- Megaureter (MGU) is defined as a ureteral diameter greater than 7 mm. MGU can be classified based on its cause as refluxing, obstructed, both refluxing and obstructed, or nonrefluxing and nonobstructed. - MGU is a common finding in neonates referred for urologic evaluation and accounts for up to 23% of cases of urinary tract dilatation seen on prenatal ultrasound. - Evaluation of MGU involves ultrasound to assess anatomy and severity, VCUG to check for reflux, renal scan to evaluate function, and potentially MRI urography. - Management depends on etiology but

2.  Normal ureteral diameter in children is rarely > 5
mm
 Ureters > 7 mm are considered MGUs
 The dilated ureter or MGU can be classified into
one of four groups based on the cause of the
dilatation:
› (1) refluxing
› (2) obstructed
› (3) both refluxing and obstructed
› (4) both nonrefluxing and nonobstructed.

3.  In one series, MGU comprised 20% of
antenatally diagnosed urologic anomalies,
much higher than in historical series b/c most
were discovered only after they became
symptomatic
 If left undetected, many MGUs might never
become symptomatic
› An observation that raises serious questions with
regard to treatment

5.  Common finding in neonates referred for
urologic evaluation.
 Prenatal USG series suggest UVJ
obstruction in up to 23% of patients with
urinary tract dilatation.
 Primary MGU is two to four times more
common in boys than girls, has a slight
prediction (1.6 to 4.5 times) for left side
and is bilateral in app 25% of patients.

6.  In up to10% to 15% of children the contra
lateral kidney may be absent or
dysplastic and concomitant obstruction
of the ipsilateral UPJ area has been
described on rare occasion.
 No clear evidence of hereditary
predisposition.
 Clinically patients have UTIs, PAIN or
HEMATURIA.

7.  The distal end of ureter as it becomes
intramural and subsequently sub mucosal,
rearranges the muscular layers in its wall.
 All layers become longitudinally oriented
and the ureteral adventitia fuses to the
bladder trigone by attachment to
Waldyer’s sheath.
 Sympathetic and parasympathetic
innervations to the distal ureter and UVJ
area is believed to modulate primarily
ureteral peristalsis; however its exact role in
regulating urine transport is unclear

8.  Primary refluxing megaureters are associated
with congenital anomalies of the UVJ where a
deficiency of the longitudinal muscle of the
intravesical ureter results in an inadequate
valvular mechanism
 Secondary refulxing megaureters are caused by
bladder obstruction and the elevated
pressures that accompany it
› Examples include PUV (most common) as well as
neurogenic bladders and non-neurogenic
neurogenic bladders and Prune Belly Syndrome.

9. ALOO BUKHARA

11.  secondary to PUV or NGB when elevated bladder pressures
cause decompensation of the UVJ.

12.  The cause of primary obstructive MGU typically is
an aperistaltic juxtavesical segment 3 to 4 cm
long that is unable to propagate urine at
acceptable rates of flow
 True stenosis is rare, but histologic disorientation
of muscle, muscular hypoplasia, muscular
hypertrophy, mural fibrosis and excess collagen
deposition (Type 1) have been described

13.  Altered peristalsis prevents the free outflow of
urine
› Retrograde regurgitation occurs as urine boluses are
unable to fully traverse the aberrant distal segment
 Resulting ureteral dilatation depends on the
amount of urine that is forced to coalesce
proximally because of incomplete passage.
 Other rare causes of primary obstructive MGU
include congenital ureteral strictures and
ureteral valves

15.  Most commonly occurs with neurogenic and non-neurogenic
voiding dysfunction or infravesical
obstructions such as PUV
 The ureter struggles with propulsion of urine
when pressure is > 40 cm H2O across the UVJ.
 Ureteral dilatation, decompensation of the UVJ,
reflux, and renal damage result if pressures
continue unchecked
 Dilatation largely resolves once the elevated
intravesical pressures are addressed

16.  Sometimes, the ureter remains dilated due to altered
compliance or a damaged peristaltic mechanisms.
› Transmural scarring from chronic infection is seen in some cases.
› Obstruction is not truly present but elevated intravesical pressures
are projected proximally as a noncompliant column
 Other obstructive causes of ureteral dilatation include
ureteroceles, ureteral ectopia, bladder diverticula,
periureteral postreimplantation fibrosis, neurogenic
bladder, and external compression by retroperitoneal
tumors, masses, or aberrant vessels

17.  Once VUR, obstruction, and secondary causes of
dilatation have been ruled out diagnosis of primary
nonrefluxing, nonobstructive MGU
› Most newborn MGUs fall in this category
 Possible causes: increased fetal UOP, persistent
fetal folds, delayed ureteral patency, immature
peristalsis, hyperreflexic bladder of infancy,
transient urethral obstruction

18.  The newborn ureter is a more compliant
conduit than that of the adult
 The kidneys of newborns are probably better
buffered from the pressures of any partial or
transient obstructions that might occur early
in development than are kidneys obstructed
at more proximal levels (UPJ) or at a later
age

19.  More common than originally thought, and often
have an identifiable cause
 Can result from acute UTI with bacterial
endotoxins that inhibit peristalsis
› Resolution with appropriate antibiotic therapy
 Nephropathies and other conditions lead to
increased UOP that overwhelm max peristalsis
which leads to progressive dilatation

20.  These include lithium toxicity, diabetes
insipidus or mellitus, sickle cell nephropathy,
and psychogenic polydipsia
 The most extreme examples of nonobstructed
ureteral dilatations occur with the prune-belly
syndrome

21.  Studies showed that clinically significant MGU
accounted for 8% of children found to have
hydronephrosis on imaging studies, preceded
by UPJ obstruction 22%, PUV 19% andectopic
ureterocele 14%.
 MGU are reported to occur in app 23% of
neonates noted to have antenatal
hydroureteronephrosis.
 Ranking 2nd in D/D of neonates with
hydronephrosis after UPJ obstruction.
 More often in boys and on left side.

22.  Ultrasound is the initial study obtained in any
child with a suspected urinary abnormality
 Usually distinguishes MGU from UPJ as the
most common cause of hydronephrosis
 Provides useful anatomic detail of the renal
parenchyma, collecting system, and bladder
 Baseline standard for the degree of
hydroureteronephrosis for serial future studies

24.  The presence of ureteral dilatation
› VCUG to rule out reflux and assess the quality of
the bladder and urethra
 Neurogenic dysfunction or outlet obstruction
are common causes of secondary MGU
 Need to assess renal function

25.  Renal scans offers objective, reproducible parameters of
function and obstruction
 99m Tc-DTPA and 99m Tc-Mertiatide (MAG3) are most
commonly used assess function and clearance.
 Renal scan shortcomings: standardized tracer dosing,
timing in diuretic dosing, and patient hydration ensure
valid comparison of results
 should defer the study for 3 months for glomerular
maturation
 Scans that evaluate drainage (half-life) alone routinely
yield values indicative of obstruction because of the
dilatation of the collecting system

26.  Renal scan estimate GFR and absolute renal
function by measuring the uptake of radionuclide
(DTPA) early after its systemic administration
 This may indicate the impact of megaureter on
renal parenchymal level, rather than within the
collecting system, where slow rates of washout
are to be expected because of dilatation
 Magnetic resonance urography has the
capability of providing greater anatomic
abnormalities.
 Percutaneous perfusion studies (Whitaker
perfusion test) can also be used.

28.  Routinely recommending surgery in newborns and
infants with grades IV-V reflux is not appropriate
 Medical management is appropriate during infancy and is
continued if a trend to resolution is noted
 Surgery remains the recommendation for persistent high-grade
reflux in older children and adults
 In the rare infant for whom medical management has
failed but who is considered too small for reconstructive
surgery, distal ureterostomy for unilateral reflux or
vesicostomy for bilateral disease provides an ideal
temporizing solution

29.  Management of secondary MGUs is directed at their cause
 Reflux and dilatation improve with the ablation of PUV or
medical management of neurogenic bladder
 MGUs from prune-belly syndrome, diabetes insipidus, or
infection, require no more than observation alone
 Some degree of nonobstructed hydroureteronephrosis
usually persists, even after primary or secondary causes
have been corrected
 Re-evaluation is often necessary

30.  The complication rate of surgery is higher in infants
› repeat surgeries were required for 12% infants
operated on before 8 mo in one series
 As long as renal function is stable and UTIs are not
a problem, expectant management is preferred
 Antibiotic suppression with close radiologic
surveillance is appropriate in most cases
 U/A and RUS every 3 to 6 months during the first
year

31.  Severe hydroureteronephrosis that shows no
signs of improvement or the clinical status
worsens, correction is undertaken when it is
technically feasible, usually between the ages of 1
and 2 years.
 For the occasional newborn who presents with
massive ureteral dilatation or poor renal function
(which is rare with MGUs) or develops recurrent
infections, distal ureterostomy provides an
effective means for poor drainage until the child is
old enough to undergo reimplantation.

32.  Ureteral tailoring is usually necessary to achieve
the proper length-to-diameter ratio
 Narrowing of the ureter may enable the walls to
coapt, leading to more effective peristalsis
 Revising the distal segment intended for
reimplantation is all that is usually required
 The proximal segments regain tone once they
are unobstructed. Kinking is usually
nonobstructive and will resolve.
 Extended stent drainage after tapering
decompresses the system
› Leads to peristaltic recovery

33.  Plication or infolding is useful for the moderately
dilated ureter.
 Ureteral vascularity is preserved, and the revision
can be taken down and redone if vascular
compromise is suspected
 Bulk is a problem with the extremely large ureter
 Excisional tapering is preferred for the more
severely dilatated or thickened ureter
› Plication of ureters greater than 1.75 cm in diameter
experienced more complications in one series

34.  Remodeled MGUs have been generally
reimplanted with standard cross-trigonal or
Leadbetter-type techniques
 Extravesical repairs can also be successfully
done
 The success with reimplantation of remodeled
MGUs is 90-95% regardless of technique
› Compares to 95-99% of non-megaureter reimplants

35.  Tapering
 Starr Plication
 Kalicinski Plication

39.  Politano-Leadbetter Technique
 Cohen Cross-Trigonal Technique
 Glenn-Anderson Technique
 Gil-Vernet Technique

42.  The reimplantation of MGUs has the same
complications (i.e., persistent reflux and
obstruction) as that of nondilated ureters, but at
increased rates
 Complications can occur regardless of whether
excisional tapering or a folding technique is used
 Better results with obstructive MGU and higher
rates of unresolved reflux after tailoring of
refluxing variants
› Higher incidence of bladder dysfunction associated
with the latter and more dramatic abnormalities of their
musculature.

43.  Increased collagen deposition in refluxing MGUs
and altered smooth muscle ratios
 In contrast, obstructive MGUs were not found to
be statistically different from controls
 Increased levels of type III collagen in refluxing
MGUs
› Leads to an intrinsically stiffer ureter that lessens the
surgical success in reimplantation
 Rarely, reflux persists despite adequate ureteral
tunnels in both tapered and normal-sized
ureters.
› Leads to intrinsic ureteral dysfunction caused by
transmural scarring