What is the most likely diagnosis for a woman with urinary frequency, urgency, and dysuria, and a history of similar episodes, with pending urine culture results and normal urinalysis?

Most Likely Diagnosis: Interstitial Cystitis/Bladder Pain Syndrome

The most likely diagnosis is interstitial cystitis/bladder pain syndrome (IC/BPS), given the chronic recurrent nature of symptoms (three weeks current episode, similar episodes over six months), normal urinalysis, and absence of infection on initial testing. 1

Key Diagnostic Features Supporting IC/BPS

The clinical presentation strongly suggests IC/BPS rather than acute infection:

• Chronic symptom pattern: Symptoms present for three weeks with recurrent similar episodes over six months, which is characteristic of IC/BPS requiring at least six weeks of symptoms for diagnosis 1
• Normal urinalysis: The absence of pyuria, bacteriuria, or other abnormalities on urinalysis effectively rules out acute uncomplicated cystitis 1
• Classic symptom triad: Urinary frequency, urgency, and dysuria without evidence of infection are hallmark features of IC/BPS 1, 2
• Irregular menstrual periods: Suggests possible perimenopausal status, which increases likelihood of genitourinary syndrome of menopause contributing to symptoms 3

Why Other Diagnoses Are Less Likely

Urinary Tract Infection (UTI): This is effectively excluded by the normal urinalysis. In uncomplicated cystitis, diagnosis can be made clinically based on symptoms alone, but the normal urinalysis makes active infection highly unlikely 1. The European Association of Urology guidelines state that in patients with typical cystitis symptoms, urinalysis adds minimal diagnostic accuracy, but when performed and normal, it argues against acute infection 1

Pyelonephritis: Definitively ruled out by absence of fever, normal vital signs, no costovertebral angle tenderness, and normal urinalysis 1. Pyelonephritis presents with systemic signs of inflammation including fever and flank pain 1

Bacterial Vaginosis: The thin, clear, non-malodorous vaginal discharge is not consistent with bacterial vaginosis, which typically presents with malodorous discharge 3. Additionally, the predominant symptoms are urinary rather than vaginal 3

Trichomoniasis: While pending cultures will confirm, the clear non-malodorous discharge and absence of cervical motion tenderness make this unlikely 3. Trichomoniasis typically presents with purulent, malodorous discharge 3

Critical Diagnostic Considerations

The recurrent nature over six months is the most important diagnostic clue 1. IC/BPS is characterized by chronic bladder/pelvic pain and pressure associated with urinary frequency and urgency, often with a relapsing-remitting pattern 1, 2.

Normal urinalysis in the setting of chronic urinary symptoms should immediately raise suspicion for IC/BPS 1, 3. The 2022 AUA/SUFU guidelines emphasize that IC/BPS is a clinical diagnosis requiring symptoms present for at least six weeks with documented negative urine cultures 1

Important Pitfalls to Avoid

• Do not treat empirically with antibiotics: With normal urinalysis and chronic symptoms, empiric antibiotic treatment is inappropriate and may delay correct diagnosis 1
• Pyuria alone would not be diagnostic: Even if present, pyuria has low positive predictive value and can indicate non-infectious genitourinary inflammation 3, 4
• Consider atrophic vaginitis: Given irregular menses suggesting perimenopause, vaginal atrophy may be contributing to symptoms and should be evaluated 3
• Await pending cultures: While IC/BPS is most likely, the pending urine culture will definitively exclude occult infection with lower bacterial counts that might not show on dipstick 1, 4

Next Steps in Management

Document baseline symptom severity using a voiding diary (at minimum one day) to establish frequency and pain levels for monitoring treatment response 1. The AUA guidelines recommend baseline assessment before initiating therapy 1

Consider cystoscopy only if Hunner lesions are suspected, as this is the only consistent cystoscopic finding diagnostic for IC/BPS 1. Most IC/BPS patients do not require cystoscopy for diagnosis 1

Initial treatment should be non-surgical and may include behavioral modifications, oral medications, or bladder instillations 1. The 2022 guidelines no longer use tiered treatment approaches, emphasizing individualized concurrent multi-modal therapies based on patient phenotype 1