Overview
Background
In clinical practice, urodynamics are obtained to reproduce clinical symptoms while allowing for precise measurements in order to identify the underlying causes for the symptoms and to quantify the related pathophysiologic processes.
Urodynamics may confirm a diagnosis or result in a new diagnosis. A careful assessment of the patient’s history and physical examination helps determine the question(s) that one hopes to answer with urodynamic evaluation.
In an effort to provide some standardization to urodynamic studies, the International Continence Society has developed guidelines for good urodynamic practice for the measurement, quality control, and documentation of urodynamic studies in both clinical and research environments.
In addition, the report from the standardization subcommittee of the International Continence Society provides definitions for urodynamic observations.
Practitioners performing and interpreting urodynamic studies should be aware of such guidelines and terminology.
Indications
Urodynamic studies may be obtained for various lower urinary tract symptoms, including the evaluation of incontinence, overactive bladder symptoms, and urinary retention.
Urodynamics may be obtained to guide initial treatment, to follow progress with treatment or to evaluate treatment failures. In patients with neurogenic bladder/sphincter dysfunction, urodynamics are often obtained to evaluate the risk for upper urinary tract damage in those with bladder/sphincter dysfunction.
Contraindications
Urodynamics should not be performed in the setting of a symptomatic urinary tract infection. Urodynamics should be obtained to assist in further management of a patient’s lower urinary tract symptoms.
Technical Considerations
Urodynamic study has several components, as follows: (1) uroflowmetry, (2) filling cystometry (cystometrogram, CMG), (3) pressure flow study of voiding, and (3) electromyelography (EMG).
An image depicting a cystometrogram can be seen below.
Cystometrogram (CMG) demonstrating poor bladder compliance. Detrusor pressure increases with bladder filling.
The choice of which components to perform depends on the patient’s symptoms and the urodynamic questions one seeks to answer. Having a bladder diary completed for 2 days before performing the urodynamic evaluation is helpful. The bladder diary serves to confirm the patient’s symptoms as well as provide some assistance with the urodynamic studies. For example, one can determine the average volume voided during the bladder diary, which will help prevent over-filling of the patient’s bladder during the cystometrogram.
Potential complications from an urodynamic evaluation include urethral trauma leading to hematuria, dysuria, or false passage. In addition, although infrequent, the risk of developing a urinary tract infection exists. Thus, placement of the urethral catheter during the study should be performed using sterile technique with a well-lubricated catheter. In patients with a history of recurrent urinary tract infections and those on clean intermittent catheterization, a urine dipstick should be checked prior to starting the urodynamic evaluation. If significant pyuria on the dipstick exists, then the procedure is not performed and the urine is sent for culture. Patients with chronic indwelling catheters should have urine cultures obtained and be treated just prior to urodynamics.
Relevant Anatomy
The anatomy of the bladder forms an extraperitoneal muscular urine reservoir that lies behind the pubic symphysis in the pelvis. A normal bladder functions through a complex coordination of musculoskeletal, neurologic, and psychological functions that allow filling and emptying of the bladder contents. The prime effector of continence is the synergic relaxation of detrusor muscles and contraction of the bladder neck and pelvic floor muscles. See the image below.
Gross anatomy of the bladder.
For more information about the relevant anatomy, see Bladder Anatomy.