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  • conjenital
  • acquired

Congenital UPJ obstruction typically results from
intrinsic disease
A frequently found defect is
the presence of an aperistaltic segment of the ureter,

 perhaps similar to that found in primary obstructive megaureter
histopathologically :

 the spiral musculature

normally present has been replaced by
abnormal longitudinal muscle bundles or fibrous tissue

this results in failure to develop N peristaltic wave
etiology of UPJ obstruction in children
decreased interstitial cells of Cajal at the UPJ in children
less frequent intrinsic cause of congenital UPJ obstruction
true ureteral stricture

Such congenital ureteral strictures are most frequently found at the UPJ, although they may be located at sites anywhere along the lumbar ureter.

excessive collagen deposition at the site of the stricture    
Intrinsic obstruction at the UPJ may also result from
kinks or valves produced by infoldings of the ureteral mucosa and musculature

In these cases,

the obstruction may actually be at the level of the proximal ureter
  “aberrant” vessels in the etiology of UPJ obstruction
Controversy persists regarding the potential role of “aberrant” vessels in the etiology of UPJ obstruction
lower pole vessels have often been referred to as aberrant,

but  these segmental vessels
may be branches from the main renal artery or arise directly from the aorta,

 are usually normal variants
precise location of crossing vessels
did not correspond to the obstructive transition point

in patients with UPJ obstruction

most certainly has a detrimental effect on the success rates of endopyelotomy
the presence of crossing vessels
UPJ obstruction as  result from acquired lesions

in children
vesicoureteral reflux

can lead to upper tract dilatation with subsequent elongation, tortuosity, and kinking of the ureter.
true UPJ obstruction may definitely  coexist with
vesicoureteral reflux,

although it may be difficult to determine whether the anomalies are merely coincident or whether the upper tract ureteral obstruction has resulted from the reflux
1-st line for DD
UPJ obstruction vs VUR
diuretic renography
Other acquired causes of obstruction at the UPJ include
 - fibroepithelial polyps

 - urothelial malignancy, 

  - stone disease, 

  - postinflammatory or postoperative scarring or ischemia
In neonates and infants,

the Dx of UPJ obstruction

has generally been suggested
either by routine performance of maternal ultrasonography

 or by the finding of a flank mass
renal ultrasonography
is usually the first radiographic study
ultrasonography should be able to visualize dilatation of the collecting system to help differentiate
UPJ obstruction vs  multicystic kidney
and determine the level of obstruction
UPJ obstruction and multicystic kidneys are distinguishable in the majority of cases
by US  alone
UPJ obstruction,

the pelvis is visualized as
 - a large, medial sonolucent area  

 - surrounded by smaller, rounded sonolucent structures representing dilated calyces.
cysts of multicystic kidneys

are visualized as
various-sized sonolucent areas in random distribution
confusion in the diagnosis UPJ obstruction vs multicystic kidney
large, centrally located cyst
in setting

large, centrally located cyst : DD
Tc99m-diethylenetriamenepentacetic acid (99mTc-DTPA) scan allows differentiation of these two entities.    
DTPA scan & multicystic kidney
Multicystic kidneys rarely reveal concentration of this isotope
In contrast,

neonatal kidneys with UPJ obstruction
generally exhibit good concentration of the isotope.
commonly used study for diagnosing both UPJ and ureteral obstruction
Diuretic renography

because it provides quantitative data regarding differential renal function and obstruction,

 even in hydronephrotic renal units.
Ideally diuretic renography can be used
to follow patients for functional loss
Retrograde pyelography
for confirmation of the diagnosis  and

for demonstration of the exact site and nature of obstruction

before repair
retrograde pyelography is indicated emergently
whenever the UPJ obstruction requires acute decompression, such as in the setting of infection or compromised renal function
In cases in which cystoscopic retrograde manipulation has been unsuccessful or may be hazardous
- particularly in neonates or infants

 - placement of a percutaneous nephrostomy is preferred.
Whitaker test
renal pelvis is continuously perfused at 10 mL/min with normal saline solution
Whitaker test :

 - renal pelvic pressure during this infusion :

 12-15 cm H2O - nonobstructed

 excess of 15 to 22 cm H2O -
functional obstruction

pressure between these extremes - nondiagnostic
Indications and
               Options for Intervention
Contemporary indications for intervention for UPJ obstruction include
 - presence of symptoms associated with the obstruction,

-  impairment of overall renal function  -  progressive impairment of ipsilateral function, - development of stones or infection, 

 -  rarely, causal hypertension
UPJ obstruction may not become apparent until
middle age or later
procedure of choice
has historically been dismembered pyeloplasty

-  less invasive endourologic approaches have a role as an alternative in many centers
success rates with most endourologic techniques
 to be comparable with those of

 open, laparoscopic, or robotic pyeloplasty
have not proven
“secondary” UPJ obstruction, it remains reasonable to recommend
an open or laparoscopic approach to any patient who has failed primary endourologic management


an endourologic approach to those who have failed open or laparoscopic repair

can provide
quantitative measures of renal function,

 kidneys with less than 15% differential function are nonsalvageable  

in adults
Endourologic Management

advantages of endourologic approaches include
- reduced hospital stays  

 - postoperative recovery


open, laparoscopic or robotic :

success rate
does not approach
open, laparoscopic, or robotic pyeloplasty can be applied to
almost any anatomic variation of UPJ obstruction
any of the less invasive alternatives require that the surgeon take into account :
- degree of hydronephrosis,

- ipsilateral renal function,

- concomitant calculi,

-  presence of crossing vessels
basic concept of the endopyelotomy is
a full-thickness lateral incision

 through the obstructing proximal ureter,

 from the ureteral lumen out to the peripelvic and periureteral fat
retrograde approach most used today
is the ureteroscopic approach, typically using the holmium laser to incise the UPJ under direct visual control
a cautery wire balloon endopyelotomy, which incises the UPJ under fluoroscopic control,

 percutaneous endopyeloplasty
As far as efficacy
there is little evidence for significant differences between endopyelotomy techniques.

 The differences lie in technical considerations and complications.
Percutaneous Antegrade Endopyelotomy

indications to intervene
for any patient with UPJ obstruction include
1. presence of symptoms

2. progressive or overall impairment of renal function

3. development of upper tract stones

4. infection

5. rarely , causal hypertension
Even with the acceptance of laparoscopic pyeloplasty,

percutaneous endopyelotomy is also appropriate for
those patients with UPJ obstruction and concomitant pyelocalyceal stones, which can then be managed simultaneously
Contraindications to a

percutaneous endopyelotomy

 are similar to the contraindications to any endourologic approach and include
- long segment (>2 cm) of obstruction,

 - active infection,
 - untreated coagulopathy    
impact of crossing vessels is
mere presence of crossing vessels is not a contraindication to an endopyelotomy

significant entanglement of the UPJ by crossing vessels can occasionally be identified and this may render any endourologic approach unsuccessful
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