E2057. Fetal Bladder: Clue to Genitourinary Abnormalities with Prenatal/Postnatal Imaging Correlation
  1. Mark Sugi; University of California San Francisco
  2. Priyanka Jha; University of California San Francisco
  3. Dorothy Shum; University of California San Francisco
  4. Tara Morgan; University of California San Francisco
  5. Liina Poder; University of California San Francisco
  6. Vickie Feldstein; University of California San Francisco
Fetal megacystis is defined by enlargement of the fetal bladder, which can be diagnosed as early as the first trimester and is much more common in male than female fetuses. This condition can be seen in isolation or in association with a number of fetal genitourinary, genetic and chromosomal abnormalities. A pattern-based approach to the enlarged fetal bladder that takes into account fetal sex, renal pathology, amniotic fluid volume and genetic pre-natal testing can help to develop a more specific differential diagnosis.

Educational Goals / Teaching Points
1. Develop an algorithmic approach to assess the fetal urinary bladder and associated genitourinary abnormalities using kidneys, amniotic fluid volume and sex as key observations. 2. Review the prenatal staging of lower urinary tract obstruction (LUTO) and indications for surgical intervention. 3. Highlight alternative diagnoses that may explain fetal bladder abnormalities other than LUTO. 4. Discuss the role of noninvasive prenatal testing and implications of these conditions on parental counseling for current and future pregnancies.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
1. Embryology of the fetal urinary tract 2. Prenatal/Postnatal imaging correlation with US and MRI 3. Fetal bladder a. Distended urinary bladder +/- hydronephrosis and normal or low amniotic fluid volumes (AFV) b. Non-visualized bladder with normal or low AFV c. Hydronephrosis with normal bladder and AFV 4. Distended bladder (megacystis) a. Lower urinary tract obstruction i. Posterior urethral valves ii. Distal urethral obstruction or stenosis iii. Urethral atresia iv. Non-neurogenic neurogenic bladder (Hinman syndrome) b. Megacystis-Microcolon-Intestinal Hypoperistalsis syndrome c. Genetics and aneuploidy 5. Non-visualized bladder

Fetal megacystis is defined by enlargement of the fetal bladder and can be seen at any point of gestation. Identifying cases in which this is more likely to represent an isolated finding or is associated with other fetal anomalies, including chromosomal abnormalities or genetic syndromes, can help to guide prenatal counseling.