Urinary incontinence is a symptom, not a disease. A number of medical problems can give you this symptom. Identifying the problem is the first step in treating it.

The process of diagnosing the problem usually begins with a physical exam, including a pelvic exam, and a frank discussion of your complaints or symptoms and urinating habits. You may be asked to keep a "voiding diary," a record of how often you urinate, what times of day, how much each time, how soon after drinking, etc.  Your doctor needs these details to understand the problem.

Then one or more diagnostic tests may be ordered.  Some common tests are:

• Postvoid residual (PVR) measurement: measures the bladder's capacity and its ability to empty itself completely
• Stress test: as its name implies, this tests for the presence of stress incontinence; for example, you will be checked for urine leakage while you cough
• Urinalysis: laboratory analysis of a urine sample can uncover evidence of urinary tract infection (UTI), urinary tract stones (blockages in the urinary tract), and other causes of incontinence
• Blood test: similarly, laboratory analysis of a blood sample can find various chemicals, substances and other possible causes of incontinence
• Imaging tests: images of the urinary tract can show abnormalities or problems; a number of different imaging techniques are available, including:
• Ultrasound: sound waves are bounced off the organs of the urinary tract to produce images of them (similar to ultrasound imaging used with pregnant women to produce images of fetuses)
• Cystoscopy: looking directly into the bladder by inserting a cystoscope (a thin, telescope-like instrument with a fiber-optic lighting system and a special lens) up the urethra and into the bladder
• Urodynamic studies: a general term for a group of techniques (ranging from simple observation to using sophisticated measuring equipment) to examine various functional aspects of the urinary system, including
• Pressure on the bladder
• Strength and functionality of bladder muscles
• Bladder contractions
• Bladder's ability to empty steadily and completely
• Urine flow
  

You can find detailed descriptions of most of these tests at the National Institute of Diabetes and Digestive and Kidney Diseases web site.

When the specific problem has been diagnosed, its causes can be understood, and a plan of treatment designed.   Some of  the conditions, disorders and diseases that can cause incontinence are specific to women, others are specific to men, and still others can affect both.

Causes of incontinence specific to women include:

• Pregnancy, childbirth and menopause: these can all weaken the pelvic floor muscles that support the bladder; weakened muscles can lead to stress incontinence
• Prolapsed bladder: also known as a dropped bladder or cystocele, it happens when the wall between the bladder and the vagina weakens and stretches and lets the bladder droop into the vagina; this can cause stress incontinence, problems fully emptying the bladder and urge incontinence / overactive bladder
• Interstitial cystitis (IC): this is a chronic inflammation of the bladder wall; although both men and women can have the condition, 90% of people with IC are women
• IC is not the same as common cystitis, a bacterial infection that most often causes urinary tract infections.  IC is chronic or persistent.
• IC is not caused by bacteria and is not treated with antibiotics
• Hysterectomy: this surgery to remove the uterus can weaken or damage urinary tract nerves and muscles which can cause incontinence

Causes of incontinence specific to men include:

• Prostate gland problems, such as
• Benign prostatic hyperplasia (BPH): fairly common in older men, this is a benign (non-cancerous) enlargement of the prostate that can cause blockages in the urinary tract, leading to incontinence
• Prostatitis: inflammation of the prostate gland
• Prostate cancer
• Side effects of prostate cancer treatment
• Prostatectomy: this surgery to remove the prostate can weaken or damage urinary tract nerves and muscles which can cause incontinence

Causes of incontinence that affect women and men include:

• Blockages in the urinary tract; these can result from several conditions, such as
• Benign tumors or masses
• Cancerous tumors
• Urinary tract infections (UTIs): bacterial infections in the urinary tract can cause urge incontinence
• Both men and women can get UTIs, though they affect women more frequently
• Interstitial cystitis, mentioned above, can affect men as well as women
• Neurogenic bladder: a condition in which the nerves that carry messages between the bladder and brain that control urination are damaged, something related to diseases such as diabetes, spinal stenosis and multiple sclerosis.

There are also a number of risk factors that may increase the likelihood of developing incontinence. They include:

• Gender: twice as many women as men are affected with incontinence
• Age: although incontinence is not inevitable with aging, it does occur more often in older adults
• Diet: 
• A number of common foods can irritate the bladder, leading to incontinence; these foods include
• Products with caffeine, such as coffee, tea, colas, and chocolate
• Acidic fruit juices
• Alcoholic beverages
• Not drinking enough fluid can cause urine to become concentrated which can irritate the bladder
• Drinking a lot of fluid in a short time can cause temporary urinary frequency
• Medicines: some medications have side effects that lead to incontinence, such as
• Diuretics (water pills)
• Some sedatives, muscle relaxants and antidepressants
• High blood pressure and heart medicines
• Cold pills
• Diet pills
• Damaged nerves or nerve pathways: as mentioned above, this can cause neurogenic bladder
• Neurological injury or disease, such as multiple sclerosis and strokes
• Congenital physical abnormalities in the urinary tract