THE DILATED URETER
By Stephen D. Confer, MD, Dominic Frimberger, MD, and Bradley P. Kropp, MD
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The release date for this activity is June 1, 2006. The
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This activity has been planned and implemented in
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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.
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.
44 CONTEMPORARY UROLOGY JUNE 2006
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
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.
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
lumen by a membrane. This membrane, known as the
week of gestation. A diverticulum arises from the
Chwalle’s membrane, disappears by the middle of
posteriomedial aspect of the lower portion of the bilateral
the eighth week. At approximately the ninth week of
mesonephric ducts. It then elongates posteriorly to meet the
gestation, muscularization is induced by the passing of
metanephric blastema, thus inducing nephrogenesis. The tip
the first excreted urine. At 18 weeks, normal physiologic
of the ureteric bud dilates to form the collecting system from
narrowing can be discerned at the ureteropelvic junction
the ureterovesical junction (UVJ ) to the level of the
(UPJ) and the UVJ. It is at this time that dilation of the
collecting duct. During the sixth through the ninth weeks,
ureter may be observed. After 19 weeks, the ureter
the embryonic kidney ascends from its pelvic position.
continues to grow; however, the normal ureteral
During the ascent of the kidneys, the ureters elongate.
diameter in the fetal population rarely exceeds 5 mm.1
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
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
devised by the Society
for Fetal Urology
(SFU). It assigns a
➤ While US is highly sensitive in
grade from 0 to 4
detecting dilated ureters, it lacks
based on the degree
specificity for diseases that require
of upper urinary tract
intervention. We recommend US
dilation. In grade 0,
and VCUG within 48 hours of birth
the central renal comin antenatally diagnosed infants.
plex is intact. In grade
1, there is mild split-
UROlogic
46 CONTEMPORARY UROLOGY JUNE 2006
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
FIGURE 1
bias.7,9,10
Initial radiographic evaluation of suspected urologic
abnormality
Nevertheless, these studies
document a shift from the traditional
approach of surgical management to
SUSPECTED UROLOGIC ABNORMALITY
the current trend of surveillance.
(prenatal US or symptoms)
Between 1981 and 1987, Keating
and colleagues assessed 44 renal units
in 35 neonates with primary obstructUS shows dilation
ed megaureter.7 Infants with ureters
dilated down to the UVJ with varying
degrees of hydronephrosis were included in the study. Infants with secPerform VCUG
ondary 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
Reflux
No reflux
for the remaining 21 units were made
on the basis of symptomatic complaints due to UTI or the presence of a
Vesicoureteral
Perform DTPA diuresis
flank mass, or they were incidentally
reflux
renography
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
No obstruction
obstruction on DTPA diuresis renogram and increased dilation on US.
The authors suggested that a decision
Obstructed
Nonobstructing,
to manage asymptomatic patients
megaureter
nonrefluxing
conservatively should be based on an
megaureter
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 col- dian follow-up was 25.8 months. A total of 69 units
leagues’7 carefully selected group and found that 10 of were confirmed postnatally using various imaging
the original 35 neonates with 44 renal units ultimately modalities. Antibiotic prophylaxis was continued until
underwent surgery. The remaining 25 were observed the children were between the ages of 9 and 12 months,
and managed with serial urinary tract imaging using depending on physician’s preference. No child had a
DTPA diuresis renography, intravenous pyelography culture-documented UTI.
(IVP), and/or renal US. Seventeen of the 25 were diagResolution, defined as a decrease in hydronephrosis to
nosed antenatally, 2 were identified due to infection, SFU grade 1 without hydroureter or minimal residual
and 6 incidentally diagnosed. Mean follow-up was 7.3 hydroureter, occurred in 39 (72%) patients.10 Five payears for 24 patients. One patient was lost to follow-up tients (9%) had no resolution during the surveillance peafter 1.5 years. The conservatively managed patients riod, and 10 (19%)
demonstrated no decline of renal function on DTPA underwent surgery.
diuresis renography during the observation period. The presenting grade
The authors concluded that conservatively managed of hydronephrosis appatients should be monitored closely as indications for peared to be an im➤ Aggressive surgical management is
surgical repair may arise.9
portant predictor of
recommended for most adults with
McLellan and co-workers evaluated the records of the resolution rate.
primary obstructed megaureter.
54 newborns who were prenatally diagnosed with pri- SFU hydronephrosis
10
mary obstructed megaureter from 1993 to 1998. Me- grades 1 to 3 were
UROlogic
JUNE 2006 CONTEMPORARY UROLOGY 47
PRIMARY OBSTRUCTED MEGAURETER
SURGICAL METHODS OF REPAIR
“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
conservative therapy
and required surgical
repair—3 due to
➤ In most antenatally diagnosed
breakthrough infecchildren, the condition resolves
tions and 8 because
spontaneously. Consequently,
of deteriorating funcasymptomatic patients can be
tion.8 The remaining
56 (83%) patients
followed conservatively with US.
were managed conIf dilation increases on US, DTPA
servatively by perioddiuresis renography should be
ic followup with US
performed.
and DTPA diuresis
renography.
UROlogic
48 CONTEMPORARY UROLOGY JUNE 2006
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
US, VCUG, and DTPA diuresis renography
Primary megaureter
High-grade ureteral
obstruction
Low- to mid-grade ureteral
obstruction
Perform serial US
imaging
Worsening renal
function
Infection or pain
Surgical repair
Improvement or
no change
Resolution of
obstruction
Increased dilation
No further
imaging
DTPA diuresis
renography
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
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.
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):614617.
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