This is a medical question of type : exams and tests 
 How to diagnose Fecal Incontinence ? 
 Health care providers diagnose fecal incontinence based on a persons medical history, physical exam, and medical test results. In addition to a general medical history, the health care provider may ask the following questions:
                
- When did fecal incontinence start?  - How often does fecal incontinence occur?  - How much stool leaks? Does the stool just streak the underwear? Does just a little bit of solid or liquid stool leak out or does complete loss of bowel control occur?  - Does fecal incontinence involve a strong urge to have a bowel movement or does it happen without warning?  - For people with hemorrhoids, do hemorrhoids bulge through the anus? Do the hemorrhoids pull back in by themselves, or do they have to be pushed in with a finger?  - How does fecal incontinence affect daily life?  - Is fecal incontinence worse after eating? Do certain foods seem to make fecal incontinence worse?  - Can passing gas be controlled?
                
People may want to keep a stool diary for several weeks before their appointment so they can answer these questions. A stool diary is a chart for recording daily bowel movement details. A sample stool diary is available on the Bowel Control Awareness Campaign website at www.bowelcontrol.nih.gov.
                
The person may be referred to a doctor who specializes in problems of the digestive system, such as a gastroenterologist, proctologist, or colorectal surgeon, or a doctor who specializes in problems of the urinary and reproductive systems, such as a urologist or urogynecologist. The specialist will perform a physical exam and may suggest one or more of the following tests:
                
- anal manometry  - anal ultrasound  - magnetic resonance imaging (MRI)  - defecography  - flexible sigmoidoscopy or colonoscopy  - anal electromyography (EMG)
                
Anal manometry. Anal manometry uses pressure sensors and a balloon that can be inflated in the rectum to check the sensitivity and function of the rectum. Anal manometry also checks the tightness of the anal sphincter muscles around the anus. To prepare for this test, the person should use an enema and not eat anything 2 hours before the test. An enema involves flushing water or a laxative into the anus using a special squirt bottle. A laxative is medication that loosens stool and increases bowel movements. For this test, a thin tube with a balloon on its tip and pressure sensors below the balloon is inserted into the anus until the balloon is in the rectum and pressure sensors are located in the anal canal. The tube is slowly pulled back through the sphincter muscle to measure muscle tone and contractions. No anesthesia is needed for this test, which takes about 30 minutes.
                
Anal ultrasound. Ultrasound uses a device, called a transducer, that bounces safe, painless sound waves off organs to create an image of their structure. An anal ultrasound is specific to the anus and rectum. The procedure is performed in a health care providers office, outpatient center, or hospital by a specially trained technician, and the images are interpreted by a radiologista doctor who specializes in medical imaging. Anesthesia is not needed. The images can show the structure of the anal sphincter muscles.
                
MRI. MRI machines use radio waves and magnets to produce detailed pictures of the bodys internal organs and soft tissues without using x rays. The procedure is performed in an outpatient center or hospital by a specially trained technician, and the images are interpreted by a radiologist. Anesthesia is not needed, though people with a fear of confined spaces may be given medication to help them relax. An MRI may include the injection of special dye, called contrast medium. With most MRI machines, the person lies on a table that slides into a tunnel-shaped device that may be open ended or closed at one end; some newer machines are designed to allow the person to lie in a more open space. MRIs can show problems with the anal sphincter muscles. MRI is an alternative to anal ultrasound that may provide more detailed information, especially about the external anal sphincter.
                
Defecography. This x ray of the area around the anus and rectum shows how well the person can hold and evacuate stool. The test also identifies structural changes in the rectum and anus such as rectocele and rectal prolapse. To prepare for the test, the person uses two enemas and does not eat anything 2 hours prior to the test. During the test, the health care provider fills the rectum with a soft paste that shows up on x rays and is the same consistency as stool. The person sits on a toilet inside an x-ray machine. The person is first asked to pull in and squeeze the sphincter muscles to prevent leakage and then to strain as if having a bowel movement. The radiologist studies the x rays to identify problems with the rectum, anus, and pelvic floor muscles.
                
Flexible sigmoidoscopy or colonoscopy. These tests are used to help diagnose problems causing fecal incontinence. The tests are similar, but colonoscopy is used to view the rectum and entire colon, while flexible sigmoidoscopy is used to view just the rectum and lower colon. These tests are performed at a hospital or outpatient center by a gastroenterologist. For both tests, a health care provider will provide written bowel prep instructions to follow at home. The person may be asked to follow a clear liquid diet for 1 to 3 days before either test. A laxative may be required the night before the test. One or more enemas may be required the night before and about 2 hours before the test.
                
In most cases, people will be given light anesthesia, and possibly pain medication, to help them relax during flexible sigmoidoscopy. Anesthesia is used for colonoscopy. For either test, the person will lie on a table while the gastroenterologist inserts a flexible tube into the anus. A small camera on the tube sends a video image of the intestinal lining to a computer screen. The test can show problems in the lower GI tract that may be causing the bowel control problem. The gastroenterologist may also perform a biopsy, a procedure that involves taking a piece of tissue from the bowel lining for examination with a microscope.
                
The person will not feel the biopsy. A pathologista doctor who specializes in diagnosing diseasesexamines the tissue in a lab to confirm the diagnosis.
                
Cramping or bloating may occur during the first hour after these tests. Driving is not permitted for 24 hours after flexible sigmoidoscopy or colonoscopy to allow the anesthesia time to wear off. Before the appointment, a person should make plans for a ride home. Full recovery is expected by the next day and the person is able to go back to a normal diet.
                
Anal EMG. Anal EMG checks the health of the pelvic floor muscles and the nerves that control the muscles. The health care provider inserts a very thin needle electrode through the skin into the muscle. The electrode on the needle picks up the electrical activity given off by the muscles and shows it as images on a monitor or sounds through a speaker. An alternative type of anal EMG uses stainless steel plates attached to the sides of a plastic plug instead of a needle. The plug is inserted into the anal canal to measure the electrical activity of the external anal sphincter and other pelvic floor muscles. The average amount of electrical activity when the person relaxes quietly, squeezes to prevent a bowel movement, and strains to have a bowel movement shows whether there is damage to the nerves that control the external sphincter and pelvic floor muscles.