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SMFM Fetal Anomalies Consult Series #4: Genitourinary anomalies

      Introduction

      The fetal genitourinary system includes the fetal kidneys, ureters, and bladder and internal and external genitalia. The standard ultrasound examination of the fetal genitourinary system after the first trimester of pregnancy includes visualization of the fetal kidneys and bladder (Figures 1, A and B and 2). The renal pelvis should be assessed for dilation in an axial view of the anteroposterior diameter in the second and third trimesters of pregnancy (Figure 1, C). The fetal genitalia should be examined in multiple gestations, as this can aid in determination of chorionicity, or when medically indicated as when a patient is at risk of an X-linked genetic disorder (Figure 3). In addition, measurement of the amniotic fluid volume should be performed (Figure 4), as it provides a functional assessment of the fetal kidneys, which produce amniotic fluid after 16 to 17 weeks of gestation. Renal pathology can therefore result in both increased and decreased amniotic fluid volume.
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      Figure 1Evaluation of the fetal kidneys
      A, Coronal view of the fetal kidneys in the first trimester of pregnancy. B, Sagittal view of the fetal kidneys in the second trimester of pregnancy. C, Anteroposterior assessment of the fetal pelvis in the second trimester of pregnancy.
      Society for Maternal-Fetal Medicine. SMFM Fetal Anomalies Consult Series #4. Am J Obstet Gynecol 2021.
      Figure thumbnail gr2
      Figure 2Fetal bladder
      Fetal bladder in the (A) first and (B) second trimesters of pregnancy.
      Society for Maternal-Fetal Medicine. SMFM Fetal Anomalies Consult Series #4. Am J Obstet Gynecol 2021.
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      Figure 3Female and male genitalia in the second trimester of pregnancy
      A, Female genitalia in the second trimester of pregnancy. B, Male genitalia in the second trimester of pregnancy.
      Society for Maternal-Fetal Medicine. SMFM Fetal Anomalies Consult Series #4. Am J Obstet Gynecol 2021.
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      Figure 4Amniotic fluid assessment
      Society for Maternal-Fetal Medicine. SMFM Fetal Anomalies Consult Series #4. Am J Obstet Gynecol 2021.
      When indicated, a detailed ultrasound examination (76811) may include an examination of the adrenal glands and interrogation of the renal arteries (Figure 5). Examination of the fetal genitalia is also included.
      AIUM practice parameter for the performance of detailed second- and third-trimester diagnostic obstetric ultrasound examinations.
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      Figure 5Coronal image of the kidneys
      A, Coronal image demonstrating interrogation of the renal arteries. B, First trimester of pregnancy image of adrenal glands superior to the kidneys (arrows).
      Society for Maternal-Fetal Medicine. SMFM Fetal Anomalies Consult Series #4. Am J Obstet Gynecol 2021.
      Abnormalities of the genitourinary system are among the most common fetal structural malformations. Such anomalies range from mild (eg, mild urinary tract dilation) to severe life-threatening anomalies (eg, bilateral renal agenesis). Because the kidneys are responsible for the production of amniotic fluid, serious renal abnormalities that impair the production or excretion of urine (eg, urinary tract obstruction) can result in severe oligohydramnios, which can lead to pulmonary hypoplasia and can be life-threatening. The fetal bladder and renal pelvis are relatively easily visualized, and therefore, renal abnormalities are usually readily detected. Those abnormalities that are more difficult to identify, such as unilateral renal agenesis or a pelvic kidney, are less likely to be life-threatening or harmful to the fetus.
      Most renal anomalies are isolated, and as a general rule, the risk of underlying aneuploidy or genetic syndromes is low. The exception is polycystic kidneys, which can be associated with autosomal recessive or dominant disorders. Other genetic syndromes can be characterized by various forms of multicystic or polycystic kidneys. Therefore, cystic kidney disease should prompt careful assessment to look for other anomalies and inherited diseases.
      This Consult reviews the ultrasonographic diagnosis, genetic evaluation, and potential treatment and outcome of the following genitourinary abnormalities:
      • Adrenal neuroblastoma
      • Autosomal recessive polycystic kidney disease
      • Bladder outlet obstruction
      • Duplicated collecting system
      • Ectopic ureterocele
      • Hydroureter
      • Hypospadias
      • Multicystic dysplastic kidney
      • Ovarian cyst
      • Pelvic kidney
      • Renal agenesis
      • Renal pelvic dilation
      • Urinoma

      Coding

      When coding for fetal genitourinary anomalies, the Society for Maternal-Fetal Medicine Coding Committee recommends utilizing the International Classification of Diseases, Tenth Revision, code series O35.8XX.

      Acknowledgments

      The authors wish to acknowledge Mary E. Norton, MD; Jeffrey A. Kuller, MD; and Angie C. Jelin, MD, for providing a review of the genetics content and Joseph Wax, MD, for providing a general review of this Consult.

      Reference

      1. AIUM practice parameter for the performance of detailed second- and third-trimester diagnostic obstetric ultrasound examinations.
        J Ultrasound Med. 2019; 38: 3093-3100