How is interstitial cystitis diagnosed?
Because the symptoms of IC/PBS are similar to those of other disorders of the urinary system and because there is no definitive test to identify IC/PBS, doctors must exclude other conditions before making a diagnosis of IC/PBS. Among the disorders to be excluded are urinary tract or vaginal infections, bladder cancer, bladder inflammation or infection caused by radiation to the abdomen, eosinophilic and tuberculous cystitis, kidney stones, endometriosis, neurological disorders, sexually transmitted diseases, urinary tract infection with small numbers of bacteria, and, in men, chronic bacterial and nonbacterial prostatitis.
Medical tests that help identify other conditions include a urinalysis, urine culture, cystoscopy, and biopsy of the bladder wall and, in men, laboratory examination of prostatic secretions.
Physical examination of an individual with IC/PBS may reveal tenderness of the bladder either when pushing on the abdomen over the bladder (just above the pubic bone) or during the pelvic examination in women. No specific physical findings are associated with IC/PBS.
Urinalysis and urine culture: These tests can detect and identify the most common bacteria in the urine that may be causing IC/PBS-like symptoms. A urine sample is obtained either by catheterization or by the "clean catch" method. For a clean catch, the patient washes the genital area before collecting a sample of urine "midstream" in a sterile container. White and red blood cells and bacteria in the urine suggest an infection of the urinary tract that can be treated with antibiotics. If urine is sterile for weeks or months while symptoms persist, a doctor may consider a diagnosis of IC/PBS.
Culture of prostatic secretions: In men, the doctor can obtain a sample of prostatic fluid. This fluid is examined under the microscope for signs of an infection such as red and white blood cells and also can be cultured for bacteria. Prostatic infections can be treated with antibiotics.
Potassium sensitivity test: A test known as the intravesical potassium sensitivity test (PST) has been developed to evaluate the leakiness of the protective lining of the bladder. Some experts recommend its use in the evaluation of IC/PBS, but it is no longer used routinely for this purpose because the results are not specific for IC/PBS; abnormal results can also be due to other conditions. The test also can be painful. Many people with IC/PBS have an abnormal PST suggesting an overly leaky urothelium (bladder lining). In the PST test, two different solutions (sterile water and a solution of potassium) are instilled separately into the bladder. The patient rates the severity of pain and/or urgency that occur when each solution is instilled. Using a scale of 0 to 5, the test is considered abnormal (positive) if the potassium solution induces at least a pain level of "2" and causes more pain than the sterile water.
Lidocaine instillation. Filling the bladder with a solution containing the local anesthetic drug lidocaine has been described as an "anesthetic bladder challenge." Improvement of symptoms after lidocaine has been instilled into the bladder suggests IC/PBS. However, like the potassium sensitivity test, this test is not specific for IC/PBS and is not routinely performed.
Cystoscopy under anesthesia with bladder distension. During cystoscopy, the doctor uses a cystoscope -- an instrument made of a hollow tube about the diameter of a drinking straw with several lenses and a source of light - to look inside the bladder and urethra. The doctor will also distend or stretch the bladder to its capacity by filling it with a liquid or gas. Because bladder distension is painful in IC/PBS patients, before the doctor inserts the cystoscope through the urethra into the bladder, the patient must be given either regional or general anesthesia. Cystoscopy with distension of the bladder with fluid can detect inflammation (visually or with biopsies), a thick and stiff bladder wall, and Hunner's ulcers. After the fluid has been drained from the bladder, small red spots, called glomerulations, that represent enlarged blood vessels and pinpoint areas of bleeding can be seen in the bladder's lining.
The doctor also may determine a patient's bladder capacity -- the maximum amount of liquid or gas the bladder can hold under anesthesia. (Without anesthesia, capacity is limited by either pain or a severe urge to urinate.) Most people without IC/PBS have normal or large maximum bladder capacities under anesthesia. A small bladder capacity (due to scarring) under anesthesia helps to support the diagnosis of IC/PBS.
Before the relatively recent development of the PST, cystoscopy was the best diagnostic test available for IC/PBS. However, cystoscopy has its limitations. Ulcers are generally not observed in mild or early cases of IC/PBS, and glomerulations have been observed in normal individuals without symptoms of IC/PBS. Due to these limitations, cystoscopy is recommended only to exclude other possible causes of symptoms and not as the definitive diagnostic test for IC/PBS.
It is important to note that the distension often performed with cystoscopy may lead to relief of symptoms in some patients with IC/PBS, which generally lasts from several weeks to months following the procedure.
Biopsy: A biopsy is a microscopic examination of a small sample of tissue. Samples of the bladder and urethra may be removed during cystoscopy and examined with a microscope later. A biopsy helps to exclude bladder cancer. It also may confirm the presence of mast cells or inflammation of the bladder wall that are consistent with a diagnosis of IC/PBS. Nevertheless, there is nothing on the biopsy that can make an absolute diagnosis of IC/PBS.