Management of Bilateral Flank Pain with Urinary Symptoms and Normal Urinalysis
The next step is to obtain non-contrast CT of the abdomen and pelvis, which is the gold standard imaging modality with 98-100% sensitivity and specificity for detecting urinary stones and identifying alternative diagnoses in approximately one-third of patients. 1, 2
Rationale for Imaging Despite Normal Urinalysis
A normal urinalysis does not exclude significant urologic pathology. While hematuria supports the diagnosis of renal colic, over 20% of patients with confirmed urinary stones may have negative urinalysis, particularly if the stone is completely obstructing without mucosal trauma 3, 1
The bilateral nature of symptoms raises concern for either bilateral stone disease, bilateral obstruction from another cause (such as retroperitoneal pathology), or an alternative diagnosis entirely 1, 2
The 2-week duration with persistent urgency and pressure suggests this is not self-limited and warrants definitive imaging 3, 1
Why Non-Contrast CT is the Preferred Modality
Non-contrast CT detects stones of any size, location, and chemical composition with near-perfect accuracy and simultaneously identifies extraurinary causes of flank pain in one-third of patients 1, 2, 4
The American College of Radiology designates non-contrast CT as the imaging study of choice for evaluating flank pain, with the ability to detect secondary signs of obstruction including hydronephrosis, perinephric stranding, and periureteral inflammation 1, 2
Contrast-enhanced CT should be avoided as the initial study because it can obscure stones within the renal collecting system 5, 2
Alternative Diagnoses to Consider
The bilateral presentation and normal urinalysis should prompt consideration of non-stone etiologies:
Gynecologic causes including benign adnexal masses or pelvic congestion syndrome can present with bilateral flank pain and urinary pressure symptoms 1
Gastrointestinal pathology such as colonic diverticulitis or inflammatory bowel disease may manifest as flank pain 1
Musculoskeletal pain from paraspinal muscles or facet joints typically worsens with positional changes, which helps differentiate it from renal colic 1
Rare entities like medullary sponge kidney with nephrocalcinosis can present with recurrent symptoms and bilateral involvement 6
Clinical Pitfalls to Avoid
Do not assume the absence of hematuria excludes stone disease. The urinalysis was performed 5 days ago, and the clinical picture may have evolved 3, 1
Do not delay imaging in women of reproductive age—ectopic pregnancy or ovarian pathology can mimic urologic symptoms and require urgent intervention 1
Bilateral symptoms warrant more aggressive evaluation than unilateral presentations, as they may indicate systemic disease, bilateral obstruction, or alternative diagnoses requiring different management 1, 2
Immediate Management Considerations
If the patient develops fever, hemodynamic instability, or signs of sepsis, immediate hospital admission is required regardless of imaging results 3
Pain control should be addressed promptly with non-steroidal anti-inflammatory drugs (diclofenac 75 mg intramuscular preferred) if not contraindicated, with reassessment within one hour 3, 1
Failure of adequate analgesia within one hour mandates immediate hospital admission 3, 1
Follow-Up Based on Imaging Results
If stones <5 mm are identified: Conservative management with hydration, analgesia, and urine straining is appropriate, with urology follow-up within 7-14 days 1
If stones >5 mm or complete obstruction: Urgent urology referral for consideration of intervention (retrograde ureteral stenting or percutaneous nephrostomy) 3, 1
If no stones but alternative diagnosis identified: Management directed at the specific pathology found 1, 2
If imaging is negative: Only 14% of such patients require hospitalization and 4% undergo surgical intervention, suggesting most can be managed conservatively with close follow-up 1