Ebook Diagnostic imaging obstetrics (2nd edition): Part 2

(BQ) Part 2 book Diagnostic imaging obstetrics presents the following contents: Genitourinary tract, musculoskeletal, placenta, membranes and umbilical cord, multiple gestations, aneuploidy, syndromes and multisystem disorders, infection, fluid, growth and well-being, maternal conditions in pregnancy, postpartum complications.

Diagnostic Imaging Obstetrics, 2nd Edition Diagnostic Imaging Obstetrics, 2nd Edition Table of Contents Diagnostic Imaging Obstetrics, 2nd Edition Cover Authors Dedication 10 Preface 10 Acknowledgements 11 Section - First Trimester .12 I Introduction and Overview .12 Embryology and Anatomy of the First Trimester 12 Approach to the First Trimester 27 II Intrauterine Gestation 32 Failed First Trimester Pregnancy 32 Perigestational Hemorrhage 39 Chorionic Bump 45 III Ectopic Gestation 48 Tubal Ectopic .48 Interstitial Ectopic .58 Cervical Ectopic 64 C-Section Scar Ectopic 71 10 Abdominal Ectopic 74 11 Heterotopic Pregnancy 77 Section - Brain 80 I Introduction and Overview .80 12 Embryology and Anatomy of the Brain 80 13 Approach to the Supratentorial Brain 99 14 Approach to the Posterior Fossa 107 II Cranial Defects 116 15 Exencephaly, Anencephaly 116 16 Acalvaria, Acrania 122 17 Occipital, Parietal Cephalocele 128 18 Frontal Cephalocele .137 III Midline Developmental Anomalies .141 19 Agenesis of the Corpus Callosum .141 20 Atelencephaly, Aprosencephaly .147 21 Alobar Holoprosencephaly 153 22 Semilobar Holoprosencephaly 160 23 Lobar Holoprosencephaly 166 24 Septo-Optic Dysplasia 172 25 Syntelencephaly 178 IV Cortical Developmental Anomalies .184 26 Schizencephaly 184 27 Lissencephaly 191 28 Gray Matter Heterotopia 197 29 Pachygyria, Polymicrogyria 200 V Cysts .206 30 Choroid Plexus Cyst 206 31 Arachnoid Cyst 213 32 Glioependymal Cyst .219 VI Destructive Lesions 226 33 Intracranial Hemorrhage 226 34 Encephalomalacia, Porencephaly 232 Diagnostic Imaging Obstetrics, 2nd Edition 35 Hydranencephaly 239 VII Posterior Fossa Malformations 245 36 Aqueductal Stenosis 245 37 Chiari 252 38 Chiari 259 39 Dandy-Walker Malformation 262 40 Vermian Agenesis - Partial Or Complete 268 41 Blake Pouch Cyst .272 42 Mega Cisterna Magna 278 43 Cerebellar Hypoplasia 281 44 Rhombencephalosynapsis .287 VIII Vascular Malformations .290 45 Vein of Galen Malformation 290 46 Arteriovenous Fistula 296 47 Dural Sinus Malformation 300 IX Tumors .303 48 Parenchymal Brain Tumors 303 49 Choroid Plexus Papilloma 309 50 Lipoma 313 Section - Spine 316 51 Embryology and Anatomy of the Spine 316 52 Approach to the Fetal Spine 327 53 Spina Bifida 329 54 Iniencephaly 336 55 Caudal Regression Sequence .343 56 Kyphosis, Scoliosis .350 57 Tethered Cord .357 58 Diastematomyelia .360 59 Sacrococcygeal Teratoma 363 Section - Face and Neck .369 60 Embryology and Anatomy of the Face and Neck 369 61 Approach to the Fetal Face and Neck 383 62 Cleft Lip, Palate 389 63 Absent Nasal Bone 399 64 Dacrocystocele 406 65 Coloboma 409 66 Epignathus 412 67 Goiter 418 68 Cystic Hygroma 425 69 Cervical Teratoma .432 Section - Chest 438 70 Embryology and Anatomy of the Chest 438 71 Approach to the Fetal Chest 449 72 Congenital Diaphragmatic Hernia 452 73 Congenital Pulmonary Airway Malformation .459 74 Pleural Effusion 465 75 Bronchopulmonary Sequestration .472 76 Bronchogenic Cyst .479 77 Congenital High Airway Obstruction Sequence 482 78 Pulmonary Agenesis 485 79 Lymphangioma 488 80 Mediastinal, Pulmonary Teratoma .495 Section - Heart 498 I Introduction and Overview 498 Diagnostic Imaging Obstetrics, 2nd Edition 81 Embryology and Anatomy of the Cardiovascular System 498 82 Approach to the Fetal Heart 515 II Abnormal Location 524 83 Situs Inversus 524 84 Heterotaxy, Cardiosplenic Syndromes .527 85 Ectopia Cordis 533 III Septal Defects 540 86 Ventricular Septal Defect 540 87 Atrioventricular Septal Defect 543 88 Foramen Ovale Aneurysm .549 IV Right Heart Malformations 553 89 Ebstein Anomaly 553 90 Tricuspid Dysplasia 556 91 Tricuspid Atresia 559 92 Pulmonary Stenosis, Atresia 562 V Left Heart Malformations 568 93 Hypoplastic Left Heart .568 94 Coarctation and Interrupted Aortic Arch 575 95 Aortic Stenosis .581 96 Double Inlet Left Ventricle .588 VI Conotruncal Malformations 591 97 Tetralogy of Fallot 591 98 Transposition of the Great Arteries 598 99 Truncus Arteriosus 604 100 Double Outlet Right Ventricle 611 VII Myocardial and Pericardial Abnormalities 614 101 Echogenic Cardiac Focus 614 102 Hypertrophic Cardiomyopathy .618 103 Dilated Cardiomyopathy 624 104 Rhabdomyoma 631 105 Pericardial Effusion 637 106 Pericardial Teratoma .641 VIII Abnormal Rhythm 644 107 Irregular Rhythm 644 108 Tachyarrhythmia 647 109 Bradyarrhythmia 653 Section - Abdominal Wall and Gastrointestinal Tract 660 I Introduction and Overview 660 110 Embryology and Anatomy of the Abdominal Wall and GI Tract 660 111 Approach to the Abdominal Wall and Gi Tract .674 II Abdominal Wall Defects 682 112 Gastroschisis 682 113 Omphalocele 688 114 Pentalogy of Cantrell .695 115 Body Stalk Anomaly .698 116 Bladder Exstrophy 705 117 Cloacal Exstrophy - OEIS Syndrome 708 III Bowel Abnormalities 714 118 Esophageal Atresia 714 119 Duodenal Atresia 720 120 Jejunal Ileal Atresia 727 121 Anal Atresia 733 122 Cloacal Malformation 739 123 Volvulus 746 Diagnostic Imaging Obstetrics, 2nd Edition 124 Enteric Duplication Cyst 749 IV Peritoneal Abnormalities .752 125 Ascites 752 126 Meconium Peritonitis, Pseudocyst 759 127 Mesenteric Cyst 765 V Hepatobiliary Abnormalities 769 128 Gallstones .769 129 Choledochal Cyst 772 130 Infantile Hemangioendothelioma 775 131 Mesenchymal Hamartoma 781 132 Malignant Liver Tumors 785 Section - Genitourinary Tract .791 I Introduction and Overview 791 133 Embryology and Anatomy of the Genitourinary Tract 791 134 Approach to the Fetal Genitourinary Tract .808 II Renal Developmental Variants 813 135 Unilateral Renal Agenesis 813 136 Duplicated Collecting System .817 137 Pelvic Kidney 823 138 Horseshoe Kidney 826 139 Crossed Fused Ectopia 829 III Renal Malformations 833 140 Bilateral Renal Agenesis .833 141 Mild Pelviectasis 839 142 Ureteropelvic Junction Obstruction .846 143 Urinoma 853 144 Obstructive Renal Dysplasia 856 145 Multicystic Dysplastic Kidney 863 146 Autosomal Recessive Polycystic Kidney Disease .870 147 Mesoblastic Nephroma 876 IV Adrenal Abnormalities 882 148 Adrenal Hemorrhage .882 149 Neuroblastoma .886 V Bladder Malformations 892 150 Posterior Urethral Valves .892 151 Prune Belly Syndrome 898 152 Ureterocele 905 153 Urachal Anomalies .911 VI Genital Abnormalities 917 154 Ambiguous Genitalia .917 155 Hypospadias 928 156 Hydrocele 931 157 Testicular Torsion 934 158 Inguinal Hernia 938 159 Ovarian Cyst 941 160 Hydrocolpos 947 Section - Musculoskeletal 951 I Dysplasias 951 161 Approach to Skeletal Dysplasias 951 162 Achondrogenesis, Hypochondrogenesis 962 163 Achondroplasia .971 164 Amelia, Micromelia .978 165 Asphyxiating Thoracic Dysplasia 984 166 Atelosteogenesis 990 Diagnostic Imaging Obstetrics, 2nd Edition 167 Campomelic Dysplasia 993 168 Chondrodysplasia Punctata 999 169 Hypophosphatasia 1005 170 Osteogenesis Imperfecta 1008 171 Short Rib-Polydactyly Syndrome 1015 172 Thanatophoric Dysplasia 1018 II Extremity Malformations 1027 173 Clubfoot 1027 174 Rockerbottom Foot 1034 175 Sandal Gap Foot 1037 176 Radial Ray Malformation 1040 177 Clinodactyly 1047 178 Polydactyly 1050 179 Syndactyly 1057 180 Split Hand - Foot Malformation 1063 181 Arthrogryposis, Akinesia Sequence 1070 182 Proximal Focal Femoral Dysplasia 1079 Section 10 - Placenta, Membranes, and Umbilical Cord 1086 I Introduction and Overview 1086 183 Approach to the Placenta and Umbilical Cord 1086 II Placenta and Membrane Abnormalities 1095 184 Placental Abruption 1095 185 Placenta Previa 1102 186 Vasa Previa 1109 187 Placenta Accreta Spectrum 1112 188 Placental Lake, Intervillous Thrombus 1119 189 Succenturiate Lobe 1126 190 Circumvallate Placenta 1129 191 Marginal Cord Insertion 1133 192 Velamentous Cord Insertion 1136 193 Chorioangioma 1140 194 Placental Teratoma 1146 195 Chorioamniotic Separation 1150 III Umbilical Cord Abnormalities 1153 196 Single Umbilical Artery 1153 197 Umbilical Cord Cyst 1161 198 Umbilical Vein Varix 1168 199 Umbilical Artery Aneurysm 1174 200 Persistent Right Umbilical Vein 1178 201 Umbilical Vessel Thrombosis 1181 Section 11 - Multiple Gestations 1185 202 Approach to Multiple Gestations 1185 203 Dichorionic Diamniotic Twins 1190 204 Monochorionic Diamniotic Twins 1196 205 Monochorionic Monoamniotic Twins 1203 206 Discordant Twin Growth 1209 207 Twin-Twin Transfusion Syndrome 1215 208 Twin Reversed Arterial Perfusion 1221 209 Conjoined Twins 1227 210 Triplets and Beyond 1233 211 Fetus-in-Fetu 1239 Section 12 - Aneuploidy 1245 212 Screening for Aneuploidy 1245 213 Trisomy 21 1251 Diagnostic Imaging Obstetrics, 2nd Edition 214 Trisomy 18 1261 215 Trisomy 13 1271 216 Turner Syndrome 1281 217 Triploidy 1288 Section 13 - Syndromes and Multisystem Disorders 1295 218 22Q11 Deletion Syndrome 1295 219 Aicardi Syndrome 1298 220 Amniotic Band Syndrome 1304 221 Apert Syndrome 1311 222 Beckwith-Wiedemann Syndrome 1317 223 Carpenter Syndrome 1323 224 CHARGE Syndrome 1326 225 Cornelia De Lange Syndrome 1329 226 Cystic Fibrosis 1333 227 Diabetic Embryopathy 1336 228 Fryns Syndrome 1342 229 Holt-Oram Syndrome 1345 230 Joubert Syndrome 1351 231 Meckel-Gruber Syndrome 1354 232 Multiple Pterygium Syndromes 1360 233 Neu-Laxova Syndrome 1364 234 PHACES Syndrome 1367 235 Pfeiffer Syndrome 1370 236 Pierre Robin Anomaly 1376 237 Sirenomelia 1379 238 Smith-Lemli-Opitz Syndrome 1385 239 Tuberous Sclerosis 1392 240 VACTERL Association 1398 241 Valproate Embryopathy 1405 242 Warfarin Embryopathy 1408 243 Walker-Warburg Syndrome 1411 Section 14 - Infection 1414 244 Cytomegalovirus 1414 245 Parvovirus 1420 246 Toxoplasmosis 1424 247 Varicella 1426 Section 15 - Fluid, Growth, and Well-Being 1430 248 Approach to Fetal Well-Being 1430 249 Polyhydramnios 1438 250 Oligohydramnios 1445 251 Intrauterine Growth Restriction 1452 252 Macrosomia 1459 253 Hydrops 1462 254 Fetal Anemia 1469 Section 16 - Maternal Conditions in Pregnancy 1476 I Gestational Trophoblastic Disease 1476 255 Complete Hydatidiform Mole 1476 256 Invasive Mole 1483 257 Choriocarcinoma 1486 II Uterus 1492 258 Incompetent Cervix 1492 259 Myoma in Pregnancy 1499 260 MüLlerian Duct Anomalies in Pregnancy 1506 261 Synechiae 1513 Diagnostic Imaging Obstetrics, 2nd Edition 262 Uterine Rupture 1516 III Ovary 1523 263 Corpus Luteum Cyst 1523 264 Theca Lutein Cysts 1526 265 Hyperstimulation Syndrome 1532 IV Gastrointestinal and Genitourinary Tracts 1539 266 Appendicitis in Pregnancy 1539 267 HELLP Syndrome 1542 268 Maternal Hydronephrosis 1548 Section 17 - Postpartum Complications 1555 269 Retained Products of Conception 1555 270 Endometritis 1558 271 Bladder Flap Hematoma 1561 272 Ovarian Vein Thrombosis 1564 Index 1571 0-9 1571 A 1571 B 1573 C 1576 D 1579 E 1581 F 1582 G 1584 H 1585 I 1588 J 1589 K 1589 L 1589 M 1590 N 1592 O 1593 P 1594 Q 1596 R 1596 S 1597 T 1600 U 1602 V 1604 W 1605 Y 1605 Z 1605 Diagnostic Imaging Obstetrics, 2nd Edition Diagnostic Imaging Obstetrics, 2nd Edition Cover Authors Authors Paula J Woodward MD Professor of Radiology David G Bragg, MD and Marcia R Bragg Presidential Endowed Chair in Oncologic Imaging University of Utah School of Medicine Salt Lake City, UT Anne Kennedy MD Professor of Radiology Adjunct Professor of Obstetrics and Gynecology Executive Vice Chair of Radiology Co-Director of Maternal Fetal Diagnostic Center University of Utah School of Medicine Salt Lake City, UT Roya Sohaey MD Professor of Radiology Professor of Obstetrics and Gynecology Director of Ultrasound Diagnostic Imaging Obstetrics, 2nd Edition Oregon Health and Science University Portland, OR Janice L B Byrne MD Associate Professor of Obstetrics and Gynecology/Maternal-Fetal Medicine Adjunct Associate Professor of Pediatrics/Medical Genetics Director of Fetal-Neonatal Treatment Program University of Utah School of Medicine Salt Lake City, UT Karen Y Oh MD Associate Professor of Radiology Associate Professor of Obstetrics and Gynecology Director of Breast Imaging Oregon Health and Science University Portland, OR Michael D Puchalski MD Associate Professor of Pediatrics Adjunct Associate Professor of Radiology Director of Noninvasive Imaging University of Utah School of Medicine Salt Lake City, UT Thomas C Winter III MD Professor of Radiology Adjunct Professor of Obstetrics and Gynecology Director of Body Imaging University of Utah School of Medicine Salt Lake City, UT Logan A McLean MD Neuroradiology Fellow University of Utah School of Medicine Salt Lake City, UT Contributing Authors Akram M Shaaban, MBBCh David Holznagel, MD Nelangi Pinto, MD Asha Sarma, BA Nicole Winkler, MD Marcia L Feldkamp, PhD, PA Antonio E Frias, Jr., MD Shawn E Gurtcheff, MD, MS Sonographers Brooke Axberg, RDMS Jeanne Baker, RDMS Kara Bridges, RDMS Jenny Burke, RDMS Angie Crist, RDMS Chelsea Day, RDMS Porsche Fletcher, RDMS Danielle Galbreath, RDMS Kristina Gudonaviciute, RDMS Pam Guy, RDMS Deanna Hecker, RDMS Adrian Lethbridge, RDMS Naomi Maggio, RDMS Diagnostic Imaging Obstetrics, 2nd Edition (Top) The fetal kidney has a distinct lobular contour (fetal lobulation), reflecting the developmental process between the ureteric bud forming the calyces and the metanephric blastema forming the nephrons (Bottom) Aberration in the development and ascent of the kidneys causes an array of anomalies Renal developmental variants include unilateral renal agenesis (A), pelvic kidney (B), crossed fused renal ectopia (C), and horseshoe kidney (D) Errors of formation, fusion, and ascent lead to these anomalies P.8:10 FEMALE GENITAL TRACT 800 Diagnostic Imaging Obstetrics, 2nd Edition (Top) The fallopian tubes, uterus, and upper vagina form from the paired paramesonephric (müllerian) ducts, which develop on either side of the midline lateral to the mesonephric ducts (the mesonephric ducts regress in a female fetus) (Middle) The paramesonephric ducts must meet in the midline and fuse to form the uterus and upper portion of the vagina (uterovaginal canal) The unfused portions will form the fallopian tubes The development of the kidney (metanephros) is closely related to uterine development, and coexistent renal and müllerian duct anomalies are common (Bottom) The distal portion of the vagina is formed from the caudal urogenital sinus, which splits to form the urethra anteriorly and the vagina posteriorly The allantois involutes to form the urachus P.8:11 MALE GENITAL TRACT 801 Diagnostic Imaging Obstetrics, 2nd Edition (Top) The mesospheric ducts (only shown) persist in a male and will form the epididymides, vas deferens, seminal vesicles, and ejaculatory ducts (Middle) The caudal urogenital sinus forms the penile urethra The allantois involutes and forms the urachus (Bottom) The processus vaginalis is a sock-like evagination of the peritoneum, which elongates caudally through the abdominal wall It forms just anterior to the developing testes and, along with the gubernaculum (a ligamentous cord extending from the testis to the labioscrotal fold), aids in their descent As the processus vaginalis evaginates, it becomes ensheathed by fascial extensions of the abdominal wall, which ultimately form the layers of the scrotum and spermatic cord P.8:12 URINARY TRACT 802 Diagnostic Imaging Obstetrics, 2nd Edition (Top) Axial ultrasound shows the appearance of the kidneys in a 20-week fetus They are mildly hypoechoic and uniform in echogenicity, lacking the normal corticomedullary differentiation seen later in gestation (Middle) Renal anatomy is far better delineated in this 34-week fetus There is clear corticomedullary differentiation with distinct renal pyramids A small amount of urine with the renal pelvis is normal (Bottom) Color Doppler ultrasound shows normal renal vasculature P.8:13 803 Diagnostic Imaging Obstetrics, 2nd Edition (Top) Axial ultrasound shows normal-appearing kidneys in a 3rd trimester fetus (Middle) A similarly positioned axial T2WI MR in another 3rd trimester fetus shows normal kidneys, which are higher in signal intensity than either the surrounding musculature or liver Urine within the renal pelvis is high in signal intensity Because of its high contrast resolution, MR is an excellent modality for evaluating urinary tract anomalies (Bottom) Color Doppler shows the umbilical arteries flanking the bladder P.8:14 804 Diagnostic Imaging Obstetrics, 2nd Edition ADRENAL GLANDS (Top) Graphic shows a fetal adrenal gland Fetal adrenal glands are large, up to 20x larger than an adult adrenal gland relative to body size The bulk of the gland is predominantly from the cortex, which rapidly decreases in size during the 1st year of life (Middle) Axial ultrasound of a 3rd trimester fetus shows the classic “ice cream sandwich” appearance of the adrenal glands, with a hypoechoic cortex and hyperechoic medulla (Bottom) Axial ultrasound of a neonate shows a similar appearance of the adrenal gland The 805 Diagnostic Imaging Obstetrics, 2nd Edition normal adrenal gland typically has a” V” or “Y” shape The corticomedullary differentiation of the kidney is also well seen The renal pyramids are hypoechoic relative to the cortex and should not be mistaken for hydronephrosis P.8:15 GENITALIA 806 Diagnostic Imaging Obstetrics, 2nd Edition (Top) Normal female genitalia as seen in the 3rd trimester is shown (Middle) Normal male genitalia as seen in the 3rd trimester is shown Small hydroceles are normal and aid in the visualization of the testes (Bottom) Sagittal T2WI MR shows normal male genitalia in a 3rd trimester fetus 807 Diagnostic Imaging Obstetrics, 2nd Edition 134 Approach to the Fetal Genitourinary Tract > Table of Contents > Section - Genitourinary Tract > Introduction and Overview > Approach to the Fetal Genitourinary Tract Approach to the Fetal Genitourinary Tract Paula J Woodward, MD Imaging Techniques and Normal Anatomy Ultrasound The American Institute of Ultrasound in Medicine requires documentation of the kidneys and bladder in all 2nd and 3rd trimester fetuses Evaluation of fetal sex is only required for the determination of zygosity in multiple gestations A qualitative or semiquantitative estimate of amniotic fluid volume should also be performed These are considered the minimum requirements; if any anomaly is suspected, a detailed examination should ensue The components of the genitourinary tract include the kidneys, ureters, bladder, urethra, adrenal glands, and the internal and external genitalia Knowledge of the normal developmental appearance of each of these structures is needed to in order to recognize pathologic processes Kidneys can be identified by 12-14 weeks gestation using endovaginal sonography; internal architecture can be resolved as early as 16-18 weeks The external renal contour is lobular (fetal lobulation), a finding that may persist into adulthood The cortex is intermediate in echogenicity, and the hypoechoic medullary pyramids are arranged symmetrically around the renal sinus, which appears as a fluid-filled “slit” in the center of the kidney By the 3rd trimester, renal sinus and perinephric fat deposition increases conspicuity of the renal pelvis The anterior-posterior diameter of the renal pelvis changes throughout gestation but should measure < mm at gestational age < 22 weeks and < mm from 33 weeks to term Larger measurements are concerning for obstruction or reflux Normative data are available for renal size throughout gestation The ratio of renal circumference to abdominal circumference is stable throughout pregnancy with values from 0.27-0.30 Color Doppler ultrasound is helpful in the assessment of fetal vessels When questioning renal agenesis, the identification of renal arteries is crucial Be aware that the lumbar and adrenal arteries can appear quite prominent and may be mistaken for renal arteries Color Doppler can also be used to identify the bladder between the umbilical arteries This view also documents umbilical arteries; renal anomalies are associated with a single umbilical artery Amniotic fluid volume (AFV) is evaluated in every 2nd and 3rd trimester study AFV can be assessed subjectively or semiquantitatively by measuring fluid pockets The maximum vertical pocket (MVP) measurement is the anterior to posterior distance of the largest fluid pocket within the uterus, void of fetal parts and umbilical cord The “vertical” in the name implies that the measurement is obtained with the transducer perpendicular to the maternal abdomen Oblique measurements are not reproducible and may lead to errors in assessment of fluid volume The more commonly utilized amniotic fluid index (AFI) measurement is the sum of the MVPs in quadrants of the uterus In the 3rd trimester especially, it may be hard to tell if a “pocket” is fluid-filled or contains loops of umbilical cord Color Doppler is very useful to make this distinction This is important as the differential diagnosis for anhydramnios is different than that for oligohydramnios; the former generally has a much worse prognosis In general, MVP values of 5-8 and AFI values of 5-20 are considered normal The normal adrenal gland has a characteristic “ice cream sandwich” appearance with hyperechoic medulla (the “ice cream” filling) surrounded by hypoechoic cortex The normal adrenal is triangular or Y-shaped and relatively large, when compared with the kidney, in fetal life Although assessment of fetal gender is not required in low-risk pregnancies, it is often the most pressing question for the parents The first trimester phallus has a similar appearance in males and females; although it “points” caudally in females and cranially in males, it is wise to avoid committing to gender before it can be clearly identified This also holds true later in pregnancy as mild clitoromegaly is considered normal If gender determination remains indeterminate (i.e., ambiguous genitalia), a careful search should begin for various syndromes and aneuploidy Gender assessment is essential when diagnosing anomalies that affect only one gender (e.g., posterior urethral valves in males, Turner syndrome in females) or in evaluating disorders that only affect 808 Diagnostic Imaging Obstetrics, 2nd Edition monochorionic twins (e.g., twin-twin transfusion syndrome) in which the twins must have the same gender MRI MRI is very helpful when US visualization is limited T2WI is essential for the evaluation of renal anatomy The renal parenchyma is intermediate in signal (i.e., < fluid, > liver or muscle) while the collecting system and the bladder should contain high signal urine The adrenal glands are seen best later in gestation; they are low signal, similar to liver, on T2WI with the medulla being somewhat higher in signal T1WI may allow differentiation of adrenal hemorrhage (high signal blood products) from fetal neuroblastoma (intermediate signal mass) Meconium-filled bowel is high signal, which can be helpful in differentiating it from urine-filled structures, which are low signal It also helps to look at the course of the colon and rectum and to determine the location and patency of the anus, if there is concern for cloacal or bowel anomalies Approach to the Abnormal Urinary Tract The first step in evaluation of any abdominal abnormality is to decide if it involves the urinary tract or the gastrointestinal tract Peritoneal boundaries are not clear in the fetus, so care needs to be taken in deciding what organ system is involved A dilated tubular structure may be either ureterectasis or obstructed bowel A solid mass may be coming from the kidney (e.g., mesoblastic nephroma), the adrenal (e.g., neuroblastoma), or the liver (e.g., hepatoblastoma) Once the urinary tract is established as the site of origin, it is important to have a systematic approach to form an appropriate differential diagnosis Are there two kidneys? If so, where are they? If both kidneys are absent, there will be anhydramnios in the 2nd trimester The kidneys are not a major contributor to amniotic fluid until 16 weeks gestation The adrenal glands are very prominent early in gestation, and the diagnosis of renal agenesis could potentially be missed unless careful evaluation is performed If there is normal fluid after this time, at least one kidney must be P.8:17 present Evaluate the renal fossa carefully, and if there is only one kidney, begin a careful search to see if the other is absent (i.e., unilateral renal agenesis) or in an aberrant location (e.g., pelvic kidney, crossed fused ectopia) Is the renal size and echogenicity normal? Increased renal echogenicity may be seen in autosomal recessive polycystic kidney disease and MeckelGruber syndrome, or in association with aneuploidy, typically trisomy 13 In these conditions, the kidneys are usually enlarged, sometimes massively so The kidneys may also be echogenic in obstructive cystic dysplasia but are often small, and there should be obvious signs of an underlying urinary tract obstruction Beckwith-Wiedemann syndrome may present as renal enlargement, but the normal corticomedullary differentiation is usually preserved, unlike autosomal recessive polycystic kidney disease Unilateral enlargement is unusual, and a renal mass (e.g., mesoblastic nephroma) should be considered Are anechoic structures renal cysts or hydronephrosis? Before you ask this question, make sure that the finding is real, not just hypoechoic renal pyramids, which can be quite prominent in the 3rd trimester If there are truly cystic areas within the kidney, realtime evaluation is essential If they connect centrally with the renal pelvis, explore causes of hydronephrosis (e.g., ureteropelvic junction obstruction, ureterovesicle obstruction, and bladder outlet obstruction) If they not connect with each other or the renal pelvis, then the differential diagnosis is that for multiple discrete cysts (e.g., multicystic dysplastic kidney, cystic dysplasia) Are the ureters visible? Normal ureters are never seen sonographically If the ureters are dilated, consider obstruction, reflux, or primary megaureter Is the bladder normal in size? The bladder should fill and empty during the course of a scan Always check the bladder at the beginning and end of the exam to make sure that the observation of a “too big” or “too small” bladder is persistent In a female fetus, the presence of a persistent, fluid-filled lesion in the pelvis should lead to consideration of a cloacal anomaly If the “bladder” has a fluid-fluid level, it is much more likely to be a distended, obstructed vagina than the actual urinary bladder, which is often compressed and hard to see 809 Diagnostic Imaging Obstetrics, 2nd Edition An “absent” bladder is most commonly due to failure of urine production, in which case look for bilateral renal anomalies This can also occur with decreased renal perfusion (e.g., intrauterine growth restriction, donor twin in twin-twin transfusion) Some structural malformations prevent normal bladder development including cloaca and bladder extrophy If the bladder is distended and fails to empty, posterior urethral valves (PUV) and prune belly syndrome should be considered Demonstration of a dilated penile urethra in a male fetus with a large bladder differentiates prune belly syndrome from PUV, in which the dilated posterior urethra creates the classical “keyhole” shape to the bladder Amniotic fluid is usually decreased in these conditions Are the adrenal glands normal in size and morphology? In renal agenesis, the adrenal gland loses its triangular shape and flattens out into the renal fossa where it may be mistaken for the kidney This is the “lying down” adrenal sign Enlarged adrenals are unusual but may be seen in congenital adrenal hyperplasia (look for virilization of female fetus) The differential for a unilateral suprarenal mass is neuroblastoma, adrenal hemorrhage, or extralobar sequestration The latter is a pulmonary malformation and does not actually arise from the adrenal To make this diagnosis, look for normal adrenal gland displaced by mass with prominent feeding vessel arising from aorta Are the genitalia normal? Anomalous genitalia are seen in structural malformation sequences that affect bladder development (e.g., bladder exstrophy), aneuploidy (e.g., trisomy 13, trisomy 18, triploidy), and syndromes (e.g., Smith-LemliOpitz, Prader-Willi) Clinical Implications Abnormalities of the GU tract can be lethal (e.g., bilateral renal agenesis) or of minor importance (e.g., small fetal ovarian cyst) A systematic approach to evaluation will help you to reach the correct diagnosis, which is essential in order to manage the pregnancy appropriately Image Gallery (Left) Gross pathology example from a 2nd trimester fetus shows the relatively large size of the fetal adrenal compared with the fetal kidney (note the fetal lobulations) It is important not to mistake adrenal glands for kidneys in cases of renal agenesis (Right) Composite axial US in the 3rd trimester shows the “ice cream sandwich” appearance of the adrenal glands , just cephalad of the kidneys , which are round in cross section with nice corticomedullary differentiation P.8:18 810 Diagnostic Imaging Obstetrics, 2nd Edition (Left) Axial T2WI MR of a 3rd trimester fetus shows normal signal intensity and configuration of the adrenal glands Note the low signal cortex and high signal medulla creating the MR version of the “ice cream sandwich.” (Right) Immediately below the adrenal glands are the kidneys , which are predominately intermediate in signal with a high signal renal pelvis The external contour has the typical fetal lobulations (Left) Coronal cut section of a 3rd trimester fetal kidney shows the lobulated cortical margin (fetal lobulations) and distinct renal pyramids arrayed around the renal pelvis (Right) Coronal ultrasound of the kidney in a 3rd trimester fetus shows the normal hypoechoic pyramids These should not be confused with dilated calyces 811 Diagnostic Imaging Obstetrics, 2nd Edition (Left) Coronal ultrasound shows multiple anechoic structures within the right kidney, which appear to cluster around what could be a dilated renal pelvis Real-time imaging is essential to determine if these communicate In this case, they did not This is a multicystic dysplastic kidney, not hydronephrosis (Right) Conversely, in this case, the peripheral “cysts” communicate with the central fluid collection (i.e., the renal pelvis) This fetus had bilateral UPJ obstructions P.8:19 (Left) Axial color Doppler ultrasound shows bilateral umbilical arteries This is the anatomic landmark for the fetal bladder, but none was seen Normal amniotic fluid and kidneys (not shown) make an anomaly unlikely (Right) Another image minutes later shows the bladder starting to fill, confirming that this fetus is indeed normal The bladder often changes appearance during the examination 812 Diagnostic Imaging Obstetrics, 2nd Edition (Left) Coronal ultrasound shows a very distended bladder extending up to the liver margin If this were persistent, it would be concerning for a bladder outlet obstruction (Right) A follow-up image at the end of the exam shows the bladder has decompressed and now has a normal appearance The urinary tract is a dynamic system, with the collecting system (both kidneys and bladder) filling and decompressing Before diagnosing an abnormality, it is essential to determine if the finding is persistent (Left) Color Doppler US can be very helpful in evaluating urinary tract anomalies, especially to look for renal arteries in the setting of possible renal agenesis In this coronal image of the aorta, no renal arteries are seen (Right) It is important to be aware of potential pitfalls When the transducer is angled posteriorly, multiple lumbar arteries are seen One of these could be easily confused with a renal artery Understanding normal anatomy and attention to detail is imperative in making the correct diagnosis II Renal Developmental Variants 135 Unilateral Renal Agenesis > Table of Contents > Section - Genitourinary Tract > Renal Developmental Variants > Unilateral Renal Agenesis Unilateral Renal Agenesis Karen Y Oh, MD David Holznagel, MD Key Facts Imaging 813 Diagnostic Imaging Obstetrics, 2nd Edition Diagnosis of exclusion Must exclude asymmetric horseshoe kidney, pelvic kidney, and crossed ectopic kidney Adrenal gland fills empty renal fossa in globular instead of triangular shape Shape and position of adrenal can mimic kidney Colon in empty renal fossa may also mimic kidney Absent renal artery Color Doppler confirms diagnosis Beware of adrenal or lumbar arteries mimicking renal artery Compensatory hypertrophy of remaining kidney in 44% of cases Seen as early as 22 weeks Look for associated findings Single umbilical artery VACTERL association Top Differential Diagnoses Pelvic kidney Aplastic kidney Pathology Associated with multiple chromosomal abnormalities Uterine duplication anomalies can be present Clinical Issues Often incidental finding Occurs in up to 1:1,000 live births Postnatal ultrasound to confirm diagnosis Diagnostic Checklist If diagnosed in 2nd trimester, follow-up ultrasound in 3rd trimester to assess for pelvic kidney (Left) Although subtle in the mid 2nd trimester, this axial view shows an empty left renal fossa and a normal right kidney (Right) Color Doppler interrogation of the same fetus shows only renal artery Be careful when performing color Doppler as the lumbar and adrenal arteries may mimic a renal artery 814 ... 129 5 21 8 22 Q11 Deletion Syndrome 129 5 21 9 Aicardi Syndrome 129 8 22 0 Amniotic Band Syndrome 1304 22 1 Apert Syndrome 1311 22 2 Beckwith-Wiedemann... 123 3 21 1 Fetus-in-Fetu 123 9 Section 12 - Aneuploidy 124 5 21 2 Screening for Aneuploidy 124 5 21 3 Trisomy 21 125 1 Diagnostic Imaging Obstetrics, ... 1317 22 3 Carpenter Syndrome 1 323 22 4 CHARGE Syndrome 1 326 22 5 Cornelia De Lange Syndrome 1 329 22 6 Cystic Fibrosis 1333 22 7 Diabetic