Pediatric ureterocele complicated by urolithiasis

A 9-year-old boy, suffering from frequent urination, weak stream and enuresis, was presented to the hospital for a check-up. Ultrasonography and cystoradiography revealed hydronephrosis and hydroureter on the right side, accompanied by multiple stones in the distal ureter. An abdominal contrast CT examination was requested for further evaluation, prior to the cystourethroscopy procedure.

CT images showed a markedly dilated right renal pelvis and calyces as well as the right ureter, indicating hydronephrosis and hydroureter. Multiple smooth round stones, measuring 4 – 5 mm in diameter, were seen in the distal segment of a single dilated right ureter, which protruded into the bladder lumen. The right ureteral orifice was not visible. A single stone, located inferiorly in the dilated renal calyx and posteriorly in the protruded ureterocele, was also seen. The left renal system was unremarkable. CT findings suggested an ureterocele with urolithiasis.

Subsequently, the patient underwent a successful ureterocele resection, stones extraction and stent implementation between the renal pelvis and the bladder via cystoscopy. 25 stone pieces were extracted and the laboratory analysis revealed calcium-oxalate stones with 50/50 weddellite and whewellite. A follow-up session of cystourethroscopy was scheduled to extract the residual stones in the kidney.

Fig. 2: An axial image (Fig. 2a) and a cVRT image (Fig. 2b) show the ureterocele protruding into the bladder (arrows) and multiple stones in the dilated distal ureter (dotted arrow).

An ureterocele is a congenital abnormal dilation of the distal-most portion of the ureter, protruding into the bladder. It can be asymptomatic and is often diagnosed later in life due to urolithiasis or is incidentally found through diagnostic imaging performed for other reasons than a suspicious ureterocele. Ureteroceles complicated by urolithiasis are not uncommon. Ultrasonography is primarily used for imaging diagnosis in pediatric patients. CT or MRI are valuable to further define the ureterocele anatomy in complex cases to guide surgical procedures.

This case is performed on a dual source photon-counting CT (PCCT), NAEOTOM Alpha®. It provides energy-resolved CT data without electronic noise, which is eliminated by setting up a predefined digital threshold for counting X-ray photons far above the electronic noise floor. [2] In the image reconstruction process, a model based iterative reconstruction approach – Quantum Iterative Reconstruction (QIR) – is applied for further image noise reduction. These improvements contribute to the reduction of image noise as well as radiation dose. By using an optimized 70 kV protocol, a CTDI value as low as 0.77 mGy is achieved for the entire abdominal and pelvic scan. Less image noise also contributes to a three-dimensional demonstration of anatomical details. Slices, as thin as 0.4 mm, can be used to create lifelike images using cinematic volume rendering technique (cVRT), assisting the surgeons in planning an appropriate procedure. Note that the contrast agent is administered using a two-bolus protocol – 30 mL in the first bolus and 25 mL in the second, both with a 25 mL saline chaser. After the first contrast bolus, there is a waiting period of 1.5 hours to secure a well-filled dilated excretory system. A start delay of 40 seconds is applied after the second bolus for better vascular and parenchymal enhancement. Using this approach, only one scan, instead of two, is necessary, further reducing the radiation exposure to the pediatric patient. As shown in this case, with the advanced PCCT Quantum technology, optimal image quality with reduced radiation dose can be achieved for pediatric scans in clinical routine.