Most common obstructive lesion,
most common cause of hydronephrosis in
- Most cases
are detected in newborns during routine in utero renal ultrasonography.
- Believed to
be related to abnormal embryologic development of the proximal (upper) ureter.
- Usually caused by intrinsic stenosis.
constriction (focal narrowing or adynamic segments)
- External compression:
or angulations or abnormal vessel crossing, i.e. an accessory artery to
the lower pole of the kidney
- Renal function may be impaired from pressure atrophy.
- There is a whole segment
of UPJ abnormalities called anomalous UPJ.
- UPJ obstruction most commonly presents:
- may be asymptomatic
- maternal US shows fetal
palpable renal mass in
- abdominal/flank/back pain
- febrile UTI
- hematuria after minimal trauma;
mild or moderate UPJ obstruction may be undetected until there is trauma to
the kidney or an abnormal flow of urine into the obstructed area. Such
insults can occur after copious
intake of fluids or the use of diuretics
- 60% on Left
- 10% bilateral
- more in males 2:1
- Renal US
will reveal hydronephrosis
- In a fetus where renal pelvis dilation seen on prenatal US and baby is
asymptomatic, dx is
difficult. Repeat US after DOL 3 (nbn oliguria may mask). If US negative, repeat
US in one month.
- Because the
significance/grade of the obstruction (eg, complete or partial) is
essential to determining ultimate management, diuretic renography (renal scan)
should follow the ultrasonography. Using a tracer such as Mag 3, a renal scan
will assess the uptake of blood by the kidney and excretion of urine. If there
is a delay in excretion, a small dose of a diuretic (eg, furosemide) is
administered. Subsequently, the extent of excretion of urine and time course
necessary for complete emptying of the renal collecting system determines the
extent of the obstruction.
- VCUG (15% have
- The cause
and extent of the obstruction is vital to the ultimate management.
newborns who have UPJ obstruction have only mild hydronephrosis, and surgery
is usually unnecessary.
- In more
severe cases of obstruction, the patient is vulnerable to the development of
urinary tract infection and subsequent renal scarring, and surgery may be
- Repair of
UPJ obstruction remains a controversial topic.
- Mild UPJ
obstruction usually does not require repair because the efficacy of surgery is
not guaranteed and the risk for kidneys exhibiting minor obstruction is
Moderate-to-severe obstruction, as indicated by delayed washout of the tracer
on diuretic renography, usually requires surgical repair. T
- he surgery
involves excision of the obstruction, reconnection of the renal pelvis and
ureter, and reduction, if present, of the oversized renal pelvis. The
complication rate is low (success 91-98%), but some patients will experience a
recurrence of the obstruction. Hence, repeat ultrasonography and renography
are required within the first 6 months after surgical repair.
• megacalyciosis: congenital, nonobstructive calyx dilation without pelvic or
• vesiculureteral reflux
• midureter or distal obstruction when ureter not well visualized on urogram