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The ultrasound diagnosis of hydatidiform mole
Clin. Radiol. (1977) 28,637-645
THE ULTRASOUND DIAGNOSIS OF HYDATIDIFORM MOLE AFFRA M. BAIRD, D. E. BECKL¥* and F. G. M. ROSS D e p a r t m e n t o f Radiology, Bristol Royal Infirmary
Experience with ultrasound compound 'B' scanning in 18 cases of hydatidiform mole is presented. The scan appearances are analysed with respect to the presence or absence of transonic areas, and to the uniformity of echogenicity elsewhere in the uterus. The differential diagnosis is discussed. The commonest appearance seen in a hydatidiform mole is the combination of multiple small transonic areas with uneven echogenicity in the remainder of the uterine cavity. The condition most likely to cause diagnostic confusion is early normal pregnancy with a bulky decidua, but incomplete abortion and uterine fibroid may also be confused with hydatidiform mole.
INTRODUCTION Hydatidiform mole complicates 1 in 2000 pregnancies in the United Kingdom. The incidence is higher in some tropical countries (Ag/iero et al., 1973; Ang et al., 1975) and in women approaching the menopause. It is thought to arise by progressive swelling of the chorionic villi following the death or absence of the embryo, and this almost always occurs in the first three to four weeks of development. MacroscopicaUy a hydatidiform mole is made up of discrete rounded vesicles varying from several millimetres up to 1 - 2 cm in size, which usually occupy the whole of the uterine cavity, but occasionally an intact amniotic sac may be present (Robbins, 1974). Haemorrhage within a hydatidiform mole is common. The classical clinical features are vaginal bleeding, hyperemesis, pre-eclampsia in early pregnancy, and a uterus that is too large for the period of amenorrhoea (Baird, 1969). However, in 50% of cases bleeding does not occur until after 20 weeks gestation (Greenbaum et al., 1969; Leopold, 1971). In only half the cases is the uterus too large for dates; in a quarter of cases it is too small, and in a further quarter it is consistent with the period of amenorrhoea (McVicar and Donald, 1963; Greenbaum et al., 1969; Leopold, 1971). Urinary chorionic gonadotrophic (HCG) levels are increased in patients with a hydatidiform mole, but this is not specific for a diagnosis of hydatidiform mole. High levels
* Present address: Department of Radiology, Plymouth General Hospital, Plymouth, Devon. Address for reprints: I~ A. M. Baird, Department of Radiology, Bristol Royal Infirmary, Bristol BS2 8HW.
occasionally occur in the first 14 weeks of normal pregnancy and even after this period a twin gestation may give high values (Gottesfeld et al., 1967). On rare occasions a patient with a hydatidiform mole may have normal HCG levels (Baird, 1969). The variability of the clinical picture is such that, unless the passage of molar lissues is observed, the provisional diagnosis rarely amounts to more than a strong clinical suspicion (Ang et al., 1975), For this reason a number of diagnostic methods have been employed in order to confirm the diagnosis. These include plain radiography (Johnson and Lachman, 1973), amniography (Bayan and Apelo, 1957; Apelo and Cunanan, 1966; Wilson et al., 1964; Highman and Sutton, 1964; Wilson et 1970; Ang et al., 1975), arteriography (Cockshott et al., 1964; Highman and Sutton, 1964 ; Wilson et al., 1966; Takahashi and Nagata, 1971), and a clinical probe test (Acosta-Sison, 1958). None of these methods is entirely satisfactory. More recently ultrasonic 'B' scanning has been employed to make the diagnosis (Gottesfeld et al,, 1967; Kohorn and Blackwell, 1968; Kohorn et al., 1969; Leopold, 1971; Donald, 1972; Birnholz and Barnes, 1973; Barnett and Morley, 1974; Leopold and Asher, 1974; Salem et al., 1974). This technique has the advantage of being simple, non-invasive and relatively cheap. The appearances are said to be characteristic, making diagnostic confusion rare (Gottesfeld et al., 1967; Kohorn and Blackwell, 1968; Kohorn et al., 1969). Nevertheless, it has been our experience that diagnostic difficulties may arise, particularly when the period of amenorrhoea has been short. Furthermore, it is at just this early stage that diagnosis is considered most desirable (Leopold, 1971; Birnholz and Barnes, 1973; Anget al., 1975).
638
CLINICAL
RADIOLOGY
THE PATIENTS This series consists of 25 cases, collected over a period of five years, in which h y d a t i d i f o r m mole was considered in the differential diagnosis on abdominal ultrasound scanning. Molar pregnancy was not thought to be the most likely diagnosis in all these cases, but in each case it was entertained as a possibility. In 18 of these cases a h y d a t i d i f o r m mole was subsequently proven. In the remaining seven cases the condition proved to be other than a hydatidiform mole. The distribution o f cases according to gestation period and uterine size is shown in Table 1.
CLINICAL The uterus was large for dates in all those cases of molar pregnancy seen before 20 weeks gestation, whereas all but one of those cases presenting after 20 weeks had a uterus which was small or normal for dates. The five patients with normal pregnancies and one case o f uterine fibroid all had a uterus which was large for the period of amenorrhoea. One patient in the series was subsequently shown to have had an
incomplete abortion. The uterus in this case was small for the period of gestation. METHOD
The apparatus used was designed and built by the Physics Department of the United Bristol Hospitals (now Bristol Health District (Teaching)). The. crystal frequency used is 2.0MHz. Pulse repetition frequency is made dependent on scanned arc and is 120 pulses/degree. Dot brightness on the photographic display bears a linear relationship to echo amplitude over a limited range. The amplitude of the transmitted signal can be varied b y the operator. No facility for the prevention o f the overwriting phenomenon is currently incorporated, thus if the same area is scanned twice, the echoes will be summated on the Polaroid print. Longitudinal and transverse scans were made in each case. Longitudinal scans were made at the midline and at successive 1 cm intervals either side of this until the entire uterus had been covered. Transverse scans were made at 1 - 3 cm intervals, sufficient scans again being made to cover the whole uterus. In
Table 1 - Distribution of cases according to gestation period and uterine size
~_
INE SIZE FOR DATES Sinai( Norma[
1
Large
4"
~30. S T A 25. T I 0 20. N A L 15.
4"
41'
0
÷
+
4. .IF ÷
A 6 E I0_.
+
+
•
+
÷
•
+
• It
W e
e 5.. k s O=Incomptete abortion. t
+:Mole.
O=Norma[ pregnancy.
A:Fibroid
THE
ULTRASOUND
DIAGNOSIS
each case a Doppler examination was also carried out in order to detect the presence of a foetal heartbeat. In each examination the patient was required to have a full bladder. The echo appearance within the uterine cavity has been analysed with regard to (a) the presence or absence of transonic areas, (b) the uniformity or otherwise of echogenicity, and (c) the relationship of highly echogenic areas to transonic areas (Table 2). For the purposes of this study a transonic area has been defined as an entirely echo-free zone, measuring at least 1 cm in its smallest dimension (2 m m on our scan), and which remains echo-free at high transmitted amplitude. Echogenicity is a term which relates to the number and amplitude of echoes arising in a given area. Thus, an area o f high echogenicity is one which appears very white on the Polaroid print. Conversely, an area of low echogenicity is one which appears relatively
OF HYDATIDIFORM
639
MOLE
dark on the print. In assessing uniformity o f echogenicity, transonic areas were excluded from consideration. RESULTS
These are shown diagrammatically in Table 2. Transonic A r e a s . - Eighteen cases in the series
showed multiple transonic areas in the uterine cavity. Of these 17 were hydatidiform moles (Fig. 1), and one case was an early pregnancy (Fig. 2). In four cases there was a single transonic area, and all four cases were normal pregnancies (Fig. 3). In three cases there was no transonic area, this group consisting o f one case each o f hydatidiform mole, incomplete abortion and uterine fibroid (Fig. 4,5,6). E c h o g e n i c i t y . - In six of the 25 cases in our series there was relatively uniform echogenicity in the
Table 2 - Distribution of cases according to ultrasound signs
-TRANSONICITY No Transonic area Singte Transonic area E C H 0 G E N I C I T V
Muttipte Transonic areas
6-Motes
N o n u n i f
1.Mote
t.,. Pregnancies
ll.Mo[es I. Pregnancy
l.[ncomptete abortion 1. Fibroid
0 r m
i:;;>1= Incomplete abortion
I'~i = Pregnancy
l=
Hydatidiform = Fibroid
mole
640
CLINICAL RADIOLOGY
uterine cavity (Fig. 7). All six of these cases were hydatidiform moles. In the remaining 19 cases echogenicity was nonuniform (Fig. 8). Of these cases 12 were hydatidiform moles, Five were normal pregnancies, one case was an incomplete abortion, and one case a uterine fibroid. C o m b i n a t i o n o f Signs. - In five cases highly echogenic areas were confined to the immediate vicinity
Key for figures. - (a) Transverse scan - patient viewed from
feet. (b) Longitudinal scan - patient viewed with feet to the right, head to the left. Fig. 1 - Hydafidiform mole. Longitudinal scan showing multiple transonic areas (small arrowheads). A large transonic area is seen lying deeper in the pelvis (large arrowhead), which represents a theca lutein cyst.
o f a single transonic area (Fig. 3). All five of these cases were normal pregnancies. In the remaining cases areas of high echogenicity when present were not closely related to the transonic areas. Multiple transonic areas associated with otherwise uniform echogenicity were seen in six of 18 hydatidiform moles and in no other condition. Multiple transonic areas with non-uniform echogenicity were seen in 13 cases, of which 12 were hydatidiform moles. This was the commonest appearance seen in hydatidiform mole (Fig. 1, 8). The remaining case in this category was an early pregnancy. The combination of non-uniform echogenicity with no transonic area was seen in three cases (one hydatidiform mole, one incomplete abortion and one uterine fibroid).
DISCUSSION The appearance of a 'snowstorm' of echoes throughout the uterus has been described as typical of a hydatidiform mole (McVicar and Donald, 1963; Taylor e t al., 1964; Donald 1965a, b; Birnholz and Barnes, 1973). Few variations on this pattern have been described, although some authors mention areas of transonicity within the uterine cavity due to haemorrhage (Leopold, 1971; Barnett and Morley, 1974; Leopold and Asher, 1974). Considerable stress has been placed on the fact that the echoes from a hydatidiform mole disappear when the gain settings of the apparatus are reduced by only a small amount
Fig. 2 - Early pregnancy. Longitudinal scan (a) showing multiple small transonic areas (small arrows). However, there is also a larger transonic area (large arrowhead), and the transverse scan (b) shows high amplitude echoes arising from foetal parts within the larger transonic area.
THE ULTRASOUND DIAGNOSIS OF HYDATIDIFORM MOLE
641
(Donald, 1965a; Gottesfeld e t al., 1967; Leopold and Asher, 1974; K o h o m e t al., 1969) (Fig. 9a, b). This phenomenon is, however, seen with a normal placenta (Gottesfeld e t al., 1967), and was also seen in the case of incomplete abortion (Fig. 10a, b). It merely reflects the relative uniformity of echogenicity of the tissues being scanned. Thus, if all the echoes are of a similar amplitude there will be a sharp 'cut-off' as gain is reduced below the point at which that particular amplitude of echo is displayed. Since this phenomenon is seen in the conditions most
readily confused with hydatidiform mole, its diagnostic value would appear minimal. Scanning of the entire uterus is of great importance because the normal decidua occupies a large part of the uterus in early pregnancy, and can be mistaken for a hydatidiform mole if the part of the uterus containing the amniotic sac and foetal parts is not scanned. Occasionally very large transonic areas may be present in a uterus containing a hydatidiform mole, and these are a potential source of confusion (Fig. 11). In one case a well-developed 'white line' was
Fig. 3 Early pregnancy. Transverse scan shows that the uterus is,bulky and contains multiple small echoes resembling the appearances seen in a hydatidiform mole. However, a single transonic area is present (large arrow). Highly echogenic areas representing foetal parts are seen adjacent to it (small arrow).
Fig. 4 -Hydatidiform mole. Longitudinal scan showing no transonic area within the uterine cavity. Multiple formless echoes are present.
Fig. 5 - Incomplete abortion. Longitudinal scan. No transonic areas are present within the uterine cavity,
Fig. 6 - Uterine fibroid. Transverse scan. No transonic areas are present in the uterine cavity.
642
CLINICAL RADIOLOGY
Fig. 7 - Hydatidiform mole. Longitudinal scan. Multiple small transonic areas are present within the uterus but the echogerdcity o f the intervening tissue is uniform.
Fig. 8 - H y d a t i d i f o r m mole. Transverse scan showing transonic areas. The echogenicity of the intervening tissue is uneven.
Fig. 9 - Hydatidiform mole. Transverse scan. (a) The uterine cavity is filled with multiple random echoes. (b) When the gain is reduced many o f the echoes disappear.
Fig. 1 0 - Incomplete abortion. Longitudinal scan. (a) The uterine cavity is Filled with multiple random echoes. (b) When the gain is reduced many of the echoes disappear.
THE ULTRASOUND
DIAGNOSIS OF HYDATIDIFORM
Fig. 11 - Hydatidiform mole. Transverse scan. Several very large transonic areas are present within the uterine cavity (arrowheads). At delivery this mole was found to contain large areas of haemorrhage.
MOLE
643
Fig. 1 2 - H y d a t i d i f o r m mole. Transverse scan showing a well-developed white line along the surface of the mole (arrows). This feature has previously only been described in relation to normal placenta.
such case has been encountered by the authors and it has not been included in the analysis of this series. These cases present special diagnostic difficulty because the size of the normal placenta is very variable, making it hard to determine the presence of pathological enlargement due to hydatidiform mole. Multiple transonic areas within the mole may, however, provide the distinction just as in those cases without coexisting pregnancy. However, it is important in those cases of suspected hydatidiform mole which are scanned in the early weeks not to exclude the diagnosis if multiple transonic areas are not present. These cases should be rescanned in a fortnight. CONCLUSION F i g . 1 3 - H y d a t i d i f o r m mole. Transverse scan showing a large transonic area in the pelvis behind and separate from the uterus (arrows), due to a theca lutein cyst.
present on the surface of a hydatidiform mole (Fig. 12). This sign has previously only been described in relation to normal placenta. Theca lutein cysts of the ovary occur in approximately 50% cases of hydatidiform mole (Baird, 1969) and these will be shown on the scan as large transonic areas in the pelvis (Fig. 13). Their regression following combined surgical and drug treatment can be monitored by serial ultrasonography (Scheer and Goldstein, 1973). A foetus may coexist with a hydatidiform mole, although this is very rare (Bruce, 1972). Only one
Ultrasonic compound 'B' scanning is considered to be the method of choice in confirming the diagnosis of hydatidiform mole. Difficulties in differential diagnosis may arise, but these can be minimised by attention to specific signs in the interpretation of the scans. Multiple transonic areas with uniform or nonuniform echogenicity are characteristic of a hydatidiform mole. A single transonic area with an area of high echogenicity within or adjacent to it is typical of early normal pregnancy. A small number of cases of hydatidiform mole occur in which there is no transonic area in the uterine cavity. From a diagnostic viewpoint this is the least satisfactory category, as it may be seen in a hydatidiform mole and also in
644
CLINICAL RADIOLOGY
Fig. 14 - Hydatidiform mole. Grey scale presentation. The enlarged uterus is filled with multiple echoes within which are several small transonic areas.
Fig. 15 - Hydatidiform mole. Grey scale presentation. There are multiple large transonic areas within the enlarged uterus as well as many fine echoes.
incomplete abortion and uterine fibroid. However o n l y t h r e e o f 25 cases in o u r series fell i n t o this category.
Birnholz, J. C. & Barnes, A- B. (1973). Early diagnosis of hydatidiform mole by ultrasound imaging. Journal of the American Medical Association, 225, 1359 1360. Bruce, J. E. F. (1972). Hydatidiform mole with coexistent foetus. Proceedings of the Royal Society of Medicine, 65,864-865_ Cockshott, W. P., Evans, K. T. & Hendriekse, J_ P. deV. (1964)_ Arteriography in trophoblastic turnouts. Clinical Radiology, 15, 1 - 8 . Donald, I. (1965a). Diagnostic uses of sonar in obstetrics and gynaecology. Journal o f Obstetrics and Gynaecology of the B,ritish Commonwealth, 72, 907_ Donald, I. (1965b). Ultrasonic echo-sounding in obstetrics and gynecological diagnosis_ American Journal of Obstetrics and Gynecology, 93,935. Donald, I. (1972). Diagnostic sonar in obstetrics and gynaecology. Obstetric and Gynaecology Annual 1972, ed. Wynn, Ralph M. Vol. 1, pp. 245 271. Appleton-CenturyCrofts, New York. Gottesfeld, K. R., Taylor, E_ S_, Thomson, H. E. & Holmes, J. H. (1967). Diagnosis of hydatidiform mole by ultrasound. Obstetrics and Gynecology, 30, 163-171. Greenbaum, E. I., Podolak, G. & O'Loughlin, B. J_ (1969). The use of hysterography in the detection of hydatidiform mole. American Journal of Roentgenology, 105, 885-889. Highman, J. H. & Sutton, D. (1964). Angiography in hydatidiform mole and chorionepithelioma. Clinical Radiology, 15, 9 - 1 3 . Johnson, J. M. & Lachman, R. (1973). Amniographic patterns in the diagnosis of hydatidiform mole. Journal of the Canadian Association o f Radiologists, 2 4 , 1 5 7 - 1 6 0 . Kohorn, E. I. & Blackwell, R. J. (1968)_ Diagnosis of hydatidiform mole by ultrasonic scanning. Journal of Obstetrics and Gynaeeology of the British Commonwealth, 75, 1014-1018. Kohorn, E. I., Morrison, J., Ashford, C. & Blackweil, R. J. (1969). Ultrasonic scanning in obstetrics and gynaecology. Obstetries and Gynecology, 3 4 , 5 1 5 - 5 2 2 .
A d d e n d u m . - Since t h e p r e p a r a t i o n o f this p a p e r we have h a d t h e o p p o r t u n i t y o f s t u d y i n g t w o cases o f h y d a t i d i f o r m m o l e using t h e D i a s o n o g r a p h N E 4 1 0 2 w i t h grey scaling. T h e a p p e a r a n c e s are similar t o t h o s e o b t a i n e d w i t h o u r older a p p a r a t u s , a n d it is o f i n t e r e s t t h a t small t r a n s o n i c areas were also seen in t h e s e cases (Fig. 14, 15). Acknowledgements. - W e are grateful to Mr E. J. Turnbull and Mr J. Hancock for preparation of the illustrations. REFERENCES Acosta-Sison, H. (1958). Obstetrics and Gynecology, 12, 205 -208. Agfiero, O., Kiser, S. & Pinedo, G. (1973). Hydatidiform mole in Concepi6n Palacios Maternity Hospital. American Journal of Obstetrics and Gynecology, 116, 1117-1120. Ang, A. H., Chan, W. F. & Ng, K. K. (1975). Amniography in the early diagnosis of hydatidiform mole. British Journal of Radiology, 4 8 , 9 7 9 - 9 8 1 . Apelo, R. & Cunanan, R. (1966). Value of hysterogram in diagnosis of hydatidiform mole. Philippine Journal o f Surgery, 2 1 , 2 8 3 - 2 8 7 . Baird, D. (1969). Combined Textbook o f Obstetrics and Gynaecology, p. 252. E. S_ Livingstone, Edinburgh and London. Bayan, F. & Apelo, R. (1957). Direct and positive diagnosis of hydatidiform mole. Philippine Journal of Surgery, 12, 1 - 6 . Barnett, E. & Morley, P. (1974). Ultrasound in Diagnosis o f Abdominal Conditions, pp. 102-104. Butterworth, London.
THE U L T R A S O U N D DIAGNOSIS OF H Y D A T I D I F O R M MOLE Leopold, G. R. (1971). Diagnostic ultrasound in the detection of molar pregnancy. Radiology, 9 8 , 1 7 1 - 1 7 6 . Leopold, G. R. & Asher, W. M. (1974). Ultrasound in obstetrics and gynecology. Radiological Clinics o f North America, XlI (1), 127-146. MacVicar, J. & Donald, I. (1963)_ Sonar in the diagnosis of early pregnancy and its complications. Journal o f Obstetrics and Gynaecology o f the British Commonwealth, 70, 387-395. Robbins, S. L. (1974). Pathological Basis o f Disease, pp. 1259 1261. W. B_ Saunders, Philadelphia, London, Toronto. Salem, S., O'Malley, B. P. & Weisbaum, S_ D. (1974). Ultrasound in the diagnosis of hydatidiform mole. Journal o f the Canadian Association o f Radiologists, 25,135-139. Scheer, K_ & Goldstein, D. P. (1973). Use of ultrasonography
645
to follow regression of theca lutein cysts_ Radiology, 108, 673-674_ Takahashi, M. & Nagata, Y. (1971). Angiography of trophoblastic turnouts. American Journal o f Roentgenology, 112, 779-787. Taylor, E_ S., Holmes, J. H., Thompson, H. E. & Gottesfeld, K. R. (1964). Ultrasound diagnostic techniques in obstetrics and gynecology. American Journal o f Obstetrics and Gynecology, 90, 655. Wilson, G_, Colodny, S. & Weidner, W. (1966). Comparison of amniography and pelvic angiography in diagnosis of hydatidiform mole. Radiology, 87, 1076 - 1079. Zarou, D. M., Imblean, Y_ & Zarou, G. S. (1970). Radiographic diagnosis of molar pregnancy. Obstetrics and Gynecology, 35, 89-92.
THE ULTRASOUND DIAGNOSIS OF HYDATIDIFORM MOLE AFFRA M. BAIRD, D. E. BECKL¥* and F. G. M. ROSS D e p a r t m e n t o f Radiology, Bristol Royal Infirmary
Experience with ultrasound compound 'B' scanning in 18 cases of hydatidiform mole is presented. The scan appearances are analysed with respect to the presence or absence of transonic areas, and to the uniformity of echogenicity elsewhere in the uterus. The differential diagnosis is discussed. The commonest appearance seen in a hydatidiform mole is the combination of multiple small transonic areas with uneven echogenicity in the remainder of the uterine cavity. The condition most likely to cause diagnostic confusion is early normal pregnancy with a bulky decidua, but incomplete abortion and uterine fibroid may also be confused with hydatidiform mole.
INTRODUCTION Hydatidiform mole complicates 1 in 2000 pregnancies in the United Kingdom. The incidence is higher in some tropical countries (Ag/iero et al., 1973; Ang et al., 1975) and in women approaching the menopause. It is thought to arise by progressive swelling of the chorionic villi following the death or absence of the embryo, and this almost always occurs in the first three to four weeks of development. MacroscopicaUy a hydatidiform mole is made up of discrete rounded vesicles varying from several millimetres up to 1 - 2 cm in size, which usually occupy the whole of the uterine cavity, but occasionally an intact amniotic sac may be present (Robbins, 1974). Haemorrhage within a hydatidiform mole is common. The classical clinical features are vaginal bleeding, hyperemesis, pre-eclampsia in early pregnancy, and a uterus that is too large for the period of amenorrhoea (Baird, 1969). However, in 50% of cases bleeding does not occur until after 20 weeks gestation (Greenbaum et al., 1969; Leopold, 1971). In only half the cases is the uterus too large for dates; in a quarter of cases it is too small, and in a further quarter it is consistent with the period of amenorrhoea (McVicar and Donald, 1963; Greenbaum et al., 1969; Leopold, 1971). Urinary chorionic gonadotrophic (HCG) levels are increased in patients with a hydatidiform mole, but this is not specific for a diagnosis of hydatidiform mole. High levels
* Present address: Department of Radiology, Plymouth General Hospital, Plymouth, Devon. Address for reprints: I~ A. M. Baird, Department of Radiology, Bristol Royal Infirmary, Bristol BS2 8HW.
occasionally occur in the first 14 weeks of normal pregnancy and even after this period a twin gestation may give high values (Gottesfeld et al., 1967). On rare occasions a patient with a hydatidiform mole may have normal HCG levels (Baird, 1969). The variability of the clinical picture is such that, unless the passage of molar lissues is observed, the provisional diagnosis rarely amounts to more than a strong clinical suspicion (Ang et al., 1975), For this reason a number of diagnostic methods have been employed in order to confirm the diagnosis. These include plain radiography (Johnson and Lachman, 1973), amniography (Bayan and Apelo, 1957; Apelo and Cunanan, 1966; Wilson et al., 1964; Highman and Sutton, 1964; Wilson et 1970; Ang et al., 1975), arteriography (Cockshott et al., 1964; Highman and Sutton, 1964 ; Wilson et al., 1966; Takahashi and Nagata, 1971), and a clinical probe test (Acosta-Sison, 1958). None of these methods is entirely satisfactory. More recently ultrasonic 'B' scanning has been employed to make the diagnosis (Gottesfeld et al,, 1967; Kohorn and Blackwell, 1968; Kohorn et al., 1969; Leopold, 1971; Donald, 1972; Birnholz and Barnes, 1973; Barnett and Morley, 1974; Leopold and Asher, 1974; Salem et al., 1974). This technique has the advantage of being simple, non-invasive and relatively cheap. The appearances are said to be characteristic, making diagnostic confusion rare (Gottesfeld et al., 1967; Kohorn and Blackwell, 1968; Kohorn et al., 1969). Nevertheless, it has been our experience that diagnostic difficulties may arise, particularly when the period of amenorrhoea has been short. Furthermore, it is at just this early stage that diagnosis is considered most desirable (Leopold, 1971; Birnholz and Barnes, 1973; Anget al., 1975).
638
CLINICAL
RADIOLOGY
THE PATIENTS This series consists of 25 cases, collected over a period of five years, in which h y d a t i d i f o r m mole was considered in the differential diagnosis on abdominal ultrasound scanning. Molar pregnancy was not thought to be the most likely diagnosis in all these cases, but in each case it was entertained as a possibility. In 18 of these cases a h y d a t i d i f o r m mole was subsequently proven. In the remaining seven cases the condition proved to be other than a hydatidiform mole. The distribution o f cases according to gestation period and uterine size is shown in Table 1.
CLINICAL The uterus was large for dates in all those cases of molar pregnancy seen before 20 weeks gestation, whereas all but one of those cases presenting after 20 weeks had a uterus which was small or normal for dates. The five patients with normal pregnancies and one case o f uterine fibroid all had a uterus which was large for the period of amenorrhoea. One patient in the series was subsequently shown to have had an
incomplete abortion. The uterus in this case was small for the period of gestation. METHOD
The apparatus used was designed and built by the Physics Department of the United Bristol Hospitals (now Bristol Health District (Teaching)). The. crystal frequency used is 2.0MHz. Pulse repetition frequency is made dependent on scanned arc and is 120 pulses/degree. Dot brightness on the photographic display bears a linear relationship to echo amplitude over a limited range. The amplitude of the transmitted signal can be varied b y the operator. No facility for the prevention o f the overwriting phenomenon is currently incorporated, thus if the same area is scanned twice, the echoes will be summated on the Polaroid print. Longitudinal and transverse scans were made in each case. Longitudinal scans were made at the midline and at successive 1 cm intervals either side of this until the entire uterus had been covered. Transverse scans were made at 1 - 3 cm intervals, sufficient scans again being made to cover the whole uterus. In
Table 1 - Distribution of cases according to gestation period and uterine size
~_
INE SIZE FOR DATES Sinai( Norma[
1
Large
4"
~30. S T A 25. T I 0 20. N A L 15.
4"
41'
0
÷
+
4. .IF ÷
A 6 E I0_.
+
+
•
+
÷
•
+
• It
W e
e 5.. k s O=Incomptete abortion. t
+:Mole.
O=Norma[ pregnancy.
A:Fibroid
THE
ULTRASOUND
DIAGNOSIS
each case a Doppler examination was also carried out in order to detect the presence of a foetal heartbeat. In each examination the patient was required to have a full bladder. The echo appearance within the uterine cavity has been analysed with regard to (a) the presence or absence of transonic areas, (b) the uniformity or otherwise of echogenicity, and (c) the relationship of highly echogenic areas to transonic areas (Table 2). For the purposes of this study a transonic area has been defined as an entirely echo-free zone, measuring at least 1 cm in its smallest dimension (2 m m on our scan), and which remains echo-free at high transmitted amplitude. Echogenicity is a term which relates to the number and amplitude of echoes arising in a given area. Thus, an area o f high echogenicity is one which appears very white on the Polaroid print. Conversely, an area of low echogenicity is one which appears relatively
OF HYDATIDIFORM
639
MOLE
dark on the print. In assessing uniformity o f echogenicity, transonic areas were excluded from consideration. RESULTS
These are shown diagrammatically in Table 2. Transonic A r e a s . - Eighteen cases in the series
showed multiple transonic areas in the uterine cavity. Of these 17 were hydatidiform moles (Fig. 1), and one case was an early pregnancy (Fig. 2). In four cases there was a single transonic area, and all four cases were normal pregnancies (Fig. 3). In three cases there was no transonic area, this group consisting o f one case each o f hydatidiform mole, incomplete abortion and uterine fibroid (Fig. 4,5,6). E c h o g e n i c i t y . - In six of the 25 cases in our series there was relatively uniform echogenicity in the
Table 2 - Distribution of cases according to ultrasound signs
-TRANSONICITY No Transonic area Singte Transonic area E C H 0 G E N I C I T V
Muttipte Transonic areas
6-Motes
N o n u n i f
1.Mote
t.,. Pregnancies
ll.Mo[es I. Pregnancy
l.[ncomptete abortion 1. Fibroid
0 r m
i:;;>1= Incomplete abortion
I'~i = Pregnancy
l=
Hydatidiform = Fibroid
mole
640
CLINICAL RADIOLOGY
uterine cavity (Fig. 7). All six of these cases were hydatidiform moles. In the remaining 19 cases echogenicity was nonuniform (Fig. 8). Of these cases 12 were hydatidiform moles, Five were normal pregnancies, one case was an incomplete abortion, and one case a uterine fibroid. C o m b i n a t i o n o f Signs. - In five cases highly echogenic areas were confined to the immediate vicinity
Key for figures. - (a) Transverse scan - patient viewed from
feet. (b) Longitudinal scan - patient viewed with feet to the right, head to the left. Fig. 1 - Hydafidiform mole. Longitudinal scan showing multiple transonic areas (small arrowheads). A large transonic area is seen lying deeper in the pelvis (large arrowhead), which represents a theca lutein cyst.
o f a single transonic area (Fig. 3). All five of these cases were normal pregnancies. In the remaining cases areas of high echogenicity when present were not closely related to the transonic areas. Multiple transonic areas associated with otherwise uniform echogenicity were seen in six of 18 hydatidiform moles and in no other condition. Multiple transonic areas with non-uniform echogenicity were seen in 13 cases, of which 12 were hydatidiform moles. This was the commonest appearance seen in hydatidiform mole (Fig. 1, 8). The remaining case in this category was an early pregnancy. The combination of non-uniform echogenicity with no transonic area was seen in three cases (one hydatidiform mole, one incomplete abortion and one uterine fibroid).
DISCUSSION The appearance of a 'snowstorm' of echoes throughout the uterus has been described as typical of a hydatidiform mole (McVicar and Donald, 1963; Taylor e t al., 1964; Donald 1965a, b; Birnholz and Barnes, 1973). Few variations on this pattern have been described, although some authors mention areas of transonicity within the uterine cavity due to haemorrhage (Leopold, 1971; Barnett and Morley, 1974; Leopold and Asher, 1974). Considerable stress has been placed on the fact that the echoes from a hydatidiform mole disappear when the gain settings of the apparatus are reduced by only a small amount
Fig. 2 - Early pregnancy. Longitudinal scan (a) showing multiple small transonic areas (small arrows). However, there is also a larger transonic area (large arrowhead), and the transverse scan (b) shows high amplitude echoes arising from foetal parts within the larger transonic area.
THE ULTRASOUND DIAGNOSIS OF HYDATIDIFORM MOLE
641
(Donald, 1965a; Gottesfeld e t al., 1967; Leopold and Asher, 1974; K o h o m e t al., 1969) (Fig. 9a, b). This phenomenon is, however, seen with a normal placenta (Gottesfeld e t al., 1967), and was also seen in the case of incomplete abortion (Fig. 10a, b). It merely reflects the relative uniformity of echogenicity of the tissues being scanned. Thus, if all the echoes are of a similar amplitude there will be a sharp 'cut-off' as gain is reduced below the point at which that particular amplitude of echo is displayed. Since this phenomenon is seen in the conditions most
readily confused with hydatidiform mole, its diagnostic value would appear minimal. Scanning of the entire uterus is of great importance because the normal decidua occupies a large part of the uterus in early pregnancy, and can be mistaken for a hydatidiform mole if the part of the uterus containing the amniotic sac and foetal parts is not scanned. Occasionally very large transonic areas may be present in a uterus containing a hydatidiform mole, and these are a potential source of confusion (Fig. 11). In one case a well-developed 'white line' was
Fig. 3 Early pregnancy. Transverse scan shows that the uterus is,bulky and contains multiple small echoes resembling the appearances seen in a hydatidiform mole. However, a single transonic area is present (large arrow). Highly echogenic areas representing foetal parts are seen adjacent to it (small arrow).
Fig. 4 -Hydatidiform mole. Longitudinal scan showing no transonic area within the uterine cavity. Multiple formless echoes are present.
Fig. 5 - Incomplete abortion. Longitudinal scan. No transonic areas are present within the uterine cavity,
Fig. 6 - Uterine fibroid. Transverse scan. No transonic areas are present in the uterine cavity.
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Fig. 7 - Hydatidiform mole. Longitudinal scan. Multiple small transonic areas are present within the uterus but the echogerdcity o f the intervening tissue is uniform.
Fig. 8 - H y d a t i d i f o r m mole. Transverse scan showing transonic areas. The echogenicity of the intervening tissue is uneven.
Fig. 9 - Hydatidiform mole. Transverse scan. (a) The uterine cavity is filled with multiple random echoes. (b) When the gain is reduced many o f the echoes disappear.
Fig. 1 0 - Incomplete abortion. Longitudinal scan. (a) The uterine cavity is Filled with multiple random echoes. (b) When the gain is reduced many of the echoes disappear.
THE ULTRASOUND
DIAGNOSIS OF HYDATIDIFORM
Fig. 11 - Hydatidiform mole. Transverse scan. Several very large transonic areas are present within the uterine cavity (arrowheads). At delivery this mole was found to contain large areas of haemorrhage.
MOLE
643
Fig. 1 2 - H y d a t i d i f o r m mole. Transverse scan showing a well-developed white line along the surface of the mole (arrows). This feature has previously only been described in relation to normal placenta.
such case has been encountered by the authors and it has not been included in the analysis of this series. These cases present special diagnostic difficulty because the size of the normal placenta is very variable, making it hard to determine the presence of pathological enlargement due to hydatidiform mole. Multiple transonic areas within the mole may, however, provide the distinction just as in those cases without coexisting pregnancy. However, it is important in those cases of suspected hydatidiform mole which are scanned in the early weeks not to exclude the diagnosis if multiple transonic areas are not present. These cases should be rescanned in a fortnight. CONCLUSION F i g . 1 3 - H y d a t i d i f o r m mole. Transverse scan showing a large transonic area in the pelvis behind and separate from the uterus (arrows), due to a theca lutein cyst.
present on the surface of a hydatidiform mole (Fig. 12). This sign has previously only been described in relation to normal placenta. Theca lutein cysts of the ovary occur in approximately 50% cases of hydatidiform mole (Baird, 1969) and these will be shown on the scan as large transonic areas in the pelvis (Fig. 13). Their regression following combined surgical and drug treatment can be monitored by serial ultrasonography (Scheer and Goldstein, 1973). A foetus may coexist with a hydatidiform mole, although this is very rare (Bruce, 1972). Only one
Ultrasonic compound 'B' scanning is considered to be the method of choice in confirming the diagnosis of hydatidiform mole. Difficulties in differential diagnosis may arise, but these can be minimised by attention to specific signs in the interpretation of the scans. Multiple transonic areas with uniform or nonuniform echogenicity are characteristic of a hydatidiform mole. A single transonic area with an area of high echogenicity within or adjacent to it is typical of early normal pregnancy. A small number of cases of hydatidiform mole occur in which there is no transonic area in the uterine cavity. From a diagnostic viewpoint this is the least satisfactory category, as it may be seen in a hydatidiform mole and also in
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CLINICAL RADIOLOGY
Fig. 14 - Hydatidiform mole. Grey scale presentation. The enlarged uterus is filled with multiple echoes within which are several small transonic areas.
Fig. 15 - Hydatidiform mole. Grey scale presentation. There are multiple large transonic areas within the enlarged uterus as well as many fine echoes.
incomplete abortion and uterine fibroid. However o n l y t h r e e o f 25 cases in o u r series fell i n t o this category.
Birnholz, J. C. & Barnes, A- B. (1973). Early diagnosis of hydatidiform mole by ultrasound imaging. Journal of the American Medical Association, 225, 1359 1360. Bruce, J. E. F. (1972). Hydatidiform mole with coexistent foetus. Proceedings of the Royal Society of Medicine, 65,864-865_ Cockshott, W. P., Evans, K. T. & Hendriekse, J_ P. deV. (1964)_ Arteriography in trophoblastic turnouts. Clinical Radiology, 15, 1 - 8 . Donald, I. (1965a). Diagnostic uses of sonar in obstetrics and gynaecology. Journal o f Obstetrics and Gynaecology of the B,ritish Commonwealth, 72, 907_ Donald, I. (1965b). Ultrasonic echo-sounding in obstetrics and gynecological diagnosis_ American Journal of Obstetrics and Gynecology, 93,935. Donald, I. (1972). Diagnostic sonar in obstetrics and gynaecology. Obstetric and Gynaecology Annual 1972, ed. Wynn, Ralph M. Vol. 1, pp. 245 271. Appleton-CenturyCrofts, New York. Gottesfeld, K. R., Taylor, E_ S_, Thomson, H. E. & Holmes, J. H. (1967). Diagnosis of hydatidiform mole by ultrasound. Obstetrics and Gynecology, 30, 163-171. Greenbaum, E. I., Podolak, G. & O'Loughlin, B. J_ (1969). The use of hysterography in the detection of hydatidiform mole. American Journal of Roentgenology, 105, 885-889. Highman, J. H. & Sutton, D. (1964). Angiography in hydatidiform mole and chorionepithelioma. Clinical Radiology, 15, 9 - 1 3 . Johnson, J. M. & Lachman, R. (1973). Amniographic patterns in the diagnosis of hydatidiform mole. Journal of the Canadian Association o f Radiologists, 2 4 , 1 5 7 - 1 6 0 . Kohorn, E. I. & Blackwell, R. J. (1968)_ Diagnosis of hydatidiform mole by ultrasonic scanning. Journal of Obstetrics and Gynaeeology of the British Commonwealth, 75, 1014-1018. Kohorn, E. I., Morrison, J., Ashford, C. & Blackweil, R. J. (1969). Ultrasonic scanning in obstetrics and gynaecology. Obstetries and Gynecology, 3 4 , 5 1 5 - 5 2 2 .
A d d e n d u m . - Since t h e p r e p a r a t i o n o f this p a p e r we have h a d t h e o p p o r t u n i t y o f s t u d y i n g t w o cases o f h y d a t i d i f o r m m o l e using t h e D i a s o n o g r a p h N E 4 1 0 2 w i t h grey scaling. T h e a p p e a r a n c e s are similar t o t h o s e o b t a i n e d w i t h o u r older a p p a r a t u s , a n d it is o f i n t e r e s t t h a t small t r a n s o n i c areas were also seen in t h e s e cases (Fig. 14, 15). Acknowledgements. - W e are grateful to Mr E. J. Turnbull and Mr J. Hancock for preparation of the illustrations. REFERENCES Acosta-Sison, H. (1958). Obstetrics and Gynecology, 12, 205 -208. Agfiero, O., Kiser, S. & Pinedo, G. (1973). Hydatidiform mole in Concepi6n Palacios Maternity Hospital. American Journal of Obstetrics and Gynecology, 116, 1117-1120. Ang, A. H., Chan, W. F. & Ng, K. K. (1975). Amniography in the early diagnosis of hydatidiform mole. British Journal of Radiology, 4 8 , 9 7 9 - 9 8 1 . Apelo, R. & Cunanan, R. (1966). Value of hysterogram in diagnosis of hydatidiform mole. Philippine Journal o f Surgery, 2 1 , 2 8 3 - 2 8 7 . Baird, D. (1969). Combined Textbook o f Obstetrics and Gynaecology, p. 252. E. S_ Livingstone, Edinburgh and London. Bayan, F. & Apelo, R. (1957). Direct and positive diagnosis of hydatidiform mole. Philippine Journal of Surgery, 12, 1 - 6 . Barnett, E. & Morley, P. (1974). Ultrasound in Diagnosis o f Abdominal Conditions, pp. 102-104. Butterworth, London.
THE U L T R A S O U N D DIAGNOSIS OF H Y D A T I D I F O R M MOLE Leopold, G. R. (1971). Diagnostic ultrasound in the detection of molar pregnancy. Radiology, 9 8 , 1 7 1 - 1 7 6 . Leopold, G. R. & Asher, W. M. (1974). Ultrasound in obstetrics and gynecology. Radiological Clinics o f North America, XlI (1), 127-146. MacVicar, J. & Donald, I. (1963)_ Sonar in the diagnosis of early pregnancy and its complications. Journal o f Obstetrics and Gynaecology o f the British Commonwealth, 70, 387-395. Robbins, S. L. (1974). Pathological Basis o f Disease, pp. 1259 1261. W. B_ Saunders, Philadelphia, London, Toronto. Salem, S., O'Malley, B. P. & Weisbaum, S_ D. (1974). Ultrasound in the diagnosis of hydatidiform mole. Journal o f the Canadian Association o f Radiologists, 25,135-139. Scheer, K_ & Goldstein, D. P. (1973). Use of ultrasonography
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to follow regression of theca lutein cysts_ Radiology, 108, 673-674_ Takahashi, M. & Nagata, Y. (1971). Angiography of trophoblastic turnouts. American Journal o f Roentgenology, 112, 779-787. Taylor, E_ S., Holmes, J. H., Thompson, H. E. & Gottesfeld, K. R. (1964). Ultrasound diagnostic techniques in obstetrics and gynecology. American Journal o f Obstetrics and Gynecology, 90, 655. Wilson, G_, Colodny, S. & Weidner, W. (1966). Comparison of amniography and pelvic angiography in diagnosis of hydatidiform mole. Radiology, 87, 1076 - 1079. Zarou, D. M., Imblean, Y_ & Zarou, G. S. (1970). Radiographic diagnosis of molar pregnancy. Obstetrics and Gynecology, 35, 89-92.