Diagnostic Ultrasound - Abdomen and Pelvis

Ureteropelvic Junction Obstruction
Diagnoses: Urinary Tract
TERMINOLOGY
• Ureteropelvic junction (UPJ) obstruction, pelviureteric
junction obstruction (PUJO)
• Obstruction of urine flow at level of ureteropelvic junction
IMAGING
• Marked hydronephrosis to level of UPJ without dilatation
of ureter
• Renal pelvis disproportionately enlarged compared to
calyces
• Presence of crossing vessel
• Nuclear renal scan: Hydronephrosis with poor drainage,
suggesting obstruction
• Imaging recommendations
○ Ultrasound in both prenatal and postnatal evaluation
○ Nuclear renal scan to determine whether
hydronephrosis is obstructive and degree of obstruction
○ CT or MR to detect crossing vessel
KEY FACTS
TOP DIFFERENTIAL DIAGNOSES
• Multicystic dysplastic kidney
• Hydronephrosis of other etiology
PATHOLOGY
• Intrinsic vs. extrinsic causes
○ Abnormal peristalsis at UPJ secondary to abnormal
muscle or nerve fibers
○ Crossing vessels near UPJ (50% of older children)
CLINICAL ISSUES
• M > F
• Most common cause of antenatal and neonatal
hydronephrosis
• Prognosis generally good, depends on degree of preserved
renal function
• Treatment: Pyeloplasty (open, laparoscopic, or roboticassisted
laparoscopic)
(Left) Graphic shows a
markedly dilated renal pelvis
and calyces ſt in a
ureteropelvic junction
obstruction. The ureter st is
not dilated. (Right)
Longitudinal image of the left
kidney demonstrates marked
dilatation of the renal pelvis
ſt as well as the renal calyces
st. Note the severe cortical
thinning .
(Left) Longitudinal image of
the left kidney demonstrates
moderate dilatation of the
renal pelvis ſt and the calyces
st. (Right) Delayed static
image of a diuresis MAG 3
radioisotope scan shows stasis
of the tracer within a dilated
collecting system above the
UPJ in both 1 hour (left)
and 3 hour (right) delayed
scan.
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