1. Ureterocele
Saccular out-pouching of the distal ureter into the urinary bladder
Arise from abnormal embryogenesis, with anomalous development of the intravesical ureter, the kidney, and the collecting system
May be asymptomatic or may cause a wide range of clinical signs and symptoms, from recurrent cystitis to bladder outlet obstruction

2. Types of ureteroceles classified by their association with the renal unit
Single-system ureteroceles
associated with a single kidney, a single collecting system, and a solitary ureter
Duplex-system ureteroceles
associated with kidneys that have a completely duplicated collecting system and 2 ureters.
Orthotopic ureterocele
orifice is located in a normal anatomic (orthotopic) position within the bladder
usually arises from a single renal unit with one collecting system and is more common in adults
Ectopic ureterocele
orifices are located in an ectopic position, such as the bladder neck or urethra
arise from the upper pole moiety of a duplicated collecting system and are more common in the pediatric population

3. Classification based on the features of the affected ureteral orifice
Stenotic ureteroceles
located inside the bladder with an obstructing orifice
Sphincteric ureterocele
refers to those that lie distal to the internal sphincter
the ureterocele orifice may be normal or patulous, but the distal ureter leading to it becomes obstructed by the activity of the internal sphincter
Sphincterostenotic ureteroceles
have characteristics of both stenotic and sphincteric ureteroceles
Cecoureteroceles
elongated beyond the ureterocele orifice by tunneling under the trigone and the urethra

4. Etiology Several theories exist, including:
obstruction of the ureteral orifice
incomplete muscularization of the intramural ureter
excessive dilatation of the intramural ureter during the development of the bladder and trigone
Obstruction of the ureteral orifice during embryogenesis, with incomplete dissolution of the Chwalla membrane
the most commonly accepted theory behind ureterocele formation
Chwalla membrane
primitive thin membrane that separates the ureteral bud from the developing urogenital sinus
failure to completely perforate during development of the ureteral orifice is thought to explain the occurrence of a ureterocele

5. Epidemiology 1 in every 4000 children Most commonly in white persons
F:M ratio - 4-7:1
Although a slight left-sided preponderance appears to exist, approximately 10% of ureteroceles occur bilaterally
Ectopic ureteroceles has been reported to be approximately 80% in most pediatric series
Similarly, approximately 80% of ureteroceles are associated with the upper pole moiety of a duplex system
Single-system ectopic ureteroceles are uncommon and are most often found in males

6. Pathophysiology Embryogenesis of the kidney and ureter
Ureteral bud: primitive analog of the ureter, branches off the caudal portion of the Wolffian (mesonephric) duct during the first 4-6 weeks of gestation
Cranial portion of the ureteral bud: joins with the metanephric blastema, a primitive analog of the kidney, and begins to induce nephron formation
The ureteral bud subsequently branches into the renal pelvis and the calyces and induces nephron formation
Caudally, the mesonephric duct and the ureteral bud are incorporated into the cloaca (urogenital sinus) as it forms the bladder trigone
At this point, the Chwalla membrane perforates to allow the formation of a normal ureteral orifice
If the membrane does not completely perforate, an orthotopic ureterocele results

7. Because the lower pole ureteral bud is absorbed more rapidly, the detrusor submucosal tunnel becomes short
This short submucosal tunnel predisposes the lower pole ureter to reflux
In contrast, the upper pole ureteral bud is absorbed slowly, resulting in a long submucosal tunnel
At this point, the Chwalla membrane must perforate to allow the formation of a normal ureteral orifice
This results in an ectopic ureter
If the Chwalla membrane does not perforate completely, a ureterocele results, most likely in an ectopic location

8. Clinical Manifestations
Urinary tract infection
Urosepsis
Obstructive voiding symptoms
Urinary retention
Failure to thrive
Hematuria
Cyclic abdominal pain
Ureteral calculus

9. Diagnostic Procedures
Laboratory Studies
Urinalysis
Urine culture
Complete blood cell count
Serum chemistries, especially BUN and serum creatinine
Blood cultures
Fungal cultures: obtained in infants who have been on long-term antibiotic therapy or in immunocompromised patients with clinical evidence of UTI

10. Imaging Studies Renal or bladder ultrasonography
First-line imaging study for evaluating the upper and lower urinary tract in the pediatric population
Seen as a fluid-filled cystic intravesical mass
Aka "cyst within a cyst"
Hydroureteronephrosis is noted as a dilatation of renal pelvis and the proximal ureter
Also provides information on the thickness of renal cortex and echogenicity of renal parenchyma
Degree of echogenicity is indirectly proportional to the degree of renal dysplasia that is present
Bladder ultrasonography documents the efficiency of bladder emptying by noting the amount of postvoid residual urine that is present

11. Voiding cystourethrography
Appears as a smooth, round filling defect along the base of the bladder
Can be used to document the efficiency of bladder emptying with assessment of the amount of postvoid residual urine that is present
Vesicoureteral reflux of the ipsilateral lower pole ureters approaches 50%, whereas only 25% of the contralateral renal units have vesicoureteral reflux
Vesicoureteral reflux into the ureterocele is rare, but it may occur following spontaneous ureterocele rupture or after unroofing of the ureterocele

12. Diuretic nuclear renography (nuclear renal scan)
Nuclear renal scan using technetium 99m diethylenetriaminepentaacetic acid (DTPA) is an excellent study for establishing the differential renal function objectively and the efficiency of drainage of the dilated collecting system (washout times)
DTPA is cleared almost exclusively by glomerular filtration
Its rate of clearance provides an excellent estimate of glomerular filtration rate (GFR)
Alternatively, technetium 99m mercaptoacetyltriglycine (MAG3) may be used
This radioisotope is rapidly cleared by tubular secretion and is not retained by the kidneys
MAG3 is an excellent replacement for DTPA (eg, diuretic renography) in the pediatric population

13. Intravenous pyelography
Useful for delineating renal anatomy and providing a subjective estimation of relative renal function
The following may be seen on IVP:
Hydronephrosis, revealing dilatation of collecting system
Hydronephrotic upper pole displacing the lower pole moiety laterally and inferiorly (ie, the "drooping lily")
Ureteral displacement by the hydroureter or hydronephrotic upper pole moiety
Cobra-head extension of the distal ureter (ureterocele) (seen in adults)

14. Magnetic resonance imaging
Excellent anatomical study for evaluating rare cases with suspected dysplastic, nonfunctioning, ectopic renal moieties and ectopic ureteral insertion

15. CT scanning of the abdomen and pelvis
If renal ultrasonography and IVP findings are equivocal, CT scanning may provide additional clues for diagnosing simple or ectopic ureterocele
Can reveal the presence of a duplicated collecting system, hydronephrotic upper pole segment, or dysplastic upper pole moiety

16. Cystoscopy, vaginoscopy, or retrograde pyelography
Endoscopic procedures that allow direct inspection and examination of the lower urinary tract, as well as the female genitalia
For optimal demonstration of a ureterocele, one must examine the bladder when it is both full and empty
When radiologic suspicion of a ureterocele in an adult is aroused, cystoscopy often confirms radiographic findings
If clinically indicated, the ureterocele may be treated with endoscopic incision or unroofing at the same setting

17. Treatment Medical Therapy
Observation alone is rarely a good option in symptomatic ureteroceles
Must rapidly initiate aggressive antibiotic therapy
Antibiotics should be instituted during the initial diagnostic evaluation and during surgical intervention

18. Surgical Therapy Goals of treatment include the following:
Control of UTI
Preservation of renal function
Protection of ipsilateral and contralateral renal units
Maintenance of urinary continence

19. Surgical Therapy Surgical approach is selected based on the following:
Age of the patient
Size and location of ureterocele
Degree of renal function
Presence and degree of vesicoureteral reflux
Comorbid conditions (risk of anesthesia)

20. Endoscopic incision
Least invasive method for decompressing the ureterocele
Ideal method for dealing with a neonate with ureterocele-induced obstructive uropathy and sepsis
Performed via the cystoscope, a small puncture is created at the base of the ureterocele
In addition to its therapeutic value, this technique may be used when the contribution of the associated renal moiety to overall renal function is indeterminate
Also allows palliative decompression in children at high risk (secondary to concurrent medical illness), so that definitive reconstruction can be delayed until an adequate healing period has occurred
Definitive therapy in only 10-40% of patients with ectopic ureteroceles, compared to 90% of the patients with a single system intravesical ureterocele

21. Upper pole heminephrectomy and partial ureterectomy
Involves removal of the upper pole of the kidney, as well as the affected proximal ureter to the level of iliac vessels
Remaining distal ureterocele is not excised but rather is decompressed
Definitive treatment in patients with an obstructed ectopic ureterocele and a dysplastic upper pole, but without associated vesicoureteral reflux
Excellent first-line procedure for the child with a ureterocele that affects only the ipsilateral upper pole
Good choice in the child with a ureterocele with only ipsilateral renal involvement (which may include upper pole obstruction and lower pole reflux, for example)

22. Ureteropyelostomy
Operation that joins the upper pole ureter to the lower pole renal pelvis
Preferred if the affected renal unit demonstrates significant function
Alternatively, a high ureteroureterostomy may also be performed
This is true for both pediatric and adult populations

23. Excision of the ureterocele and ureteral reimplantation
Indicated as a primary procedure if the patient has significant vesicoureteral reflux in the lower pole moiety and a well-functioning upper pole moiety and/or significant contralateral vesicoureteral reflux
Both ipsilateral ureters may be reimplanted within a common sheath or via ureteroureterostomy
This operation is commonly delayed until the child is older (aged approximately 2 y/o)
However, this operation should be performed before the child is toilet trained since it is rather extensive surgery

24. In the pediatric population, the excision and reimplantation procedure commonly is used as a secondary procedure (after previous heminephrectomy or endoscopic incision of a ureterocele) because of UTI, voiding disturbance, persistent vesicoureteral reflux, or obstruction
If this procedure is selected as the first-line treatment in the appropriate patient, the rate of secondary surgery is low

25. Nephroureterectomy
Performed in patients with single system ureterocele and a nonfunctioning kidney
The traditional method of correcting an ectopic ureterocele in a duplex system has been to perform a total reconstruction
This involved a bladder surgery, followed by renal surgery
The bladder surgery required excision of a ureterocele, reconstruction of the detrusor, and reimplantation of the ipsilateral ureter.
This was followed by a flank incision and upper pole heminephrectomy
Since most ureteroceles typically present in young children (often <1 y), total reconstruction was technically challenging, and complications were common

26. Complications Endoscopic incision of ureterocele
Iatrogenic VUR occurs in 40-50% of pediatric patients
This is infrequently definitive therapy, except in cases of a single system intravesical ureterocele
Upper pole heminephrectomy
Highest risk of intraoperative blood loss
Vascular compromise of lower pole with potential loss of renal function
Need for further lower tract reconstruction due to persistent reflux, infection, or failure to decompress the ureterocele
Excision of ureterocele and ureteral reimplantation
Problematic hematuria and/or bladder spasms
Damage to bladder neck or continence mechanism
Injury to the contralateral ureteral orifice
Compromise of blood supply to the lower pole ureter