What are the common causes of sharp, intermittent right pelvic pain?

Common Causes of Sharp, Intermittent Right Pelvic Pain

Sharp, intermittent right pelvic pain in reproductive-age women most commonly results from ovarian cysts (including hemorrhagic and ruptured cysts), appendicitis, ovarian torsion, ectopic pregnancy (if pregnant), pelvic inflammatory disease, and right colonic diverticulitis. 1, 2

Gynecologic Causes (β-hCG Negative)

Most Common Etiologies

• Ovarian cysts represent the leading gynecologic cause, including hemorrhagic cysts and ruptured follicular cysts that produce acute intermittent pain 2, 3
• Ovarian torsion presents with asymmetrically enlarged ovary with twisted pedicle, often requiring urgent surgical intervention 1
• Pelvic inflammatory disease manifests with tubal wall thickening, pyosalpinx, or tubo-ovarian abscess 1, 2
• Endometriosis can cause acute exacerbations, particularly with ruptured endometriomas ("chocolate cysts") 1, 4
• Pelvic congestion syndrome from dilated pelvic veins, though more commonly causes chronic pain, can present acutely 1, 5

Less Common but Important

• Degenerating or torsed uterine leiomyomas occur in reproductive-age women and cause acute pain episodes 3, 4

Pregnancy-Related Causes (β-hCG Positive)

• Ectopic pregnancy is the critical diagnosis to exclude, with transvaginal ultrasound showing positive likelihood ratio of 111 for adnexal mass without intrauterine pregnancy 1
• Corpus luteum cysts in early pregnancy can cause significant pain 4
• Threatened or spontaneous abortion presents with pain and irregular endometrial echo 4

Non-Gynecologic Causes

Gastrointestinal

• Appendicitis remains the most common surgical emergency and must always be considered in right lower quadrant pain, with CT sensitivity of 95% and specificity of 94% 1
• Right colonic diverticulitis accounts for 8% of right lower quadrant pain cases 1
• Inflammatory bowel disease including terminal ileitis can mimic gynecologic pathology 1, 2
• Infectious enterocolitis (typhlitis, gastroenteritis) presents with similar pain patterns 1
• Bowel obstruction occurs in 3% of right lower quadrant pain presentations 1

Genitourinary

• Ureteral calculi cause colicky right-sided pain radiating to the pelvis 1
• Pyelonephritis with right-sided involvement 2

Diagnostic Approach by Clinical Scenario

When Gynecologic Etiology Suspected (β-hCG Negative)

• Transvaginal ultrasound is the first-line imaging modality due to superior sensitivity for ovarian pathology, lack of radiation, and wide availability 1, 3
• CT should be reserved for inconclusive ultrasound or when life-threatening diagnosis is considered 1

When Gynecologic Etiology Suspected (β-hCG Positive)

• Transvaginal ultrasound combined with serial β-hCG levels is the diagnostic standard for ectopic pregnancy evaluation 1
• Endometrial thickness <8 mm excludes normal intrauterine pregnancy; thickness ≥25 mm virtually excludes ectopic pregnancy 1

When Etiology Uncertain (Nonspecific Right Lower Quadrant Pain)

• CT abdomen and pelvis with IV contrast is the preferred initial imaging because it has high diagnostic yield for both appendicitis and alternative diagnoses including gynecologic pathology 1
• CT identifies non-appendiceal diagnoses in 94.3% of cases, with common findings including benign adnexal mass, gastroenteritis, colitis, constipation, inflammatory bowel disease, and pelvic congestion syndrome 1

Critical Diagnostic Pitfalls

• Missing ectopic pregnancy by failing to obtain β-hCG in all reproductive-age women before imaging decisions 1, 2
• Assuming appendicitis without considering ovarian torsion, which requires urgent surgical intervention and has overlapping CT findings 1
• Overlooking tubo-ovarian abscess versus peri-appendiceal abscess—the presence of right ovarian vein entering a right pelvic abscess has 100% specificity and 94% sensitivity for tubo-ovarian abscess 1
• Relying solely on ultrasound when clinical suspicion is high but ultrasound is negative, as sensitivity for some conditions (like ectopic pregnancy without yolk sac) is only 13% 1
• Dismissing pelvic inflammatory disease in patients without classic risk factors, as it remains a frequent cause of acute pelvic pain 2, 3