Video Urodynamics
Video urodynamic (VUD) testing consists of simultaneous measurement of the typical urodynamic parameters in conjunction with imaging of the lower urinary tract (LUT) ( Fig. 11.1 ). It is thought by most to provide the most precise evaluation of LUT dysfunction ( ). VUDs are similar to conventional urodynamics with the addition of contrast media as the filling solution and the use of fluoroscopy. This allows for simultaneous anatomic and functional evaluation of the LUT.
Indications
Although the indications for VUD testing are controversial, most would agree they are most useful in women with a known neurologic condition that is felt to affect LUT function. In 2009 the Fourth Consultation on Incontinence Committee on dynamic testing made the following grade B/C recommendation on the basis of the available evidence-based literature ( ): Patients with suspected neurogenic dysfunction of the LUT should receive comprehensive urodynamic evaluation including VUDs, if possible, to establish the state and function of the lower tract. VUDs can identify certain pathologies and are important when trying to answer a specific clinical question. The American Urological Association (AUA) Urodynamics Guidelines state, “VUDS can be performed in properly selected patients to localize the level of obstruction, particularly for diagnosing primary bladder neck obstruction” ( ). In younger patients, with voiding dysfunction VUDs can differentiate between functional obstruction and dysfunctional voiding ( ).
A VUD study can provide objective documentation of the effect of the neurologic lesion on vesicourethral function as well as assess for the presence of certain risk factors that could decompensate the upper urinary tract. These risk factors include detrusor external sphincter dyssynergia (DESD), low bladder compliance, and sustained high-magnitude detrusor contractions. Without effective therapy, patients with these risk factors have up to an 85% chance of developing hydronephrosis, vesicoureteral reflux, and/or urosepsis within 5 years ( ). In cases of impaired compliance in which there is compensation by a “pop-off” mechanism of vesicoureteral reflux, the impaired compliance may not be identified unless the reflux is also recognized by fluoroscopy. Also, an accurate detrusor leak point pressure (DLPP) can be obtained in cases where it would otherwise be impossible to observe any leakage.
In women with bladder outlet obstruction (BOO), VUD testing is the only way to localize the exact level of obstruction. If there is no obvious anatomic cause of obstruction, VUDs can differentiate between functional causes of obstruction such as primary bladder neck obstruction and dysfunctional voiding. Other indications may include any patient who is at high risk for complicated voiding dysfunction in which an accurate diagnosis cannot otherwise be obtained. This could include unexplained urinary retention in women, prior radical pelvic surgery, urinary diversion, prerenal or postrenal transplant, or prior pelvic radiation. Finally, VUDs may be helpful in some women with severe recurrent stress urinary incontinence (SUI) and intrinsic sphincter deficiency (ISD) as visualizing the urethra during provocation may be clinically useful. Table 11.1 reviews possible indications for VUDs and lists additional information that can be obtained when compared with conventional urodynamics.
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Technique
The Video Urodynamic Lab
The urodynamic room should be set up in a way that minimizes patient discomfort and anxiety. The room should be large enough to fit all the equipment necessary for the procedure including the fluoroscopy machine and the fluoro-compatible chair ( Fig. 11.2 ). The disposables required for the procedure should be kept and organized in cabinets within the room to avoid running in and out of the room during the procedure. A C-arm is preferable over fixed fluoroscopy machines because it allows different angles of view and flexibility during patient positioning.
Patient Positioning
VUD testing can be done in the supine, sitting, or standing positions. The test is usually begun in the sitting position with the understanding that changing patient position may become necessary at certain points of the test. For example, changing from the sitting to the standing positions may be necessary to demonstrate SUI. Likewise, a change from a supine to a lateral position may be needed to further localize certain anatomic findings such as bladder or urethral diverticula.
Use of Fluoroscopy and Tips to Minimize Radiation Exposure
VUD testing comes with the cost of risking radiation exposure to both the staff and patient. In a study of radiation exposure during VUDs in the pediatric population, reported a mean radiation exposure of 10 mGy per study. Radiation exposure has many known biological effects including the risk for secondary cancer ( ). This makes it crucial to take all possible precautions to minimize radiation exposure for both the staff and patients. The staff should wear lead protection shields and use radiation exposure monitors to track their cumulative exposure time. The number of images should be kept to a minimum and only taken for the high yield parts of the study. Intermittent (as opposed to continuous) fluoroscopy should be used. Modern fluoroscopy machines are equipped with the “last image hold” feature that can keep the last image frozen so the physician can use that image as a reference for next steps without the need to repeat that image. Other important features of modern fluoroscopy machines include “pulsed fluoroscopy” in which the radiation beams are emitted in intermittent pulses and a “dose-spreading technique.” During VUDs, most of the images are focused on the pelvic area, which may predispose certain areas of the patient’s skin to radiation. One way to avoid this is to rotate the fluoroscope around a central area within the anatomy of interest. Furthermore, it is advisable to keep the image source away from the patient while keeping the image receptor close to her ( ).
Performing the Video Study
The actual technique of VUD testing is very similar to the technique used for conventional urodynamics (see Chapter 10 ) except that contrast is the filling media and fluoroscopic images are obtained during filling and voiding. The study usually begins with a noninstrumented uroflow as described in Chapter 10 . The authors generally obtain five basic images during VUDs. The first is a scout film to visualize any significant radiopaque shadows or bony abnormalities within the pelvic region. After filling is started, a second image assures appropriate positioning of the urodynamic catheter in the bladder. The next image is usually taken as continuous fluoroscopy during Valsalva and cough stress tests. This is done at an initial bladder volume of 150 mL. If the patient does not leak at the initial filling volumes, we repeat this step after every 100 mL of infused contrast until the patient reaches her maximum cystometric capacity, or until an obvious abnormality such as SUI, impaired compliance, or detrusor overactivity (DO) is demonstrated. A voiding film is obtained during the emptying phase of the study. This image is particularly important to assess the bladder outlet in patients with obstructive voiding symptoms. The last image is taken after the patient voids to completion to assess for any postvoid residual contrast. Additional images are taken during the test as needed such as during rises in true detrusor pressure or when low bladder compliance is noticed in order to identify any vesicoureteral reflux and/or urinary incontinence.
Interpretation
The scout film should be free of abnormal radiopaque shadows in the pelvic region. This film should be examined for bony lesions such as spine fracture, plates and screws, spina bifida, sacral agenesis, etc. These lesions may predispose to neuropathic disease and development of neurogenic bladder. Bony anatomic abnormalities also may contraindicate certain treatments such as sacral nerve stimulation. In patients who were previously treated for urinary incontinence, the initial fluoroscopy image may show a migrated or malpositioned Interstim lead or a radiopaque bulking agent at the bladder neck area.
Patients with neuropathy and LUT dysfunction can present clinically with incontinence which may be of bladder origin (DO or impaired compliance) or sphincter origin. They also may present with difficulty emptying, which can be of bladder origin (impaired detrusor contractility) or sphincter origin (dyssynergia). Finally, some neuropathic patients may present with upper urinary tract decompression with hydroureter, hydronephrosis, and even renal insufficiency without any bothersome LUT symptoms.
During bladder filling, the cystogram should be free of filling defects, and the bladder outline should be smooth without sacculae or diverticula. The ureters should not be seen during the filling cystogram or during the voiding cystourethrogram. The bladder neck should be closed during the filling phase of the study, irregardless of patient position or activity (resting, Valsalva or cough). The lower border of the bladder should be at the level of the symphysis pubis. Deviation from these normal findings during filling cystometry may suggest bladder and/or bladder outlet pathology. Examples include ISD, bladder diverticula, vesicoureteral reflux, cystocele, bladder tumors, bladder stones or foreign bodies, and previously injected urethral bulking agents.
During filling the detrusor pressure ( P det ) should be closely observed. Any rise in P det needs to be looked at closely to determine if it is simple accommodation or a true decrease in compliance. Also, DO, particularly if the contraction is sustained and of low amplitude, can be confused with impaired compliance. If filling is stopped and the pressure returns to baseline, then the compliance is not impaired. A number of “pop-off” mechanisms can make bladder compliance appear better than it actually is. Examples of this would be vesicoureteral reflux, which basically means bladder pressure is being transferred to the reflexing renal unit that, over time will be harmful to the upper tract. Figure 11.3 demonstrates vesicoureteral reflux into a transplanted kidney. Another example is a large bladder diverticulum that may provide a protective effect on the upper tract. Finally, an incompetent outlet may be a pop-off mechanism. It may only become apparent when outlet resistance is increased, which can be demonstrated during filling cystometry by occluding the urethra. It can occur surgically after placement of a suburethral sling.
During the voiding phase, the bladder neck should be open and the urethra should be relaxed and free of strictures, diverticula, or filling defects. This part of the study is aimed at diagnosing BOO. The diagnosis of BOO in women is more difficult compared with men because there is a lack of standardized nomograms available to help establish the diagnosis. Furthermore, it is well-known that many women can void to completion without a significant rise in detrusor pressure. This makes it difficult to use the detrusor pressure parameters as used in men to diagnose BOO. Also, women with BOO may present with symptoms more consistent with storage abnormalities, such as urgency and frequency, in contrast to the typical symptoms consistent with difficult voiding.
BOO in women can be either anatomic or functional ( Fig. 11.4 ). Anatomic causes are primarily iatrogenic. In a retrospective study of 86 women with anatomic BOO, found anti-incontinence surgery to be the most common cause. Other causes included pelvic organ prolapse, external compression, urethral diverticulum, and urethral stricture. Functional BOO, on the other hand, refers to failure of relaxation of the bladder neck and/or the urethral sphincter in coordination with detrusor muscle contraction during urination. VUDs have the unique advantage of differentiating different forms of female BOO. This is because of its ability not only to capture the detrusor pressure/uroflow parameters, but also to localize the level of obstruction. Diagnosis of anatomic BOO is largely based on the history and physical examination, which are usually able to detect the cause. In the patient with functional BOO with a history of neurogenic bladder (typically suprasacral lesions), failure of sphincter relaxation is termed DESD ( Fig. 11.5 ). If the patient has no history suggestive of neurogenic bladder, the condition is termed dysfunctional voiding . Primary bladder neck obstruction is the term used to describe the rare patient who is neurologically intact and shown on VUDs to have a closed bladder neck during attempts at voiding.
