THE DILATED URETER - OU Medicine

THE DILATED URETER
FREE CME ONLINE
FREE CME ONLINE
To earn CME credit for this activity, participants should read
the article and log onto www.contemporaryurology.com,
where they must pass a post-test. After completing the test
and online evaluation, a CME letter will be emailed to them.
The release date for this activity is June 1, 2006. The
expiration date is June 1, 2007.
Accreditation
This activity has been planned and implemented in
accordance with the Essential Areas and policies of the
Accreditation Council for Continuing Medical Education
(ACCME) through the joint sponsorship of Thomson
American Health Consultants (AHC) and Contemporary
Urology. AHC is accredited by the ACCME to provide
continuing medical education for physicians.
AHC designates this educational activity for a maximum
of 1 AMA PRA Category 1 Credit(s). Physicians should
only claim credit commensurate with the extent of their
participation in the activity.
Target audience
This activity is designated for urologists.
Educational objectives
After completing the following CME activity, the reader
should be able to:
• Outline the basic embryologic development of the ureter.
• Classify the adult and pediatric patient with a megaureter
based on the etiology of the condition.
• Utilize imaging and clinical signs and symptoms to
identify patients with primary obsructed megaureter who
may be candidates for surveillance.
• List 3 indications that should prompt consideration of
repair of the primary obstructed megaureter.
Faculty disclosures
The authors (Stephen D. Confer, MD, Dominic Frimberger,
MD, and Bradley P. Kropp, MD), reviewers of CME content
(Culley C. Carson, MD and Stephen E. Strup, MD) and staff
editors (Nancy Lucas, Editor and Beverly Lucas, Senior
Editor) report no relationships with companies having ties to
this field of study.
44 CONTEMPORARY UROLOGY JUNE 2006
By Stephen D. Confer, MD, Dominic Frimberger, MD, and Bradley P. Kropp, MD
While dilated ureters are usually identified
in adults when they present with symptomatic
complaints, in children, identification
is most likely due to aggressive screening
with perinatal ultrasonography (US). Urologists who primarily
treat adults should be familiar with the principles of evaluation
and management options for adult, pediatric, and fetal populations
as they may be asked to consult on a newborn or fetus with
a dilated ureter. See “Embryology,” page 45, for a brief review of
ureteral development.
A variety of terms have been applied to ureters of abnormal
caliber, including megaloureter, megaureter, dilatation of the
ureter, and widened ureter. King has suggested the term megaureter
to describe any ureter that is found to be dilated. 1 This
broad term is defined further by 3 etiologic categories: obstructed
megaureter, refluxing megaureter, and nonrefluxing nonobstructed
megaureter (Table 1). Each category is further classified into
primary and secondary subgroupings. This article focuses on diagnosis
and management of primary obstructed megaureter.
ETIOLOGY AND PRESENTATION
Primary obstructed megaureter occurs in both pediatric and
adult populations. 2 Rather than being caused by a lumenal obstruction,
the condition is due to an intrinsic abnormality or an
adynamic segment of the distal ureter that leads to a functional
obstruction. In the past, the functional obstruction was thought
to be similar to that seen in Hirschsprung’s disease of the colon.
However, this has been disproven as excised samples demonstrated
the presence of neural plexuses. 3,4
Approximately two thirds of reported patients are males;
however, 1 series displayed a female predominance. 5 The abnormality
is unilateral in approximately two thirds of cases. 5 The
Dr. Confer is a Resident in Urology; Dr. Frimberger is Assistant
Professor, Section of Pediatric Urology; and Dr. Kropp is Professor
and Chief of Pediatric Urology, Section of Urology, and Vice
Chairman of the Department of Urology; University of Oklahoma
Health Sciences Center, Oklahoma City.

WHAT EVERY UROLOGIST SHOULD KNOW
The most important aspect in the management of the dilated ureter in adults and
children is identification of patients who will need and benefit from surgical repair.
presence of other anomalies, such as contralateral ureteropelvic
junction (UPJ) obstruction, renal agenesis or ectopia, and
ureteral duplication associated with primary obstructed megaureters,
may be seen in up to 40% of affected patients. 5
In adults, primary obstructed megaureter is usually detected
when patients present with pain or other symptoms from urinary
tract infection (UTI), calculi, or decreased renal function. 2
In mild cases, however, patients are typically asymptomatic, and
the condition is found during an unrelated workup.
In the pediatric population, routine perinatal US has dramatically
increased the likelihood of detection of the dilated
ureter. 6 The megaureter can be dilated up to 3 cm and thus is
easily identified on US as a hypoechoic cystic-appearing mass in
the retroperitoneum that may extend from the UPJ to the
ureterovesical junction (UVJ). 7 In a 5-year series in which US
was performed on 3,856 fetuses after 28 weeks of gestation, the
prevalence of primary megaureter at the level of the UVJ was
approximately 1 in 2,000. 8
GRADING
Several different grading systems have been promulgated, but
none is useful in predicting which patients will require surgery
and which will benefit from observation. The earliest classification
system, devised in 1978 by Pfister and Hendren, categorizes
Embryology
T
he development of the ureter begins around the fifth
week of gestation. A diverticulum arises from the
posteriomedial aspect of the lower portion of the bilateral
mesonephric ducts. It then elongates posteriorly to meet the
metanephric blastema, thus inducing nephrogenesis. The tip
of the ureteric bud dilates to form the collecting system from
the ureterovesical junction (UVJ ) to the level of the
collecting duct. During the sixth through the ninth weeks,
the embryonic kidney ascends from its pelvic position.
During the ascent of the kidneys, the ureters elongate.
The lumen of the forming ureter develops from the
midureter cranially and caudally until the eighth week.
The urogenital sinus remains separated from the ureteric
UROlogic
➤ Primary obstructed megaureter is
caused by an intrinsic abnormality
or an adynamic segment of the
distal ureter that leads to a
functional obstruction.
➤ While adults typically present with
hematuria or symptomatic
complaints from UTI or stone
disease, most cases in children are
detected antenatally.
lumen by a membrane. This membrane, known as the
Chwalle’s membrane, disappears by the middle of
the eighth week. At approximately the ninth week of
gestation, muscularization is induced by the passing of
the first excreted urine. At 18 weeks, normal physiologic
narrowing can be discerned at the ureteropelvic junction
(UPJ) and the UVJ. It is at this time that dilation of the
ureter may be observed. After 19 weeks, the ureter
continues to grow; however, the normal ureteral
diameter in the fetal population rarely exceeds 5 mm. 1
REFERENCE
1. Cussen LJ. The morphology of congenital dilatation of the ureter: intrinsic lesions.
Aust NZ J Surg. 1971;441:185-194.
JUNE 2006 CONTEMPORARY UROLOGY 45

PRIMARY OBSTRUCTED MEGAURETER
TABLE 1
Differential diagnosis of megaureter
OBSTRUCTED MEGAURETER
Primary: This condition is due to an intrinsic abnormality or an adynamic
segment of the distal ureter that leads to a functional obstruction.
Secondary: Any cause of ureteral obstruction not due to an adynamic
segment. Etiologies include congenital lesions (ureteropelvic junction
obstruction, ectopic ureterocele), inflammatory conditions (tuberculosis,
schistosomiasis, Crohn’s disease, pelvic inflammatory disease, pelvic
abscess), trauma, tumors, lower urinary tract conditions, neurogenic
bladder, benign prostatic hypertrophy, pelvic lipomatosis, and urethral
obstruction.
REFLUXING MEGAURETER
Primary: This condition occurs most often in children and describes a wide
ureter secondary to vesicoureteral reflux (VUR), when an abnormality of
the ureteral orifice (or tunnel length) is the cause of the reflux.
Secondary: Reflux due to high bladder pressures from a neurogenic
bladder or bladder outlet obstruction.
NONREFLUXING, NONOBSTRUCTED MEGAURETER
Primary: Dilation not due to obstruction or reflux (prune-belly syndrome.)
Secondary: In this condition, ureters remain dilated after the correction of
initial pathology.
primary obstructive megaureter in children and adults
according to the degree of dilatation of the proximal
ureter. 5 In grade 1, the dilatation is limited to the distal
ureteral segment. In grade 2, the dilation extends into
the proximal ureter and there may be mild caliectasis.
In grade 3, the entire ureter is dilated proximal to the
adynamic segment and there is moderate to severe
caliectasis. One drawback to Pfister and Hendren’s
grading system is that excretory urography, which is
rarely necessary today, is required.
The most commonly used classification for neonates,
which is now standard
in adults, was
UROlogic
➤ While US is highly sensitive in
detecting dilated ureters, it lacks
specificity for diseases that require
intervention. We recommend US
and VCUG within 48 hours of birth
in antenatally diagnosed infants.
46 CONTEMPORARY UROLOGY JUNE 2006
devised by the Society
for Fetal Urology
(SFU). It assigns a
grade from 0 to 4
based on the degree
of upper urinary tract
dilation. In grade 0,
the central renal complex
is intact. In grade
1, there is mild split-
ting of the renal complex. In grade 2,
the pelvis is dilated but the calyces are
not dilated. In grade 3, the pelvis is
markedly split and the calyces are uniformly
dilated but the renal parenchyma
is normal. Grade 4 shares the characteristics
of grade 3, but there is thinning
of the renal parenchyma.
EVALUATION OF PRENATALLY
DIAGNOSED MEGAURETER
While US is highly sensitive for the detection
of a dilated ureter, it lacks specificity
for diseases that will actually require
intervention. Classification of
megaureters based on the etiology of
the dilation allows the clinician to better
inform patients about the treatment options
and their risks and benefits. Thus,
at our institution, we recommend that
newborns with prenatally diagnosed
megaureters undergo US and voiding
cystourethrography (VCUG) within 48
hours of birth. If reflux is ruled out on
VCUG, we proceed to DTPA diuresis
renography to better evaluate renal
function and to determine the degree of
ureteral obstruction (Figure 1).
MANAGEMENT IN ADULTS
Adults with primary obstructed megaureter typically
present with pain, infection, or hematuria. Radiologic
evaluation (Figure 1) usually reveals pathology in the
distal ureter. Therefore, aggressive surgical management
has been recommended for adults.
Hemal and colleagues identified 53 of 55 adult primary
obstructed megaureters on the basis of studies obtained
to evaluate symptoms. 2 While the authors advocated
surgical management in most instances, they
found it unrewarding in patients with bilateral disease
who have advanced renal failure. Of 5 patients with bilateral
primary obstructed megaureter and uremia, 3
underwent ureteral reimplantation. Of that group, only
1 improved with adequate drainage, and the other 2 patients
died. 2
MANAGEMENT IN CHILDREN
While surgery is the first-line therapy for primary obstructed
megaureter in adults, the approach in children
is evolving. Several studies have compared surgical
outcomes with conservative management, but all are
retrospective and involve a considerable selection

ias. 7,9,10 Nevertheless, these studies
document a shift from the traditional
approach of surgical management to
the current trend of surveillance.
Between 1981 and 1987, Keating
and colleagues assessed 44 renal units
in 35 neonates with primary obstructed
megaureter. 7 Infants with ureters
dilated down to the UVJ with varying
degrees of hydronephrosis were included
in the study. Infants with secondary
obstructed megaureters were
eliminated from the analysis. Antenatal
diagnosis was made by US in 23 of
44 units. Of the 23 units, 87% were
managed nonoperatively. Diagnoses
for the remaining 21 units were made
on the basis of symptomatic complaints
due to UTI or the presence of a
flank mass, or they were incidentally
discovered. Only 12 of the 21 symptomatic
units were managed conservatively.
Subsequently, surgery was performed
on 2 of the 12 conservatively
managed units because of increased
obstruction on DTPA diuresis renogram
and increased dilation on US.
The authors suggested that a decision
to manage asymptomatic patients
conservatively should be based on an
estimate of absolute renal function as
determined by diuresis renography. 7
In 1994, Baskin and associates 9
provided a long-term follow up of Keating and colleagues’
7 carefully selected group and found that 10 of
the original 35 neonates with 44 renal units ultimately
underwent surgery. The remaining 25 were observed
and managed with serial urinary tract imaging using
DTPA diuresis renography, intravenous pyelography
(IVP), and/or renal US. Seventeen of the 25 were diagnosed
antenatally, 2 were identified due to infection,
and 6 incidentally diagnosed. Mean follow-up was 7.3
years for 24 patients. One patient was lost to follow-up
after 1.5 years. The conservatively managed patients
demonstrated no decline of renal function on DTPA
diuresis renography during the observation period.
The authors concluded that conservatively managed
patients should be monitored closely as indications for
surgical repair may arise. 9
McLellan and co-workers evaluated the records of
54 newborns who were prenatally diagnosed with primary
obstructed megaureter from 1993 to 1998. 10 Me-
FIGURE 1
Initial radiographic evaluation of suspected urologic
abnormality
Reflux
Vesicoureteral
reflux
SUSPECTED UROLOGIC ABNORMALITY
(prenatal US or symptoms)
US shows dilation
Perform VCUG
Obstructed
megaureter
dian follow-up was 25.8 months. A total of 69 units
were confirmed postnatally using various imaging
modalities. Antibiotic prophylaxis was continued until
the children were between the ages of 9 and 12 months,
depending on physician’s preference. No child had a
culture-documented UTI.
Resolution, defined as a decrease in hydronephrosis to
SFU grade 1 without hydroureter or minimal residual
hydroureter, occurred in 39 (72%) patients. 10 Five patients
(9%) had no resolution during the surveillance period,
and 10 (19%)
underwent surgery.
The presenting grade
of hydronephrosis appeared
to be an important
predictor of
the resolution rate.
SFU hydronephrosis
grades 1 to 3 were
No reflux
Perform DTPA diuresis
renography
Obstruction No obstruction
Nonobstructing,
nonrefluxing
megaureter
UROlogic
➤ Aggressive surgical management is
recommended for most adults with
primary obstructed megaureter.
JUNE 2006 CONTEMPORARY UROLOGY 47

PRIMARY OBSTRUCTED MEGAURETER
“Parents of children with primary obstructed
megaureter should be reassured that the
condition is likely to resolve spontaneously.”
more likely to resolve within 12 to 36 months. Increasing
or severe hydronephrosis, decreasing renal function,
and/or retrovesical ureteral diameter greater than 1 cm
seemed to correlate with the need for surgical repair.
Multiple reports support conservative management
for primary obstructed megaureter detected in asymptomatic
neonates. 6,7,9,10 We follow these patients with
serial US and DTPA diuresis renography if increased
dilation is observed on US (Figure 2). Once vesicoureteral
reflux has been excluded by VCUG, antibiotic
prophylaxis can be discontinued.
INDICATIONS FOR SURGERY
The absolute indications for surgical intervention have
yet to be determined. Indications for surgery suggested
by Simoni and associates include significant impairment
of urine flow on renal scan, worsening renal
function during observation, and recurrent UTI in
spite of adequate antibiotic prophylaxis. 11
Stehr and colleagues proposed 3 indications for
surgery using US, VCUG, IVP, and MAG-3 renal scan:
initial impaired renal function with an obstructive pattern,
normal function and at least an equivocal urinary
drainage pattern with no improvement, or deterioration
of the urinary drainage and/or function during follow-up.
Using these criteria, only 5 (9.6%) of 42 patients
were managed surgically. 12
Liu and co-workers studied 67 units with pathology
at the UVJ. 13 Eleven
(17%) patients failed
UROlogic
➤ In most antenatally diagnosed
children, the condition resolves
spontaneously. Consequently,
asymptomatic patients can be
followed conservatively with US.
If dilation increases on US, DTPA
diuresis renography should be
performed.
48 CONTEMPORARY UROLOGY JUNE 2006
conservative therapy
and required surgical
repair—3 due to
breakthrough infections
and 8 because
of deteriorating function.
8 The remaining
56 (83%) patients
were managed conservatively
by periodic
followup with US
and DTPA diuresis
renography.
SURGICAL METHODS OF REPAIR
In uncomplicated nondilated ureters, reported success
rates for the various open reimplantation techniques
are well over 95% in children 1 year of age or
older. 14 However, for large dilated ureters requiring
plication or tapering in addition to the usual intravesical
reimplant, no conclusive data have been published.
Glassberg and associates reported a 99% success
rate with tapering using a transverse ureteral advancement
technique of ureteroneocystostomy (Cohen
reimplant) in 7 primary obstructed megaureters. 14
They noted that megaureters measuring 8 to 12 mm in
width, regardless of etiology, can be reimplanted successfully
without tapering.
Hospitalization following reimplantation usually
only requires an overnight stay. A double-pigtail
ureteral stent is routinely placed and is removed at
1 month. Ureteral reimplantation in the neonatal period
can be difficult due to the discrepancy in size between
the megaureter and the small neonatal bladder.
Should surgery become necessary in the neonatal
period, we recommend that a cutaneous ureterostomy
be performed. This procedure is followed in the first
year of life by open intravesical reimplantation with or
without the tapering. The need for surgery is based on
initial poor renal function tests, a 10% reduction in serial
renal function tests, worsening serial US findings,
and/or the presence of breakthrough infections.
CONCLUSION
The most important aspect in the management of the
dilated ureter is identification of patients who will need
and benefit from surgical repair. Historically, patients
with dilated ureters presented with symptomatic complaints,
and diagnosis preceded surgical correction.
Today, antenatal US screening identifies most cases in
children. The antenatal diagnosis of a dilated ureter
with or without hydronephrosis warrants postnatal
confirmation by US and institution of antibiotic prophylaxis.
Ominous signs include bilaterally dilated systems,
anuria, maternal oligohydramnios, or poor renal
function, and necessitate more aggressive evaluation
within the first 48 hours of life.
Most patients with primary obstructed megaureter
detected antenatally can be followed conservatively
with US. DTPA diuresis renography may be performed
after identification of increased dilation on US. Following
antenatal diagnosis of primary obstructed megaureter,
72% resolve spontaneously, 19% will need operative
repair, and 9% will have persistent dilation on
imaging without symptoms or deterioration of func-

FIGURE 2
Management of primary megaureter
tion. 13 Predictors for the need for surgical management
include severe or worsening hydronephrosis, ureteral
dilation greater than 1 cm in diameter, and worsening
renal function. 10
While aggressive surgical management is usually
recommended for adults with primary obstructed
megaureter, parents of children with the condition
should be reassured that it is likely to resolve spontaneously.
However, surgical management, when indicated,
is usually successful.
CU
REFERENCES
Improvement or
no change
Perform serial US
imaging
Resolution of
obstruction
No further
imaging
1. King LR. Megaloureter: definition, diagnosis and management. J Urol.
1980;123(2):222-223.
2. Hemal AK, Ansari MS, Doddamani D, et al. Symptomatic and complicated
adult and adolescent primary obstructive megaureter—indications for surgery:
analysis, outcome, and follow-up. Urology. 2003;61(4):703-707.
3. Dunnick NR, McCallum RW, Sandler CM. Textbook of Uroradiology. 1st
ed. Baltimore, Md: Williams & Wilkins; 1991.
4. Leibowitz S, Bodian M. A study of the vesical ganglia in children and the
relationship to the megaureter megacystis syndrome and Hirschsprung’s disease.
J Clin Pathol. 1963;16:342-350.
US, VCUG, and DTPA diuresis renography
Primary megaureter
Low- to mid-grade ureteral
obstruction
Worsening renal
function
Increased dilation
DTPA diuresis
renography
Infection or pain
High-grade ureteral
obstruction
Surgical repair
Decreased function
(>10%) or increased
obstruction
5. Pfister RC, Hendren WH. Primary megaureter in children and adults. Clinical
and pathophysiologic features of 150 ureters. Urology. 1978;12(2):
160-176.
6. Manzoni C. Megaureter. Rays. 2002;27(2):83-85.
7. Keating MA, Escala J, Snyder HM et al. Changing concepts in management
of primary obstructive megaureter. J Urol. 1989;142(2 pt 2):636-640.
8. Gunn TR, Mora JD, Pease P. Antenatal diagnosis of urinary tract abnormalities
by ultrasonography after 28 weeks’ gestation: incidence and outcome.
Am J Obstet Gynecol. 1995;172(2 pt 1):479-486.
9. Baskin LS, Zderic SA, Snyder HM, et al. Primary dilated megaureter: long
term followup. J Urol. 1994;152(2 pt 2):618-621.
10. McLellan DL, Retik AB, Bauer SB, et al. Rate and predictors of spontaneous
resolution of prenatally diagnosed primary nonrefluxing megaureter.
J Urol. 2002;168(5):2177-2180.
11. Simoni F, Vino L, Pizzini C, et al. Megaureter: classification, pathophysiology,
and management. Pediatr Med Chir. 2000;22(1):15-24.
12. Stehr M, Metzger R, Schuster T, et al. Management of the primary obstructed
megaureter (POM) and indications for operative treatment. Eur J Pediatr
Surg. 2002;12(1):32-37.
13. Liu HY, Dhillon HK, Yeung CK, et al. Clinical outcome and management
of prenatally diagnosed primary megaureters. J Urol. 1994;152(2 pt 2):614-
617.
14. Glassberg KI, Laungani G, Wasnick RJ, et al. Transverse ureteral advancement
technique of ureteroneocystostomy (Cohen reimplant) and a modification
for difficult case (experience with 121 ureters). J Urol. 1985; 134(2):
304-307.
JUNE 2006 CONTEMPORARY UROLOGY 49