Radiologic Diagnosis of Fetal Hydronephrosis:

Transcription

1 March 2003 Radiologic Diagnosis of Fetal Hydronephrosis: Associated Abnormalities and Fetal Outcome Sabrina Vineberg, Harvard Medical School, Year III

2 Fetal Imaging Modalities BIDMC PACS Levine D. and R. R. Edelman. Abdominal Imaging. 22: , Ultrasound: Fast and safe (no ionizing radiation) Allows for good visualization of fetal anatomy and live, real-time imaging Efficient method to survey for fetal anomalies MRI: Better soft tissue contrast for characterization of anomalies Better than US in patients with oligohydramnios Currently no known adverse effects 2

3 Diagnosis of Fetal Hydronephrosis on Ultrasound Index patient: Mrs. S. is a 34 y.o. G2P1 who presented to BIDMC at 29+6 weeks GA for a follow-up fetal ultrasound after a routine fetal survey at an outside hospital documented unilateral fetal hydronephrosis. 3

4 Mrs. S. s Ultrasound Spine Calyceal dilatation Left kidney, sagittal view Right kidney, sagittal view R R = dilated renal pelvis L L All images from BIDMC PACS Transverse view Sagittal view US findings: mild hydronephrosis on the right with central dilatation of 8-9 mm and severe hydronephrosis on the left with a large extrarenal pelvis measuring 2.8 cm 4

5 Normal Fetal Kidneys Fetal kidneys are ovoid bilateral paraspinous structures: - Renal pelvis slit-like lucency within central portion of kidney. - Medulla hypoechoic regions surrounding renal sinuses. - Cortex thin and difficult to visualize on US. - Retroperitoneal fat echogenic density surrounding kidneys. S = spine Kidneys outlined by arrowheads Gabbe: Obstetrics - Normal and Problem Pregnancies, 4th ed., Copyright 2002 Churchill Livingstone, Inc. 5

6 Renal Development Timeline and Important Structures Ureteral bud (week 4) mesoderm, arises from oupouching of mesonephric/wolffian ducts, opens into urogenital sinus. Gives rise to ureter, renal pelvis, calyces and collecting system Metanephric cap (week 5-6) mesoderm, interacts with structures of ureteral bud to form functional renal parenchyma Cloaca (week 4) endoderm, divides into urogenital sinus (cranial) and anorectal canal (caudal). Urogenital sinus gives rise to bladder and urethra Fetal kidneys begin to function at the start of the 2 nd trimester. By week they become the major source of amniotic fluid for the fetus 6

7 Renal Development Embryo 5-6 weeks Mesonephric Duct Migration of the fetal kidneys Urogenital Sinus Ureteric bud Metanephric cap Week 6 Week 8 Week 10 Sweeney, Lauren J. Basic Concepts in Embryology. A Student's Survival guide. New York: The McGraw-Hill Companies,

8 Fetal Anatomy Bladder Kidney Spleen Lungs Amniotic fluid Iliac Wing Liver Nyberg, David A., Barry S. Mahony and Dolores H. Pretorius. Diagnostic Ultrasound of Fetal Anomalies: Text and Atlas. Chicago: Year Book Medical Publishers,

9 Hydronephrosis Hydronephrosis (HN) dilatation of the pelvis and/or calyces of the kidney Diagnosis of fetal HN is increasing with increased use of ultrasound in pregnant women 1-2% of pregnancies may show evidence of HN, and it accounts for 50-75% of prenatally diagnosed renal abnormalities. Degree of dilatation required for diagnosis of HN varies with gestational age, and is determined using the anteroposterior diameter of the renal pelvis. 9

10 Measuring Renal Dilatation Close-up of a mildly dilated right fetal kidney on ultrasound (short arrows outlining kidney) S = Spine Image from BIDMC PACS APD Anteroposterior diameter (APD): Size of the renal pelvis measured in the anterior posterior direction on a transverse view through the abdomen. For a diagnosis of hydronephrosis, APD must be greater than: - 6mm at < 20 weeks GA - 8 mm at weeks GA - 10mm at > 30 weeks GA 10

11 Grades of Fetal Hydronephrosis Gloor, J.M. Mayo Clinic Proceedings. 70: ,

12 Natural History of Fetal Hydronephrosis Most cases of prenatally diagnosed HN (~90%) will resolve spontaneously before birth or after delivery. Of those cases that do not resolve on their own, the majority are amenable to surgical or medical correction after delivery. Surgery is best performed within the first year of life to minimize irreversible damage. 12

13 Causes of Fetal Hydronephrosis Physiologic: Urine production 4-6x greater before delivery Increased compliance of fetal ureter Partial/transient obstructions associated with development Pathologic: Almost always due to obstruction, which can occur anywhere in the urinary tract Degree of dilatation depends on the severity and location of obstruction Severe or longstanding obstruction of the urinary tract can lead to permanent renal damage and to systemic problems for the fetus Non-obstructive causes of HN include vesicoureteric reflux (VUR), prune belly syndrome and renal cysts. 13

14 Radiologic Findings Can be unilateral or bilateral Severity of dilatation depends on the level of obstruction. Common locations include: Ureteropelvic junction most common location of obstruction Vesicoureteral junction with or without reflux Vesicouretheral junction often due to posterior urethral valves Renal parenchymal changes Amount of amniotic fluid: With severe obstruction and renal atrophy, the fetus can t produce or excrete amniotic fluid, leading to oligohydramnios Oligohydramnios is a poor prognostic sign for the fetus risk of pulmonary hypoplasia - lack of amniotic fluid causes compression of fetal lungs which prevents lung development. 14

15 Radiologic Findings US Dilatation of Renal Pelvis and Calyces Patient A - Transverse view R. kidney Spine L. kidney Patient A: Follow-up US for known HN, 27 weeks GA US Report: Worsening bilateral central renal collecting system dilatation, left greater than right, which is out of proportion to caliectasis and suggests UPJ obstruction. Patient B: Routine fetal survey, 22 weeks GA US report: Mild bilateral hydronephrosis. Follow-up is recommended in six weeks and post Calyceal dilatation partum. All images from BIDMC PACS Patient B - Sagittal view = dilated renal pelvis 15

16 Radiologic Findings US Dilatation of Renal Pelvis and Ureters Patient C - Transverse view Patient C L. ureter Spine Bladder Kidneys Dilated ureter Kidney Patient C: US with biophysical profile for post-dates at 40 weeks GA US report: Bilateral hydroureteronephrosis. Follow up study of the kidneys is recommended after the baby is born. Dilated ureter Aortic bifurcation Dilated ureter Patient D - Sagittal view All images from BIDMC PACS Ribs Spine = dilated renal pelvis Patient D: Routine fetal survey, 28 weeks GA US Report: Central renal dilatation of 11 mm on the left and 8 mm on the right, out of proportion to caliceal dilatation along with intermittent visualization of the ureters, which appear mildly dilated. Findings are suggestive of vesicoureteral reflux. 16

17 Radiologic Findings - MRI K= maternal kidney A = amniotic fluid P = placenta A Fetal kidneys Dilated fetal kidney K P Spine Fetal Brain T2W MRI scan at 32 weeks GA showing moderate fetal HN Sagittal MRI showing severe HN in a 33 week old fetus with obstruction due to posterior urethral valves. US study limited by severe oligohydramnios. Fradin, J.M. et al. Urology. 53: , Miller, O.F. et al. The Journal of Urology. 168: ,

18 Amount of Amniotic Fluid Normal amniotic fluid Normal fetus Severe oligohydramnios Fetus with renal agenesis All images from BIDMC PACS 18

19 Why is prenatal diagnosis important? With severe obstruction and oligohydramnios: Fetus at risk of renal dysplasia and pulmonary hypoplasia which is often fatal Prenatal intervention can be lifesaving: i. Percutaneous fetal shunt catheters a route for amniotic fluid to leave the urinary tract and return to the amniotic cavity ii. Surgical exteriorization of fetal urinary tract Knowledge of moderate severe cases of HN antenatally allows for appropriate follow-up and prompt correction after birth 19

20 Management of Hydronephrosis In the Fetus and Neonate Callen, Peter W. Ultrasonography in Obstetrics and Gynecology. 2nd ed. Philadelphia: WB Saunders Co.,

21 Management of Hydronephrosis in the Neonate Prophylactic antibiotics to prevent UTI and pyelonephritis associated with reflux Follow-up ultrasound, at least 72 hours after birth Other imaging studies include voiding cystourethrogram (VCUG) or DMSA scan Prompt surgical correction of obstruction if necessary, to prevent irreversible renal parenchymal damage 21

22 Radiologic Work-up of Hydronephrosis in the Neonate Ultrasound Right kidney Left kidney Voiding cystourethrogram Radiologic imaging of a newborn diagnosed with hydronephrosis in utero: US: Bilateral dilatation of the renal collecting system VCUG: Significant reflux bilaterally DMSA scan: Decreased uptake bilaterally, L>R DMSA scan All images from ACR Pediatric Learning File,

23 References American College of Radiology Pediatric Learning File. Version CD-ROM. ACRI Software Development, Callen, Peter W. Ultrasonography in Obstetrics and Gynecology. 2nd ed. Philadelphia: WB Saunders Co., De Bruyn, R. and I. Gordon. Postnatal investigation of fetal renal disease. Prenatal Diagnosis. 21: , Fradin, J.M. et al. Hydronephrosis in pregnancy: simultaneous depiction of fetal and maternal hydronephrosis by magnetic resonance urography. Urology. 53: , Gabbe, Steven G., Jennifer R. Niebyl and Joe Leigh Simpson. Gabbe: Obstetrics - Normal and Problem Pregnancies. 4th ed. New York: Churchill Livingstone, Gloor, J.M. Management of Prenatally Detected Fetal Hydronephrosis. Mayo Clinic Proceedings. 70: , Levine, D. and R.R. Edelman. Fast MRI and its application in obstetrics. Abdominal Imaging. 22: , Miller, O.F. et al. Diagnosis of urethral obstruction with prenatal magnetic resonance imaging. The Journal of Urology. 168: , Mouriquand, P.D.E. et al. Pathophysiology, diagnosis and management of prenatal upper tract dilatation. Prenatal Diagnosis. 21: , Nyberg, David A., Barry S. Mahony and Dolores H. Pretorius. Diagnostic Ultrasound of Fetal Anomalies: Text and Atlas. Chicago: Year Book Medical Publishers, Poutamo, J. et al. Diagnosing fetal urinary tract abnormalities: benefits of MRI compared to ultrasonography. Acta Obstetricia et Gynocologica Scandinavica. 79: 65-71, Sairam, S. et al. Natural history of fetal hydronephrosis diagnosed on mid-trimester ultrasound. Ultrasound in Obstetrics and Gynecology. 17: , Shokeir, A.A. and R.J.M. Nijman. Antenatal hydronephrosis: changing concepts in diagnosis and subsequent management. BJU International. 85: , Sherer, D.M. Is fetal hydronephrosis overdiagnosed. Ultrasound in Obstetrics and Gynecology. 16: , Sweeney, Lauren J. Basic Concepts in Embryology. A Student's Survival guide. New York: The McGraw-Hill Companies,

24 Acknowledgements Pamela Lepkowski Deborah Levine, MD Tejas Mehta, MD Joseph Makris, MD Dan Saurborn, MD Larry Barbaras and Cara Lyn D amour 24