What are the common causes of right lower quadrant (RLQ) or right pelvic pain?

Common Causes of Right Lower Quadrant (RLQ) or Right Pelvic Pain

Appendicitis is the most common surgical emergency causing RLQ pain, but CT imaging identifies alternative diagnoses in 23-45% of cases, including right-sided colonic diverticulitis, bowel obstruction, colorectal malignancy, gynecologic pathology, urinary tract conditions, and mesenteric ischemia. 1, 2

Gastrointestinal Causes

Most Common

• Acute appendicitis remains the leading surgical cause requiring emergency intervention, with CT achieving 95% sensitivity and 94% specificity for diagnosis 1, 2
• Right-sided colonic diverticulitis accounts for 8% of RLQ pain cases and precisely mimics appendicitis clinically, increasing in frequency with age 1, 2
• Gastroenteritis and colitis are among the most common non-surgical diagnoses identified on CT in patients without appendicitis 1
• Constipation frequently causes RLQ pain, particularly in pediatric patients and elderly populations 3

Other Gastrointestinal Etiologies

• Bowel obstruction occurs in 3% of RLQ pain presentations, with adhesive small bowel obstruction having 85% sensitivity in patients with prior abdominal surgery 1, 2
• Colorectal malignancy accounts for approximately 60% of large bowel obstructions in elderly patients, especially with rectal bleeding or weight loss history 2
• Inflammatory bowel disease (Crohn's disease with terminal ileitis) presents with RLQ pain and inflammatory changes 1, 4
• Infectious enterocolitis including typhlitis and inflammatory terminal ileitis 1
• Mesenteric adenitis mimics appendicitis, often following viral illness in children 3

Gynecologic Causes (in Females)

• Ovarian cyst (ruptured or large) causes acute pain, with combined transabdominal and transvaginal ultrasound achieving 97.3% sensitivity and 91% specificity for detection 2, 5
• Ovarian/adnexal torsion is a surgical emergency that must be considered in any female with RLQ pain 3, 5
• Pelvic inflammatory disease develops in approximately 15% of untreated chlamydia infections and presents with RLQ pain 5
• Ectopic pregnancy is misdiagnosed in approximately 40% of presenting visits and requires immediate urine pregnancy test or beta-hCG in all sexually active premenopausal patients 5
• Benign adnexal mass is among the most common CT diagnoses in patients without a final clinical diagnosis 1
• Pelvic congestion syndrome identified on CT in patients with chronic-acute presentations 1

Urinary Tract Causes

• Urinary tract infection/pyelonephritis presents with abdominal pain, particularly in young children who may not localize symptoms well 3, 5
• Ureteral stone disease (urolithiasis) causes RLQ pain when affecting the right ureter 1
• Nephrolithiasis should be excluded with urinalysis in all patients 3

Vascular Causes

• Mesenteric ischemia is a critical diagnosis in elderly patients with cardiovascular disease and must be identified urgently 2, 6

Pediatric-Specific Considerations

• Intussusception is more common in children under 5 years, typically presenting with intermittent colicky pain, vomiting, and potentially bloody stools 3
• Children under 5 years present with atypical symptoms more frequently and have higher rates of perforated appendicitis due to delayed diagnosis 3

Age-Specific Patterns

Elderly Patients

• Atypical presentations are the norm, with blunted inflammatory responses and later presentation with higher complication rates 2
• Broader differential includes colorectal malignancy, diverticulitis, and mesenteric ischemia as primary considerations 2
• Normal laboratory values do not exclude serious pathology in this population 2

Women of Reproductive Age

• Gynecologic causes account for a significant proportion, with pelvic ultrasound (transabdominal + transvaginal) achieving 97.3% sensitivity when performed by experienced operators 2, 5
• Pregnancy status must be established immediately as first diagnostic step 5

Critical Clinical Pitfall

The appendix is not visualized on ultrasound in 20-81% of cases, creating diagnostic uncertainty, and equivocal ultrasound results require CT anyway, resulting in diagnostic delay without avoiding radiation. 2 CT abdomen and pelvis with IV contrast remains the workhorse imaging modality for adults, identifying the cause of RLQ pain in 94.3% of cases with concordance to final clinical diagnosis, and 41% of patients with non-appendiceal diagnoses require hospitalization with 22% undergoing surgical or image-guided intervention. 1, 4