- Author: Ganesh Raj, MD, PhD; Chief Editor: Eugene C Lin, MD more...
A ureterocele is a submucosal cystic dilation of the terminal segment of the ureter. A ureterocele may be classified most easily as intravesical, defined by its presence entirely within the bladder, or extravesical, defined by the permanent presence of some portion of the ureterocele at the bladder neck or urethra. Other classification systems for ureteroceles are based on the location of insertion of the ureter into the bladder (simple [orthotopic] and ectopic) or based on their association with a single or duplicated system. (See the images below.)
According to their morphology, ureteroceles may be stenotic (obstructive ureteral orifice within the bladder), sphincteric (ureteral orifice at the bladder neck), or sphincteric stenotic (obstructive ureteral orifice at the bladder neck). In addition, they can also be cecoureteroceles (extension of the ureterocele past the bladder neck into the urethra).
Ureteroceles are most commonly found in association with complete ureteral duplication (80%), but they can also be seen at the terminus of a single system. The association of a fluid-filled structure within the bladder leading to an ectopic dilated ureter and a hydronephrotic upper pole of a kidney is the sine qua non of a ureterocele associated with a duplicated system. The function of the upper pole segment is variable, depending on the relative degree of obstruction caused by the ureterocele.
A ureterocele associated with the upper-pole moiety is located medially and inferiorly to the lower-pole ureter, inserting in a more superolateral location (Weigert-Meyer rule). Intravesical single-system ureteroceles are typically associated with good renal function (>80% with excretory function), whereas extravesical single-system ureteroceles are seen with poor renal function (< 30% with excretory function), dysplastic kidneys, and bladder outlet obstruction.
Increasingly, ureteroceles are detected on antenatal sonograms. Initial findings often include hydronephrosis and a fluid-filled structure within the bladder. Antenatal findings must be correlated with results of postnatal studies, including ultrasonography, cystography, and functional studies. Vesicoureteral reflux (VUR) is present in 50% of ipsilateral lower-pole moieties in duplex systems and present in 10-25% of contralateral moieties in single and duplex systems.
Radiologic evaluation of a ureterocele in an adult usually includes kidney-bladder ultrasonography. Ultrasonography can be the initial study performed, and it can be used to detect prenatal ureteroceles. Ultrasonography noninvasively depicts anatomic changes in the kidney and bladder.
Sonography should be performed with the bladder empty and with it filled to eliminate nonvisualization of ureteroceles due to either compression of the bladder or the ureterocele. Ultrasonography is the most sensitive test and often the only radiologic evaluation required for the diagnosis of ureteroceles.
Functional studies of the renal system include intravenous pyelography, computed tomography (CT) scanning, and renal scanning. These contrast-enhanced studies help to delineate the relevant renal anatomy, especially with regard to potential renal duplications. They are also useful in evaluating the differential renal function. Contrast-enhanced studies help to identify ureteroceles within the bladder as a thin, nonenhancing rim around contrast enhancement within the ureterocele.
These functional studies often add supplemental information that is useful in the treatment of patients with ureteroceles, but they are typically not used as first-line imaging modalities for the diagnosis of suspected ureteroceles.
Limitations of techniques
Ultrasonography is the most sensitive test for the detection of ureteroceles, but it may cause ureteroceles to be missed if the patient's bladder is empty or fully distended, if the ureteroceles are small, or if the patient's body habitus precludes proper examination. Ultrasonographic findings are relatively specific for ureteroceles, because the other etiologies of a cyst within a cyst are relatively rare.
CT scans, intravenous pyelograms, and renal scans are less sensitive for ureteroceles, but they help to more clearly delineate the functional anatomy of the kidneys.
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 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.
The classic finding on an intravenous urogram (IVU) is a round radiopacity in the bladder surrounded by a radiolucent rim, as in the image below.
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; as seen in the image below). 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), as demonstrated in the image below. 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.
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.
Widespread use of CT scanning 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 the images below). Ureteroceles may be seen as cobra-head deformities (as demonstrated in the fourth image below). 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.
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
Magnetic resonance imaging (MRI) is usually not applicable, but it should be as effective as the IVU (as with MR urography with or without contrast enhancement) and CT scanning.[3, 4, 5]
Cerwinka et al examined the potential for misidentifying dextranomer/hyaluronic acid copolymer (Deflux) implants used in the endoscopic treatment of VUR as ureteroceles on MRI scans. The authors found that on T2-weighted MRI scans, the implants can appear as bright structures that could be misinterpreted as uroceles. (The implants were not seen on T1-weighted MRI or excretory MR urography scans.)
The investigators concluded that in instances in which a structure that could be interpreted as a ureterocele appears on a T2-weighted MRI scan, physicians can avoid making a misdiagnosis by considering whether a patient has a history of VUR treatment and possesses a single urinary system.
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.
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, as in the first 2 images below. Occasionally, the dilated intramucosal section of the ureter may be visualized as it inserts into the bladder and terminates in the ureterocele, as seen in the last 3 images below. 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.
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.
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.
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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