eMedicine Specialties > Radiology > Genitourinary

Ureterocele: Imaging

Author: Ganesh Raj, MD, PhD, Staff Physician, Department of Surgery, Division of Urology, Duke University Medical Center
Coauthor(s): John S Wiener, MD, FACS, FAAP, Chief, Division of Urology, Professor, Department of Surgery, Division of Urology, Professor, Department of Pediatrics, University of Mississippi Medical Center; Richard A Leder, MD, Department of Radiology, Associate Clinical Professor, Division of Abdominal Imaging, Duke University School of Medicine
Contributor Information and Disclosures

Updated: Sep 21, 2007

Radiography

Findings

Voiding cystourethrography

Voiding cystourethrography (VCUG) should be performed in all newborns with fetal hydronephrosis. Early imaging prior to complete opacification of the bladder with contrast material may show the ureterocele as a filling defect. VCUG defines the degree of vesicoureteral reflux in both ipsilateral and contralateral systems and also identifies possible inferior displacement of the lower pole as a large obstructed upper pole. The drooping lily sign is a classic description of moderate- to high-grade reflux into a displaced lower pole.

In addition, VCUG may be performed to evaluate the size, position, tension, degree of detrusor backing, and compressibility of ureteroceles. Eversion of ureteroceles on VCUGs may be seen as protrusions outside the urethral or vesical wall (see Image 7).

Intravenous urogram

The classic finding on an intravenous urogram (IVU) is a round radiopacity in the bladder surrounded by a radiolucent rim (see Images 8-9).

If function of the affected kidney is poor, the upper-pole system may not be seen. Very few calices may be noted in the lower-pole system, with a downward and laterally displaced lower-pole moiety (drooping lily sign) (see Image 10). The lower-pole ureter may be displaced laterally or looped around the dilated upper-pole ureter near the sacrum.

Defects in the lower urinary tract are more evident in single-system ureteroceles subtending well-functioning kidneys. The contrast agent–filled ureterocele may be separated from contrast medium in the bladder by a thin lucent halo of the ureterocele wall (spring-onion or cobra-head deformity) (see Image 9). Radiopaque stones within ureteroceles are often seen as opacities on the scout image. On the other hand, radiolucent stones are often seen as filling defects within the ureterocele during the excretory phase of the urogram.

Degree of Confidence

VCUGs are used routinely to visualize the bladder and evaluate the accompanying reflux. Larger ureteroceles are clearly identifiable as areas of cystic lucency within the bladder. VCUG is the diagnostic procedure of choice for evaluating and grading the vesicoureteral reflux. It also helps in therapeutic decision making.

IVUs are not typically obtained in infants because the procedure is more invasive and the results are less informative. The reason is the failure of infant kidneys to concentrate the contrast agent. IVUs are more commonly performed in adults, in whom ureteroceles may be serendipitously depicted.

False Positives/Negatives

With VCUG, pseudoureteroceles, bladder diverticula, and mesonephric duct cysts may all resemble the ureterocele as a cystic lucency on the radiologic imaging, and they may contribute to false-positive findings. A pseudoureterocele is so named because it can mimic the appearance of a ureterocele on VCUGs or IVUs. A pseudoureterocele can have etiologies such as edema due to impaction or passage of calculi, radiation cystitis, and transitional cell carcinoma. Because ureteroceles are compressible, they can be missed when the patient's bladder is full. Small (<1 cm) ureteroceles may also be missed.

With IVU, bladder diverticula and mesonephric duct cysts may all resemble ureteroceles as a cystic lucency on the radiologic imaging, and they may contribute to false-positives findings. Pseudoureteroceles can mimic either an obstructed ureterocele (lucent filling defect) or a nonobstructed ureterocele (lucent halo surrounding the ureteral orifice), depending on the size of the abnormality and degree of the obstruction. Rarely, a focal bladder tumor can cause a similar appearance. Because ureteroceles may change size and shape, depending on the degree of filling, they may not be visible in all phases of the urogram. Finally, because the IVU depends on kidney function for optimal visualization, the use of IVU for diagnosing ureteroceles may be compromised.

Computed Tomography

Findings

Widespread use of CT for diagnostic imaging has allowed the functional and anatomic identification of ureteroceles in a single study. CT scans without and with intravenous contrast enhancement can be used to define the size, shape, and location of the ureterocele (see Images 11-14). Ureteroceles may be seen as cobra-head deformities (see Image 14). In addition, CT scans enable identification of duplicated renal systems, the renal and ureteral contours, the degree of hydronephrosis, the cortical thickness of each moiety, and the functional ability of the kidneys to excrete contrast material, as well as other anatomic anomalies.

Degree of Confidence

CT scans offer greater anatomic resolution of the entire urinary tract, especially in complicated cases. Ureteroceles can be identified accurately and consistently by using CT scans.

False Positives/Negatives

CT scans can cause ureteroceles to be missed, especially if the ureteroceles are compressed. The acquisition of images at multiple time points after the administration of contrast material increases the likelihood of detecting a ureterocele during various filling phases. Minimal bladder filling must be performed to avoid compressing the ureterocele. Rarely, visual identification with cystoscopy may be needed to confirm the diagnosis and to define the morphology of the ureterocele.

Magnetic Resonance Imaging

Findings

MRI is not usually applicable, but it should be as effective as the IVU (as with magnetic resonance urography with or without contrast enhancement) and CT scanning.⁴

Ultrasonography

Findings

Antenatal ultrasonography

On antenatal sonograms, the typical presentation is that of an enlarged hydronephrotic fetal kidney. Renal duplication and/or ureteral duplication may be seen. Intravesical cystic dilation or septa within the bladder (which represent ureterocele walls) suggest that the etiology of the hydronephrosis may be a ureterocele. Such antenatal ultrasonographic findings warrant comprehensive postnatal evaluation and confirmation of the diagnosis.

Renal/bladder ultrasonography

The initial study performed for the evaluation of a neonate with fetal hydronephrosis with or without a suspected ureterocele should be renal and/or bladder ultrasonography. During every postnatal ultrasonographic evaluation of antenatal hydronephrosis, examining the bladder is imperative to avoid missing associated ureteroceles. The sonographic finding of a well-defined cystic intravesical mass within the posterior bladder wall is suggestive of a ureterocele.

The classic description is that of a cyst within a cyst (see Images 1-3). Occasionally, the dilated intramucosal section of the ureter may be visualized as it inserts into the bladder and terminates in the ureterocele (see Images 4-6). Ultrasonography also defines the degree of hydronephrosis, and it possibly depicts renal dysplasia as cortical thinning. With their distinct echogenic renal pelves, duplex renal systems may also be identified on the initial ultrasonographic examination. This finding should exclude any solid periureteric orifice mass in the bladder, such as a pseudoureterocele.

Degree of Confidence

Antenatal ultrasonography is increasingly becoming the modality for diagnosing prenatal ureteroceles. Findings of a cyst within the bladder and hydronephrosis are virtually diagnostic of a ureterocele. However, any finding on antenatal sonography must be confirmed with comprehensive postnatal ultrasonographic evaluation. Hydronephrosis may be associated with ureteroceles, but it is not pathognomonic.

Renal and/or bladder ultrasonography is highly sensitive for the detection of ureteroceles and widely used. Similar to all other imaging modalities, smaller ureteroceles may be compressed and thus missed on sonograms.

False Positives/Negatives

With antenatal ultrasonography, prolapsed ureters, bladder diverticula, and mesonephric duct cysts may resemble the ureterocele on prenatal images, and they may contribute to false-positive findings; however, the finding of a cyst within a cyst should be diagnostic. The habitus of the mother, orientation of the fetus, filling status of the fetal bladder, motion artifacts, presence of comorbid conditions in the fetus or mother, and skill of the sonographer may significantly affect the quality of prenatal sonograms. The fetal bladder must be visualized to make the diagnosis. Often, the fetal bladder may not be imaged adequately, or the ureteroceles may be compressed, leading to false-negative findings. In such cases, associated hydronephrosis is often detected.

With renal and/or bladder ultrasonography, prolapsed ureters, bladder diverticula, and mesonephric duct cysts all may resemble ureteroceles on postnatal sonograms, and they may contribute to false-positive findings. The detection of ureteroceles is compromised in patients with unobstructed or minimally obstructed systems because of the small size of the ureteroceles and the lack of associated ureteral or pelvic dilation. Furthermore, because ureteroceles are compressible, they may be missed when the bladder is full. If the bladder is empty, sonography may not discriminate between ureterocele and bladder walls. For optimal visualization of the ureterocele, sonography must be performed with the patient's bladder distended and empty.

Nuclear Imaging

Findings

Radionuclide renal scans obtained with dimethylsuccinic acid, diethylenetriamine pentaacetic acid, or mercaptotriglycylglycine may be useful in evaluating baseline renal function in the ipsilateral and contralateral units. These scans commonly demonstrate minimal or no function in the upper-pole moiety of the duplicated system, with ureteral obstruction at the point of the ureterocele. A single intravesical system is typically associated with good renal function.

Degree of Confidence

Renal radionuclide scanning is not used to detect ureteroceles, but it may aid in therapeutic decision making. Evaluation of the function of the affected renal units may help in deciding whether partial or radical nephrectomy is indicated.

False Positives/Negatives

The dilated hydronephrotic kidney takes longer to fill and longer to empty because of its size. The function of the hydronephrotic kidney may be underestimated or overestimated.

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