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Fetal Hepatic Calcification

Introduction Fetal hepatic calcifications are divided into three categories: peritoneal, parenchymal, and vascular. This chapter addresses parenchymal hepatic calcifications and, to a lesser degree, vascular calcifications, which may be included in the differential diagnosis of parenchymal calcifications. Disorder Definition Fetal hepatic calcifications are single or multiple echogenic areas of various sizes (usually small, punctate) within the fetal hepatic parenchyma detected by ultrasound (US). They can be…

Echogenic Bowel

Introduction Fetal echogenic bowel (FEB) is typically seen during second trimester prenatal ultrasound. FEB occurs when the fetal bowel appears with the same or greater echogenicity than do surrounding bony structures. When seen in the second trimester, FEB has been associated with increased risk for fetal cystic fibrosis, aneuploidy, gastrointestinal abnormalities, growth restriction, and viral infections. However, it is important to realize that the majority of…

Omphalocele

Introduction Omphalocele is classified as a ventral wall defect in which there is midline herniation of abdominal viscera into the base of the umbilical cord. Before the 1950s, gastroschisis was considered a variant of omphalocele. It is now known that each entity has a separate etiology, unique risk factors, and distinct outcomes. As a result of widespread use of prenatal screening with maternal serum alpha-fetoprotein (MSAFP)…

Gastroschisis

Introduction Gastroschisis, a full thickness paraumbilical defect in the abdominal wall that results in herniation of the fetal midgut, has been considered an entity embryologically distinct from omphalocele since the mid-1950s. The widespread availability of prenatal ultrasound (US) and of maternal serum alpha-fetoprotein screening allows for routine antepartum diagnosis of gastroschisis with high accuracy. For reasons not well defined, the prevalence of gastroschisis has continued to…

Cloacal Abnormalities

Introduction Cloaca is derived from the Latin word for sewer or drain. Anatomically, it is used to describe a confluence of the urinary, genital, and gastrointestinal (GI) tracts. While this is the norm in birds, reptiles, and amphibians, most mammals have separate outlets for each system. In humans, there is a wide range of cloacal abnormalities. Mild forms may involve only a persistent urogenital sinus opening…

Ambiguous Genitalia

Introduction While not of primary focus for the medically minded sonographer or sonologist, sex determination is often the most important question for parents during a fetal ultrasound (US) examination. Sex determination, however, can be medically important in the diagnosis of zygosity or chorionicity in multiple gestations, for counseling regarding X-linked diseases, and in cases of ambiguous genitalia. The diagnosis of ambiguous genitalia, which has various causes,…

Fetal Adrenal Abnormalities

Introduction The fetal adrenal glands can be reliably imaged on prenatal ultrasound. The adrenal glands are located in a retroperitoneal, paraspinous location, cephalad to the upper renal poles. The gland is composed of a hypoechogenic cortex and a thin echogenic medulla ( Fig. 17.1 ). Adrenal abnormalities can be divided into three categories and are listed in Table 17.1 : 1. masses (neuroblastoma) 2. bleeding (hemorrhage…

Autosomal Recessive (Infantile) Polycystic Kidney Disease

Introduction Autosomal recessive polycystic kidney disease (ARPKD) is a chronic, progressive condition that affects the kidneys and liver, causing cystic dilatation of the renal collecting ducts and congenital hepatic fibrosis (CHF), or Caroli disease. ARPKD is also called infantile polycystic kidney disease and ARPKD ARPKD is caused by mutations of a large, complex gene, PKHD1, and it has an unusually wide spectrum of phenotypic variability. Diagnosis…

Multicystic Dysplastic Kidney

Introduction Multicystic dysplastic kidney (MCDK) is a form of severe renal dysplasia that typically results in a nonfunctioning kidney. The parenchyma is replaced by numerous cysts of varying size, with echogenic intervening tissue and an atretic ureter. Microscopically, undifferentiated epithelium and primitive ducts are surrounded by fibromuscular connective tissue. Bilateral MCDK usually results in Potter sequence (see Chapter 10 ), with early and severe oligohydramnios conferring…

Posterior Urethral Valves

Introduction Posterior urethral valves (PUV) are the most common cause of fetal lower urinary tract obstruction, also called bladder outlet obstruction. Membranous tissue in the posterior urethra results in varying degrees of obstruction. The condition occurs only in males, although other etiologies of bladder outlet obstruction can affect females and males. There is a wide range of severity prenatally and postnatally. Lack of amniotic fluid during…

Duplicated Collecting System

Introduction Duplication of the renal collecting system, also termed duplex kidney, is one of the few renal anomalies more common in females. Duplex kidneys have an upper pole and a lower pole, called moieties, each drained by a ureter. Approximately one-third of the duplex kidney is drained by the upper pole ureter, with two-thirds drained by the lower pole ureter. Many individuals with duplex kidneys are…

Renal Pelvis Dilatation

Introduction Fetal renal pelvis dilatation (or dilation) is a common ultrasound (US) finding, identified in 1% to 5% of pregnancies. There is a strong correlation between the degree of renal pelvis dilatation and the likelihood of postnatal urinary pathology, particularly ureteropelvic junction (UPJ) obstruction and vesicoureteral reflux (VUR). However, the normal renal pelvis diameter also increases with advancing gestation, and mild dilatation is a transient, normal…

Unilateral Renal Agenesis

Introduction Unilateral renal agenesis, also called solitary kidney, is a common congenital anomaly. Affected individuals are usually asymptomatic, and if a diagnosis is not made prenatally, they may not receive medical attention until complications arise. If unilateral renal agenesis is diagnosed in childhood, nearly 50% of affected children have an associated renal abnormality, including 30% with vesicoureteral reflux (VUR). Being born with one kidney is not…

Bilateral Renal Agenesis

Introduction Bilateral renal agenesis is a uniformly lethal anomaly. Absence of the kidneys causes anhydramnios, resulting in pulmonary hypoplasia, characteristic facies, and positional extremity abnormalities ( Fig. 10.1 ). This constellation of findings was first described by Edith Potter, and bilateral renal agenesis has been termed Potter syndrome . The deformation sequence itself, which can occur following lack of amniotic fluid from any early insult (not…

Abnormal Kidney Size

Introduction The fetal kidneys are routinely imaged in the second and third trimester, but they are not usually measured unless an abnormality is suspected. Nomograms are available not only for kidney length ( Table 9.1 ) but also for anterior-posterior diameter ( Table 9.2 ) and transverse diameter ( Table 9.3 ). An abnormality of kidney size can occur as a normal variant, as a physiologic…

Abnormal Kidney Location

Introduction There are three types of abnormalities of renal location: simple renal ectopia (e.g., pelvic kidney), crossed renal ectopia, and horseshoe kidney. They are collectively termed renal ectopia . During normal development, the metanephros migrates from the pelvis to the abdomen, and rotates about its longitudinal axis. Abnormalities of renal location may occur because of failure of ascent of the metanephric buds or because of fusion…

Other Thoracic Tumors and Masses

Introduction Among rare thoracic tumors not described in previous chapters, two are the most common. Bronchogenic cysts are derived from abnormal budding of the ventricular diverticulum in the mediastinum or the lung. Lymphangiomas arise from the lymphatic system and develop more frequently in the thorax, head, and neck. Bronchogenic Cyst Definition A bronchogenic cyst is a cystic duplication of the tracheobronchial tree, derived from an abnormal…

Thymus

Introduction The thymus is a lymphoepithelial organ with key adaptive immune functions during both intrauterine and extrauterine life. The thymus develops from the third pharyngeal pouch, which gives rise to endodermal-derived thymic cortical epithelium, and the third pharyngeal cleft, which is thought to give rise to ectodermal-derived medullary thymic epithelium. The thymus enlarges in the ninth gestational week when lymphocytes and hematopoietic cells migrate from embryonal…

Scimitar Syndrome

Introduction Scimitar syndrome (SS) is a rare congenital anomaly characterized by a partial (usually the right lower lobe) or complete unilateral anomalous pulmonary venous drainage in association with ipsilateral lung hypoplasia. The anomaly, also known as pulmonary venolobar syndrome or hypogenetic lung syndrome , was first described in 1836. The term scimitar was first used by Halasz et al. to describe the radiographic appearance of the anomalous…

Hydrothorax

Introduction Fetal hydrothorax is an intrathoracic effusion arising in the fetus, which may occur unilaterally or bilaterally, and may be primary or secondary. Disease Definition Fetal hydrothorax (also pleural effusion) is an intrathoracic effusion, which may occur unilaterally or bilaterally. It constitutes a nonspecific finding, since it generally is the clinical manifestation of subjacent pathology. If primary and isolated, it is termed primary fetal hydrothorax ,…