Diagnostic Ultrasound - Abdomen and Pelvis

Ureteropelvic Junction Obstruction
Diagnoses: Urinary Tract
• Calyces not dilated
• Much smaller in size than UPJ obstruction
Pararenal Cyst
• Lymphatic in origin or develops from embryologic rests
• Well-defined anechoic renal sinus mass not communicating
with calyces
PATHOLOGY
General Features
• Etiology
○ Intrinsic
– Abnormal peristalsis at UPJ, secondary to abnormal
muscle or nerve fibers
– Stenosis from scarring of ureteral valves
– Intraluminal lesions
□ Tumors: Benign polyps, urothelial carcinoma,
squamous carcinoma, metastases
□ Others: Stone, clot, papilla, fungus ball
○ Extrinsic
– High insertion of ureter at renal pelvis
– Crossing vessels near UPJ (50% of older children)
– Abnormal rotation of kidney
– Secondary UPJO: Prior surgery, inflammation, trauma,
or stone disease
• Associated abnormalities
○ Higher incidence in multicystic dysplastic kidneys
○ Can be present in upper or lower moiety of duplex
kidney
○ Renal ectopia and fusion anomalies
○ VACTERL spectrum
Microscopic Features
• Decreased number of nerve and muscular fibers with
abnormal increased collagen deposition within ureteric wall
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Neonates
– Often diagnosed by prenatal screening
– Palpable, sometimes visible abdominal mass
○ Children and adults
– Intermittent abdominal or flank pain, nausea,
vomiting, failure to thrive
– Hematuria, renovascular hypertension (rare)
– Can present after minor trauma, possibly with rupture
Demographics
• Age
○ Can present at any age; more common in pediatric
population
• Gender
○ Overall, M:F = 2:1
○ In infants, M:F = 5:1
• Epidemiology
○ 1 in 1,000 to 1,500 newborns
○ Most common cause of antenatal and neonatal
hydronephrosis
– 50% of all patients with antenatal hydronephrosis
Natural History & Prognosis
• May improve or worsen spontaneously
• Prognosis generally good, depends on degree of preserved
renal function
• After successful surgery, dilatation of renal pelvis and
calyces may persist for years on US
○ Evaluate interval renal growth and good drainage on
postsurgical imaging
Treatment
• Pyeloplasty (open, laparoscopic, or robotic-assisted
laparoscopic)
○ Resection of narrowed segment at UPJ
○ Crossing vessel is rerouted
○ Ureteral stents often left in place for several weeks
postoperatively
○ Preferred approach when crossing or aberrant vessels
are present; hemorrhage as complication of endoscopic
approach
• Endopyelotomy: Endoscopic incision
• Endopyeloplasty: Horizontal percutaneous suturing of
conventional longitudinal endopyelotomy incision
• Percutaneous nephrostomy, as temporary measure,
especially if infected
DIAGNOSTIC CHECKLIST
Consider
• CT or MR to evaluate potential acquired etiologies of UPJ
obstruction
• CTA or MRA to look for crossing vessel
Image Interpretation Pearls
• Look for presence of crossing vessel on all modalities
SELECTED REFERENCES
1. Arora S et al: Predictors for the need of surgery in antenatally detected
hydronephrosis due to UPJ obstruction - A prospective multivariate analysis.
J Pediatr Urol. ePub, 2015
2. Lin L et al: Role of endoluminal sonography in evaluation of obstruction of
the ureteropelvic junction. AJR Am J Roentgenol. 191(4):1250-4, 2008
3. Calder AD et al: Contrast-enhanced magnetic resonance angiography for the
detection of crossing renal vessels in children with symptomatic
ureteropelvic junction obstruction: comparison with operative findings.
Pediatr Radiol. 37(4):356-61, 2007
4. Williams B et al: Pathophysiology and treatment of ureteropelvic junction
obstruction. Curr Urol Rep. 8(2):111-7, 2007
5. Jones RA et al: Dynamic contrast-enhanced MR urography in the evaluation
of pediatric hydronephrosis: Part 1, functional assessment. AJR Am J
Roentgenol. 185(6):1598-607, 2005
6. McDaniel BB et al: Dynamic contrast-enhanced MR urography in the
evaluation of pediatric hydronephrosis: part 2, anatomic and functional
assessment of uteropelvic junction obstruction. AJR Am J Roentgenol.
185(6):1608-14, 2005
7. Khaira HS et al: Helical computed tomography for identification of crossing
vessels in ureteropelvic junction obstruction-comparison with operative
findings. Urology. 62(1):35-9, 2003
8. Rooks VJ et al: Extrinsic ureteropelvic junction obstruction from a crossing
renal vessel: demography and imaging. Pediatr Radiol. 31(2):120-4, 2001
9. Keeley FX Jr et al: A prospective study of endoluminal ultrasound versus
computerized tomography angiography for detecting crossing vessels at the
ureteropelvic junction. J Urol. 162(6):1938-41, 1999
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