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D H Pretorius

Publications and source records attributed to D H Pretorius.

At least 91 records · Page 5Linked to original sources
PubMed1991

Ossification of the fetal spine.

The neural arch ossification centers in the distal fetal spine were evaluated with ultrasound (US) during the second trimester of pregnancy in 239 fetuses. Ossification of the neural arch centers occurred in a predictable pattern and in a caudal direction. An additional vertebral level became ossified every 2-3 weeks from L-5 through S-5 after 16 weeks gestational age; by 22 weeks, S-2 was ossified in all fetuses studied. Radiographic and histologic correlation was performed in one fetus, and the method of establishing vertebral level with US proved accurate. In addition, the origin of the echoes at US corresponded to the histologic ossification centers. In 95% of the fetuses, S-1 was at the top of the iliac wing. Therefore, the level of ossification in the distal fetal spine could be rapidly assessed. Ossification to S-2 by 22 weeks, with a normal transverse configuration, normal overlying integument, and normal cranial structures, should lead to reassurance in excluding neural tube defects, except for distal sacral lesions.

Female↗
PubMed1991

Significance of nonvisualization of the fetal urinary bladder.

The fetal urinary bladder was visualized sonographically in 1254 (94%) of 1335 consecutive fetuses of 14 weeks of development or older, but it could not be seen in 81 cases (6%). Five of these cases were lost to follow-up and were excluded from the study. Of the remaining 76 cases, 69 (91%) of the pregnancies progressed to term, and the infants were normal at birth and at 6 week perinatal follow-up. Seven (9%) of the fetuses had a variety of associated obstetrical abnormalities that resulted in fetal demise or termination of the pregnancy (oligohydramnios, hydrops, intrauterine growth retardation [IUGR], ventriculomegaly, diaphragmatic hernia, cystic hygroma, and triploidy). Notably, none of these were renal tract anomalies. We concluded that (1) nonvisualization of the fetal urinary bladder with an otherwise normal sonogram, including normal volume of amniotic fluid and normal renal areas, is of no clinical concern and does not require follow-up, and (2) nonvisualization of the fetal urinary bladder in the setting of associated obstetrical abnormalities may be secondary to renal tract anomalies or may only be a consequence of the associated abnormalities.

Female↗
PubMed1990

Device for the calibration of flow-velocity-measuring Doppler ultrasound equipment.

A new device is described for verifying the calibration accuracy of flow-velocity Doppler ultrasound (US) equipment. A rotating circular disk whose circumferential velocity may be fixed or modulated provides a strong signal source suitable for calibrating clinical Doppler US instruments. Circumferential edge velocity, derived from the disk angular frequency, is used to verify the accuracy of Doppler instrument calibration. A limited survey of routinely used Doppler US instruments demonstrates that calibration accuracy generally is satisfactory for clinical purposes, with minimal variation between instruments. Factors that affect measurements include transducer type, scale range, and display size. All transducers used on a specific piece of equipment need to be tested because the transducer design is an important part of the instrument operation. Variations were observed in reported velocities obtained from different transducers on the same equipment and for the same transducer with different scale ranges. In particular, some scales were more accurate than others, suggesting that individual scales should be tested when performing clinical Doppler US instrument calibration. Other measures of performance including scale display range, sample depth, aliasing, and transducer selection may be studied to identify their effect on measurement accuracy. Temporal modulation of angular velocity produces waveforms that may be used to simulate pulsatile velocity characteristics. The device is simple to construct and use, and it provides a convenient way to verify high-quality instrument performance.

Blood Flow Velocity↗
PubMed1989

Dandy-Walker syndrome: a review of fifteen cases evaluated by prenatal sonography.

Fifteen cases of the Dandy-Walker syndrome evaluated by prenatal sonography were reviewed retrospectively. A posterior fossa cyst communicating with the fourth ventricle was a feature in each case. Hydrocephalus was present in 53% of fetuses. Extracranial congenital malformations were documented in 60% of cases. Cardiac, genitourinary, gastrointestinal, and skeletal anomalies were noted. Of 12 available karyotypes, 4 (33%) were abnormal, including two cases of trisomy 18. Excluding terminated pregnancies, there was an overall mortality of 55%. Associated congenital defects contributed to 83% of the postnatal deaths. The Dandy-Walker syndrome can be accurately diagnosed in utero by sonographic demonstration of characteristic morphologic changes in the fetal posterior fossa. The prenatal examination should include an evaluation of associated supratentorial and extracranial defects. Coexisting structural and chromosomal anomalies occur frequently and adversely affect survival.

Abnormalities, Multiple↗
PubMed1989

Disparity of amniotic fluid volume and fetal size: problem of the stuck twin--US studies.

The "stuck twin" phenomenon in monochorionic diamniotic (MCDA) pregnancies is characterized by marked disparity in both fluid volume and fetal size between the twin gestations. To determine the prevalence, sonographic characteristics, and clinical outcome of this phenomenon, discharge summaries, placental pathologic reports, and prenatal sonograms from 307 twin pregnancies were reviewed. Of 52 cases of MCDA pregnancies, 18 (35%) demonstrated marked disparity in amniotic fluid volume. In 16 of these 18 cases there was discordant twin growth, further suggesting the diagnosis of twin transfusion syndrome. All 16 cases and an additional nine cases supplied by another center demonstrated a small, morphologically normal fetus in an oligohydramniotic sac suspended anteriorly (72%) or laterally (28%) in the uterus. The amniotic membrane separating this twin from the larger twin in the polyhydramniotic sac was thin, closely applied to the smaller fetus, and difficult to detect. Perinatal morbidity was 100% for all twin pairs, and premature labor occurred in all cases. Perinatal mortality ranged from 88% for the larger/poly twin to 96% for the small/oligo twin.

Adult↗
PubMed1989

Fetal omphalocele: prenatal US detection of concurrent anomalies and other predictors of outcome.

Forty-six consecutive fetuses with an identified omphalocele were examined with prenatal ultrasound (US) to determine the accuracy of detecting concurrent malformations and to evaluate other possible indicators of fetal outcome. In 43 fetuses with adequate follow-up, 29 (67%) had additional malformations, including 23 with major malformations and six with minor malformations. Thirty-six fetuses (78%) died at termination of pregnancy (n = 23) or spontaneously (n = 13). With the exclusion of pregnancy terminations, fetal mortality was strongly associated with the presence of concurrent malformations, (P less than .001). In 10 surviving fetuses, only three had concurrent malformations, and all were minor. Fetal mortality was also found to be statistically associated with anomalies detected at US (P = .01) and abnormal amniotic fluid volume but was not associated with fetal ascites (P = .64) or omphalocele size (P = .65). Chromosome abnormalities correlated with the absence of liver in the omphalocele sac (P less than .001) and with abnormal amniotic fluid volume (P = .02). Prenatal US can help predict the outcome in fetuses with an omphalocele.

Abnormalities, Multiple↗
PubMed1989

Chromosomal abnormalities in fetuses with omphalocele. Significance of omphalocele contents.

Twenty-six consecutive fetuses with a sonographically detectable omphalocele and known karyotype were reviewed to identify risk factors that might be associated with chromosomal abnormalities. Risk factors that were analyzed included contents of the omphalocele sac, maternal age, fetal sex, sonographically detectable concurrent anomalies, and any major concurrent anomaly. Chromosomal abnormalities were found in 10 cases (38%) from trisomy 18 (n = 4), trisomy 13 (n = 4), trisomy 21 (n = 1), or 45, X (n = 1). The absence of liver from the omphalocele sac (intracorporeal liver) was strongly associated with an abnormal karyotype; chromosomal abnormalities were present in all 8 fetuses with an intracorporeal liver compared to 2 of 18 fetuses with an extracorporeal liver (p less than .0001, two-tailed Fisher exact test). Other risk factors that were statistically associated with chromosomal abnormalities included advanced maternal age (greater than or equal to 33 years, p = .03) and sonographically detectable concurrent malformations (p = .05). We conclude that sonographic findings can help determine the relative risk of chromosomal abnormalities in fetuses with omphalocele; abnormal karyotypes were significantly associated with the absence of liver from the omphalocele sac and sonographically detectable concurrent malformations in this series. Sonographers should also be aware that omphaloceles that contain bowel alone tend to be small and can be missed or mistaken for other abdominal wall defects (gastroschisis or umbilical hernia).

Adolescent↗
PubMed1988

Accuracy of ultrasound diagnoses in pregnancies complicated by suspected fetal anomalies.

Referral of pregnancies complicated by suspected fetal anomalies to level III perinatal centres for further evaluation and management is increasing as use of real-time ultrasound spreads, but the sensitivity and specificity of the prenatal diagnoses made in this population are unknown. We undertook a prospective study that followed pregnancies referred to a designated programme dealing with suspected fetal abnormalities. Follow-up of 257 pregnancies revealed that 282 separate anomalies were accurately diagnosed in 212 cases. Normal anatomy was correctly predicted in 42 cases, 16 per cent of the referred population. False-positive and false-negative rates were 1.5 per cent (4/257) and 2 per cent (1/46), respectively. However, 37 per cent of those infants born with anomalies had additional problems not prenatally detected by ultrasound. These results indicate that prenatal ultrasound diagnoses are remarkably accurate overall but that they may be insensitive to associated anomalies in individual cases.

Congenital Abnormalities↗
PubMed1988

The Doppler signal: where does it come from and what does it mean?

Doppler sonographic measurement of blood velocity and associated physiologic parameters is a powerful diagnostic technique. State-of-the-art instrumentation incorporates velocity measurement with two-dimensional imaging capability; it uses intensity and color coding to display complex physiologic and anatomic data to the observer in an easily understood format. Although the concepts underlying Doppler sonography are not complex, mastery of the technique requires extra training and commitment. The principal features and clinical practicalities associated with Doppler sonography are summarized in the following paragraphs. Continuous-wave Doppler is very sensitive to small vessels and has no upper velocity limit. In addition, the instrumentation is not complex and produces relatively low acoustic power. A significant drawback to continuous-wave Doppler is that there is no depth sensitivity, and thus complex structures or multiple vessels can give conflicting information. Pulsed Doppler (including duplex and color-flow) instrumentation has the capability of depth resolution and a variable sample volume. Pulsed Doppler equipment is prone to aliasing (false velocity indications) under some circumstances and also produces higher peak power levels than does continuous-wave equipment. Duplex equipment is more complex and expensive than continuous-wave equipment because the two-dimensional and Doppler modes must be synchronized in operation and display. Color-flow equipment is extremely complex and expensive. Color flow provides information of a qualitative and limited quantitative value. Absolute measurement still requires range-gate measurements. Technical and anatomic factors will affect the measured velocity profiles. Thus, it is important to fully appreciate the anatomy of the vessel and the angle between the vessel and the ultrasound beam when making quantitative measurements. Measurements that evaluate the velocity waveform and make use of ratios, such as the pulsatility index, eliminate the need for angular corrections; however, artifacts due to unappreciated anatomic or wall characteristics may lead to incorrect information if all parameters are not fully understood. Doppler sonographic measurements may be used to determine the presence of flow, determine the direction of flow, identify time-varying velocity characteristics, and detect velocity disturbances. Because flow and velocity are related, it is possible to estimate flow from velocity measurements with careful calibration and proper precautions. Velocity is related to flow, which, in turn, is related to both pressure and vascular resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Flow Velocity↗
PubMed1988

Sonographic evaluation of the fetal stomach: significance of nonvisualization.

The stomach was successfully visualized in 1051 (98%) of 1071 consecutive sonograms obtained in 995 fetuses after 14 weeks gestational age. All patients were studied prospectively. Stomach nonvisualization was associated with an abnormal outcome in 55% of the fetuses studied after 14 weeks and in 100% of the fetuses studied after 19 weeks. Fetal abnormalities included gastrointestinal and CNS malformations. Oligohydramnios was often present. The absence of a stomach on fetal sonograms obtained after 14 weeks gestational age strongly suggests fetal abnormality. Repeat sonograms should be obtained in all such cases.

Female↗
PubMed1988

Doppler ultrasound of twin transfusion syndrome.

Doppler sonography of umbilical arteries was used to evaluate eight cases of twin transfusion syndrome (TTS). Data were collected regarding the Doppler and real-time sonographic evaluation, clinical course, and outcome. In addition, the literature was reviewed. An abnormal peak systolic velocity (A) to end diastolic velocity (B) ratio, as defined by Giles et al, was seen in at least one twin in five cases. A difference in the A/B ratios between the two twins was greater than 0.4 in all eight cases. Doppler studies were able to suggest which fetus was encountering greater placental resistance, however they could not differentiate donor from recipient or provide prognostic data regarding outcome. Doppler evaluation was helpful when there was uncertainty as to whether growth discrepancy in a twin pregnancy was significant enough to suggest a pathologic state. In the future, Doppler sonography may be helpful in evaluating the effectiveness of therapy in TTS. Variable Doppler findings confirm that TTS is an extremely complex dynamic physiologic state.

Blood Flow Velocity↗
PubMed1988

Posterior urethral obstruction. Prenatal sonographic findings and clinical outcome in fourteen cases.

Fourteen cases of fetal urethral obstruction were reviewed retrospectively. The purpose of this study was to emphasize the following: 1) prenatal sonographic findings: 2) clinical outcome: and 3) associated congenital anomalies. Decreased amniotic fluid volume complicated 12 pregnancies (86%). A dilated posterior urethra was identified in nine fetuses (64%) and an enlarged bladder in 13 (93%). Evaluation of the fetal kidneys revealed hydronephrosis in 81%, increased parenchymal echogenicity in 73% and macroscopic renal cysts in 15%. There were seven live births, but only two neonates survived beyond 5 weeks. Pulmonary hypoplasia contributed to the five postnatal deaths. Associated congenital anomalies were noted at autopsy in six cases.

Amniotic Fluid↗
PubMed1987

High resolution proton NMR spectroscopy of human amniotic fluid.

Human amniotic fluid (HAF) is a dynamic system whose characteristics depend on continuous interchanges between fetal and maternal circulations. HAF reflects not only the environment of the fetus but may also provide information about fetal development or pathology. The concentration of HAF constituents varies with gestational age and pathological states. The number of the compounds currently implicated in fetal developmental pathology are relatively few. Currently used assay methods are not adequate to totally explain or predict the complex biochemistry of the fetus. The purpose of this work was to investigate HAF with NMR spectroscopy. In the present study HAF was obtained from 47 women undergoing routine amniocentesis. Cells were separated for karyological analysis and the supernatant was acid-extracted, lyophilized and re-suspended in D20 resulting in a concentration increase over native fluid. 1H NMR spectra were obtained at 360 MHz and 60 MHz. Eighteen compounds including several amino acids, were identified using parallel reference and standard addition protocols. NMR spectroscopy detected compounds of known clinical importance including glucose, leucine, isoleucine, lactate and creatinine. In conclusion, we have demonstrated that a number of physiologically relevant compounds are readily observable in HAF using 1H NMR spectroscopy. This technique can currently provide valuable information regarding HAF composition and has the potential of being used in vivo in the future.

Amniotic Fluid↗
PubMed1987

Severe polyhydramnios: incidence of anomalies.

The sonograms of 195 singleton pregnancies complicated by polyhydramnios were reviewed, and follow-up information was obtained on 191 patients. A grading system was developed that differentiated mild from severe polyhydramnios using real-time or static sonographic equipment. Mild polyhydramnios was present in 138 (71%), and severe polyhydramnios was present in 57 (29%). Previously it has been reported that 60% of cases of polyhydramnios are idiopathic and the pregnancies have a normal outcome. Twenty percent are associated with maternal abnormalities and 20% are associated with fetal anomalies. In this study, pregnancies with severe polyhydramnios had a much greater prevalence of fetal anomalies (75%) than pregnancies with mild polyhydramnios (29%). The 57 singleton pregnancies with severe polyhydramnios were analyzed in depth. Fourteen (25%) of the fetuses were normal; 43 (75%) had significant congenital abnormalities that predominantly involved the CNS, gastrointestinal tract, heart, and genitourinary tract. In all fetuses with primary CNS abnormalities, polyhydramnios was diagnosed at or before 30 weeks of gestation, while in most of the fetuses (83%) with gastrointestinal abnormalities it was diagnosed after 30 weeks. Sonographic findings correlated closely with the findings noted at birth or autopsy. In patients with severe polyhydramnios, normal sonograms were sensitive in excluding major congenital anomalies and, thus, were helpful in providing the parents with favorable prognoses. Sonograms should be performed in patients with polyhydramnios to identify congenital anomalies and to provide information regarding prognosis for fetal outcome.

Adult↗
PubMed1987

Diagnosis of autosomal dominant polycystic kidney disease in utero and in the young infant.

Autosomal dominant polycystic kidney disease (ADPKD), once thought to be a disease of the adult, is now being reported with increasing frequency in childhood. We report five cases and review eight cases from the literature of ADPKD diagnosed in the fetus or the young infant by sonographic evaluation and a positive family history. Renal enlargement (85%) was the most common and most helpful sonographic finding. Approximately 50% of the patients already had cysts large enough to detect by ultrasound. Increased renal echogenicity was present in nine of 10 cases. Although every case in this review had one parent affected with ADPKD, only five of 13 (38%) were aware of their disease prior to their pregnancy. Renal cystic disease diagnosed in the fetus and young infant should trigger an investigation of the family history and sonographic screening.

Female↗
PubMed1987

Kleeblattschadel anomaly. In utero sonographic appearance.

Four cases of Kleeblattschadel demonstrated on prenatal ultrasound examinations are reported. Five additional cases from the literature are reviewed. Sonographic features include enlarged trilobed skull, hydrocephalus, polyhydramnios, and frequent association with thanatophoric dwarfism. The most common error in diagnosis was misinterpretation of this skull anomaly as encephalocele.

Adult↗