What is the appropriate evaluation and treatment for a patient with right lower quadrant (RLQ) pain and no other symptoms?

Evaluation and Management of Isolated Right Lower Quadrant Pain

For a patient with isolated RLQ pain and no other symptoms, CT abdomen and pelvis with IV contrast is the first-line imaging study to establish a definitive diagnosis, as it achieves 95% sensitivity and 94% specificity for appendicitis while identifying alternative diagnoses in 23-45% of cases. 1

Initial Clinical Assessment

Before imaging, obtain targeted history focusing on:

• Prior abdominal surgery (85% sensitivity and 78% specificity for adhesive small bowel obstruction if present) 2, 1
• Last bowel movement and flatus passage (absence suggests possible obstruction) 2, 1
• History of rectal bleeding or unexplained weight loss (suggests colorectal malignancy, which causes 60% of large bowel obstructions in elderly patients) 2, 1
• Chronic constipation history (suggests volvulus or diverticular disease) 2, 1
• Age and sex (influences differential diagnosis significantly) 1

Perform focused physical examination for:

• Peritoneal signs (rebound tenderness, guarding) 1
• Localized tenderness at McBurney's or Lanz point 3
• Hip flexion weakness or pain with hip extension (suggests psoas involvement or retroperitoneal pathology) 4

Obtain basic laboratory tests:

• Complete blood count (leukocytosis supports but does not confirm infection; normal values do not exclude serious pathology in elderly patients) 1, 5
• Urinalysis (rules out urinary tract infection) 6
• C-reactive protein if available (elevated in appendicitis and diverticulitis) 5

Imaging Algorithm

First-Line Imaging: CT Abdomen and Pelvis with IV Contrast

CT with IV contrast is the imaging modality of choice for adults with isolated RLQ pain because:

• Superior diagnostic accuracy: 95% sensitivity and 94% specificity for appendicitis 1
• Identifies alternative diagnoses: Detects diverticulitis, bowel obstruction, colorectal malignancy, mesenteric ischemia, and other pathology in 23-45% of cases initially suspected to be appendicitis 1, 7, 8
• Single comprehensive study: Evaluates bowel, mesentery, vasculature, urinary and reproductive systems simultaneously 8

Oral contrast may be added for better bowel luminal visualization but is not mandatory 2, 1

Alternative Imaging Considerations

Ultrasound may be considered first in specific populations:

• Women of reproductive age: Combined transabdominal and transvaginal ultrasound achieves 97.3% sensitivity and 91% specificity for gynecologic causes while avoiding radiation 1
• Pediatric patients: Ultrasound is the initial imaging modality of choice due to zero radiation exposure 6

Critical limitations of ultrasound in adults:

• High non-visualization rates: Appendix not visualized in 20-81% of cases 1
• Operator-dependent performance: Sensitivity ranges from 21% to 95.7% depending on experience and patient body habitus 1
• Equivocal results require CT anyway, resulting in diagnostic delay 1

Differential Diagnosis Based on Imaging Findings

Most Common Causes in Adults

Appendicitis remains the leading surgical cause, though it presents atypically in elderly patients with higher perforation rates 1

Right-sided colonic diverticulitis is increasingly common with age and can precisely mimic appendicitis 1

Adhesive small bowel obstruction accounts for 55-75% of small bowel obstructions, particularly in patients with prior abdominal surgery 2

Colorectal malignancy causes approximately 60% of large bowel obstructions in elderly patients 2, 1

Other important considerations include:

• Mesenteric ischemia (especially in patients with cardiovascular disease) 1
• Urinary tract pathology (nephrolithiasis, pyelonephritis) 1, 8
• Gynecologic pathology in women (ovarian torsion, ovarian cyst, pelvic inflammatory disease) 1, 8
• Epiploic appendagitis 8

Management Based on Imaging Results

If Appendicitis Confirmed

Proceed to appendectomy as standard treatment 1, 6

For perforated appendicitis with abscess: Percutaneous drainage followed by interval appendectomy with broad-spectrum antibiotics 6, 4

If Bowel Obstruction Identified

Immediate management priorities while awaiting surgical consultation:

• NPO status 1
• IV fluid resuscitation 1
• Nasogastric decompression 1
• Broad-spectrum antibiotics if signs of ischemia or perforation 1

If Alternative Diagnosis Established

Management depends on specific diagnosis (diverticulitis, malignancy, gynecologic pathology, etc.) and should be guided by appropriate specialty consultation 1, 8

Critical Pitfalls to Avoid

Do not assume normal laboratory values exclude serious pathology, especially in elderly patients who frequently have blunted inflammatory responses 1

Do not rely on classic symptom presentation alone, as atypical presentations are common, particularly in elderly and very young patients 1, 6

Do not delay imaging in patients with peritoneal signs or high clinical suspicion, as complications like perforation and sepsis require prompt intervention 1, 4

If thigh weakness accompanies RLQ pain, immediately consider psoas abscess or retroperitoneal pathology rather than typical intra-abdominal causes 4