Dyspareunia is another common symptom in patients who have IC/PBS. Pain during intercourse appears to arise from tenderness in the pelvic floor muscles as well as the bladder. It may also occur upon vaginal entry due to associated vulvar vestibulitis.8 In postmenopausal women, vulvovaginal atrophy may contribute to dyspareunia as well.
Also consider IC/PBS when a patient continues to experience pelvic pain after treatment of endometriosis or after hysterectomy. In one study, 80% of women who had persistent chronic pelvic pain after hysterectomy had interstitial cystitis.9 Among women who have endometriosis, we have found that 35% have IC/PBS (unpublished data). Chung reported that 85% of women who have endometriosis also have IC/PBS.10
Which diagnostic studies are useful?
To some extent, IC/PBS is a diagnosis of exclusion, as other possible causes of pelvic pain, urinary frequency, urinary urgency, and nocturia must be excluded. Urinalysis and urine culture are essential tests in the evaluation of women suspected of having interstitial cystitis. Urinary tract infection must be excluded with a negative urine culture. If a patient has hematuria, urine cytology or cystoscopy is recommended to exclude malignancy. Urine cytology or cystoscopy is also recommended if the patient has a history of smoking (because of the strong association between bladder cancer and smoking) or is older than 50 years.
Some experts still insist that cystoscopic hydrodistention is necessary. Cystoscopy with hydrodistention under general or regional anesthesia has long been considered the “gold standard” diagnostic test for IC. Identification of a Hunner ulcer is pathognomonic, but it is an uncommon finding and one usually discovered only in advanced cases. More often, cystoscopy with hydrodistention in a patient who has IC reveals glomerulations, which are mucosal hemorrhages that exhibit a characteristic appearance upon second filling of the bladder (FIGURE 1).
The value of cystoscopy has recently been questioned because at least 10% of patients who have clear clinical evidence of interstitial cystitis have normal findings at the time of cystoscopic hydrodistention.11 Glomerulations have also been observed in asymptomatic patients after hydrodistention with as much as 950 mL of water. In at least one published study, glomerulations did not distinguish patients who had a clinical diagnosis of IC from asymptomatic women.12
The potassium sensitivity (parsons) test (PST) may be a useful diagnostic test for IC. It is based on the concept that patients who have the disease have a defective urothelium that allows cations to penetrate the bladder wall and depolarize the sensory C-fibers, generating lower urinary tract symptoms.13 An alternative explanation for this test may be that it identifies patients who have a hyperalgesic or allodynic bladder, whether or not there is a defect in the urothelium.
The test is performed by instilling 40 mL of sterile water into the bladder for 5 minutes. The patient is then asked to rate any change in urgency and pain over baseline levels. The water is drained and 40 mL of a 0.4-molar solution of potassium chloride (40 mEq in 100 mL of water), containing a total of 16 mEq of potassium chloride, are instilled into the bladder for 5 minutes. The patient is again asked to rate any change in urgency and pain over baseline levels. The test is positive when the patient reports a change of two points or more on the pain or urgency scale after instillation of potassium chloride solution.
The PST is negative in 96% of normal controls and positive in 70% to 80% of patients who have IC.14 Patients who have radiation cystitis or bacterial cystitis also have a positive response to the PST. Sensitivity of the test may decrease if the patient has recently been treated for IC, especially if the therapy involved dimethylsulfoxide (DMSO) or instillation of an anesthetic.
The PST can trigger the flare of severe symptoms in patients who have IC, so all women who have a positive test should receive a “rescue cocktail” after the potassium chloride solution is drained. Two of the most common rescue solutions are:
- 20,000 U of heparin mixed with 20 mL of 1% lidocaine
- a 15-mL mixture of 40,000 U of heparin, 8 mL of 2% lidocaine, and 3 mL of 8.4% sodium bicarbonate.
The rescue cocktail usually reverses the urgency and pain brought on by potassium chloride.
A patient who has a high level of pain with IC may be unable to discern a change when potassium chloride solution is instilled, or she may be unable to tolerate the discomfort it causes. Instillation of an anesthetic agent into the bladder may be a useful diagnostic test in such a case. The rescue cocktail described above also provides an opportunity for patient and clinician to see whether her symptoms abate after introduction of the anesthetic agent.