Contrast-enhanced voiding urosonography (ceVUS) is most commonly used to assess for vesicoureteral reflux (VUR) and anatomic abnormalities of the urethra. Like fluoroscopic voiding cystourethrography (VCUG) examinations, in ceVUS, contrast is administered into the urinary bladder, and images are obtained of the kidneys, ureters, bladder, and urethra during filling and voiding phases.
As a department, we have performed hundreds of ceVUS exams since we began clinical studies almost 7 years ago. I have learned to ask several questions before beginning each ceVUS to help the exam go smoothly.
Does the patient/family know what will happen during the ceVUS?
Ultrasound is a workhorse for pediatric imaging because of the inherent qualities of the modality: no ionizing radiation, patients in close proximity to family members, calm and darkened exam rooms, non-imposing equipment infrastructure, and (usually) the absence of sedation or anesthesia. Most of these attributes hold for ceVUS, but bladder catheterization changes the non-invasive use of US to an invasive examination. Even so, I have been amazed by the distances that families will travel to seek ceVUS in place of VCUG for their children.
Patient and family preparation is a vital first step for ceVUS. To best image the urethra and bladder base, the probe will be positioned on the lower abdomen, perineum, and over the genitals. Discussion of catheterization and probe positioning on the body in a manner appropriate for the child’s age is critical prior to beginning. Childlife specialists can help prepare the child and family as well as provide support and distraction techniques during the examination.
How will the child void during the examination?
Prior to the voiding phase images during an examination on a young adult, the patient told us that she could not void in the supine position. Unprepared for that moment, we stretched the US unit power cord (and ourselves) to follow her into the adjoining restroom and image her kidneys while she sat on the commode.
A major benefit of ceVUS over VCUG is that the patient is not confined to voiding in a supine position when imaging with ultrasound. While a small percentage of children will not void during either a VCUG or ceVUS, making a plan for how they will void will set the patient up for success during the study. Absorbent pads, bedpans, urinals, training toddler seats, and full-size commodes are all options. When planned for, we often can still obtain urethral images while permitting the patient modesty through appropriate draping.
Which probe positions will be optimal for this patient?
Another benefit of ceVUS over VCUG is that the patient’s anatomy can be visualized even when there is no VUR. When obtaining pre-contrast images, you should start by determining the best window to visualize each kidney.
When VUR occurs, the kidney-ureter unit can be observed with probe positioning from the flank. This position may allow visualization of both the right and left refluxing unit in young children. A transperineal view may not only help to see the urethra but also the bladder base and ureteral insertions.
During VCUG, an imaging team may be accustomed to placing tape on the suprapubic region to secure the bladder catheter. However, US images cannot be obtained through tape. Anticipating the best view of the urethra will help avoid an inopportune tape placement, which will obscure visualization during voiding. In the bladder filling phase, the contrast is following through the catheter, which demarcates the entire course of the urethra. Practicing probe position from a suprapubic or transperineal window during bladder filling will help identify the best window to use when voiding begins. With these preliminaries in mind, we’ve had tremendous success with ceVUS at our institution.
Susan J. Back, MD, is a pediatric radiologist at Children’s Hospital of Philadelphia.
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