TY - CHAP M1 - Book, Section TI - Hydronephrosis: Ureteropelvic Junction Obstruction A1 - Bianchi, Diana W. A1 - Crombleholme, Timothy M. A1 - D'Alton, Mary E. A1 - Malone, Fergal D. PY - 2015 T2 - Fetology: Diagnosis and Management of the Fetal Patient, 2e AB - Key PointsUreteropelvic junction obstruction (UPJ) prevents urinary flow from the renal pelvis to the ureter, and is the most common cause of significant neonatal hydronephrosis.The timing of onset of obstruction determines the clinical presentation, ranging from multicystic dysplastic kidney to pelvicaliceal dilation for first trimester compared with third trimester obstruction respectively.Most cases are unilateral, with bilateral cases, or cases in which the contralateral kidney has multicystic dysplastic changes, having much worse prognosis.Pregnancy management is generally unchanged in unilateral UPJ cases, while fetal intervention by means of urinary shunting may be necessary in rare cases of severe bilateral UPJ.Management of the neonate usually includes delaying imaging until 3–7 days of life to allow completion of normal physiologic diuresis and initiation of prophylactic antibiotics.Indications for surgical intervention include renal function less than 40% expected, worsening hydronephrosis, renal pelvic diameter greater than 5 cm, or febrile morbidity. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - obgyn.mhmedical.com/content.aspx?aid=1106399503 ER -