fever with leukocytosis suggesting acute cholecystitis or cholangitis. 4

Common Pitfalls to Avoid

• Do not rely on clinical signs alone – Physical examination can be misleadingly benign even with catastrophic conditions like ruptured abdominal aortic aneurysm or mesenteric ischemia in elderly patients. 2, 3
• Do not assume normal labs exclude serious pathology – Typical signs of abdominal sepsis may be masked in elderly patients, leading to delayed diagnosis and high mortality. 1, 2
• Do not order CT without IV contrast – Critical findings like gallbladder wall enhancement, bowel ischemia, and adjacent liver parenchymal hyperemia cannot be detected without contrast. 4
• Do not skip pregnancy testing – Beta-hCG must be checked before imaging in all women of reproductive age. 1, 4
• Do not delay imaging in elderly patients – Advanced age with concerning features mandates hospital admission and prompt imaging, as morbidity and mortality are significantly higher in this population. 2, 3

Disposition Decision-Making

Strong indications for hospital admission:

• Advanced age (60 years) with any concerning features. 2
• Inability to exclude surgical pathology. 2
• Abnormal vital signs or laboratory markers suggesting serious pathology. 2
• CT findings requiring surgical consultation or intervention. 2