Urology & Urogynecology > Education and Reference

Mechanical obstructions of the lower urinary tract can be caused by:

The importance of the urodynamicist having access to the patient’s history is readily demonstrated on the patient population with mechanical obstruction of the lower urinary tract.

Special considerations include patients with:

• Tumors or cancers of the urethra or prostate or urethral polyps because catheterization is typically more difficult and results in bleeding.
• True clinical infection of the lower urinary tract. These patients should absolutely not undergo urodynamic testing. Dipstick analysis (at a minimum) should be performed on all patients from either the preliminary free uroflow or on the catheterized residual urine before proceeding to fill the patient.

There have been reported cases of death from sepsis following urodynamics on a patient with
clinical bladder infection.

• Bladder stones that might interfere with catheter placement and pressure measurements. It would be very important for troubleshooting to know that a patient had stones.

Structural defects of the lower urinary tract include:

• Bladder diverticulum
• Urethral fistula
• Urethral diverticulum

Bladder diverticuli cause of frequency/urgency symptoms. This often occurs in patients with a large diverticulum that empties into the bladder after micturition is complete, causing a sudden return of the sensation of fullness again. Urgency symptoms may also be due to the distortion of bladder anatomy, particularly the detrusor muscle wall.

Patients with urethral fistulas or diverticulum typically complain of incontinence, but careful history taking usually reveals a small spontaneous leak within a few minutes of standing up in either of these cases. During voiding, a diverticulum in the urethra fills with urine and then empties later, after the patient stands up and moves around. Urine will pass into the vagina through a urethral fistula. Then, when the patient stands up, the urine “leaks” out of the vagina.

Diverticuli and fistulas are best seen on video urodynamic studies.

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