We are pleased to present an intriguing case that underscores the potential for misinterpretation
of ultrasound findings, particularly in the context of a relatively common clinical
scenario.
During a routine ultrasound examination of a 12-year-old boy with a history of left-sided
vesicoureteric reflux (VUR), a distinct hyperechoic focus measuring approximately
1.7 cm with posterior shadowing was observed at the left vesicoureteric junction (VUJ)
([Fig. 1A]). Notably, color Doppler imaging revealed a characteristic twinkling artifact ([Fig. 1B]), alongside the presence of ureteric jets from both VUJs into the bladder ([Fig. 1C]).
Fig. 1 Ultrasound image of the bladder shows (A) a well-defined hyperechoic focus with posterior shadowing at the left vesicoureteric
junction (VUJ) (arrow). On color Doppler, there was (B) twinkling artifact (arrowhead). Doppler also showed ureteric jet from both VUJ into
the bladder (C).
Regrettably, in the enthusiasm of identifying what was presumed to be a 1.7-cm nonobstructive
calculus, the crucial step of detailed patient history examination was overlooked.
Subsequent inquiry into the patient's medical background revealed a history of successful
treatment for left-sided VUR 3 years prior, through the administration of Deflux injection
at the VUJ. This revelation challenged the initial diagnosis of VUJ calculus, shedding
light on the possibility of Deflux injection mimicking such calcific appearances.
Deflux injection, comprising a biodegradable dextranomer-hyaluronic acid copolymer,
is commonly employed in the management of vesicoureteral reflux in pediatric patients
([Fig. 2]). Its mechanism involves inducing a mass effect at the VUJ, thereby enhancing valve
competency and preventing reflux. Deflux injections are administered into specific
layers of the ureter and the bladder. Subureteral injections are administered beneath
the ureteral orifice, targeting the submucosal layer of the ureter at the VUJ ([Fig. 3A])—also known as STING (subureteric injection). Another technique called the hydrodistension
implantation technique (HIT) consists of introducing the needle into the mucosa inside
the ureteral tunnel. Finally, the double HIT is currently the most performed technique
for endoscopic correction of VUR in the United States. It consists of two intraluminal
ureteric tunnel injections with hydrodistension. The first injection of the bulking
agent aims to coapt the detrusor tunnel whereas the second injection in a more distal
intramural tunnel leads to coaptation of the ureteric orifice. These intravesical
injections are administered at the detrusor muscle layer ([Fig. 3B]). Endoscopic injections, performed via a urethral endoscope, can target either the
submucosal layer of the ureter or the detrusor muscle layer.[3]
Fig. 2 Diagrammatic representation of Deflux injection at vesicoureteric junction (VUJ)
through cystoscopy approach.
Fig. 3 (A) Diagrammatic representation of STING (subureteric injection) technique with submucosal
injection of Deflux into the ureter. (B) Diagrammatic representation of double hit technique of Deflux injection into the
detrusor muscle in the urinary bladder and the submucosal layer of the ureter.
On ultrasound, these implants may initially appear isoechoic, later transitioning
to a hyperechoic state with postacoustic shadowing and twinkle artifacts. On noncontrast
computed tomography (CT) scans Deflux appears hypodense. But density can change over
time depending on biodegradation, displacement, dissolution, calcification, or disruption.[4]
In distinguishing Deflux injection from calculus on ultrasound, certain key considerations
merit attention. First, meticulous patient history remains paramount. Additionally,
the absence of hydronephrosis despite the presence of a seemingly large calculus,
coupled with the persistence of ureteric jets into the bladder, can serve as crucial
discriminators. Similarly, on CT absence of back pressure changes in the form of hydronephrosis
and density < 400 HU were highly suggestive of calcified Deflux.[4]
The overarching lesson derived from this case extends beyond mere differentiation
between Deflux injection and calculus. It underscores the fundamental principle of
diagnostic medicine: the imperative to recognize the subtleties of individual patient
presentations amidst the broader statistical landscape. While the majority of cases
may conform to expected patterns, it is the identification and interpretation of atypical
findings that truly distinguish clinical acumen.
In conclusion, this case serves as a poignant reminder of the nuanced nature of diagnostic
radiology, urging practitioners to exercise diligence, clinical judgment, and an unwavering
commitment to patient-centered care.
