A ureterocele is a balloon-like swelling at the lower end of the ureter, where it enters the bladder. The thin wall of the ureter pouches inward, creating a cyst-like bulge inside the bladder that can block urine flow, cause infections, and sometimes damage the kidney above it. Most ureteroceles are now caught before birth on routine ultrasound, though some go unnoticed until adulthood. The condition is more common than many people realize, and how it gets managed has shifted considerably over the past two decades, with a growing number of cases monitored rather than immediately treated.
What a Ureterocele Actually Looks Like
The ureter is the tube that carries urine from the kidney down to the bladder. Normally it passes through the bladder wall and opens via a small slit. In a ureterocele, the very end of the ureter balloons out beneath the bladder lining, forming a fluid-filled pouch that can range from a few millimeters to several centimeters across. On ultrasound it looks like a thin-walled cyst sitting inside the bladder. On older imaging studies using contrast dye, it produces a distinctive rounded shadow sometimes called a “cobra head” sign because the dilated tip of the ureter resembles the hood of a cobra.
Ureteroceles fall into two broad groups based on where the swelling sits. An intravesical (or orthotopic) ureterocele is entirely inside the bladder. An ectopic ureterocele extends beyond the bladder, sometimes reaching down into the urethra. Ectopic ureteroceles tend to be larger, cause more obstruction, and are more often linked to a duplicated collecting system, where the kidney drains through two ureters instead of one. In duplicated systems the ureterocele almost always involves the ureter draining the upper portion of the kidney.
How Ureteroceles Are Found
The majority of ureteroceles are now detected during pregnancy. A study of prenatally diagnosed cases found the average gestational age at first detection was around 24 to 25 weeks, and the diagnosis was confirmed after birth in over 90 percent of cases.1PubMed. Antenatally detected ureterocele: Associated anomalies and postnatal prognosis The classic ultrasound picture is a duplex kidney with a dilated upper portion and a cyst visible in the fetal bladder. But that textbook pattern accounts for only about half of prenatal detections. The rest present with variations: hydronephrosis without a visible cyst, a multicystic segment of kidney, or other atypical features.2American Journal of Obstetrics & Gynecology. Antenatal ultrasound detection and natural history of fetal ureterocele Those variant patterns are more common in males and tend to require surgery somewhat less often.
When a ureterocele is not picked up prenatally, it usually comes to attention in early childhood because of urinary tract infections, sometimes severe enough to cause fever and sepsis. Less commonly, children present with an abdominal mass, difficulty urinating, or urine leaking between normal voids. In adults the story is different: most ureteroceles found later in life are discovered incidentally during imaging for unrelated complaints.3PubMed Central. An adult ureterocele complicated by a large stone: A case report
The Duplex Kidney Connection
About 70 to 80 percent of ureteroceles occur alongside a duplex (duplicated) collecting system, where the kidney has two separate drainage pathways.4PubMed. Antenatally detected ureterocele: Associated anomalies and postnatal prognosis In a duplex system the ureter from the upper pole of the kidney inserts lower and more toward the midline of the bladder than the ureter from the lower pole, a relationship known as the Weigert-Meyer rule. It is that upper-pole ureter that tends to end in a ureterocele. Because the ureterocele obstructs drainage, the upper pole frequently suffers. Tissue studies of upper poles removed at surgery show dysplasia, where kidney tissue never developed normally, in roughly two-thirds of specimens.5PubMed. The predictive value of diagnostic imaging for histological lesions of the upper poles in duplex systems with ureteroceles That damage often exists from before birth, meaning the upper pole may never have contributed much useful kidney function.
The remaining ureteroceles, roughly a quarter to a third, involve a single collecting system. Single-system ureteroceles tend to be intravesical, smaller, and generally easier to manage. They are also the type most commonly found incidentally in adults.
When No Treatment Is Needed
One of the biggest shifts in ureterocele management is the recognition that not every case needs surgery. A large study comparing operative and non-operative approaches found that about 23 percent of ureteroceles could be managed without any procedure. Those patients needed later surgery far less often, around 9 percent, compared with 34 percent of patients who had an initial endoscopic puncture going on to need a secondary operation.6PubMed. Think before you pop: Outcomes of non-operative management of ureteroceles The ureteroceles that did well without intervention shared a profile: smaller size, intravesical location, single collecting system, absence of significant reflux, and milder degrees of hydronephrosis.
Active surveillance, meaning close monitoring with periodic ultrasound and urine testing, has been studied specifically for antenatally diagnosed cases. In single-system ureteroceles the success rate of surveillance is high. For duplex-system ureteroceles the picture is more guarded; surveillance succeeded in roughly 30 percent of carefully selected patients, typically females without significant dilation on the opposite side.7PubMed. Active surveillance for antenatally detected ureteroceles: Predictors of success Because routine antenatal ultrasound now catches ureteroceles that might never have caused symptoms, some proportion of what gets detected today represents milder disease that genuinely can be left alone. Still, surveillance requires commitment: missed infections in a young infant can cause rapid kidney damage, so families choosing this path need close follow-up.8Egyptian Pediatric Association Gazette. Duplex system ureterocoele: a contemporary review
Endoscopic Puncture and the Reflux Trade-Off
For ureteroceles causing obstruction or recurrent infections, the most common first step is endoscopic puncture, sometimes called decompression or incision. A small instrument is passed through the urethra into the bladder, and the ureterocele wall is punctured or cut to let urine drain freely. It is minimally invasive, can be done in very young infants, and in many cases resolves the obstruction without further surgery. Various studies report successful decompression rates ranging from about 90 to 96 percent.9PubMed. Comparison of endoscopic ureterocele decompression techniques10PubMed. A novel approach for an old debate in management of ureterocele: long-term outcomes of double-puncture technique
The catch is vesicoureteral reflux, where urine flows backward from the bladder up toward the kidney. Puncturing the ureterocele can create a new reflux pathway that did not exist before. In one study of 50 children who had puncture, new-onset reflux appeared in 40 percent of cases, though most of those reflux episodes resolved on their own over time: spontaneous resolution or improvement occurred in about 72 percent of observed patients.11PubMed. Clinical evolution of vesicoureteral reflux following endoscopic puncture in children with duplex system ureteroceles The reflux tends to occur into the lower pole of the same kidney or into the opposite kidney rather than back through the punctured ureterocele itself.
The technique used for puncture matters. A meta-analysis comparing laser puncture to electrosurgical incision found significantly lower rates of new reflux with the laser approach.12PubMed Central. De Novo Vesicoureteral Reflux Following Ureterocele Decompression in Children: A Systematic Review and Meta-Analysis Comparing Laser Puncture versus Electrosurgical Incision Techniques The reason likely comes down to how much tissue is disrupted: a small laser hole collapses the ureterocele while leaving more of its wall intact as a flap-valve to prevent backflow, whereas a wider electrosurgical cut can destroy that valve mechanism more completely. Ectopic ureteroceles, which extend beyond the bladder, are harder to treat endoscopically and more likely to fail, sometimes requiring a second procedure or open surgery.13PubMed Central. Clinical outcomes and risk factor analysis of early endoscopic puncture decompression for ureterocele associated with duplex kidney in children: a single-center retrospective study
When Bigger Surgery Is Needed
Some ureteroceles require open or reconstructive surgery, either as a primary approach or after endoscopic puncture fails to resolve the problem. The main scenarios include a non-functioning upper pole that is acting as a source of infection, persistent significant reflux, a large ectopic ureterocele causing bladder outlet obstruction, or a ureterocele that prolapses through the urethra (more common in girls).
The most common definitive procedure for a non-functioning upper pole in a duplex system is upper-pole heminephrectomy, the removal of just the damaged upper segment and its ureter. This can be done through a small flank incision or laparoscopically. The goal is to eliminate the source of infection and obstruction while preserving the healthy lower pole. Laparoscopic upper-pole heminephrectomy has been performed safely in children with good results: the indication is typically a non-functioning upper pole causing reflux-related infections.14PubMed Central. Laparoscopic upper pole heminephroureterectomy in children: Seven-year experience
When the ureterocele itself needs to be removed and the ureter reimplanted into the bladder, a technique called common-sheath reimplantation can address both the upper and lower pole ureters through a single bladder operation. In reported series, this approach has eliminated reflux and recurrent infections.15PubMed. Common sheath reimplantation with ureteral plication: a useful technique for the management of ectopic ureterocele Robotic-assisted surgery is also entering the picture. A recent report described a transvesical robotic approach used to excise a 15-centimeter ureterocele and reconstruct the bladder in pediatric and young adult patients.16Urology Video Journal. Transvesicoscopic Robotic-Assisted excision of giant ureterocele and bladder neck reconstruction: A novel approach in pediatric and young adult patients These newer approaches are not yet widespread, but they illustrate how the surgical options continue to evolve.
Ureteroceles in Adults
Adult ureteroceles are almost always the simpler orthotopic, single-system variety. Many adults live their entire lives without knowing they have one. When symptoms do appear, they tend to involve intermittent flank pain, recurrent urinary tract infections, or stones. Stones form inside the ureterocele because urine pools and stagnates there. The reported incidence of stones within a ureterocele ranges from about 4 to 39 percent depending on the study.17PubMed Central. An adult ureterocele complicated by a large stone: A case report In a series of 16 adults treated endoscopically with a holmium laser, most ureteroceles were single-system, and a quarter of patients also had stones higher up in the urinary tract.18PubMed. Endoscopic management of adult orthotopic ureterocele and associated calculi with holmium laser: experience with 16 patients over 4 years and review of literature
Management in adults is generally more straightforward than in children. An incidentally found ureterocele with no symptoms, no infection, and no obstruction can simply be watched. When intervention is needed, endoscopic incision is usually enough to relieve obstruction and can be combined with laser lithotripsy to break up any stones at the same sitting. Open reconstruction is rarely required in adults.
Pseudoureteroceles and Misdiagnosis
Not every cystic-looking bulge at the end of the ureter is a true ureterocele. A pseudoureterocele is an acquired dilation of the lowest part of the ureter that mimics the appearance of a congenital ureterocele on imaging. The distinction matters because pseudoureteroceles in adults are frequently caused by a tumor involving the bladder wall or a nearby stone eroding into the ureteral opening.19PubMed. Ureteroceles vs. pseudoureteroceles in adults. Urographic diagnosis Pseudoureteroceles tend to be asymmetric, with thicker and more irregular walls compared to the thin, smooth wall of a true ureterocele. They also tend to come with more severe upper-tract obstruction and other signs of the underlying disease.20PubMed. Ureterocele and pseudoureterocele: cobra versus cancer Radiologists sometimes summarize the clue as: a true ureterocele has a thin halo, while a pseudoureterocele has a thick, poorly defined one. In an older adult with no prior history who shows what looks like a ureterocele for the first time, the possibility of an underlying malignancy should be investigated.
Long-Term Bladder Function After Treatment
One concern that does not get enough attention is how the bladder itself functions years after a ureterocele has been treated. A long-term follow-up study divided patients into those whose ureterocele was entirely inside the bladder and those whose ureterocele extended into the bladder neck or urethra. Among children with intravesical ureteroceles, bladder function was generally excellent: none had abnormal voiding symptom scores. But among children with ureteroceles that had extended into the bladder neck, two-thirds showed abnormal urine flow patterns and significant residual urine after voiding, and a quarter had bothersome voiding symptoms. The difference between the two groups was statistically significant and suggests that ectopic ureteroceles can leave a lasting imprint on bladder behavior even after successful decompression or reconstruction.
This finding has practical implications for follow-up. Children treated for intravesical ureteroceles likely do not need ongoing bladder-function testing once the immediate issue is resolved. But those treated for ectopic ureteroceles, especially large ones that involved the bladder neck, probably benefit from periodic assessment of how well they empty their bladder as they grow, particularly around the time of toilet training and into school age.
Is There a Genetic Component?
Ureteroceles are generally considered sporadic, but there is evidence of familial clustering. The largest reported series of familial ureterocele cases documented multiple affected family members across several pedigrees, suggesting a genetic predisposition.21PubMed. Familial ureteroceles: an evidence for genetic background? Ureteroceles likely sit on the same developmental spectrum as vesicoureteral reflux and ureteral duplication, both of which have established genetic and familial patterns. The genes involved appear to relate to how the ureteric bud forms and branches during fetal development. None of this means a parent with a ureterocele should expect their child to have one, but it does mean that when one family member is diagnosed, screening siblings or offspring with a simple ultrasound is a reasonable step, particularly if there is already a family history of reflux or duplex kidneys.
Why the Upper Pole Is Often Already Damaged
Parents who learn their child needs upper-pole removal sometimes worry about losing kidney tissue. The reassuring reality is that in most duplex-system ureteroceles, the obstructed upper pole has been abnormal from very early in development. Histological studies of removed upper poles consistently find high rates of dysplasia, fibrosis, and tubular atrophy.22PubMed. The predictive value of diagnostic imaging for histological lesions of the upper poles in duplex systems with ureteroceles In one series, dysplasia appeared in 64 percent of specimens, and the degree of damage on pathology did not reliably correlate with how the kidney looked on ultrasound, meaning some upper poles that appeared mildly affected on imaging were actually severely dysplastic under the microscope. Segmental renal dysplasia in these cases is thought to be a primary developmental problem rather than something caused solely by obstruction after birth.23Journal of Urology. Hypertension After Surgical Management of Renal Duplication Associated With an Upper Pole Ureterocele In practical terms, removing a non-functioning dysplastic upper pole does not sacrifice useful kidney capacity. It removes a segment that was never working properly and that serves mainly as a reservoir for infection.
Understanding this helps frame the treatment conversation differently. The goal is not to save the upper pole at all costs but to protect the functioning lower pole and the opposite kidney from the consequences of infection and obstruction. When imaging suggests the upper pole contributes meaningful function, which happens in a minority of cases, the surgical approach shifts toward preserving it through ureterocele decompression or ureteral reimplantation rather than removal.