What Is Intrinsic Sphincter Deficiency Causes Treatment?

Intrinsic sphincter deficiency (ISD) is a specific type of stress urinary incontinence where the urethra’s internal sphincter muscle is too weak to hold urine, even when the bladder is not under much pressure. It is a physical defect in the valve mechanism itself, rather than a problem caused by the bladder or pelvic organs shifting position. The condition causes urine to leak during everyday movements like coughing, sneezing, lifting, or simply standing up, and it requires specific diagnostic testing and targeted treatment options that differ from other forms of incontinence.

What Is Intrinsic Sphincter Deficiency?

Intrinsic sphincter deficiency is a failure of the urethral sphincter complex. This complex is the ring of muscle and tissue that surrounds the urethra and acts as a valve. In a healthy system, this valve stays tightly closed until you consciously relax it to urinate.

In ISD, the valve itself is damaged or weakened. It cannot generate enough closure pressure to keep urine inside the bladder. Even minor increases in abdominal pressure—like a small cough or a laugh—can overcome the weak sphincter and cause leakage.

This differs from urethral hypermobility, the other major cause of stress incontinence. In hypermobility, the sphincter is structurally fine, but the supportive tissue around the bladder neck and urethra has stretched. This causes the urethra to drop and rotate during physical activity, preventing it from closing properly. ISD is not a positioning problem. It is a problem with the muscle itself.

What Causes Intrinsic Sphincter Deficiency?

ISD develops when the sphincter muscle, its blood supply, or its nerve supply becomes damaged. Several distinct causes lead to this damage.

Prior pelvic surgery is one of the most common causes. Procedures such as a hysterectomy, a sling procedure, or a prior surgery for incontinence can inadvertently damage the nerves or blood vessels that serve the sphincter. Scar tissue from surgery can also stiffen the urethra and prevent it from closing completely.

Neurological conditions can also cause ISD. Conditions like multiple sclerosis, spinal cord injury, or nerve damage from diabetes can interrupt the nerve signals the sphincter needs to stay contracted.

Age and hormonal changes play a role. Estrogen helps maintain the health and thickness of urethral tissue. After menopause, lower estrogen levels can cause the urethral lining to thin and the sphincter to weaken. This is a natural process, but it can be accelerated in some women.

Radiation therapy to the pelvic area, often used to treat cancers of the cervix, uterus, or prostate, can damage the sphincter directly. Radiation causes tissue scarring and reduced blood flow, which can permanently impair sphincter function.

Congenital weakness is rare but possible. Some people are simply born with a poorly developed or weak sphincter. This may not cause symptoms until later in life.

In men, ISD most commonly occurs after prostate surgery. A radical prostatectomy, which removes the entire prostate gland, often removes a portion of the sphincter mechanism. This is the most frequent cause of persistent stress incontinence in men after cancer treatment.

What Are the Symptoms of Intrinsic Sphincter Deficiency?

The primary symptom of ISD is stress urinary incontinence. This means leaking urine when there is sudden pressure on the bladder. Common triggers include coughing, sneezing, laughing, bending over, lifting objects, or standing up from a seated position.

There are some clinical signs that help distinguish ISD from other types of stress incontinence. Leakage often occurs with very minimal physical effort. A person with ISD might leak just from standing up or taking a single step. The volume of leakage is often larger as well because the sphincter is not just weak—it is failing as a valve.

Some women with ISD report a constant low-level dampness rather than discrete leak episodes. This happens when the sphincter cannot maintain a complete seal even at rest.

It is important to note that ISD does not typically cause a sudden strong urge to urinate, frequent urination during the day, or waking up multiple times at night to urinate. Those symptoms point toward overactive bladder or other conditions. ISD is a mechanical failure, not a nerve overactivity problem.

How Is Intrinsic Sphincter Deficiency Diagnosed?

Diagnosing ISD requires more than a physical exam. The condition is confirmed with specific urodynamic testing.

The most important test is a leak point pressure measurement, often called Valsalva leak point pressure (VLPP). During this test, the bladder is filled with sterile water through a small catheter. You are asked to cough or bear down while the pressure inside the bladder is measured. If urine leaks at a low bladder pressure—generally below 60 cm of water—it suggests ISD. A well-supported sphincter usually withstands higher pressures before leaking.

A urethral pressure profile is another diagnostic tool. This measures the resting pressure along the length of the urethra. A low maximum urethral closure pressure, often below 20 cm of water, supports an ISD diagnosis.

Cystoscopy may also be used. This involves inserting a thin camera into the bladder and urethra. It allows the doctor to see the sphincter directly and check for scarring, atrophy, or a fixed open appearance of the urethra, all of which are signs of ISD.

These tests are typically performed by a urologist or a urogynecologist. It is not possible to diagnose ISD based on symptoms alone.

What Are the Treatment Options for Intrinsic Sphincter Deficiency?

Treatment for ISD depends on the severity of the condition, the underlying cause, and whether the person has had prior incontinence surgery. The approach differs from treating urethral hypermobility because the sphincter itself needs support or augmentation.

Conservative treatments are the first step. Pelvic floor muscle exercises, sometimes called Kegel exercises, can strengthen the muscles surrounding the urethra. These muscles act as a secondary support system. While they cannot repair a damaged sphincter, they can improve overall continence in mild cases. Some research suggests these exercises are most effective when guided by a physical therapist who specializes in pelvic health.

Urethral bulking agents are a minimally invasive option. This procedure injects a synthetic material into the tissue around the urethra. The material adds bulk, which helps the urethral walls coapt, or seal together. This is not a permanent fix. The body gradually absorbs the material, and repeat injections are often needed. It works best for people with mild to moderate ISD who have not had prior pelvic surgery or radiation.

Surgery is the most durable treatment for moderate to severe ISD. The most common procedure is a mid-urethral sling. A small strip of mesh or tissue is placed under the urethra to provide support. However, in cases of severe ISD, especially after prior failed surgery, a more involved procedure may be needed.

An artificial urinary sphincter is the gold standard for severe ISD, particularly in men after prostate surgery. This device is implanted entirely inside the body. It consists of a cuff that wraps around the urethra, a small balloon that regulates pressure, and a pump placed in the scrotum or labia. When you need to urinate, you squeeze the pump, which deflates the cuff and allows urine to flow. The cuff automatically refills after a few minutes. This device requires surgery to place and carries risks of infection and mechanical failure, but it has a high success rate for restoring continence.

No single treatment works for everyone. A urologist will consider the severity of leakage, prior surgical history, and overall health before recommending a plan.

What Is the Prognosis for Intrinsic Sphincter Deficiency?

The prognosis for ISD is generally good with appropriate treatment. Conservative measures and bulking agents can significantly improve quality of life for mild cases. For severe ISD, surgical options like the artificial urinary sphincter have high long-term success rates.

Without treatment, ISD does not typically resolve on its own. The sphincter does not regenerate damaged muscle tissue. Leakage may remain stable or gradually worsen over time, especially as age-related muscle weakening continues.

Untreated ISD carries secondary risks. Chronic moisture against the skin can cause irritation, fungal infections, and skin breakdown. Frequent pad use is costly and can limit physical activity. Some people reduce fluid intake to avoid leaks, which can lead to dehydration and urinary tract infections.

The emotional impact is also significant. Many people with ISD avoid social activities, exercise, and travel. Seeking evaluation is important not just for physical health but for overall quality of life.

Can Intrinsic Sphincter Deficiency Be Prevented?

Prevention of ISD is only partially possible. Some causes, like congenital weakness or neurological disease, cannot be prevented. Others are related to necessary medical treatments.

For women, the most preventable cause is surgical damage. Choosing an experienced surgeon for pelvic procedures and discussing your risk of incontinence before surgery may help. Some surgical techniques are designed to spare sphincter nerves, and these should be discussed with your surgeon.

Maintaining pelvic floor strength through regular exercise is the most evidence-based preventive measure. Strong pelvic floor muscles provide better backup support to the sphincter. This is particularly relevant for women who have given birth vaginally, as childbirth can stretch and weaken pelvic tissues.

Maintaining a healthy weight reduces pressure on the pelvic floor. Chronic coughing from smoking also stresses the sphincter over many years. Addressing these modifiable factors can reduce but not eliminate the risk of developing ISD.