Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5817_Библиотеки_им_академика_М_И_Перельмана-1.pdf
2
84
blubber
7 The Role of Doppler Ultrasound in the Diagnosis
of Ectopic Pregnancy
In the prospective, risk-oriented care of early pregnancy it is axiomatic to think of an ectopic implantation (think ectopic) until an intact intrauterine gestation has been demonstrated. Hence exclusion of an abnormal early gestation becomes the essential diagnostic goal of the first 10 weeks of pregnancy, i. e., before
3-point screenings can be instituted.
The early detection of an ectopic pregnancy has been
advanced by three basic recent developments:
1. The development of highly sensitive rapid determinations of human chorionic gonadotropin (β-hCG),
2. Improved resolution by transvaginal sonography,
3. The capability of using transvaginal color Doppler
sonography to examine extrauterine structures suspected of containing chorionic material.
The Significance of Transvaginal Sonography and Serum hCG
A number of studies agree that an ectopic pregnancy
can be detected by transvaginal sonography in 80−95 %
of cases. In these cases β-hCG levels were 6500 mIU/
mL or above. These findings lead to the conclusion that
in asymptomatic patients, when the serum β-hCG level
exceeds 6500 mIU/mL with no evidence of intrauterine
gestational material an ectopic pregnancy must be suspected. Further diagnostic studies must be performed
to confirm or exclude the diagnosis.
All patients should have transvaginal ultrasonography performed routinely in early pregnancy. Early diagnosis clearly reduces maternal risk by diagnosing ectopic pregnancy early and provides a better chance to
use laparoscopic intervention and avoid organ damage.
Such a precaution is particularly mandatory in patients
with a diagnosis of sterility or chronic relapsing inflammation, patients fitted with intraunterine devices
(IUDs), and of course women with a prior ectopic pregnancy.
Obstetric Applications of Doppler Ultrasound
Characteristic Sonographic Findings in Ectopic Pregnancy
Currently, in the presence of a positive pregnancy test,
the following transvaginal sonographic findings are
considered to be diagnostic or at least strongly suspicious of an early ectopic pregnancy:
1. Exclusion of an intrauterine gestational structure,
2. An extrauterine structure suggesting a gestational
sac,
3. The sac shows signs of cardiac activity and movement (frequency 쏝5 %),
4. The uterus is enlarged and the endometrium is
thickened and hyperechoic,
5. There is free fluid with clotting and fibrin strands in
the space of Douglas and in the pericolic recesses
(hemoperitoneum).
As the number of these coincidental or associated factors increases, it becomes more likely that the suspected diagnosis is correct.
Differential Diagnosis
Differentiating an ectopic pregnancy that is not intact
from an adnexal tumor is difficult, since the amniotic
cavity cannot always be clearly delineated from a
partly cystic, partly solid tumor. In such cases diagnosis
must be based on clinical symptoms and serial β-hCG
readings.
blubber
A pseudogestational sac seen on abdominal sonography, hence previously considered characteristic of ectopic pregnancy, may no longer appear on vaginal
sonography because of its improved resolution. If a
ring structure is seen in the uterine cavity by the vaginal route, the differential diagnosis rests between a
85
The Role of Doppler Ultrasound in the Diagnosis of Ectopic Pregnancy
86
2
threatened and an incomplete abortion, especially if
accompanied by bleeding.
Without doubt the use of improved ultrasound
methods increases the success of preoperative diagnosis. The most recent advance is the use of color Doppler
ultrasound, in an attempt to attain better differentiation of possible extrauterine gestational structures by
Transvaginal Color Doppler Ultrasound
As transvaginal color Doppler sonography spread, publications began to appear in 1990 defining the characteristics of blood circulation during early placentation.
The typical Doppler signal from the peritrophoblastic
region is characterized by a high systolic flow velocity
and low impedance, i.e., a high diastolic flow velocity.
This leads to the conclusion that there is a high pressure gradient between the maternal arteries and a perfusion space with low pressure, the intervillous space.
Physiologically, the histomorphological correlate to
this physiological event can be found in the maternal
vessels at the site of placental implantation.
In ectopic implantation corresponding phenomena
of early placentation can be demonstrated until they
are outweighed by the limitations posed by the abnormal nidation site. These induce regressivechanges that
terminate the perfusion, unless an acute event such as
abdominal pain caused by the rupture of the fallopian
tube emerges first.
After implantation of the blastocyst in the tubal mucosa, the trophoblast infiltrates the lamina propria of
the mucosa and the muscular layer. It grows primarily
between the tubal lumen and the serosa in a circular
and longitudinal direction. The vasotropic growth and
invasion of the surrounding vessels, i.e., branches of
the uterine and ovarian arteries, lead to intensified
blood flow and/or intrauterine and extrauterine bleeding. Hence only an ectopic pregnancy leads to a reduction in the normal pulsatile blood flow and high perfusion resistance in the area of the tube. These hemodynamic changes can be displayed by color Doppler ultrasound in a properly targeted examination. Certainly
the resistance changes can only be displayed by pulsed
Doppler ultrasound, but this examination does not
show the vessel directly and so wastes time and is
beset with uncertainties. Thus, it is hardly practical
when time is short. A color Doppler serves as a rapid
and precise “probe” in such cases. When a suspicious
anatomical structure is located in the pelvis by vaginal
sonography, a color display provides more extensive
information about the hemodynamics, permitting
selective display of flow waveforms and their analysis
by indices.
their increased vascularization and their characteristic
peritrophoblastic blood flow patterns.
Nevertheless, in clinical settings ectopic pregnancy
continues to pose daily diagnostic and therapeutic
challenges, both in asymptomatic and symptomatic
cases.
Diagnostic Validity
An analysis of the diagnostic validity of actual methods
used to determine ectopic pregnancy showed that the
diagnostic power of transvaginal sonography could be
enhanced from 84−95% to 87−96 % by supplementation with color Doppler ultrasound. This seems to be a
small effect, and when the conditions under which the
studies were performed are compared it is difficult to
see a convincing advantage.
Of unequivocal relevance in daily practice is the certainty with which laparoscopy can be positively indicated when ectopic pregnancy is suspected. A comparison between the preoperative suspected diagnosis
and the actual findings clarifies the rate of true positive
cases (TP) to false positives (FP). A true validation is
impossible, because true negative cases do not lead to
laparoscopy, while false negatives only b ecome apparent after a clinical lag period, so that they lead only
to secondary indications for intervention. This includes
the admittedly quite common course in which the mucosa sloughs, leading to the assumption of an interrupted early intrauterine pregnancy (incomplete or
threatened abortion), but with missing evidence of
trophoblasts in the sloughed membrane. They also include complete early abortions, but also primary
missed ectopic implants and finally the not uncommon
case of a regressive, poorly vascularized ectopic implantation. When the extent of the vascularization in
relation to trophoblastic activity as measured by the
serum hCG level is examined, a statistical correlation is
found between avascularity and a low hCG level of less
than 6000 mIU/mL. Also excluded from validation studies are emergency conditions (acute abdomen, shock)
that demand immediate action without comprehensive diagnostic studies.
Effectiveness of the Procedure
We were able to examine the robustness of the indications for laparoscopy for ectopic pregnancy by carrying
out a comparison of chart reviews.
The study included 263 patients who had undergone
laparoscopy during four years prior to the introduction
blubber
Transvaginal Color Doppler Ultrasound
Tab. 7.1 Specificity of diagnosis in ectopic pregnancy with and without color Doppler
Diagnosis without color Doppler Diagnosis with color Doppler
True positive 241 cases 91.6% True positive 57 cases 95%
False positive 22 cases 8.4% False positive 3 cases 5%
Partial/total torsion of stalk
with large corpus luteum of pregnancy 4
Large hemorrhagic corpus luteum 7 Early abortion, corpus luteum 1
Early abortion, corpus luteum 7 Early pregnancy, not detected 1
Early pregnancy, not detected 4
Positive predictive value 91.6% Positive predictive value 95%
Early abortion, hemorrhagic corpus luteum 1
of color Doppler transvaginal sonography. These were
contrasted with an analysis of 60 patients who, in the
course of one year, had been diagnosed with color
Doppler ultrasound as the principal diagnostic tool.
7.1
F
The results of the study are reproduced in
and Table
7.1.
igure
The improvement in the positive predictive value of
the examination from 91.6% to 95 % suggests that confidence in the indication increased slightly. The rate of
FP diagnoses decreased correspondingly from 8.4% to
5%, a minor improvement. Critical analysis shows that
the causes of erroneous assessments remain the same.
The sonographic display and misinterpretation of the
corpus luteum led to errors in the old as well as the
new population. Profuse hemorrhage, torsion of the
stalk, rupture with intraperitoneal collections of blood,
tenderness on sonopalpation of an adnexal tumor, or a
fluid-filled pouch of Douglas are findings that understandably influence clinical decision-making in such
situations.
Errors
No qualitative difference can be found when comparing luteal blood flow in a population of women with
intrauterine or ectopic pregnancies and nonpregnant
women in the second phase of their cycle. In 86.4% of
ectopic pregnancies the corpus luteum is found on the
same adnexal side as the pregnancy. This fact may be
helpful in a search, but should also be a warning
against a false sense of security, since the possibility
that a blastocyst may migrate to the opposite side
either internally or externally is well known.
It follows clearly that, to ensure that a measurement
of color-coded blood flow is valid, the suspicious
adnexal structure must lie outside the ovary. Of course
an extremely rare (쏝1%) ovarian implantation must be
considered in such a situation.
Additional data may be determined from the flow
resistance and pulsatility index (PI) of the uterine a.
and, where possible, selectively from the color signals
derived from the suspicious adnexal structure. For this
purpose the flow impedances of the uterine a. on the
ectopic side, the contralateral side, and the peritrophoblastic vessels can be compared. The respective impedances in the uterine aa. do not differ significantly,
but the median PI in the peritrophoblastic tubal tissue
is significantly lower, with a PI of 0.38 (p쏝0.01)
Fig. 7.2). Similar index values can be obtained from the
(
arcuate and spiral aa. in an intact intrauterine pregnancy. This may be viewed as an indication of com-
Obstetric Applications of Doppler Ultrasound
Fig. 7.1 Diagnostic efficiency
of vaginal sonographic examina-
tion for suspected extrauterine
pregnancy with and without
color Doppler.
Extrauterine laparoscopies
after transvaginal ultrasound
diagnosis without
color Doppler (n = 263)
True positive
241
91.6%
blubber
False positive
22
8.4%
Extrauterine laparoscopies
after transvaginal ultrasound
diagnosis with
color Doppler (n = 60)
True positive
57
95.0%
False positive
3
5.0%
87
The Role of Doppler Ultrasound in the Diagnosis of Ectopic Pregnancy
2
Pl
3
2
1
0
Contralateral
uterine a.
Median 10-90% Min./Max.
Fig. 7.2 Perfusion resistance of uterine and peritrophoblastic
tubal vessels in ectopic pregnancy.
Uterine a.
(extrauterine
pregnancy)
Peritrophoblastic
parable perfusion conditions. The same values cannot
be found in the color signals of intrauterine flow in an
ectopic pregnancy. Such an observation can therefore
help to exclude the diagnosis of ectopic pregnancy.
As an example,
Figures
7.3−7.6 show a typical case of
an asymptomatic tubal ectopic gestation that was detected early and treated while maintaining tubal inte-
Figures 7.7−7.9 show a case where a FP diagnosis
grity.
was made due to a highly vascularized corpus luteum.
Only after a repeated intensive search was a very small
intrauterine amniotic structure identified as an early
gestation. A history of an irregular menstrual cycle,
combined with prolonged amenorrhea, had led to an
erroneous estimate of the age of gestation, which in
fact was three weeks earlier than estimated.
88
Fig. 7.3 Echoic endometrium, representing a decidual reaction. There is no chorionic ring in the uterus (serum hCG 914 IE/
L). Vaginal sonographic display.
Fig. 7.5 Intense color Doppler signals at the edge of the
chorionic structured. The color scale was set to slow flow imaging. Display of a blood flow curve with low index values (PI = 0.7;
resistance index (RI) = 5; A/B = 2), signifying a low perfusion resistance. Note the similarity with blood flow patterns in uteroplacental vessels.
Fig. 7.4 Structure characteristic of chorion in the left adnexa,
clearly demarcated from the ovary.
Fig. 7.6 Laparoscopic image of an asymptomatic ectopic pregnancy (same case as
right tube without hemoperitoneum or sign of rupture.
Figs. 7.3,7.4,7.5). Fusiform swelling of the
blubber
Critical Evaluation
It would be an exaggeration to state that transvaginal
color Doppler ultrasound is indispensable for the diagnosis of an early ectopic pregnancy, since in any case
the diagnosis can be made with considerable confidence by an experienced clinican with correspondingly good instrumentation. As is well known, a significant improvement in our differential diagnoses can
only be accomplished with great effort. However, the
wide availability of color techniques allows many examiners to increase the confidence with which they
make a diagnosis with little extra effort, even though
the increase is statistically moderate. Because of its
many-sided clinical presentations, an ectopic pregnancy does not as a rule run a typical course. Hence
color Doppler sonography offers some help in the
differential diagnosis.
There are no consequential basic arguments against
the use of color Doppler sonography. Of course, the examiner must be aware of the high insonated energies
used when combining pulsed Doppler and color flourmapping. A very early pregnancy might be below the
lower limits of resolution and so the uterine cavity
should be shielded when the combined mode is employed, so as not to give rise to discussion regarding
possible physical damage. The significance of this
aspect will be seen in the case illustrated in
7.7−7.9.
Figures
Summary
Fig. 7.7 Tumor in the right adnexa with positive pregnancy
test and “empty” uterus on vaginal sonography, at an assumed
seventh week of gestation (7 + 7). Intense vascularization with
numerous color Doppler signals (“slow flow imaging” with a low
threshold for signal reception 쏝0.028 m/s).
Obstetric Applications of Doppler Ultrasound
Fig. 7.8 Blood flow curve with settings designed for indication
of low flow resistance at the sample depth.
Summary
The introduction of transvaginal sonography has improved diagnostic accuracy when an ectopic gestation
is suspected. A number of groups have studied and
evaluated the advantages of adding color Doppler ultrasound. They uniformly described a moderate enhancement of diagnostic accuracy, and we could confirm this in our own experience. We achieved an increase of positive predictions from 90 % to 95 %, and a
decrease in the rate of FP diagnoses from 8.4 % to 5 %.
The corpus luteum and its very variable clinical
manifestations must be considered as a possible
source of error. For safety’s sake we must warn against
blubber
Fig. 7.9 Primary assessment of an intrauterine chorion corresponding to the fifth week of pregnancy.
uncritical and prolonged insonation of the energies in
the area of the uterus.
The typical constellation indicating the use of vaginal color Doppler ultrasound includes an “empty”
uterus and a positive pregnancy test, consisting of a
serum hCG of 6500 mIU/mL or more in asymptomatic
cases. Early detection of ectopic pregnancy helps to reduce mortality and increases the chances of performing an organ-sparing laparoscopic procedure. This is an
indication of the clinical value of color Doppler ultrasound.
89
2
90
blubber
8 Indications for Obstetric Ultrasound
In what follows we will discuss the indications for the
use of Doppler ultrasound in obstetrics. We recommend the use of Doppler ultrasound in obstetrics
under the following circumstances, usually in the second half of pregnancy, except when malformations are
suspected:
1. Suspected intrauterine growth restriction (IUGR),
2. Pregnancy-induced hypertension (PIH), preeclampsia, eclampsia,
3. Status post dysmature delivery/intrauterine death,
4. Status post preeclampsia/eclampsia,
5. Abnormalities in the recorded fetal heart rate,
6. Reasonable suspicion of fetal anomalies or fetal disease,
7. Multiple pregnancy with discordant growth,
8. Suspicion of cardiac anomalies or heart disease.
Before discussing each of these indications in detail,
we must consider the diagnostic capabilities of ultrasound in principle. In the first place Doppler ultrasound can display blood flow and its direction in a
blood vessel (color Doppler), and under certain conditions estimate blood flow velocity in these vessels. This
information can be used to diagnose malformations,
especially cardiac anomalies. Secondly, the degree of
resistance in a vascular segment can be ascertained.
This information is used to determine the condition of
the fetus, especially in the third trimester. Changes in
the resistance of fetal vessels correlate with various
findings in the infant. Imminent danger to the infant
may be deduced from a redistribution of the blood
from the periphery to vital organs. Unremarkable resistance readings indicate that the infant’s nutrition is
balanced, while abnormal values suggest poor
nutritional supply, to which the infant responds with
redistribution of its blood supply.
When placental insuff iciency is compensated it is intrinsically possible for normal Doppler values to be recorded, showing a balanced supply, while abnormal
Doppler values always expose decompensation. Because of this fact it is not possible to screen for placental insufficiency with the use of Doppler ultrasound.
Rather, it is used to clarify the significance of a placental insufficiency demonstrated most often by biological measurements.
Thus, Doppler ultrasound makes it possible to distinguish between a compensated and a decompensated
placental insufficiency. This is its most important task.
Doppler ultrasound can also contribute more, but not
less, to the evaluation of the condition of the fetus.
Note also that in fetal diagnosis Doppler ultrasound
as a rule only recognizes chronic conditions, not acute
changes, i. e., it primarily helps in the detection of
chronic placental insufficiency. Cases have been recorded in which acute abruption of the placenta was
not detected when Doppler ultrasound happene d to be
used coincidentally, since the lack of blood flow in the
affected area is not accessible to the Doppler, while
blood flow in the remaining placenta is unchanged.
Moreover, Doppler ultrasound could not predict acute
placental insufficiency, only the risk associated with
chronic placental insufficiency. Clearly Doppler ultrasound is not suited to examining transmitted diseases,
since these first and foremost threaten acute placental
insufficiency.
The obstetric indications for Doppler ultrasound
listed above primarily address two situations:
− Firstly, the diagnosis and further evaluation of mal-
formations, as a rule by color Doppler. Doppler ul-
trasound is used principally to show the anatomy.
− Secondly, the diagnosis and surveillance of a high-
risk pregnancy toward the end of the second
trimester and in the third trimester. The main problem addressed is growth restriction of the fetus, i.e.,
diagnostic surveillance of the condition of the fetus.
Doppler ultrasound is used in the diagnosis of anoma-
lies to display the anatomy and, at times, the function
of the organs. As a rule this requires color Doppler ultrasound. For instance, in fetal cardiac anomalies color
Doppler sonography can demonstrate the cardiac defect and, by displaying the direction of flow, allow conclusions about their functional significance.
Determining the condition of the fetus in the third
trimester primarily requires an analysis of the
waveform. Color display of the vessels serves at best to
find and display the course of the vessel.
The most important indication for monitoring the
condition of the fetus in the third trimester is fetal
IUGR. This suggests that the most important basis for
the use of Doppler ultrasound is biological measurement. Exclusion of malformations is another strict indication for the introduction of Doppler ultrasound.
This can be justified by the fact that in growth-restricted infants malformations are seen significantly
more commonly than in eutrophic infants. Infants with
chromosomal aberrations are also often growth restricted.
Obstetric Applications of Doppler Ultrasound
91
blubber
Indications for Obstetric Ultrasound
IUGR and Biological Measurement
2
Since growth restriction is the most important indication for Doppler ultrasound this section will briefly review those measurements leading to the diagnosis.
The fundamental biological measurement is the
exact gestational age. To determine this, the sonographic measurement of crown−rump length is indispensable. The sooner this measurement is made, the
more precise is the determination of gestational age.
Basic Principles
Biological measurements primarily serve to recognize
disturbances in intrauterine growth. Reference planes
(Figs. 8.1,8.2) must be determined precisely in order to
make results reproducible and comparable. A single
measurement is not enough, as it can easily lead to
misinterpretation. For instance, biparietal measurements in a dolichocephalic skull may create doubt because they are too small.
Biological measurements are also a window into the
diagnosis of malformations. If the positional plane cannot be displayed or if measured values deviate significantly, the cause of the problem must be sought by a
thoroughgoing ultrasound examination.
The literature provides a variety of measuring techniques. In what follows we confine ourselves to what
we consider to be those most commonly employed.
Some Specific Measurements
Skull
왘 Measurements of the skull include the biparietal di-
ameter (BPD), the occipitofrontal diameter (OFD),
Fig.
and the head circumference (HC) (
왘 The reference plane is set correctly when the infan-
tile head appears oval with bony structures
throughout. The middle echo should be interrupted
by the cave of the septum pellucidum in the anterior third of the skull.
왘 If the cerebellum or the orbits are seen, the plane is
too occipital or caudal.
8.1).
Abdomen
왘 The abdominal diameter (AD), antero−posterior di-
ameter, and circumference are determined
(Fig. 8.2).
왘 The two diameters are identical in the ideal
rounded form of the abdomen.
왘 In the correct measuring plane the dorsal third of
the umbilical v. can be seen. The sections of the ribs
must be symmetrical. In addition, the three ossification centers of the vertebral column must be visible.
92
Fig. 8.1 Ultrasound scan of head. 1. Thalamic nuclei, 2. Cave of
septum pellucidum. Measurements displayed include the BPD,
the OFD, and the HC.
blubber
Fig. 8.2 Ultrasound scan of abdomen. 1. Umbilical vein, 2.
Cross section of aorta, 3. Vertebral column. Measurements dis-
played include abdominal diameter and circumference.
왘 Care must be taken not to distort the abdomen by
compression with the scanner or by respiratory
movements.
Extremities
왘 Measurement of the femoral diaphysis is now part
of a routine diagnostic study (Fig.
essary to measure other long bones if the length of
the femur deviates significantly or if its shape
shows noticeable changes (Fig. 8.4).
왘 The femur should be measured at a right angle to
the direction of the sonic beam. If the two femurs
run parallel to each other, measurement of the one
closer to the transducer is preferred, because the
measurement of the femur more distant from the
transducer tends to be too short. The distance
measured is identical to the ossified part of the
bone without consideration of any curvature that
may be present.
8.3). It is only nec-
Cerebellum
왘 Display of the fetal cerebellum is not only important
because it aids in the diagnosis of an anomaly when
it indicates the presence of spina bifida. Because its
size is essentially not influenced by intrauterine
growth disturbances, it is also suitable for the estimation of gestational age. In the second trimester
its longitudinal diameter corresponds to the ge-
stational age in weeks (Fig. 8.5).
왘 The cerebellum should be measured at its widest
point, in horizontal section through the posterior
cranial fossa.
IUGR and Biological Measurement
Fig. 8.3 Femur in its longest extent at 22nd week of gestation.
Obstetric Applications of Doppler Ultrasound
Procedure when Biological Measurements are Abnormal
왘 Determine precise gestational age by comparing
gestational age determined from the last menstrual
period with a first trimester sonographic finding.
왘 What biological measurements are abnormal?
− The extent of growth restriction is seen in
abdominal measurements,
− An isolated finding of a small head is not an indication of growth retardation (differential: microcephaly),
− A femur that is too short can also be an indication of Down syndrome. To exclude skeletal dysplasia the finding of a too short femur should be
followed by examination of the other long bones
(other femur, both humeri, both radii).
blubber
Fig. 8.4 Fetal leg with tibia and femur.
93
Fig. 8.5 Cerebellum with characteristic dorsal notch at 28th
week of gestation.