What are the next best steps in managing a 24-year-old female with bilateral flank pain and mild dysuria, with a recent urinalysis (UA) not suggestive of urinary tract infection (UTI), normal renal sonogram, and slightly thick bladder walls on pelvic sonogram, and a history of shrimp allergy?

Management of Bilateral Flank Pain and Mild Dysuria in a 24-Year-Old Female

CT abdomen and pelvis with IV contrast is the most appropriate next step for evaluating persistent bilateral flank pain with mild dysuria when initial workup including urinalysis and renal sonogram is unremarkable. 1

Diagnostic Approach Based on Current Findings

The patient presents with:

• 24-year-old female
• Bilateral flank pain and mild dysuria
• Normal urinalysis (not suggestive of UTI)
• Normal renal sonogram (no hydronephrosis, no calculi)
• Small left renal simple cyst (1.1 cm)
• Slightly thick bladder walls on pelvic sonogram
• No internal bladder lesions or stones
• Shrimp allergy

Imaging Considerations

1. CT Abdomen and Pelvis with IV Contrast

   • Most appropriate next step for evaluating flank pain with negative urinalysis and unremarkable ultrasound findings 1
   • Can identify alternative diagnoses in 15% of patients with flank pain who have negative urinalysis and no history of urolithiasis 1
   • Provides comprehensive evaluation of both urinary and non-urinary causes of flank pain
   • Allows visualization of potential subtle pathologies not detected on ultrasound

2. Contrast Administration and Shrimp Allergy

   • The patient's shrimp allergy requires consideration but is not an absolute contraindication to IV contrast
   • Consultation with radiology regarding contrast administration is appropriate, as already suggested to the patient

Additional Diagnostic Considerations

1. Cystoscopy

   • Appropriate consideration for persistent dysuria with slightly thick bladder walls
   • Can evaluate for interstitial cystitis/bladder pain syndrome, which can present with dysuria and flank pain 2
   • The recommendation to discuss cystoscopy with the patient is appropriate

2. Gynecological Evaluation

   • Appropriate to rule out fungal vaginitis or other gynecological causes that may mimic or contribute to urinary symptoms 2
   • The recommendation for GYN follow-up is appropriate

Differential Diagnosis

1. Musculoskeletal Causes

   • Most likely explanation for bilateral flank pain as already suggested
   • Often a diagnosis of exclusion after ruling out urological causes

2. Urological Causes

   • Simple renal cyst (1.1 cm) - likely incidental and not causing symptoms
   • Slightly thick bladder walls - may indicate early cystitis or interstitial cystitis
   • Occult urolithiasis not detected on ultrasound

3. Less Common Considerations

   • Loin pain-hematuria syndrome - can present with flank pain even without current hematuria 3, 4
   • Early pyelonephritis without typical urinalysis findings 5
   • Medullary sponge kidney 6

Management Algorithm

1. Immediate Next Steps:

   • Proceed with CT abdomen and pelvis with IV contrast after appropriate discussion regarding contrast administration and shrimp allergy
   • Complete the pending UA/urine culture to definitively rule out infection

2. If CT is negative:

   • Proceed with cystoscopy to evaluate for bladder pathology
   • Complete gynecological evaluation
   • Consider urodynamic testing if symptoms persist 1

3. If CT identifies pathology:

   • Direct treatment based on specific findings
   • Consider urology referral for management of any identified urological abnormalities

Important Considerations and Pitfalls

• Avoid assuming musculoskeletal origin without complete evaluation: While musculoskeletal causes are common, thorough evaluation is needed to rule out urological pathology
• Don't treat empirically for UTI with negative urinalysis: Avoid unnecessary antibiotics without confirmation of infection 1
• Don't dismiss persistent symptoms: Recurrent or persistent symptoms warrant comprehensive evaluation including imaging and potentially cystoscopy 1
• Consider non-urological causes: Gynecological and gastrointestinal conditions can mimic urinary symptoms

By following this approach, you can systematically evaluate and manage this patient's bilateral flank pain and dysuria while avoiding unnecessary treatments or missed diagnoses.