How can I differentiate between interstitial cystitis and urinary tract infections in patients presenting with pelvic pain?

Differentiating between interstitial cystitis (IC) and urinary tract infections (UTIs) in patients presenting with pelvic pain primarily hinges on the presence or absence of a bacterial infection and the chronicity of symptoms.

• Urinary Tract Infections (UTIs): UTIs are caused by bacterial infection, and a key diagnostic feature is the presence of bacteria in urine, confirmed by a urine culture NICE CKS. Symptoms typically include dysuria (painful urination), increased urinary frequency, and urgency NICE CKS. Haematuria (blood in urine) can also be present NICE NG12. UTIs usually respond to appropriate antibiotic treatment, with symptoms improving within 48 hours NICE CKS. If symptoms worsen rapidly or significantly, or do not improve within 48 hours of starting antibiotics, an alternative diagnosis or complication should be considered NICE CKS.
• Interstitial Cystitis (IC): In contrast, interstitial cystitis is a chronic inflammatory bladder condition characterized by chronic pelvic pain, urgency, and frequency, but without evidence of bacterial infection NICE CKS,NICE CKS Ratner 2001Doggweiler-Wiygul et al. 2001Dell et al. 2009. Urine cultures in patients with IC are typically sterile Ratner 2001Dell et al. 2009. The pain associated with IC often worsens as the bladder fills and temporarily improves after voiding Dell et al. 2009. IC does not respond to antibiotics Ratner 2001.

Key Differentiating Factors and Considerations:

• Infection Status: The most crucial differentiator is the presence of a positive urine culture in UTIs versus a sterile urine culture in IC (Ratner, 2001; Dell et al., 2009; NICE CKS).
• Symptom Duration and Response to Treatment: UTIs are generally acute and resolve with antibiotics NICE CKS. IC presents with persistent bladder or urethral pain that is chronic and does not respond to antibiotic therapy (Ratner, 2001; NICE CKS,NICE CKS).
• Referral Criteria: Persistent bladder or urethral pain warrants referral to an appropriate specialist (urologist, urogynaecologist, or nephrologist), with urgency if cancer is suspected NICE CKS,NICE CKS. This referral pathway is relevant for patients where IC is suspected after ruling out infection. For women aged 60 and over with recurrent or persistent unexplained UTIs, non-urgent referral for bladder cancer should be considered NICE CKS,NICE CKS,NICE NG12. Visible haematuria that is unexplained or persists/recurs after successful UTI treatment, especially in those aged 45 and over, also requires a suspected cancer pathway referral NICE CKS,NICE CKS,NICE NG12.