Fetal Hydronephrosis



Fetal Hydronephrosis


Roya Sohaey, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Ureteropelvic Junction Obstruction


  • Posterior Urethral Valves (PUV)


Less Common



  • Duplicated Collecting System with Obstruction


  • Ureterovesicle Junction Obstruction


  • Ureterocele


  • Vesicoureteral Reflux


Rare but Important



  • Prune Belly Syndrome


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Renal pelvis diameter (RPD) distention



    • Obtain midrenal axial view



      • Measure anterior-posterior RPD


    • Abnormal RPD measurements



      • > 3 mm in first trimester


      • > 4 mm at 14-22 wks


      • > 5 mm at 22-32 wks


      • > 7 mm after 32 wks


      • RPD > 1/3 renal diameter


    • Use coronal and sagittal views



      • Rule out calyceal/ureteral distention


  • Evaluate collecting system methodically to determine point of obstruction



    • Pelviectasis



      • ↑ Renal pelvis only (normal calyces)


    • Hydronephrosis



      • ↑ Renal pelvis + caliectasis


    • Hydroureter



      • Hydronephrosis + dilated ureter


    • Persistent bladder distention


    • Urethra distention



      • Best seen on sagittal view


Helpful Clues for Common Diagnoses



  • Ureteropelvic Junction Obstruction



    • Hydronephrosis without ureter distention



      • Partial or complete obstruction


    • Ultrasound findings



      • ↑ Renal pelvis ends abruptly at ureteropelvic junction (UPJ)


      • “Bullet-shaped” renal pelvis


      • Distended calyces


    • Associated anomalies



      • 10% bilateral UPJ


      • 25% contralateral renal anomaly


      • 10% non-genitourinary anomaly


    • Etiology



      • Accessory crossing vessel in 1/3


      • Abnormal muscle layer at UPJ


      • Abnormal neural innervation at UPJ


  • Posterior Urethral Valves (PUV)



    • Obstructive posterior urethral membrane



      • Acts as valves


      • Partial or complete obstruction


      • Seen in male fetuses only


    • “Keyhole” bladder is hallmark finding



      • Distended bladder + distended posterior urethra


      • Bladder wall often thick


      • Bladder may be massive


    • Variable hydronephrosis/hydroureter


    • Variable oligohydramnios



      • Partial vs. complete obstruction


      • Renal functioning ability


      • Pulmonary hypoplasia if severe/early


    • Associated anomalies in 43%



      • VACTERL association


      • Cardiac malformations


Helpful Clues for Less Common Diagnoses



  • Duplicated Collecting System with Obstruction



    • Duplicated renal parenchyma



      • Separate upper and lower pole moieties


    • Variable collecting system duplication



      • Complete = 2 separate ureters


    • Upper pole drained by ectopic ureter



      • Ectopic ureterocele at distal end


      • Upper pole ureter inserts inferior and medial to lower pole ureter (Weigert-Meyer rule)


      • Upper moiety hydronephrosis common


    • Lower pole ureter refluxes



      • Milder lower moiety hydronephrosis


  • Ureterovesicle Junction Obstruction



    • Primary megaureter


    • Congenital stenosis at ureterovesicle junction (UVJ)



      • Hypoplasia/atrophy muscle fibers


      • Paucity of ganglion cells


    • Prenatal ultrasound clue



      • Hydroureter without ureterocele or duplication


    • Differential diagnosis



      • Vesicoureteral reflux


      • Non-visualized ureterocele



  • Ureterocele



    • Cystic dilatation of distal submucosal ureter at bladder insertion



      • Partial or complete obstruction


      • Bilateral in 10%


    • Prenatal ultrasound findings



      • Anechoic, thin-walled cyst in bladder


      • Distended ureter “balloons” into bladder


      • Associated hydroureter + hydronephrosis


    • Orthotopic vs. ectopic ureterocele



      • Orthotopic associated with single collecting system


      • Ectopic associated with renal duplication


      • Ectopic 3x more common


  • Vesicoureteral Reflux



    • Retrograde flow of urine



      • Bladder image ureter or kidney


    • Ultrasound findings



      • Variable/intermittent hydronephrosis


      • ↑ Dilatation immediately after voiding


    • Definitive diagnosis made after delivery



      • Voiding cystourethrography (VCUG)


      • Nuclear cystography


    • Grading system



      • I: Reflux into ureter only


      • II: Reflux reaches pelvis (normal calyces)


      • III: Mild caliceal blunting


      • IV: Progressive caliceal dilatation


      • V: Dilated tortuous collecting system with severe caliceal dilatation


    • 80% outgrow reflux


    • Surgical treatment for persistent reflux



      • Ureteral reimplantation


      • Endoscopic periureteral injection


Helpful Clues for Rare Diagnoses

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Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Fetal Hydronephrosis

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