The generalist’s guide to interstitial cystitis
How to diagnose and treat all but refractory cases of this not-so-uncommon disease
- In early disease, bladder capacity exceeds 450 cc under anesthesia, with glomerulations and hemorrhage.
- In classic disease, bladder capacity is less than 450 cc under anesthesia, and Hunner’s ulcers and fissures are evident. Hunner’s ulcers are described as “a central scar with small fibrin deposits before distension, and post-distension edema.”7
For now, however, there are no agreed-upon markers to distinguish the 2 types of disease.
The female-to-male ratio is 9:1, and about 500,000 to more than 1 million adults in the United States are thought to have interstitial cystitis.8 Caucasian women constitute 95% of patients, and the average age at diagnosis is 45 years. Thirty percent of women with interstitial cystitis are 30 years old or younger. Significantly more women with interstitial cystitis have had a hysterectomy than controls.9
For a diagnosis, skip the NIH criteria
Symptoms
Although the National Institutes of Health (NIH) established diagnostic criteria for research subjects, the criteria are overly stringent—60% of women with symptoms typical of interstitial cystitis do not qualify, but should not necessarily be excluded from diagnosis and treatment.
When a woman has the hallmark symptoms listed on page 57, but also reports continuous pain or dysmenorrhea, other pelvic pathology such as endometriosis should be considered, although interstitial cystitis should be included in the differential diagnosis of any woman reporting pelvic pain.
Incontinence is atypical. If present, it merits an incontinence evaluation to detect detrusor hyperreflexia or detrusor-sphincter dyssynergia.
Dysuria suggests a UTI, urethral diverticulum, urogenital atrophy, or vaginitis. Many patients present with an erroneous diagnosis of “recurrent UTIs.”
Diagnostic tools
Voiding diaries are useful and can be revealing. The Pelvic Pain and Urinary Frequency (PUF) scale, developed by Parsons, is helpful in predicting interstitial cystitis (see the Clip-and-save chart). The higher the score, the greater the likelihood of interstitial cystitis, particularly with a score of more than 8.
Another tool is the O’Leary-Sant Index, which measures pain, voiding symptoms, and quality of life.
Physical examination and laboratory studies
Perform a pelvic exam to rule out other diseases and pelvic pathology, including sexually transmitted diseases, urethral diverticulum, and pelvic masses. Typically, the pelvic exam in women with interstitial cystitis is negative except for suprapubic and/or trigonal tenderness.
Urinalysis, culture, and sensitivity are warranted but are usually negative.
Cytology should be analyzed if microscopic hematuria is present, or with other risk factors such as a history of smoking or age over 40.
Obtain cultures for sexually transmitted diseases if clinically indicated.
Urodynamic studies are not necessary to diagnose interstitial cystitis. However, if incontinence is present, a cystometrogram can confirm detrusor hyperreflexia. Otherwise the cystometrogram is normal except for heightened sensation or pain with bladder filling, or a bladder capacity of less than 350 cc.
The potassium sensitivity test: Useful but painful
Women with interstitial cystitis are thought to have increased bladder permeability that allows potassium to pass through to the detrusor muscle. Thus, the potassium sensitivity test often is used to diagnose the condition. The test is an office procedure in which 2 separate solutions are instilled into the bladder: 40 cc sterile water followed by 40 cc of a solution of 400 mEq potassium per liter of water. After each solution is instilled, the patient is monitored for symptoms. The test is positive when the patient responds only to the potassium.
The response may be marked and painful, and the bladder should be emptied immediately. Subsequent irrigation with sterile water may be necessary to alleviate the discomfort caused by the potassium solution. Symptoms provoked by the test generally subside after bladder emptying, but can persist and cause moderate distress, which limits the utility of this office-based test.
Parsons et al10 demonstrated an 81% positive response (197 of 244 women) to the test among women with pelvic pain, compared with 0 of 47 patients with no pelvic pain. They also found that 70% of patients with interstitial cystitis and 4% of controls had a positive response.
If a woman is extremely volume-sensitive during the water phase, the potassium phase may not be accurate. A false-positive response can be caused by infection or prior exposure to radiation or chemotherapy. A thorough history is imperative.
The gold standard: Cystoscopy under anesthesia
Cystoscopy with hydrodistention under general anesthesia is the surest way to diagnose interstitial cystitis or rule it out. Sterile water or saline is infused until bladder capacity is reached. Bladder rupture occurs in up to 10% of patients, so careful inspection during filling is crucial. After 5 minutes of distension, bladder volume is measured into a calibrated beaker. Terminal hematuria (the last 50 cc of effluent) often is noted.
