What could be causing pain in the right lower quadrant when urinating, and what are the appropriate diagnostic steps and treatments?

Right Lower Quadrant Pain with Urination

The most likely diagnosis is nephrolithiasis (kidney stone) causing ureteral obstruction, and you should obtain a CT abdomen/pelvis without contrast as the initial imaging study. 1

Primary Differential Diagnosis

The combination of right lower quadrant pain specifically triggered by urination points strongly toward urologic pathology rather than gastrointestinal causes:

• Nephrolithiasis with ureteral obstruction is the leading diagnosis when flank/lower quadrant pain correlates with urination, as stones can cause colicky pain radiating from flank to groin that intensifies with ureteral peristalsis during voiding 2, 3
• Complicated urinary tract infection (pyelonephritis or cystitis with upper tract involvement) can present with lower quadrant pain during urination 1, 4
• Appendicitis remains in the differential for any right lower quadrant pain, though the specific association with urination makes this less likely unless there is pyuria from bladder irritation by an inflamed appendix 5, 6
• Right-sided colonic diverticulitis or gynecologic pathology (in females) are additional considerations but would not typically worsen specifically with urination 5

Immediate Diagnostic Approach

Order CT abdomen and pelvis WITHOUT contrast media as the first-line imaging study for suspected nephrolithiasis, which has near 100% sensitivity and specificity for urinary tract calculi 1

Key Clinical Features to Assess:

• Pain characteristics: Sudden onset, colicky nature, radiation to groin strongly suggests stone disease 2
• Associated symptoms: Hematuria (gross or microscopic), nausea/vomiting, fever (suggests infection/obstruction) 3
• Urinalysis: Check for hematuria, pyuria, bacteriuria, and pH 3
• Vital signs and fever: Fever with obstructing stone indicates urgent urologic emergency requiring decompression 3

Why CT Without Contrast:

• Unenhanced CT is the gold standard for stone detection with sensitivity and specificity near 100% 1
• Contrast is unnecessary for stone visualization and may obscure small calculi 1
• Can identify hydronephrosis, degree of obstruction, and alternative diagnoses 3

Alternative Imaging Considerations

Ultrasonography may be considered if:

• Pregnancy is confirmed or suspected (avoid radiation) 2
• Young patient where radiation exposure is a concern 2
• However, ultrasound has only 96% sensitivity when combining pyeloureteral dilation, direct stone visualization, and absence of ureteral ejaculation—inferior to CT 2

If CT shows no stone but pain persists:

• Consider CT abdomen/pelvis WITH contrast to evaluate for appendicitis, diverticulitis, or other inflammatory conditions 1, 5
• In females of reproductive age, add pelvic ultrasound (transvaginal + transabdominal) to exclude ovarian torsion or other gynecologic pathology 5

Critical Pitfalls to Avoid

Do not assume urinary tract infection alone if pain is severe or colicky—obstructing stones with superimposed infection (pyonephrosis) can rapidly progress to sepsis and require emergency urologic intervention 3

Do not delay imaging in patients with fever and suspected obstruction—this represents a urologic emergency requiring urgent decompression with ureteric stent or nephrostomy 3

Do not miss appendicitis with pyuria—an inflamed appendix adjacent to the bladder or ureter can cause sterile pyuria and urinary symptoms, delaying correct diagnosis and increasing perforation risk 6

Immediate Management While Awaiting Imaging

• Analgesia: NSAIDs (ketorolac) are first-line for renal colic unless contraindicated 3
• Hydration: IV fluids if unable to tolerate oral intake 3
• Urinalysis and urine culture: Obtain before antibiotics if infection suspected 4
• If infection suspected with obstruction: Start broad-spectrum antibiotics (ciprofloxacin covers common uropathogens including E. coli, Klebsiella, Proteus, Pseudomonas) and obtain urgent urology consultation 4, 3

Treatment Based on Imaging Results

If nephrolithiasis confirmed:

• Stones <5mm: Conservative management with hydration, analgesia, and medical expulsive therapy; most pass spontaneously 3
• Stones >5mm or with hydronephrosis: Urology referral for possible intervention (lithotripsy, ureteroscopy, or stent placement) 3
• Any stone with fever/infection: Emergency urologic decompression required 3

If imaging shows appendicitis:

• Surgical consultation for appendectomy 1, 5
• CT with contrast has 95% sensitivity and 94% specificity for appendicitis 5

If uncomplicated UTI/pyelonephritis:

• Ciprofloxacin 500mg PO BID for 7 days (uncomplicated cystitis) or 10-14 days (pyelonephritis) 4
• Adjust based on culture results 4