This is a medical question of type : exams and tests 
 How to diagnose Urinary Retention ? 
 A health care provider diagnoses acute or chronic urinary retention with
                
- a physical exam  - postvoid residual measurement
                
A health care provider may use the following medical tests to help determine the cause of urinary retention:
                
- cystoscopy  - computerized tomography (CT) scans  - urodynamic tests  - electromyography
                
Physical Exam
                
A health care provider may suspect urinary retention because of a patients symptoms and, therefore, perform a physical exam of the lower abdomen. The health care provider may be able to feel a distended bladder by lightly tapping on the lower belly.
                
Postvoid Residual Measurement
                
This test measures the amount of urine left in the bladder after urination. The remaining urine is called the postvoid residual. A specially trained technician performs an ultrasound, which uses harmless sound waves to create a picture of the bladder, to measure the postvoid residual. The technician performs the bladder ultrasound in a health care providers office, a radiology center, or a hospital, and a radiologista doctor who specializes in medical imaginginterprets the images. The patient does not need anesthesia.
                
A health care provider may use a cathetera thin, flexible tubeto measure postvoid residual. The health care provider inserts the catheter through the urethra into the bladder, a procedure called catheterization, to drain and measure the amount of remaining urine. A postvoid residual of 100 mL or more indicates the bladder does not empty completely. A health care provider performs this test during an office visit. The patient often receives local anesthesia.
                
Medical Tests
                
Cystoscopy. Cystoscopy is a procedure that requires a tubelike instrument, called a cystoscope, to look inside the urethra and bladder. A health care provider performs cystoscopy during an office visit or in an outpatient center or a hospital. The patient will receive local anesthesia. However, in some cases, the patient may receive sedation and regional or general anesthesia. A health care provider may use cystoscopy to diagnose urethral stricture or look for a bladder stone blocking the opening of the urethra.
                
More information is provided in the NIDDK health topic, Cystoscopy and Ureteroscopy.
                
CT scans. CT scans use a combination of x rays and computer technology to create images. For a CT scan, a health care provider may give the patient a solution to drink and an injection of a special dye, called contrast medium. CT scans require the patient to lie on a table that slides into a tunnel-shaped device where a technician takes the x rays. An x-ray technician performs the procedure in an outpatient center or a hospital, and a radiologist interprets the images. The patient does not need anesthesia. A health care provider may give infants and children a sedative to help them fall asleep for the test. CT scans can show
                
- urinary tract stones  - UTIs  - tumors  - traumatic injuries  - abnormal, fluid-containing sacs called cysts
                
Urodynamic tests. Urodynamic tests include a variety of procedures that look at how well the bladder and urethra store and release urine. A health care provider may use one or more urodynamic tests to diagnose urinary retention. The health care provider will perform these tests during an office visit. For tests that use a catheter, the patient often receives local anesthesia.
                
- Uroflowmetry. Uroflowmetry measures urine speed and volume. Special equipment automatically measures the amount of urine and the flow ratehow fast urine comes out. Uroflowmetry equipment includes a device for catching and measuring urine and a computer to record the data. The equipment creates a graph that shows changes in flow rate from second to second so the health care provider can see the highest flow rate and how many seconds it takes to get there. A weak bladder muscle or blocked urine flow will yield an abnormal test result.  - Pressure flow study. A pressure flow study measures the bladder pressure required to urinate and the flow rate a given pressure generates. A health care provider places a catheter with a manometer into the bladder. The manometer measures bladder pressure and flow rate as the bladder empties. A pressure flow study helps diagnose bladder outlet obstruction.  - Video urodynamics. This test uses x rays or ultrasound to create real-time images of the bladder and urethra during the filling or emptying of the bladder. For x rays, a health care provider passes a catheter through the urethra into the bladder. He or she fills the bladder with contrast medium, which is visible on the video images. Video urodynamic images can show the size and shape of the urinary tract, the flow of urine, and causes of urinary retention, such as bladder neck obstruction.
                
More information is provided in the NIDDK health topic, Urodynamic Testing.
                
Electromyography. Electromyography uses special sensors to measure the electrical activity of the muscles and nerves in and around the bladder and sphincters. A specially trained technician places sensors on the skin near the urethra and rectum or on a urethral or rectal catheter. The sensors record, on a machine, muscle and nerve activity. The patterns of the nerve impulses show whether the messages sent to the bladder and sphincters coordinate correctly. A technician performs electromyography in a health care providers office, an outpatient center, or a hospital. The patient does not need anesthesia if the technician uses sensors placed on the skin. The patient will receive local anesthesia if the technician uses sensors placed on a urethral or rectal catheter.