What are the differential diagnoses (DDx) for a 42-year-old female (F) with a history of open appendectomy and laparoscopic sterilization (lap sterilization) presenting with right lower quadrant (RLQ) pain?

Differential Diagnoses for RLQ Pain in a 42-Year-Old Female with Prior Appendectomy

In a 42-year-old woman with previous appendectomy presenting with RLQ pain, the primary differential diagnoses include gynecologic pathology (ovarian torsion, ruptured ovarian cyst, tubo-ovarian abscess, pelvic inflammatory disease), stump appendicitis, epiploic appendagitis, cecal diverticulitis, and adhesive disease from prior surgeries. 1, 2, 3

Gynecologic Pathology (Most Common in This Population)

Women of reproductive age have a 26% incidence of nonappendiceal pathology when presenting with RLQ pain, with 42% of those with normal-appearing appendices having gynecologic causes. 2

Key Gynecologic Differentials:

• Ovarian torsion: Must be considered urgently as it requires emergency surgical intervention to preserve ovarian function 1
• Ruptured ovarian cyst: Common cause of acute RLQ pain in premenopausal women, typically managed conservatively unless hemodynamically unstable 1
• Tubo-ovarian abscess: Presents with fever, leukocytosis, and RLQ pain; requires IV antibodies and possible drainage 1
• Pelvic inflammatory disease: Important consideration in sexually active women with RLQ pain 1
• Ectopic pregnancy: Mandatory to exclude with urine pregnancy test before any imaging, even with history of sterilization (failure rate 0.5-1%) 1

Stump Appendicitis

Stump appendicitis is a rare but important differential in patients with prior appendectomy, occurring when residual appendiceal tissue becomes inflamed. 3

• Presents identically to acute appendicitis with RLQ pain, fever, and leukocytosis 3
• Can occur years after the initial appendectomy (reported case at 3 years post-op) 3
• Diagnosis confirmed by CT imaging showing inflammation at the appendiceal stump location 3

Epiploic Appendagitis

Epiploic appendagitis mimics acute appendicitis but occurs in well-appearing patients with localized RLQ tenderness and minimal systemic symptoms. 4

• Caused by torsion and infarction of epiploic appendages along the ascending colon 4
• Presents with acute RLQ pain at McBurney's point with mild peritonism but patient appears well 4
• CT scan is diagnostic, showing focal soft-tissue attenuation with fat stranding along the lateral wall of ascending colon 4
• Treatment is conservative with NSAIDs and observation 4

Adhesive Disease

Given her history of both open appendectomy and laparoscopic sterilization, adhesive small bowel obstruction or chronic adhesive pain is a significant consideration. 2

• Open appendectomy carries higher risk of adhesion formation than laparoscopic approach
• Can present as intermittent or chronic RLQ pain
• May cause partial small bowel obstruction with colicky pain

Other Gastrointestinal Causes

• Cecal diverticulitis: More common in patients >50 years but can occur in younger adults 5
• Inflammatory bowel disease (Crohn's disease with terminal ileitis)
• Meckel's diverticulitis: Rare but should be evaluated if appendix appears normal at exploration 4

Diagnostic Approach

Immediate Essential Steps:

• Urine pregnancy test is mandatory to exclude ectopic pregnancy before imaging 1
• Complete blood count to assess for leukocytosis 1
• Urinalysis to exclude urinary tract infection or nephrolithiasis 1

Imaging Algorithm:

CT abdomen and pelvis with IV contrast is the initial imaging study of choice, with sensitivity of 95% and specificity of 94% for identifying both appendiceal and gynecologic pathology. 1, 6

• CT can identify stump appendicitis, epiploic appendagitis, ovarian pathology, and other causes 3, 4
• If CT is negative or indeterminate with high clinical suspicion, diagnostic laparoscopy is recommended as it has both diagnostic and therapeutic value 7

Critical Pitfalls to Avoid

• Never assume appendicitis is impossible after prior appendectomy—stump appendicitis remains a differential 3
• Do not skip pregnancy testing even with documented sterilization history, as tubal ligation has a known failure rate 1
• In women of childbearing age with RLQ pain, gynecologic pathology is found in 26-42% of cases and must be actively excluded 2
• Epiploic appendagitis is frequently misdiagnosed as appendicitis clinically but requires only conservative management 4