What could be causing pain in the right lower quadrant during defecation and urination?

Right Lower Quadrant Pain with Defecation and Urination

You need a contrast-enhanced CT scan of the abdomen and pelvis to identify the cause, as this presentation suggests overlapping gastrointestinal and genitourinary pathology that requires comprehensive imaging evaluation. 1, 2

Immediate Diagnostic Approach

Obtain CT abdomen and pelvis with IV contrast as the primary imaging study because:

• CT has 95% sensitivity and 94% specificity for detecting appendicitis and achieves 94.3% concordance with final clinical diagnosis for non-appendiceal causes 1
• The combination of pain during both defecation and urination indicates potential involvement of multiple organ systems (bowel, urinary tract, or gynecologic structures) that CT can simultaneously evaluate 2
• CT identifies alternative diagnoses in 23-45% of patients with right lower quadrant pain, including right colonic diverticulitis (8%), bowel obstruction (3%), urolithiasis, and gynecologic pathology 1

Most Likely Differential Diagnoses

Gastrointestinal Causes

• Appendicitis - remains the primary surgical concern despite atypical symptoms; pain with defecation suggests peritoneal irritation 1
• Right colonic diverticulitis - accounts for 8% of RLQ pain cases and can cause pain with bowel movements 1
• Inflammatory bowel disease (Crohn's terminal ileitis) - can cause pain with defecation due to bowel inflammation 1
• Bowel obstruction - adhesive small bowel obstruction represents 55-75% of cases and can present with RLQ pain, especially with history of prior surgery 1

Genitourinary Causes

• Urolithiasis (ureteral stone) - pain during urination strongly suggests urinary tract involvement; can present with RLQ pain when stone is in distal right ureter 1, 2
• Urinary tract infection/pyelonephritis - can cause both RLQ pain and dysuria 2

Gynecologic Causes (if female)

• Ovarian pathology (cyst, torsion, or pelvic inflammatory disease) - can cause pain with both defecation and urination due to anatomic proximity 1
• Endometriosis - can involve bowel and bladder, causing pain with both functions 1

Essential Laboratory Tests Before Imaging

• Urinalysis - mandatory to evaluate for infection, hematuria (suggesting stone), or proteinuria 2
• Complete blood count - leukocytosis suggests infection or inflammation 1
• C-reactive protein - elevated in appendicitis, diverticulitis, and inflammatory conditions 3
• Pregnancy test (if female of reproductive age) - essential before imaging decisions 3

Critical Imaging Considerations

Do not delay CT beyond 12 hours if serious pathology is suspected, as conditions like perforated appendicitis, bowel obstruction with ischemia, or complicated urolithiasis require urgent intervention 2

Use IV contrast unless contraindicated - non-contrast CT significantly reduces diagnostic accuracy for bowel wall enhancement, abscess formation, and vascular complications 2

Common Pitfalls to Avoid

• Do not assume urinary symptoms mean the problem is purely urologic - appendicitis and other intra-abdominal pathology can cause urinary symptoms through anatomic proximity and peritoneal irritation 2
• Do not rely on ultrasound alone in adults with nonspecific RLQ pain - while ultrasound is appropriate for pediatric patients, CT is superior for adult evaluation with sensitivity/specificity >94% versus ultrasound's 51.8-81.7% sensitivity 1, 4
• Do not miss gynecologic pathology in females - 21.6% of alternative diagnoses in RLQ pain are gynecologic; consider pelvic ultrasound if CT shows no clear cause 1

What the Radiologist Should Evaluate

The CT report must specifically address:

• Appendix - diameter, wall enhancement, periappendiceal fat stranding, fluid collections 1
• Right colon - wall thickening, diverticula, inflammatory changes 1
• Ureters and kidneys - stones, hydronephrosis, pyelonephritis 2
• Reproductive organs (if female) - ovarian masses, free fluid, tubo-ovarian abscess 1
• Mesentery and bowel - obstruction, ischemia, inflammatory bowel disease 1

If CT is Contraindicated

MRI abdomen and pelvis without IV contrast is the alternative, with 97% sensitivity and 99.4% specificity for appendicitis, though table time averages 14 minutes versus CT's rapid acquisition 1