Ultrasound in obstetrics: do the published evaluative studies justify its routine use?

A review of surveys assessing the use of ultrasound in obstetrics was undertaken to determine why this examination has spread so rapidly. Seven randomized controlled trials (RCTs) published to date as well as 182 papers published in four obstetric journals between 1979 and 1984 were reviewed. The value of routine ultrasound scanning to improve the diagnosis of intrauterine growth retardation or gestational age was demonstrated in the RCTs, but the results of the RCTs measuring the effects on health of this screening procedure did not give strong evidence for its routine use. Of the 182 papers identified, 137 were related to the diagnostic assessment of ultrasound, 14 concerned the effects on medical practice and only nine papers studied the effects of ultrasound scanning on health. Most of these 137 papers came out in favour of this procedure. Thus the spread of ultrasound scanning was based mainly on evaluative surveys which assessed its diagnostic value.

A case-control study of risk factors for hepatoblastoma. A report from the Childrens Cancer Study Group

Parents of 75 children with hepatoblastoma, registered with the Childrens Cancer Study Group, and 75 age-matched controls, who had been identified through random digit dialing were interviewed. No evidence was found to support the primary study hypotheses relating to hepatitis infection, maternal estrogen exposure, alcohol consumption, smoking, or potential sources of nitrosamines. Case mothers were more likely to report occupational exposure to metals (odds ratio [OR] = 8.0, P = 0.01), petroleum products (OR = 3.7, P = 0.03), and paints or pigments (OR = 3.7, P = 0.05). Metal exposures were commonly to welding or soldering fumes, and most occurred daily, before and during the index pregnancy. Petroleum product exposures were predominantly to lubricating oils or protective greases. The only significant paternal exposure was to metals (OR = 3.0, P = 0.01) and the risk with exposure to petroleum products was marginally significant (OR = 1.9, P = 0.06). These findings provide further evidence that occupational exposures may increase the risk of cancer in offspring.

Ultrasound guided transrectal core biopsies of the palpably abnormal prostate

Ultrasound imaging and ultrasound guided transrectal core biopsies were performed in 251 consecutive men with abnormal prostates on digital rectal examination. A hypoechoic defect on ultrasound was identified in 227 of 251 patients (90 per cent) corresponding to the area of palpable nodularity or abnormal firmness. A mean of 6.25 biopsies were obtained per patient using a commercially available spring-loaded gun. Biopsies were positive for cancer in 165 of the 251 prostates (66 per cent). Palpable nodules more often were hypoechoic and more often contained cancer than less distinct areas of abnormal firmness on digital examination. Among the clinical stages B1, B2 and B3 nodules 70, 76 and 88 per cent, respectively, were positive for cancer, as were 100 per cent of the clinical stage C prostates. Of 77 abnormally firm, nonnodular prostates 36 per cent were positive for cancer. Random biopsy of the contralateral normal lobe in 56 men with clinical stage B1 or B2 nodules showed cancer present contralaterally in 42 and 60 per cent, respectively; 20 per cent had positive biopsies despite a contralateral isoechoic ultrasound. In 78 patients with prior digitally guided biopsies, ultrasound guided biopsies confirmed previously diagnosed cancers in 94 per cent. However, in 23 of 43 patients (53 per cent) with previous negative digitally guided biopsies, ultrasound guided biopsies made the new diagnosis of cancer. Complications, including post-biopsy fever and bleeding, occurred in 6 of 251 patients (2.4 per cent). The combination of the new spring-loaded biopsy guns and transrectal ultrasound guidance of biopsies provides the urologist with a tool that allows multiple prostate cores to be obtained safely and painlessly, reducing the sampling error and increasing the accuracy in diagnosing prostate cancer in the man with a palpable abnormality of the prostate.

[Physical and biological effects of ultrasound in diagnostic conditions--a review]

Ultrasound waves spread in the body in changing the acoustic pressure in a high frequency causing heat production or acoustic cavitation. There are many adverse effects known in cell cultures or in animals. Epidemiologic studies showed no evidence at the present time that ultrasound causes any biological effects in human subjects. Therefore further observations, especially of new applications are necessary.

Intermittent fetal bradycardia induced by midpregnancy fetal ultrasonographic study

Fetal bradycardias were observed during fetal ultrasonographic and echocardiographic studies performed in the second trimester of pregnancy. The episodes of bradycardia were brief and recovery was usually rapid. Ultrasound transducer pressure applied to the maternal abdomen during the study provoked the phenomenon. Vagal discharge resulting from an increase in intrauterine pressure appeared to be the causative mechanism.

Evaluation of the bioeffects of prenatal ultrasound exposure in the cynomolgus macaque (Macaca fascicularis): I. Neonatal/infant observations

The frequency of use of ultrasonography for evaluating the developing embryo/fetus has continued to rise although the possible risks from exposure still remain uncertain. The cynomolgus macaque (Macaca fascicularis) is currently being used in our laboratory as a model to assess these risks. In utero exposure was performed utilizing a commercial real-time mechanical sector scanner with a 7.5 MHz scanhead (ATL, MK 600). Maximum acoustic power output for this unit is as follows: I(SPTA) = 12.0 mW/cm2, I(SPPA) = 98 W/cm2, and Im = 137 W/cm2. Animals exposed to ultrasound (N = 16) were scanned five times weekly on gestational days (GD) 21-35 +/- 2 for 10 minutes/exam (m/e), three times weekly on GD 36-60 +/- 2 for 10 m/e, and once weekly on GD 61-150 +/- 2 for 20 m/e. Controls (N = 14) were "scanned" with the unit placed on standby. Assessment of simian Apgar scores at 1, 5, and 10 minutes of life revealed higher scores for treated animals at 10 minutes (P less than or equal to 0.045); greater scores in muscle tone (P less than or equal to 0.013) and color (P less than or equal to 0.016) were observed. Evaluation of morphometrics at birth including weight, biparietal diameter, occipitofrontal diameter, head circumference, hand and foot lengths, humerus and femur lengths, arm circumference, chest circumference, tail length, skinfold thickness, and crown-rump length (CRL) indicated a significant reduction in only two parameters, birth weight (P less than or equal to 0.027) and CRL (P less than or equal to 0.033). Hematologic analysis at 2 +/- 1, 9 +/- 1, and 16 +/- 1 days of life revealed a significant difference in white blood cell counts (WBCs). Treated animals displayed lower WBCs with reductions in numbers of segmented neutrophils and monocytes at all ages observed. Hematologic differences were not significant by 5-6 months of age. No abortions, gross malformations, or stillbirths were observed in the exposed animals.

Diagnostic ultrasound equipment. Safety and dosimetry

A survey of present opinions on the safety of diagnostic ultrasound applications is presented together with some data on output levels. Physical mechanisms involved in potential adverse effects are described. Labelling requirements of the equipment are defined and specified. These requirements are contained in a recent proposal of the Netherlands' Committee on the Safety of Ultrasound.

Evaluation of the bioeffects of prenatal ultrasound exposure in the cynomolgus macaque (Macaca fascicularis): II. Growth and behavior during the first year

The extensive use of ultrasonography for the prenatal assessment of growth and development continues to present questions regarding biological effects. We are currently evaluating a nonhuman primate model (Macaca fascicularis) exposed to ultrasound from gestational day (GD) 21 to 152 +/- 2. Exposures were performed with a commercial real-time sector scanner (ATL, MK 600); animals were scanned five times weekly on GD 21-35 +/- 2, three times weekly on GD 36-60 +/- 2, and once weekly on GD 61-150 +/- 2. The length of exposure was approximately the same as human exposure (GD 21-60 +/- 2 = 10 min/exam and GD 61-150 +/- 2 = 20 min/exam) although the frequency of the examinations was considerably greater. Initial reports indicated differences between control and treated animals including lower birth weight, higher simian Apgar scores, and changes in select hematologic parameters. Follow-up evaluations of growth during the first year included measurements of body weight, hand and foot lengths, humerus and femur lengths, biparietal and occipitofrontal diameters, head circumference, arm circumference, chest circumference, skinfold thickness, and crown-rump length. Results indicated a significant reduction in body weight in treated animals during the first three months, with nonsignificant differences during the following nine months. Hematologic analysis including complete blood counts (CBC) and clinical biochemistry at 6, 9, and 12 months of age were not significantly different. A series of behavioral evaluations including a neurobehavioral test battery (NBT) and tests assessing motor and cognitive skills were included. The NBT revealed increased muscle tone in treated animals at one, two, and four days. In an observation cage (week 1-14) more quiet activities were displayed by treated animals. Group differences in performance of motor and cognitive tasks were observed and may be attributable to agitation and difficulties in adjusting to test environments. There were no group differences observed in discrimination learning. When considering the possible implications to the human population, it is important to consider the amount of exposure these animals received, and the fact that most of the effects observed appeared to be transitory. Although human epidemiological studies have not revealed any significant bioeffects, the "prudent use" of diagnostic ultrasound should still be kept in mind. This is especially significant with the current rise in the use of endovaginal scanning and pulsed Doppler.

Carbamazepine-induced hyponatremia after transabdominal follicular ultrasound examination

We report a serious complication after transabdominal follicular ultrasound monitoring in a patient taking CBZ for a chronic seizure disorder. She developed severe hyponatremia after a large volume of water intake for bladder filling before her scan. We recommend the use of transvaginal US scans in such patients or as an alternative to the transabdominal approach in all patients, since we have found good patient tolerance and excellent pelvic organ visualization without the need for bladder filling.

Percutaneous fetal umbilical blood sampling: procedure safety and normal fetal hematologic indices

Percutaneous umbilical blood sampling allows direct access to the fetal circulation. We describe our experience with the procedure in the first 100 patients whose fetuses were at risk for hemolytic anemia, chromosomal abnormalities, coagulopathy, or intrauterine infection. Hematologic indices, including hemoglobin, hematocrit, red blood cell count, white blood cell count, and platelet count, were analyzed from 50 of the fetuses who were normal at delivery. Normal values and gestational age regression curves (from 17 to 37 weeks' gestation) are presented. The technique and complications of the procedure are described. Percutaneous umbilical blood sampling affords useful information in prenatal diagnosis and entails a low rate of complications.

Ultrasound scanning of post-operative wounds--the risks of cross-infection

Ultrasound scanning of surgical wounds is an established procedure for the detection of abscesses. The possible risks of cross-infection resulting from this technique were examined by testing the sterility of the ultrasound probes, the coupling gel and the stand-off medium Kitecko (3 M). The coupling gel was also assessed for any bactericidal properties. Sixty-six per cent of swabs taken from machines in constant use and 33% of the total number of swabs taken were contaminated with skin flora including Staphylococcus aureus. Sterility was achieved using a 70% alcohol wipe. The coupling gel was inherently sterile but had no bactericidal action. The solid stand-off medium Kitecko grew Enterobacteriaceae and Pseudomonas species. The implications of these findings in relation to scanning post-operative wounds are discussed.

In utero exposure to diagnostic ultrasound: a 6-year follow-up

A 6-year follow-up study of height and weight was conducted between 1975 and 1983 in a total of 149 sibling pairs of the same sex, one of whom had been exposed to diagnostic ultrasound in utero. The data were analyzed for the entire sample group, as well as for subgroups defined by sex, gestational age at delivery, birth order, and gestational age at time of first exposure to ultrasound. No statistically significant differences of head circumference at birth or of height and weight between birth and 6 years of age were found between ultrasound-exposed and unexposed siblings. In our sample population, exposure of fetuses to ultrasound did not significantly affect growth in childhood up to 6 years of age.

Does exposure of preovulatory oocytes to ultrasonic radiation affect reproductive performance?

Ultrasonography of preovulatory oocytes has been reported to lead to reduced litter size in rats. Because of the growing popularity of ultrasound-guided follicular aspiration in human in vitro fertilization programs, further study of ultrasonic radiation's effect on the preovulatory oocyte is warranted. We used 106 virgin Sprague-Dawley rats which, on the evening of proestrus, received ultrasonic radiation of sham treatment after the onset of the luteinizing hormone (LH) surge. No differences were found between control (C) and experimental (US) animals in pregnancy rate, number of corpora lutea, implantations, pups, and mean pup and placental weights at autopsy on day 22 of pregnancy. Ultrasonic radiation applied to meiotically active, preovulatory oocytes did not affect the reproductive performance of these rats.

Epidemiology of human exposure to ultrasound: a critical review

Epidemiologic studies and surveys and widespread clinical usage over 25 years have yielded no evidence of any adverse effect from diagnostic ultrasound. Nonetheless, the inability to find convincing proof of an effect, either from epidemiology or from physicians' experience, does not preclude the possibility of it happening. Statistical reasoning shows that even with large population studies, it is difficult to identify a small increase in the rate of a commonly occurring event. Subtle effects, long-term delayed effects, and certain genetic effects, could easily escape detection.