URETEROCELE
A
ureterocele is a cystic dilation of the terminal ureter that balloons into the
bladder. About 80% of ureteroceles are associated with ureteral duplication,
occurring in the ureter that drains the upper pole (see Plate 2-23). About 10%
of ureteroceles are bilateral.
A ureterocele is known as
“intravesical” if it extends only into the bladder, and “ectopic” if it reaches
the bladder neck or urethra. The orifice is termed “stenotic” if a pinpoint
opening is seen and “sphincteric” if it lies distal to the bladder neck. If the
orifice possesses both of these characteristics, it is known as
“sphincterostenotic.”
The overall incidence of ureteroceles
is difficult to estimate because many small ureteroceles are not identified. The
clinical incidence of ureterocele, however, appears to range from 1 in 5000 to
1 in 12,000. In contrast, one autopsy series reported the incidence to be as
high as 1 in 500. For unknown reasons, there is a female : male ratio of 4 : 1,
and most cases occur in whites.
Pathogenesis
The embryologic basis for ureteroceles
is unknown, but several theories have been proposed. One is that ureteroceles
result from incomplete breakdown of the Chwalla membrane, a normally transient
structure that divides the ureter from the bladder. Although this theory explains
ureteroceles with stenotic orifices, it does not explain those with patent
orifices. Another theory is that the terminal ureter is lined with an inadequate
number of smooth muscle cells, which causes it to become dilated.
Presentation And Diagnosis
A ureterocele may be asymptomatic, but
it can also cause ureteral obstruction, especially when it is associated with a
duplicated system. If large enough, the ureterocele can obstruct the bladder
neck or even the contralateral ureteric orifice.
If a ureterocele is not diagnosed
using prenatal ultra-sound, it may become apparent during infancy. The most
common presentation is a urinary tract infection, which results from urinary
stasis in the obstructed system. Less often, a ureterocele can cause failure to
thrive, flank pain, or hematuria. If the ureterocele lies within the bladder
neck, voiding dysfunction may occur. If the obstruction and associated
hydronephrosis are severe, the kidney may become a palpable abdominal mass.
The diagnosis of ureterocele is typically
established using ultrasound. In most cases, ureteral duplication is also seen.
Hydroureteronephrosis may be seen if there is an obstruction. The diagnosis may
be missed if the bladder is overdistended with urine because the ureterocele may become effaced. In addition,
it is important to distinguish between a ureterocele, which is separated from
the bladder lumen by its own thin wall, and a dilated ectopic ureter, which is
separated from the bladder lumen by the thicker bladder walls.
A VCUG is helpful for further
characterizing the size and location of a ureterocele, which becomes visible as
a discrete, smooth filling defect near the trigone. In duplicated systems, the
ipsilateral lower pole ureter often exhibits vesicoureteral reflux. The reflux is
related both to the short intramural course of the lower pole ureter (see Plate
2-21) and to the deforming effect of the ureterocele on the trigone. In rare
cases, the ureterocele itself may exhibit reflux. Again, it is essential to
obtain images during early bladder filling because high intravesical pressures
can cause the ureterocele to become effaced.
An intravenous pyelogram or
contrast-enhanced CT can also be performed to characterize a ureterocele. An
obstructed ureterocele that is associated with a poorly functional renal unit,
as often seen in a duplicated system, will not fill with contrast and will
appear as a filling defect in the bladder. In contrast, a nonobstructed
ureterocele associated with a functional renal unit, as may be seen in a
nonduplicated system, will fill with contrast. The ureterocele wall will then
form a visible halo in the bladder.
If the ureterocele is large, it may be
difficult to determine from which side it originates. In such cases, it is
helpful to directly visualize the ureterocele using a cystoscope; intubate it
with a ureteral catheter and perform a retrograde pyeloureterogram, generally
at the same time that definitive repair is planned.
Treatment
Once a ureterocele has been identified,
the patient should be started on antibiotic prophylaxis to reduce the risk of
urinary tract infection. In addition, a radionuclide renal scan should be
performed to determine the functional status of the associated renal parenchyma,
especially if there is a duplicated system, because the results will determine
the optimal surgical approach.
The goals of surgical intervention
include relief of obstruction, infection, and reflux. The standard options
include endoscopic incision of the ureterocele, as well as various open or laparoscopic
procedures, such as heminephrectomy, ureteropyelostomy, ureterostomy, and
ureteral implantation.
It is impossible to offer a simple
algorithm for the management of ureteroceles. In each case, the plan must take
into account numerous variables, including patient age, the size and position
of the ureterocele, history of urinary tract infections, the presence or
absence of reflux, the presence of a single or duplicated collecting system, and
the d gree of function in the associated renal parenchyma.
