Dandy-Walker variant: prenatal sonographic features and clinical outcome.

The Dandy-Walker variant is a less severe posterior fossa anomaly than the classic Dandy-Walker malformation. In 17 consecutive fetuses, the Dandy-Walker variant was diagnosed at sonography, and associated defects, karyotypic anomalies, and outcomes were evaluated. Four of the 17 fetuses (24%) had mild ventriculomegaly. Eight of the 17 (47%) had concurrent non-central nervous system (CNS) anomalies. Five fetuses (29%) had an abnormal karyotype (two with trisomy 18, one each with trisomy 13, 21, and 11q+) and associated sonographic anomalies. Six of the 17 fetuses (35%) died in utero or during the neonatal period, two are severely handicapped, and the other nine are developing normally at ages 4 months to 4 years. Six of the nine normally developing infants (53%) lacked non-CNS sonographic findings. Because the prognosis is uncertain for an infant born with the prenatal diagnosis of Dandy-Walker variant, prenatal recognition of the anomaly allows for the option of fetal karyotyping and for arrangement for postnatal follow-up.     

Prenatal diagnosis of anencephaly: spectrum of sonographic appearances and distinction from the amniotic band syndrome

To document the characteristic sonographic abnormalities of anencephaly and to identify potentially confusing sonographic features, we reviewed 20 cases of anencephaly. All of these cases were diagnosed prenatally with sonography after 14 menstrual weeks in patients who were seen at our institution between 1984 and 1988. In all cases, the correct diagnosis was made on the prenatal sonograms and was confirmed pathologically. The sonographic diagnosis was primarily based on the absence of brain and calvarium superior to the orbits on coronal views of the fetal head. This typical appearance was altered by the presence of echogenic tissue superior to the orbits in nine (45%) of 20 cases. Pathologically, the tissue corresponded to angiomatous stroma (area cerebrovasculosa) and appeared quite sizable on sonograms in four fetuses (20%). It may appear solid or mixed solid and cystic. In one fetus, it appeared brainlike. Despite this appearance, the sonologist should not be dissuaded from the diagnosis of classic anencephaly. Hydramnios occurred in seven (35%) of 20 patients, and oligohydramnios occurred in none of the patients. Anencephaly may be distinguished from the cranial defects associated with the amniotic band syndrome (amputation defects that occur as the sequelae of amniotic disruption) on the basis of the symmetry of the cranial defects (100% of anencephalic fetuses in this series) and the absence of limb, body wall, and spinal abnormalities that typically accompany the amniotic band syndrome. Although there may be minor variations in the sonographic appearance of the cranial defect of anencephalic fetuses (i.e., much or little angiomatous stroma), we conclude that this anomaly can be accurately detected and diagnosed on fetal sonograms obtained after 14 weeks menstrual age and distinguished from the amniotic band syndrome.     

Fetal choroid plexus cysts: prevalence, clinical significance, and sonographic appearance

To determine the prevalence, sonographic appearance, and clinical significance of fetal choroid plexus cysts, we analyzed the sonograms and clinical records of 17 fetuses with cysts. Fetal and maternal age, sonographic indication, cyst size and multiplicity, and evolution on serial studies were recorded. Fetal outcome was available in 16 cases by genetic amniocentesis (n = 5) or neonatal clinical records (n = 11). The prevalence of fetal choroid plexus cysts was 0.8% (17/2084) during a 40-month period. All cysts were initially identified on sonograms performed between 14 and 21 weeks. Cysts ranged from 3 to 11 mm in size and were bilateral in four (36%) of 11 cases in which both lateral ventricles were visualized. In nine of 10 cases with serial sonograms 2-21 weeks after the initial study, the cysts were no longer present. One fetus had a small cyst persisting at term. All five cases with genetic amniocentesis had normal chromosomes. The only phenotypic abnormality in the 11 cases with clinical follow-up was a small hemangioma of the chest wall. We conclude that most fetuses with isolated choroid plexus cysts have a normal outcome and that serial sonography for cyst evaluation is not useful in determining fetal prognosis.     

Sonography of adenomyomatosis of the gallbladder: radiologic-pathologic correlation

Sonograms of six patients with adenomyomatosis of the gallbladder were reviewed and correlated with oral cholecystographic and pathologic findings. The gallbladder was visualized in four of the six patients by oral cholecystography, which also revealed intramural diverticula. Five of the six patients showed sonographic evidence of diffuse or segmental thickening of the gallbladder wall and intramural diverticula, seen as anechoic or echogenic foci within the wall. Intramural diverticula containing bile appeared as anechoic spaces; those containing biliary sludge or gallstones appeared as echogenic foci with or without acoustic shadows or reverberation artifacts. There was good correlation between sonographic and pathologic findings in three patients. The authors conclude that adenomyomatosis of the gallbladder should be suspected when (a) there is diffuse or segmental thickening of the gallbladder wall and (b) intramural diverticula are seen as anechoic or echogenic foci with or without associated acoustic shadows or reverberation artifacts.     

Bowel migration in the normal fetus: US detection

Ten fetuses underwent ultrasound scanning at 7-10 weeks gestational (postmenstrual) age. In all cases, an echogenic mass measuring 0.5-1.0 cm was demonstrated within the base of the umbilical cord at its insertion into the fetal abdomen. No area with echogenicity characteristic of the small bowel was identified within the lower part of the fetal abdomen. All fetuses were reexamined 4-12 weeks later, at which time the mass in the umbilical cord was no longer seen, and normal fetal bowel was visualized in the lower abdominal cavity of the fetus. This sequence of findings appears to represent the sonographic demonstration of normal fetal bowel migration early in gestation and should not be confused with defects of the abdominal wall such as omphalocele or gastroschisis.     

Striated intramural gallbladder lucencies on US studies: predictors of acute cholecystitis

Ultrasound scans of 51 consecutive patients with gallbladder wall thickening were reviewed, and specific sonographic features were correlated with surgical and clinical follow-up. Two patterns of thickening were identified as specific indicators of the presence or absence of acute cholecystitis. "Striated" wall thickening, consisting of several alternating, irregular, discontinuous, lucent and echogenic bands, was seen in eight of 13 patients (62%) with acute cholecystitis. This pattern was not encountered in any of the patients who did not have acute cholecystitis. Conversely, "three-layer" thickening, consisting of a single circumferential lucent zone between two relatively uniform echogenic layers, was seen in only one of 13 patients (8%) with acute cholecystitis but in 11 of 38 patients (29%) with other diagnoses. Other abnormalities, including the presence of intramural echogenic foci and wall irregularities, were more frequently seen in patients with acute cholecystitis but were not as helpful. Use of these features may suggest or help exclude a diagnosis of acute cholecystitis in those patients in whom the cause of gallbladder wall thickening is otherwise not apparent.     

Nonvisualization of the fetal gallbladder in early pregnancy: comparison with clinical outcome

PURPOSE: To prospectively assess the frequency of a nonvisualized fetal gallbladder in early pregnancy and to determine its prognostic value. MATERIALS AND METHODS: Fetal transvaginal ultrasonography (US) was performed in 29,749 consecutive pregnant women at 14-16 weeks gestation. A nonvisualized fetal gallbladder was defined if the gallbladder could not be depicted during two targeted examinations within 1 week. In such cases, women were offered an amniocentesis for fetal karyotype and hepatic enzyme analysis. Repeat transabdominal fetal US was performed at 22-26 weeks' gestation. If the gallbladder was still not depicted, US was performed postnatally. RESULTS: The gallbladder was not visualized in early pregnancy in 34 fetuses (0.1%; incidence of one in 875 pregnancies). Associated structural malformations were detected in 14 of 34 (41%) fetuses, five of which also had an abnormal karyotype. Pregnancy was terminated in nine of these 14 fetuses. In the remaining five patients who continued pregnancy, the gallbladder was detected later in pregnancy in four. However, only one infant was healthy. Nonvisualization of the gallbladder as an isolated finding was noted in 20 of 34 (59%) fetuses, all of which had a normal outcome. The gallbladder was detected later in pregnancy in 11 of these fetuses and after birth in two neonates, while no gallbladder was detected after delivery in five other neonates. Two patients were lost to follow-up. CONCLUSION: Nonvisualization of the fetal gallbladder in early pregnancy is uncommon but associated in many cases with other fetal anomalies.     

Clonorchiasis: sonographic findings in 59 proved cases

Clonorchiasis is a parasitic disease of the bile ducts that occurs in endemic areas after ingestion of the raw flesh of freshwater fish. We analyzed the sonographic findings in 59 patients with clonorchiasis, suspected prospectively from sonographic findings and proved subsequently by demonstration of eggs in their stools. Diffuse dilatation of the small intrahepatic bile ducts with no or minimal dilatation of the large intra- and extrahepatic ducts was observed in all cases. The extrahepatic ducts were patent throughout in all except one case. This characteristic finding reflects diffuse intrahepatic bile duct obstruction and resultant proximal dilatation caused by an adult worm or aggregates of worms, as worms reside diffusely in the medium and small intrahepatic bile ducts. Cholangitis and multifocal periductal fibrosis with proximal dilatation may play an additional role. Increased echogenicity of the intrahepatic bile duct wall was present in 39 cases (66%), reflecting cholangitis and periductal fibrosis. In 17 cases (29%), floating or dependent, discrete, nonshadowing, intraluminal, echogenic foci caused by adult worms in the bile were demonstrated in the gallbladder. These echogenic foci were distinguished from stones because they were fusiform, weak in echogenicity, and floated with a change in position. Clonorchiasis should be considered when sonography discloses the characteristic pattern of bile duct dilatation with increased wall echogenicity and nonshadowing, discrete, echogenic foci in the gallbladder lumen.     

Testicular neoplasms: 29 tumors studied by high-resolution US

High-resolution (10-MHz) ultrasonography produces extremely detailed anatomic images of the testis. The sonographic features most helpful in detecting tumors are mass, bright echogenic foci, and diffuse parenchymal texture change. Of 29 patients with testicular neoplasms, 21 (72%) had one or more masses, 19 (66%) had one or more echogenic foci, and nine (31%) had a diffuse parenchymal texture change. Bright echogenic foci were present in six (86%) of seven testes that had a regressed germ-cell tumor. In an attempt to define the histologic features of bright echogenic foci, we performed needle localization under real-time guidance on four operative specimens. We observed immature bone and cartilage, calcification, tubular atrophy and fibrosis, and focal noncalcific scarring. Discovery of occult testicular neoplasms was common (9/29); four patients were thought to have had "extragonadal" germ-cell tumors before abnormalities were found on the sonograms.     

Hypoechoic lesions without halo in echogenic liver. A frequent sonographic dilemma

Sonographic evaluation for the presence of hypoechoic hepatic lesions without halo was carried out in 365 consecutive patients with echogenic livers. In 115 patients (31%) such lesions could be demonstrated. Computed tomography of the liver was performed in 52 of these patients, a long term sonographic follow-up in 76, and a biopsy in 3 cases. In 103 patients the hypoechoic lesions were due to sonographic pseudolesions (PL's), probably representing normal liver tissue in otherwise diffusely fatty infiltrated livers. The PL's showed characteristic sonographic appearances such as a missing mass effect, a 'landscape'-like configuration with angulated margins and slender extensions of hypoechoic tissue. The PL's were located below the capsule, near the gallbladder (41%), and ventral to the portal vein (37%). In 75 per cent they occurred in a liver with considerably increased echogenicity. In 12 patients hypoechoic lesions were caused by circumscribed malignant or infectious involvement of the liver. They could be discriminated from PL's by their mass-like appearance in 8 subjects. In 4 of these 12 cases the foci were of PL-typical appearance, but not of PL-typical location. In the light of these results and of recently published reports a rational diagnostic approach to hypoechoic lesions without halo in echogenic livers varies, depending on such factors as known primary malignancy or site of the lesion.     

Clinical course of fetal hydrocephalus: 40 cases

The clinical course and outcome of hydrocephalus diagnosed in utero is not well understood. To approach this problem 40 cases were reviewed of intrauterine fetal hydrocephalus diagnosed with sonography, and follow-up information was obtained regarding them. Sonograms were evaluated for cerebral dimensions, biparietal diameter, brain mantle size, ventricular ratio, amount of amniotic fluid, and associated abnormalities. Neonatal brain sonograms and computed tomographic (CT) scans were reviewed also. Clinical charts were reviewed for maternal age and parity, referral source, family history, fetal age at diagnosis and delivery, mode of delivery, physical examination and/or autopsy findings, karyotype, amniotic alpha 1 fetoprotein level, cause of death, shunt placement after birth, and status of live infants. The observations indicate that the prognosis for fetal hydrocephalus is poor. Only six infants (15%) were alive after an average follow-up of 13 months. Three children were normal and the other three had neurologic abnormalities ranging from severe (paralysis and incontinence) to minimal (2-3 months delayed motor development). Thirty-four fetuses or neonates died. Nine families elected to terminate pregnancy. Ten opted for decompression at delivery for progressive hydrocephalus. Neural tube defects were present in 12 of 23 infants at delivery. Fourteen other infants had additional significant congenital abnormalities. Other abnormal sonographic findings included polyhydramnios (13 of 38), oligohydramnios or decreased fluid (nine of 38), neural tube defect (nine of 40), and other congenital abnormalities (nine of 40). These findings indicate that hydrocephalus diagnosed in utero by sonography is caused by a heterogeneous group of disorders. In general, the prognosis for normal development is poor. Individual prognoses, however, depend on the specific malformations and the interventions used.     

Down syndrome: sonographic sign for diagnosis in the second-trimester fetus

In an expanded series of patients a sonographic sign was found to correlate well with the diagnosis of Down syndrome in second-trimester fetuses. The sign is characterized by soft-tissue thickening at the back of the fetal occiput. Sonographic evaluation for this sign was done in 2,121 consecutive fetuses between 15 and 20 gestational weeks of age at the time of genetic amniocentesis. The mothers were 35 years old or older or were otherwise at increased risk for fetal trisomies. Ten fetuses had Down syndrome by karyotype and four of these (40%) had thickened soft tissues (6 mm or more) at the back of the neck or occiput. When these data are combined with those in series previously reported by the authors, similarly collected consecutively, total second-trimester fetuses studied equals 3,825. Nine of the 21 (42%) Down syndrome fetuses by karyotype from this 3,825 had the positive sonographic sign described.     

Fetal cisterna magna septa: a normal anatomic finding

A linear hyperechoic structure in the cisterna magna, previously described as the straight sinus, was investigated during routine obstetric ultrasound (US) examination. One hundred three fetal US examinations were performed to determine the prevalence and appearance of this finding. Also, US water-bath examination of 18 fixed postmortem specimens and fetuses was performed, and results were correlated with those of gross and microscopic examination of the fetal brain. The structure was identified in 95 (92%) prenatal examinations between 15 and 38 menstrual weeks. It was located posteriorly between the cerebellar hemispheres in the cisterna magna. In those 95 cases in which it was identified, it appeared as a single echogenic line in 31 cases (33%), as two echogenic lines in 47 (49%), or as three or more lines in 17 (18%). When two echogenic lines were identified, they appeared "cystlike" in 17 (18%) of the 95 examinations. Correlation of the gross and histologic findings demonstrated these lines to represent normal subarachnoid septa rather than the straight sinus.     

Significance of low level echoes within the gallbladder.

Thick bile may appear as a nonshadowing, dependent, echogenic layer within the gallbladder. In vivo sonographic imaging of the canine gallbladder showed that highly viscous, desiccated bile appeared echogenic and could potentially prevent imaging an enlarged gallbladder or dilated bile ducts. Selected clinical cases demonstrated that multiple nonshadowing calculi, pus, cholesterol crystals, and possibly abnormal mucous in the gallbladder may be sonographically indistinguishable from thick bile.     

Fetal biometry: size and configuration of the third ventricle

PURPOSE: To evaluate the normal configuration and size of the third ventricle in second and third trimester fetuses in a normal population, and to compare our values with those of previously published studies. MATERIAL AND METHODS: Evaluation of fetal third ventricular width and configuration was obtained by antenatal ultrasonography in 474 fetuses with gestational age between 12 weeks and term (mean 28 weeks). Percentiles for third ventricle width were estimated by combining separate fractional polynominal regression models fitted to the mean and standard deviation, assuming that the measurements had a normal distribution at each gestational age. Appearance of the third ventricle was correlated with each gestational age. RESULTS: The third ventricle could be visualized in 471 (99%) of 474 fetuses. The 97th percentile of the third ventricle in preterm fetuses was measured as 3.6 mm in size. The third ventricle was seen as a single echogenic line in 153 (32.4%) of 474 fetuses. Two-hundred-and-ninety-nine (61.5%) of all fetuses had parallel echogenic lines outlining a fluid-filled lumen. V-shaped third ventricular configuration was seen in only 28 (5.9%) of the fetuses. From 24 weeks to term, parallel echogenic lines were the most commonly (83.7% to 79.6%) encountered configuration for the third ventricle. CONCLUSION: The 97th percentile of the third ventricle in preterm fetuses was measured as 3.6 mm in size. In the early second trimester, 77% of the fetuses had a single echogenic line appearance on ultrasonography. As the brain and ventricular structures mature, a parallel echogenic line becomes the prominent ultrasonography appearance (>80% of fetuses) in third trimester healthy fetuses.     

Intact stones or fragments? Potential pitfalls in the imaging of patients after biliary extracorporeal shock wave lithotripsy

Ultrasound is used after extracorporeal shock wave lithotripsy of gallbladder stones to assess fragmentation. In many patients with apparently successful fragmentation, the posttreatment studies show an intraluminal, echogenic focus within the gallbladder, with posterior acoustic shadowing characteristic of an intact stone. Cholesterol gallstones were fragmented in vitro by means of lithotripsy, and the sonographic appearance of the fragmented stones was followed up over time to study factors that might affect the process. After lithotripsy, fragments settled and produced an echogenic focus with posterior shadowing indistinguishable from the appearance of an intact stone. These experimental observations led to the development of a clinical maneuver to overcome the diagnostic pitfalls posed by the reaggregation of stone fragments in situ. This rollover maneuver helps distinguish between intact stones and fragments, and prevents both diagnostic errors in follow-up and unnecessary retreatment.     

Prevalence of cystic fibrosis in fetuses with dilated bowel.

The authors reviewed the ultrasonographic images and medical records of 15 consecutive fetuses with dilated loops of bowel distal to the duodenum and determined the prevalence of cystic fibrosis among them. The criteria for dilated bowel loops included both subjective criteria and luminal measurements. Five of the fetuses (33%) had cystic fibrosis. Eleven had bowel obstruction at birth, and four of those 11 (36%) also had cystic fibrosis. One of the four fetuses without bowel obstruction at birth had cystic fibrosis. There were no differences in sonographic findings between fetuses with and without cystic fibrosis, except that one third-trimester fetus with cystic fibrosis had echogenic small bowel with shadowing. All of the fetuses with dilated bowel loops persisting at birth required surgery. Further studies are indicated to determine the exact risk of cystic fibrosis in this population.     

Bacterial meningitis in infants: sonographic findings

A retrospective study was performed on 78 patients (newborn to 2 years old) with clinically proved bacterial meningitis. Sonograms were obtained during the acute illness and medical records were reviewed. The spectrum of sonographic features of meningitis included normal scans (30 patients), ventriculomegaly (11 patients), echogenic sulci (31 patients), extra-axial fluid collections (26 patients), abnormal parenchymal echogenicity (9 patients), evidence of ventriculitis (5 patients), and brain abscess (1 patient). In 46 patients, correlation between the sonographic findings and neurologic outcome on clinical follow-up (6 months to 4 years) was made. Findings of abnormal parenchymal echogenicity and/or moderate-to-marked ventriculomegaly were associated with significant neurologic sequelae; however, echogenic sulci and small extra-axial fluid collections did not appear to have any prognostic significance. Twenty-nine of the 78 patients had sonography without clinical indication of complications of meningitis, and in no patient was a significant abnormality found. Our study suggests that sonography is indicated only when there is clinical suspicion of complications.     

Echogenic periventricular halo: normal sonographic finding or neonatal cerebral hemorrhage

Intracranial sonographic evaluation of the normal neonate frequently reveals an echogenic halo about the lateral ventricles. This periventricular halo is seen to varying degrees when scanning in both semiaxial and parasagittal planes in almost all normal infants. Among 180 consecutive premature neonates scanned serially with real-time sonography, two were prospectively diagnosed as having a form of periventricular echogenicity that was abnormal and represented periventricular hemorrhage. This hemorrhage completely surrounded the lateral ventricles and was intensely echogenic, as echogenic as the choroid plexus. This abnormal periventricular echogenicity was reproducible from multiple scan planes and hemorrhage was confirmed by computed tomography (CT). By contrast, CT scans obtained on another 53 of the 180 premature infants failed to reveal evidence of any abnormality corresponding to the periventricular echogenicity. Both neonates with periventricular hemorrhage developed bilateral multiseptate areas of porencephaly as sequelae to their hemorrhages. The differentiation between normal periventricular echogenicity and periventricular hemorrhage therefore attains great significance to the sonographer.