Also known as pelviureteric junction obstruction

Obstruction of urine flow at level of UPJ

Congenital or acquired

Marked hydronephrosis to level of UPJ without dilatation of ureter

Renal pelvis disproportionately larger than calyces

Color Doppler may detect crossing vessel

Nuclear renal scan: Hydronephrosis with poor drainage, suggesting obstruction

Ultrasound is 1st-line modality

CTA or MRA for vascular evaluation prior to surgery

Nuclear renal scan to determine relative renal function and confirm obstructive hydronephrosis

Imaging recommendations

• ○
  

  CT or MR to detect crossing vessel

Multicystic dysplastic kidney

Hydronephrosis of other etiology

Extrarenal pelvis

Pararenal cyst

Intrinsic causes: Abnormal peristalsis at UPJ, stone, clot, tumor, stenosis, scarring

Extrinsic causes: Crossing vessels near UPJ

Associated with renal ectopia and fusion anomalies

Higher incidence in multicystic dysplastic and duplicated kidneys

M > F, twice as common on left, 10-30% bilateral

1 in 1,000-1,500 newborns

Most common cause of antenatal and neonatal hydronephrosis, diagnosed by prenatal screening

Symptoms include: Intermittent abdominal or flank pain, nausea, vomiting, failure to thrive, hematuria, renovascular hypertension (rare)

Prognosis generally good, depends on degree of preserved renal function

Treatment: Pyeloplasty (open, laparoscopic, or robotic-assisted laparoscopic)

Use color Doppler for bladder jets and crossing vessels