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.

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

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.

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.

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

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-neurogenicneurogenic bladders and Prune Belly Syndrome.

ALOO BUKHARA

secondary to PUV or NGB when elevated bladder pressures

cause decompensation of the UVJ.

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

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

Most commonly occurs with neurogenic and non-neurogenic voiding dysfunction or infravesicalobstructions 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

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, neurogenicbladder, and external compression by retroperitoneal tumors, masses, or aberrant vessels

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

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

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

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

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.

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

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

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 glomerularmaturation

Scans that evaluate drainage (half-life) alone routinely yield values indicative of obstruction because of the dilatation of the collecting system

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.

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

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

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

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.

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

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

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

Tapering

Starr Plication

Kalicinski Plication

Politano-Leadbetter Technique

Cohen Cross-Trigonal Technique

Glenn-Anderson Technique

Gil-Vernet Technique

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.

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