Interstitial Cystitis

Interstitial cystitis (IC), also called bladder pain syndrome (BPS), is a chronic condition characterised by persistent bladder pain or discomfort, urinary urgency, and frequency in the absence of a confirmed bacterial infection. Although the exact cause is not fully understood, several mechanisms have been identified and guide current treatments. IC/BPS primarily affects women but can occur in anyone. Symptoms range from mild to severely debilitating and significantly impact quality of life. It is a diagnosis of exclusion — other causes of bladder symptoms must be ruled out first. Even though test results may appear normal, the pain and urinary symptoms are real and can be very disruptive.

Symptoms

Symptoms vary considerably between individuals and often come in flares, with good days and bad days. They can worsen around menstruation, after certain foods or drinks, during stress, or following sexual activity.

Pelvic pain or pressure — in or around the bladder, lower abdomen, or perineum; the hallmark symptom
Urinary urgency — a persistent or sudden strong need to urinate that is difficult to defer
Urinary frequency — needing to urinate more than 8 times per day or multiple times at night (nocturia)
Pain that worsens as the bladder fills and often improves temporarily after urination
Pain during or after sexual intercourse
In men — pain or discomfort in the scrotum, testicles, or penis

Unlike overactive bladder, most people with IC/BPS do not routinely leak urine. Urine is typically sterile — routine urine cultures are negative, and antibiotics do not relieve symptoms. This is one of the key distinguishing features from a urinary tract infection.

Causes and contributing factors

The exact cause of IC/BPS is unknown. These mechanisms likely contribute to symptoms in different ways in different people, and not everyone with IC/BPS has all of them.

Defective bladder lining (urothelium): The inner lining of the bladder normally forms a protective barrier. In IC/BPS, this barrier may be damaged or dysfunctional, allowing urine to irritate the underlying bladder wall and trigger inflammation and pain
Mast cell activation: Elevated mast cells — immune cells that release chemicals like histamine, which can increase pain and urgency — are found in the bladder wall of some people with IC/BPS
Nerve sensitisation: Altered pain processing — both locally in the bladder and centrally in the nervous system — may amplify pain signals disproportionate to the degree of tissue damage
Autoimmune factors: Some evidence suggests an autoimmune component, as IC/BPS is more common in people with other autoimmune conditions
Associated conditions: IC/BPS frequently co-occurs with fibromyalgia, irritable bowel syndrome, vulvodynia, endometriosis, and chronic fatigue syndrome, suggesting shared underlying mechanisms

Diagnosis

There is no single definitive test for IC/BPS. Diagnosis is based on symptoms, exclusion of other conditions, and in some cases specialist investigation. There is usually no need for repeated invasive tests once a clear diagnosis is made, unless new symptoms develop.

Urinalysis and urine culture — to rule out bacterial infection; urine is typically normal or may show low-grade white blood cells without infection (sterile pyuria) in some cases
Symptom assessment — validated questionnaires such as the O'Leary-Sant Symptom and Problem Index help quantify severity and monitor treatment response
Cystoscopy — examination of the bladder lining with a small camera; may reveal Hunner lesions (patches of damaged bladder lining) in a subset of patients, or glomerulations (small haemorrhages) after hydrodistension, though these findings are not present in all cases
Bladder hydrodistension — filling the bladder under anaesthesia to assess capacity and look for characteristic changes; also has short-term therapeutic benefit in some patients
Exclusion of other conditions — bladder cancer, recurrent UTI, sexually transmitted infections, endometriosis, overactive bladder, and pelvic floor dysfunction must all be considered. Some people will have additional tests such as urine cytology or imaging depending on age and risk factors

Treatment

Treatment is often a process of trial and adjustment, and may combine diet changes, medicines, and physical therapy to find what works best for each individual. Management is typically stepwise, starting with the least invasive approaches. Only a minority of people require invasive procedures — many improve substantially with lifestyle changes, oral medicines, and pelvic floor therapy.

Lifestyle and dietary modifications Many people find that certain foods and drinks trigger or worsen symptoms, including caffeine, alcohol, citrus fruits, tomatoes, spicy foods, and artificial sweeteners. An elimination approach — removing common triggers and reintroducing them one at a time — helps identify individual sensitivities without unnecessary long-term restriction. Stress management, gentle movement, pelvic floor relaxation exercises, and bladder training (gradually extending the time between urinations) are all first-line strategies.

Oral medications

Amitriptyline — a low-dose tricyclic antidepressant that reduces nerve pain and improves sleep; one of the most commonly used oral treatments
Pentosan polysulfate sodium (PPS) — thought to help restore the bladder lining; evidence is modest and onset of benefit can take months. Note: long-term PPS use has been linked to a rare eye condition affecting the retina, so people taking it for extended periods are often advised to have regular eye examinations
Antihistamines (hydroxyzine) — may help in patients with mast cell involvement
Cimetidine — an H2 blocker with some evidence of benefit
NSAIDs and analgesics — for pain management

Bladder instillations Medications delivered directly into the bladder via catheter, bypassing systemic absorption. Common agents include dimethyl sulfoxide (DMSO), heparin, lidocaine, and sodium bicarbonate, often combined.

Procedures

Bladder hydrodistension — therapeutic benefit in some patients, though effects are often temporary
Cystoscopic treatment of Hunner lesions — fulguration or steroid injection into lesions in the subset of patients who have them; often provides significant relief
Botulinum toxin (Botox) injection — injected into the bladder wall to reduce urgency and pain in refractory cases
Sacral neuromodulation — a device implanted near the sacral nerves that modulates bladder nerve signals; used in severe refractory cases

Pelvic floor physiotherapy Pelvic floor muscle dysfunction frequently co-exists with IC/BPS. Physiotherapy with a specialist in pelvic floor rehabilitation is often highly effective, particularly when muscle tenderness or spasm is identified on examination.

FAQ

Is interstitial cystitis the same as a UTI? No. IC/BPS causes similar symptoms to a UTI — urgency, frequency, and pelvic discomfort — but urine cultures are negative, and antibiotics do not help. Repeated antibiotic courses without a confirmed infection can delay correct diagnosis and cause harm.

Is interstitial cystitis curable? There is currently no cure, but symptoms can often be substantially reduced with treatment. Many people experience periods of remission. Management is long-term and typically involves a combination of lifestyle changes, medication, and physical therapy.

Does IC/BPS show up on lab tests? Routine lab results are usually normal or near-normal. Urinalysis may show mild changes such as low-grade white blood cells without bacteria. The diagnosis is primarily clinical, supported by specialist investigations such as cystoscopy. Normal lab results do not mean symptoms are not real.

Related biomarkers

Lab results in IC/BPS are mainly used to exclude other diagnoses rather than confirm IC itself. Urinalysis (including white blood cells and nitrites), urine culture, and occasionally urine cytology are used to rule out infection, bladder cancer, and other urological conditions. Tracking urinalysis results over time in HealthMatters can help document the pattern of sterile findings that supports an IC/BPS diagnosis, monitor for intercurrent infections, and provide a clear record to share with your clinician.