Abdominal Transducer Research Articles

Clinical applicability of real-time, prehospital image transmission for FAST (Focused Assessment with Sonography for Trauma)

We evaluated a real-time, prehospital ultrasound image transmission system for use in focused assessment with sonography for trauma (FAST). The wireless, real-time ultrasound image transmission system comprised an ultrasound scanner with a convex abdominal transducer and a notebook computer connected to a 3 G wireless network for video data transmission. In our simulation experiment, ultrasonography was performed by emergency medical technicians (EMTs) on a human body phantom with simulated haemoperitoneum. Transmitted ultrasound video clips were randomly rearranged and presented to emergency physicians to make a diagnosis of haemoperitoneum. A total of 21 ultrasound video clips was used and 13 emergency physicians participated in the study. The sensitivity and specificity were 90.0% (95% Confidence Interval, CI, 83.5–94.6) and 85.3% (95% CI 78.4–90.7) respectively, and the accuracy of detecting abnormal ultrasound results was 87.7% (95% CI 83.8–91.6). Diagnosis of hemoperitonuem in trauma patients by an emergency physician based on the transmitted video images of FAST performed by an EMT is feasible, and has an accuracy of about 88%.

WS1.6 The need of an appropriate diagnosis of gastroesophageal reflux disease in cystic fibrosis patients: impact on clinical management

Objectives: The gastric emptying rate (GER) may be delayed in CF, but its assessment is problematic and previous CF studies have employed scintigraphic techniques which are expensive and unsuitable for routine use. We wished to assess the use of ultrasonography for this purpose, which has been validated in a non-CF population using a 3.5-MHz abdominal transducer probe measuring gastric antral size [1]. Methods: After an overnight fast, in the supine position we looked at 12 nondiabetic subjects (mean age 26 [SD 4] years, 9 male) comparing the GER in 8 pancreatic insufficient CF patients with 4 healthy controls. Subjects consumed 113mls (made up to 200mls with water) of Polycal®, a liquid energy supplement. Ultrasound measurements were made regularly over 2 hours and gastric emptying >63% at 90 minutes was considered normal. Results: There was a significant decrease in GER at 90 minutes (p = 0.04) and 120 minutes (p = 0.02) in the CF group (see table). Conclusions: Delayed gastric emptying occurs in pancreatic insufficient patients with CF and without known cystic-fibrosis related diabetes. The novel use of bedside ultrasound in this patient group will allow timely management of patients with gastro-paresis by dietary manipulation or prokinetic therapy.

WS1.5 The use of bedside ultrasonography to identify delayed gastric emptying in cystic fibrosis

Objectives: The gastric emptying rate (GER) may be delayed in CF, but its assessment is problematic and previous CF studies have employed scintigraphic techniques which are expensive and unsuitable for routine use. We wished to assess the use of ultrasonography for this purpose, which has been validated in a non-CF population using a 3.5-MHz abdominal transducer probe measuring gastric antral size [1]. Methods: After an overnight fast, in the supine position we looked at 12 nondiabetic subjects (mean age 26 [SD 4] years, 9 male) comparing the GER in 8 pancreatic insufficient CF patients with 4 healthy controls. Subjects consumed 113mls (made up to 200mls with water) of Polycal®, a liquid energy supplement. Ultrasound measurements were made regularly over 2 hours and gastric emptying >63% at 90 minutes was considered normal. Results: There was a significant decrease in GER at 90 minutes (p = 0.04) and 120 minutes (p = 0.02) in the CF group (see table). Conclusions: Delayed gastric emptying occurs in pancreatic insufficient patients with CF and without known cystic-fibrosis related diabetes. The novel use of bedside ultrasound in this patient group will allow timely management of patients with gastro-paresis by dietary manipulation or prokinetic therapy.

Shear Wave Elastography of Abdominal and Retroperitoneal Masses and Inflammatory Processes: A Feasibility Study

The purpose of the study was to evaluate the feasibility of assessment of elasticity of abdominal and retroperitoneal masses and inflammatory processes with shear wave elastography performed during sonographic examination. We evaluated with ultrasound 18 consecutive patients with adrenal and/or liver masses and abdominal inflammatory processes. Quantitative shear wave elastography was performed with Aixplorer (Supersonic) with convex abdominal transducer and/or linear one. We evaluated with supersonic shear wave elastography 16 adrenal and 5 liver masses, Crohn's disease, ulcerative colitis and inflammatory changes related to arterial graft. All the solid adrenal, liver masses and bowel inflammatory lesions showed the elasticity map. The adrenal cysts (some not obvious on B-mode imaging) did not show elasticity signal, as shear waves do not propagate through liquids. Shear wave elastography of abdominal and retroperitoneal masses and inflammatory processes is a feasible technique that can be performed during ultrasound examination and has shown some potential for differential characterization of adrenal or liver masses and inflammatory bowel diseases. Shear wave elastography may deliver the information on the extent of inflammatory abdominal processes. Further large-scale studies evaluating the possibility of differentiation and evaluation of extent of abdominal and retroperitoneal lesions using shear wave elastography are warranted.

Prenatal US evaluation of the spinal cord using high-frequency linear transducers

We illustrate the contribution of high-frequency linear abdominal transducers in the prenatal US examination of the spinal cord. After birth, such transducers are commonly used in US examination of the spinal cord. During the third trimester of gestation, the fetal spine is commonly facing anteriorly and US images of the spinal cord can be acquired using a high-frequency linear abdominal transducer. Images of the normal spinal cord, normal variants (ventriculus terminalis, cyst of filum terminale) and spinal cord abnormalities (myelomeningocele, meningocele, diastematomyelia, tethered spinal cord and caudal regression syndrome) are presented. In this pictorial essay, comparison between images acquired with low- and high-frequency transducers are provided as well as correlation with postnatal data. In the normal spine, anatomical details such as the conus medullaris, the filum terminale and the nerve root bundles are exquisitely depicted, making it possible to differentiate normal variants from abnormalities. In abnormal cases, the position of the conus medullaris, its shape and the nerve roots can be analyzed in detail. We describe the benefits of using high-frequency linear transducers in US examination of the spinal cord, which is common after birth but has not been hitherto reported in fetuses.

Sonographic evaluation of the fetal conus medullaris at 20 to 24 weeks' gestation

To determine the normal level of the conus medullaris (CM) of the spinal cord of normal fetuses at 20 to 24 weeks' gestation using abdominal sonography. Using a 4 to 8 MHz ultrasound abdominal transducer, CM was imaged in the midsagittal plane with the fetal spine facing toward the transducer. The CM ending level was located by counting the vertebrae caudal starting at T12, which was identified by lowest fetal rib. The CM locations were defined according to their positions relative to the vertebrae. One hundred and ten consecutive pregnant women were included in the study. The CM was clearly demonstrated in 78 (71%) of these cases. Most of the scanned fetuses had the CM ending height adjacent to vertebrae L2, L2-3 inter-space and L3 (73/78, 93%). The L1-2, L2, L2-3, and L3 vertebral groups did not differ in mean gestational weeks, maternal age, or fetal gender. The level of the CM can be determined at 20 to 24 weeks' gestation in about 70% of fetuses. Most of the scanned fetuses had the CM ending height adjacent to vertebrae L2, L2-3 vertebral space, and L3 (73/78, 93%). When detected lower than the third lumbar vertebra it should prompt prenatal and postnatal surveillance.

Congenital absence of the uterus known as Mayer-Rokitansky-Kuster-Hauser (MRKH) syndrome and gestational surrogacy (GS) over a 10 year period – a means to an end

OBJECTIVE: To assess whether as GS becomes more widely accepted, an increasing number of women with MRKH syndrome (incidence 1 out of 4500, absence of upper vagina & uterus with functional ovaries) will seek GS as a means to procreate. DESIGN: Retrospective analysis. MATERIALS AND METHODS: Retrospective analysis over 10 years (1999-2009) of 30 patients (ages 25-39) with MRKH syndrome using GS. After May 2005 gamete providers were subject to FDA requirements. Standard stimulation and uterine preparation protocols were used. Egg retrievals were performed transabdominally using ultrasound visualization with the vaginal probe (less cumbersome than the abdominal transducer) on the abdomen & then inserting the needle through the abdominal wall directly into the ovary and aspirating the follicles in the standard manner under ultrasound guidance. Embryos were obtained using ICSI (90%) and PGD (30%). Transfers were performed under ultrasound guidance. Luteal phase support and post transfer monitoring were performed. Clinical pregnancies were confirmed by fetal cardiac activity on ultrasound. RESULTS: From Feb 1999 to April 2009 (10 years) 30 patients with MRKH syndrome underwent 33 GS transfers. No complications from abdominal egg retrievals were reported. There were 31 fresh embryo transfers and 2 frozen embryo transfers (FET). Clinical pregnancy was confirmed in 23 out of 33 transfers (incl 2 FET) for 69% pregnancy rate. From 1999-2004 8 MRKH patients completed 8 GS cycles. From 2005-2008 17 MRKH patients completed 18 GS cycles plus 2 FET cycles. From Jan-April 2009 5 MRKH patients completed GS cycles and all 5 achieved clincal pregnancies. CONCLUSIONS: A deduction from this modest sample is, as GS has become more widely accepted, more MRKH patients are using this treatment. Even though this syndrome does not appear to be transmitted as a dominant genetic trait more research needs to be performed. In experienced hands GS is a successful option to enable MKRH patients to have their own genetic offspring.

Volume do embrião estimado pela ultra-sonografia tridimensional entre a sétima e a décima semana de gestação

to evaluate the embryo's volume (EV) between the seventh and the tenth gestational week, through tridimensional ultrasonography. a transversal study with 63 normal pregnant women between the seventh and the tenth gestational week. The ultrasonographical exams have been performed with a volumetric abdominal transducer. Virtual Organ Computer-aided Analysis (VOCAL) has been used to calculate EV, with a rotation angle of 12 masculine and a delimitation of 15 sequential slides. The average, median, standard deviation and maximum and minimum values have been calculated for the EV in all the gestational ages. A dispersion graphic has been drawn to assess the correlation between EV and the craniogluteal length (CGL), the adjustment being done by the determination coefficient (R(2)). To determine EV's reference intervals as a function of the CGL, the following formula was used: percentile=EV+K versus SD, with K=1.96. CGL has varied from 9.0 to 39.7 mm, with an average of 23.9 mm (+/-7.9 mm), while EV has varied from 0.1 to 7.6 cm(3), with an average of 2.7 cm(3) (+/-3.2 cm(3)). EV was highly correlated to CGL, the best adjustment being obtained with quadratic regression (EV=0.2-0.055 versus CGL+0.005 versus CGL(2); R(2)=0.8). The average EV has varied from 0.1 (-0.3 to 0.5 cm(3)) to 6.7 cm(3) (3.8 to 9.7 cm(3)) within the interval of 9 to 40 mm of CGL. EV has increased 67 times in this interval, while CGL, only 4.4 times. EV is a more sensitive parameter than CGL to evaluate embryo growth between the seventh and the tenth week of gestation.

OP19.11: The distance between fetal umbilical cord insertion and symphisis pubis In utero indication for congenital bladder extrophy

Congenital Bladder Extrophy (CBE) is a severe and rare malformation never diagnosed at early second trimester. Our aim was to measure the distance between fetal Umbilical Cord Insertion (UCI) and the Symphysis Pubis (SP) in order to enhance fetal diagnosis of CBE. A prospective cross sectional study was performed on normal singleton pregnancies between 13 to 23 weeks gestation. The distance between the fetal UCI and SP was measured in a mid sagittal plain using an high resolution transvaginal and trans abdominal transducers. Adequate measurements were obtained in 150 fetuses. The distance of between fetal UCI to SP was found to have good correlation with gestational age and was expressed by regression equations and correlation coefficient, were found to be highly statistically significant (P < 0.0001). The normal mean (+/− SD) for each gestational week was defined. In two fetuses one in 14 wks' and the other in 22 wks' in whom no bladder could be visualized although the kidneys appeared normal the UCI to SP distance was found below the 5 percentile for gestational age. The present data contribute significantly to the inutero diagnosis of CBE.

The value of doppler ureteral jets evaluation by Doppler ultrasonography in upper urinary lithiasis

Introduction: The aim of our study was to asses the importance of ureteral flow analysis by Doppler ultrasonography in upper urinary tract lithiasis. We analyzed the particularities of the ureteral flow in order to find its place in the diagnostic algorithm of lithiasis. Method: Between January 2005 and January 2008, we examined 500 patients with upper urinary tract lithiasis and a number of 53 healthy volunteers. We used a General Electric 400MD device, with a 3.5MHz abdominal transducer and a 10MHz rectal transducer. Also, we used a Kretz Voluson 730 device, with 3D transducer. The ureteral flow recording was performed using the Doppler module, and the flow velocity was determined using the Pulse Doppler module. In all patients, we evaluated the renal vascularization and we calculated the resistive index (RI) as an intrarenal pressure indicator. Results: 365 patients (73%) presented hydronephrosis (stage I-III). In 63 of these cases, a weak flow was observed on the obstructed ureter, with a flow velocity 50% slower than on the opposite side. In 302 patients, a ureteral flow could not be observed. In 286 of these patients a normal contralateral flow was visible. 354 patients with hydronephrosis presented RI greater than 0.7. 135 patients had no hydronephrosis and RI was below 0.7. Conclusion: The ureteral flow analysis, both morphological (shape, dimensions) and dynamical, may be a useful addition to the diagnostic armamentarium of the upper urinary tract lithiasis. Doppler ultrasonography may offer useful information regarding the renal function and may also help establishing the surgical indication.

Training, certification and CME in obstetric ultrasound scan in Europe

In the course of the last 20 years, ultrasound has become a dominant technology in the daily practice of obstetrics and gynecology. Except for women living in rural outposts in underdeveloped countries, there is hardly a pregnant woman in the world who does not have at least one ultrasound and there are many who have five, ten or more ultrasound examinations. In some countries this is part of a structured, determined screening program, entitling every woman to one or two, sometimes three, ultrasound examinations, specifically for the purpose of finding fetal malformations and considering the option to terminate pregnancies should the malformation found on ultrasound be severe enough. In other countries, ultrasound in pregnancy is almost entirely left to the forces of the free market that happened to position themselves in that niche by buying equipment and offering their services, whether for the detection of malformations or just for the fun of watching the fetus on “baby TV”. Large regional differences in the uptake of ultrasound and in the quality of diagnosis have been observed in multicenter studies such as the Eurocat study [1]. Only a few years ago, ultrasound units in maternity hospitals were sinister dark rooms where dedicated eccentrics practiced the dark art of deducting information from the mysterious patterns of grey and black shown on their screens. Now, ultrasound machines are everywhere. There are ultrasound machines in the delivery and operating rooms, on the wards and in the outpatient units. Next to every obstetrical and gynecological chair is an ultrasound machine, usually with Doppler and color options, invariably with transvaginal and abdominal transducers. Most of the training in ultrasound is “learning by doing”—the more experienced junior doctor showing the young colleague where the knobs and switches are and encouraging him—or her—to just go ahead and scan. This is where the problems begin: in obstetrical and gynecological ultrasound, we have apparently accepted a chaotic autodidactic training system that would not be tolerated in air traffic control, cytology screening programmes or radiological breast cancer screening mammography programmes. All these occupations deal with pattern recognition—and decisions based on the interpretation of these patterns have wide-ranging consequences. As every teacher and parent knows, bad habits are acquired fast and unlearned very slowly. On the other hand, hands-on training in ultrasound is incredibly time-consuming and boring.

Investigation of the effect of subcutaneous fat on image quality performance of 2D conventional imaging and tissue harmonic imaging

Tissue harmonic imaging (THI) has been reported to improve contrast resolution, tissue differentiation and overall image quality in clinical examinations. However, a study carried out previously by the authors ( Browne et al. 2004) found improvements only in spatial resolution and not in contrast resolution or anechoic target detection. This result may have been due to the homogeneity of the phantom. Biologic tissues are generally inhomogeneous and THI has been reported to improve image quality in the presence of large amounts of subcutaneous fat. The aims of the study were to simulate the distortion caused by subcutaneous fat to image quality and thus investigate further the improvements reported in anechoic target detection and contrast resolution performance with THI compared with 2D conventional imaging. In addition, the effect of three different types of fat-mimicking layer on image quality was examined. The abdominal transducer of two ultrasound scanners with 2D conventional imaging and THI were tested, the 4C1 (Aspen-Acuson, Siemens Co., CA, USA) and the C5–2 (ATL HDI 5000, ATL/Philips, Amsterdam, The Netherlands). An ex vivo subcutaneous pig fat layer was used to replicate beam distortion and phase aberration seen clinically in the presence of subcutaneous fat. Three different types of fat-mimicking layers (olive oil, lard and lard with fish oil capsules) were evaluated. The subcutaneous pig fat layer demonstrated an improvement in anechoic target detection with THI compared with 2D conventional imaging, but no improvement was demonstrated in contrast resolution performance; a similar result was found in a previous study conducted by this research group ( Browne et al. 2004) while using this tissue-mimicking phantom without a fat layer. Similarly, while using the layers of olive oil, lard and lard with fish oil capsules, improvements due to THI were found in anechoic target detection but, again, no improvements were found for contrast resolution for any of the layer combinations. Therefore, it was felt that the lack of improvement in contrast resolution performance may be due to the test phantom design and not to whether a layer was present that caused beam distortion and phase aberrations. (E-mail: jacinta.browne@dit.ie)

The Complexity of a “Complex Mass” and the Simplicity of a “Simple Cyst”

ynecologic sonography has made considerable strides in the last 20 years. Initially, the resolution of abdominal transducers increased. Then transvaginal probes were introduced, were perfected, and have become the principal tools for evaluating the female pelvis. Correlations of sonographic images with pathologic findings have led to a substantial understanding of adnexal abnormalities. In fact, you could say, the field collectively has a learning curve just as individuals have a learning curve. The development of scoring systems to characterize and define ovarian lesions first based on morphologic characteristic and later including color Doppler flow data brought us closer to a relatively reliable distinction between benign and malignant lesions or at least a negative predictive value in the range of 97% to 99%.1–3 Despite the above achievements, it is disheartening to see today some gynecologic sonographic reports that may have been appropriate 20 years ago when resolution was more limited, as was our field’s level of understanding. We frequently see, in reports of a gynecologic patient, the wording “a left adnexal complex mass measuring 4 × 5 × 4 cm was seen.” We desperately look for a more detailed description of the finding—in vain, because there is none. Then we search for the results of a Doppler study of the vessels in or around the finding. Again, none are reported. The most alarming message comes at the end of the report in the paragraph entitled “Impression,” where we see a long list of differential diagnoses, which invariably end with the statement, “. . . ovarian malignancy cannot be ruled out.” Looking at the pictures on which these reports are issued, we can often see benign-appearing adnexal lesions such as corpora lutea, cystic teratomas, endometriomas, and even simple cysts. Much of the time, however, the diagnosis can be made with a great deal more accuracy than the clinician is currently getting. We agree that not all hemorrhagic corpora lutea, endometriomas, or benign cystic teratomas are “classic” in their sonographic appearance, but most of them are distinctive enough. Therefore, this practice of giving a differential diagnosis that includes virtually every adnexal abnormality is no longer appropriate. As a field we can do better—most of the time. What should the referring provider do reading such a report? When the adnexal mass was detected at the palpatory examination, the gynecologist knew all too well the differential diagnoses pertaining to this mass, including the possibility of cancer. The patient was sent for the sonographic scan for help in the diagnostic process, not for the purpose of reading the list of diagnoses the gynecologist knew in the first place. Imaging laboratories can and should do better much of the time.

Change in Differential Diagnosis and Patient Management With the Use of Portable Ultrasound in a Remote Setting

Physicians practicing in remote areas are typically limited in their choice of diagnostic tools. The goal of this study was to determine whether the use of a portable ultrasound (US) device on selected patients in a remote setting would alter physician diagnosis and management. This was a prospective observational study of the affects of US on physician decision making deep in the Amazon jungle. A battery-operated Sonosite 180 Plus with 2 interchangeable transducers (4-7-MHz broadband intercavitary transducer and 2-5-MHz broadband abdominal transducer) was used. The patient population consisted of local tribal people. Two of the physicians on the team performed all US examinations. Team physicians requesting US examinations filled out a survey before and after the US examination. Before the US, the referring physician filled out a survey describing the patient's initial complaint, pertinent past medical history and physical findings, and an initial (pre-US) differential diagnosis and planned treatment with expected disposition. After the results of the US were reviewed with the referring physicians, the doctors were asked to fill out the remainder of the survey, allowing comparison of pre- and post-US differential diagnosis, treatment plan, and disposition. A total of 25 US studies were performed during this study (1 trauma US scan, 6 hepatobiliary studies, 5 transabdominal pelvic scans, 7 transvaginal pelvic studies, 3 renal studies, and 3 abdominal aortic scans). The monitor on the US unit experienced a rare failure shortly after being used at 17,000 ft and then 10 times at sea level, and no further US scans could be performed. US scan results dramatically altered the disposition of 7 patients, including 4 patients who avoided a potentially dangerous 2-day evacuation to more definitive medical care. Three patients were found to need rapid referral to the nearest clinic for surgical evaluation. When used in a remote location, portable US provides a significant benefit that can dramatically alter disposition and treatment.

Abdominal pregnancy: ultrasound diagnosis aided by the balloon of a Foley catheter

Abdominal pregnancy: ultrasound diagnosis aided by the balloon of a Foley catheter

Reliability of adnexal mass mobility in distinguishing possible ectopic pregnancy from corpus luteum cysts

Study objectives: Pelvic ultrasonography for ruling out ectopic pregnancy is one of the most common emergency ultrasonographic applications but may be frustrating when a potential ectopic mass cannot be differentiated from a corpus luteum cyst. An adnexal mass adjacent to an ovary that fails to move independently from the ovary under sonographic palpation is thought unlikely to be an ectopic. We evaluate the utility of pelvic mass separation from adjacent ovary as an indicator of mass identity (corpus luteum versus other) in ruling out ectopic pregnancy. Methods: This was a retrospective quality assurance review of all pelvic ultrasonographic studies on first-trimester complication patients treated during an 18-month period at an academic Level I emergency department with hospital-based emergency ultrasonographic credentialing. All pregnant patients presenting with signs or symptoms suspicious for ectopic pregnancy were scanned when credentialed faculty were available. Each ultrasonographic examination was videotaped in entirety per department policy. When no intrauterine pregnancy was seen and an adnexal mass that was suspicious for either corpus luteum or an ectopic pregnancy was encountered, sonologists attempted to separate the mass from the ovary with abdominal palpation and endovaginal transducer movement. All such scans were reviewed by the ultrasonographic director and assistant director. A database recorded results of attempts to separate masses, quantitative β–human chorionic gonadotropin findings on follow-up, and final outcome. Patients for whom data were incomplete or inaccurate or follow-up records were missing were excluded from analysis. Separation of mass and ovary was defined as movement of the mass away from the ovary, sliding past the ovary, or rotation past the ovary. Statistical analysis included descriptive statistics, agreement analysis, sensitivity, specificity, negative and positive predictive value, and 95% confidence intervals (CIs). Results: Agreement between the reviewers was excellent for mass separation (κ=0.9). For 2 patients, records were inaccurate, and the patients were not pregnant on blood testing. A total of 63 patient scans fit the criteria when an ectopic pregnancy could neither be ruled in or out and a mass was present directly adjacent to the ovary and was not clearly identified as an ovarian cyst. Of these, 19 (30%) were ectopic pregnancies on final diagnosis, 13 (22%) were live pregnancies, and 31 (48%) were miscarriages. Among the 41 patients for whom there was no separation of mass and ovary, the final diagnosis was ectopic pregnancy in 2 (5%) patients. Lack of mass and ovary separation yielded a sensitivity of 95% (95% CI 67% to 99%) and a specificity of 77% (95% CI 55% to 92%) for ruling out an ectopic pregnancy. The negative predictive value of no mass and ovary separation was 88.7% (95% CI 66.9% to 98.7%) for the presence of an ectopic pregnancy. Separation of the mass and ovary yielded a sensitivity of 77% (95% CI 55% to 92%) and a specificity of 95% (95% CI 83% to 99%) for an ectopic pregnancy. The positive predictive value of mass separation from the ovary was 89% (95% CI 67% to 99%) for an ectopic pregnancy. Conclusion: Although frequently taught as a definitive diagnostic maneuver, lack of separation of an adjacent mass and ovary does not preclude the mass from being an ectopic pregnancy. However, according to the negative predictive value, lack of separation of mass and ovary makes it unlikely that the mass is an ectopic pregnancy and may help in risk stratification.

ABC of antenatal care. Abdominal pain in pregnancy.

Inevitable miscarriage. Pain in the stomach brings a woman to her doctor's surgery early, especially when she is pregnant. In most such cases the problem is not serious, but all cases need careful assessment as some women will need an immediate opinion at the hospital, some can wait till the next day, and others can wait till the next antenatal clinic. Abdominal pain is diagnosed mostly by clinical means. The history and examination are most important, investigations being less helpful than in other branches of medicine. The use of ultrasonography by clinical gynaecologists has considerably improved the understanding of pelvic pathology. A vaginal transducer may give better images in early pregnancy than abdominal transducers; however, the laparoscope is still a major investigative tool for lower abdominal pain in early pregnancy. Under appropriate anaesthesia a good view of the pelvis and its organs clinches a diagnosis; in some cases treatment is also possible at the same time. Pain arises either from inside an organ, involving the covering visceral peritoneum or from later involvement of the parietal peritoneum. The visceral aspects of the pain are poorly localised as they are mediated by the autonomie nervous system. Once the parietal peritoneum is affected, however, impulses travel by the somatic route and localisation may be more specific. Nausea and vomiting occur early in many pelvic conditions as well as in normal pregnancy, which might confuse the picture. Abdominal distension is not usual unless the alimentary tract is involved secondarily; furthermore, it is masked in mid and late pregnancy by the enlarging uterus. Shock may occur if acute pain is accompanied by sudden deterioration in the woman's condition such as in real hypovolaemia due to blood loss at a ruptured ectopic pregnancy or in relative hypovolaemia after excessive autonomie stimulation from peritoneal irritation of an abruptio placentae. For the sake of analysis, in this article the commoner causes of abdominal pain in pregnancy are considered as occurring in either late or early pregnancy, but some conditions can occur in both. The causes will be considered under only one heading, which does not mean, however, that they do not occur in the other half of pregnancy.

Calibration of respiratory induction plethysmography (Respitrace) in infants.

To determine whether the recently increased sensitivity of the variable frequency oscillator and the use of separate rib cage and abdominal transducers made calibration of the Respitrace system easier, we performed 106 different calibration procedures against a pneumotachygraph in 36 normal infants, 41 using 2 separate periods of quiet sleep, 49 using quiet and REM sleep, and 16 using 2 separate periods of REM sleep. When the calibration was done using 2 separate periods of quiet sleep, or using periods of quiet and REM sleep, a change of at least 50% in the amplitudes of both the abdominal and rib cage signals between the 2 sleep periods, gave accurate calibration factors in 92%, compared with only 30% when the amplitude of either signal changed by less than 50%. Calculation of the calibration factors can be done either by the least squares method or by solving simultaneous equations with no significant difference between the results.