What could be causing right lower quadrant abdominal pain that worsens with urination in an adult with nausea but no other urinary symptoms, chills, or vomiting?

Right Lower Quadrant Pain Worsening with Urination

The most likely diagnosis is nephrolithiasis (kidney stone) with ureteral obstruction, and you should immediately order a CT abdomen and pelvis WITHOUT contrast as the first-line diagnostic test. 1

Primary Differential Diagnosis

Nephrolithiasis is the leading diagnosis when right lower quadrant pain specifically worsens with urination, as ureteral stones cause colicky pain radiating from flank to groin that intensifies with ureteral peristalsis during voiding. 1 The absence of other urinary symptoms (no dysuria, frequency, or urgency) makes uncomplicated cystitis unlikely, while the presence of nausea without vomiting or fever fits the typical presentation of renal colic. 2

Key Distinguishing Features from Appendicitis

• Appendicitis typically causes nausea in 81% of cases and is associated with fever, localized McBurney point tenderness (97%), elevated C-reactive protein (mean 41 mg/L), and leukocytosis (mean 14 × 10⁹/L). 2
• Your patient lacks fever, vomiting, and chills, which makes appendicitis less likely, though it cannot be completely excluded. 2
• The pain-with-urination pattern is atypical for appendicitis—only 16% of ureteral stone patients have right lower quadrant tenderness that could be confused with appendicitis. 2

Secondary Differential Considerations

• Complicated urinary tract infection (pyelonephritis extending to lower ureter) is possible but less likely given the absence of fever, chills, and typical UTI symptoms. 1
• Appendicitis remains in the differential despite atypical features, as the classic presentation occurs in only 50% of cases. 3
• Ovarian pathology (if female patient): ovarian torsion, ruptured cyst, or ectopic pregnancy must be considered. 4

Immediate Diagnostic Workup

First-Line Imaging

Order CT abdomen and pelvis WITHOUT IV contrast immediately. 1 This is the gold standard for stone detection with near 100% sensitivity and specificity for urinary tract calculi. 1 Unenhanced CT is superior because:

• Stones are hyperdense and easily visible without contrast. 1
• It simultaneously evaluates for appendicitis (95% sensitivity, 94% specificity when performed WITH contrast, but can still identify appendicitis without contrast). 3, 1
• It identifies alternative diagnoses including ovarian pathology, bowel obstruction, and other causes of right lower quadrant pain. 5

Essential Laboratory Tests

• Urinalysis is mandatory: 92% of patients with ureteral stones have hematuria (red blood cells in urine), compared to only 26% with appendicitis. 2 However, absence of hematuria does not exclude stones.
• Complete blood count: Leukocytosis (>14 × 10⁹/L) and elevated C-reactive protein (>41 mg/L) strongly suggest appendicitis over renal colic. 2
• Pregnancy test (if female of reproductive age) before any imaging to rule out ectopic pregnancy. 4

Alternative Imaging if Specific Scenarios Apply

• If patient is pregnant or young female where radiation is a major concern: Start with ultrasound, though it has only 96% sensitivity for detecting stones. 1 If ultrasound is equivocal, proceed to MRI rather than CT. 1
• If CT without contrast is negative but clinical suspicion for appendicitis remains high: Repeat CT WITH IV contrast, as contrast enhancement is critical for detecting gallbladder wall enhancement, adjacent liver parenchymal hyperemia, and other inflammatory changes. 4

Critical Pitfalls to Avoid

• Do not assume negative CT rules out all pathology: CT has only 75% sensitivity for certain conditions like gallstones, and ultrasound may be needed as a complementary study. 4
• Do not delay imaging for oral contrast administration: Contrast-enhanced CT without enteral contrast has sensitivities of 90-100% and specificities of 94.8-100% for appendicitis, and oral contrast delays diagnosis without improving accuracy. 3
• Do not miss ectopic pregnancy in females: Always obtain pregnancy test before imaging. 4
• Recognize that pain location can be misleading: Right-sided renal colic causes right lower quadrant tenderness in 16% of cases, mimicking appendicitis. 2

Management Based on Imaging Results

If Nephrolithiasis Confirmed

• Urology consultation for stone size >5mm, complete obstruction, or signs of infection. 1
• Pain control and hydration for smaller stones with expectant management. 1

If Appendicitis Confirmed

• Immediate surgical consultation for appendectomy, as preoperative CT reduces negative appendectomy rate from 16.7% to 8.7%. 3
• Do not delay surgery while awaiting additional imaging if diagnosis is clear. 3

If Imaging is Equivocal

• For suspected appendicitis with equivocal CT: Consider ultrasound as complementary study (sensitivity 81.7%, specificity 53.9% when appendix visualized). 3
• For suspected stones with negative CT: Ultrasound may identify hydronephrosis or alternative diagnoses. 1