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ANSWERS
CASE 56
Umbilical Artery Doppler
1. A, B, C, and D
2. A
3. C
4. A
References
Alrevic Z, Neilson JP: Fetus-placenta-newborn: Doppler ultrasonography
in high-risk pregnancies: systematic review with meta-analysis. Am J Obstet
Gynecol 1995; 172(5):1379-1387.
http://www.ncbi.nlm.nih.gov/pubmed/7755042 (Accessed on June 12, 2012.)
Sepulveda W, Shennan A, Peek MJ: Reverse end-diastolic ow in the middle
cerebral artery: an agonal pattern in the human fetus. Am J Obstet Gynecol
1996; 174(5):1645-1647.
http://www.ncbi.nlm.nih.gov/pubmed/9065146 (Accessed on June 12, 2012.)
Spinillo A, Montanari L, Bergante C, et al: Prognostic value of umbilical
artery Doppler studies in unselected preterm deliveries. Obstet Gynecol 2005;
105(3):613-620.
http://www.ncbi.nlm.nih.gov/pubmed/15738033 (Accessed on June 12, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 335-337.
Comment
Umbilical Artery Waveform
Doppler ultrasound imaging has become an important component in the prenatal evaluation of high-risk pregnancies.
The umbilical artery waveform can indicate abnormal fetoplacental blood ow by showing elevated placental impedance.
An abnormal umbilical artery waveform is associated with a
higher incidence of adverse fetal outcome.
Indications for Imaging
Indications for measuring the umbilical artery waveform
include the presence of oligohydramnios and IUGR. A
waveform should be obtained from the fetal end of the cord
and from the middle and the maternal end of the cord. The
peak systolic velocity/end-diastolic velocity (S/D) ratio at
each of these three points is averaged and compared with a
chart of normal values for each gestational age (Figure A).
With increasing gestational age, the S/D ratio should decrease,
reecting decreasing impedance. The MCA index is measured
either as the S/D ratio or as a pulsatility index (i.e., peak systole
− end diastole ÷ area of one waveform; see dotted lines outlining one waveform in Figure B).
Increased Impedance
If the impedance increases, the diastolic ow decreases and
can be absent (Figure A) or reversed in the umbilical artery
(Figure C). Absence or reversal of diastolic ow has been associated with IUGR, fetal asphyxia, perinatal mortality, cerebral
palsy, and long-term permanent fetal neurologic sequelae. In
addition, there is a higher likelihood that the fetus has a chromosomal anomaly. Routine use of Doppler ultrasound of the
umbilical artery to guide obstetric management (i.e., timing of
delivery) has resulted in a lower incidence of prenatal admissions, labor induction, emergency cesarean section for fetal
distress, perinatal death, and hypoxic fetal encephalopathy.
Increased Impedance of Umbilical Artery
and Fetal Circulation Response
When fetal hypoxia results from decreased diastolic umbilical
artery ow, the fetal circulation responds with a brain-sparing
effect. The MCA index is measured either as the S/D ratio or
as a pulsatility index (Figure B). The MCA Doppler image is
evaluated to determine if blood is being redistributed from
other sources (e.g., mesenteric) to the intracranial structures.
In this case, the MCA pulsatility index is normal, reecting
redistribution of blood to the brain (Figure B). If further
decompensation occurs, the MCA pulsatility index decreases,
and diastolic ow to the brain increases.
116
CASE 57
A
B
K = left kidney.
History: A patient in the third trimester has a small-for-
dates pregnancy on physical examination.
1. What should be included in the differential diagnosis based
on the transverse ultrasound image of the third-trimester
fetus shown in Figure A? (Choose all that apply.)
A. Bilateral hydronephrosis of the fetal kidneys from
obstruction of the urethra
B. Bilateral hydronephrosis of the fetal kidneys from bilat-
eral vesicoureteral reux
C. Bilateral extrarenal pelvis of the fetal kidneys
D. Normal fetal kidneys
2. Which of the following imaging ndings is not suggestive
of an obstructive urethral etiology for hydronephrosis?
A. Thick-walled bladder
B. Normal-caliber urethra
C. Dilated urethra
D. Dilated renal pelvis
C
D
3. What is the classic appearance of the fetal bladder in cases
of posterior urethral valves (PUVs)?
A. Large postvoid residual
B. Keyhole bladder
C. Bladder diverticulum
D. Cystocele
4. In a term fetus, what is the upper limit of normal for the
renal pelvis?
A. 4 mm
B. 1 mm
C. 10 mm
D. 20 mm
117
ANSWERS
CASE 57
Posterior Urethral Valves
1. A and B
2. B
3. B
4. C
References
Hutton KA, Thomas DF, Davies BW: Prenatally detected posterior urethral
valves: qualitative assessment of second trimester scans and prediction of
outcome. J Urol 1997; 158(3 Pt 2):1022-1025.
http://www.ncbi.nlm.nih.gov/pubmed/9258134 (Accessed on June 12,
2012.)
Kaefer M, Peters CA, Retik AB, et al: Increased renal echogenicity: a sono-
graphic sign for differentiating between obstructive and nonobstructive eti-
ologies of in utero bladder distension. J Urol 1997; 158(3 Pt 2):1026-1029.
http://www.ncbi.nlm.nih.gov/pubmed/9258135 (Accessed on June 12, 2012.)
Montemarano H, Bulas DI, Rushton HG, et al: Bladder distension and pyel-
ectasis in the male fetus: causes, comparisons, and contrasts. J Ultrasound
Med 1998; 17(12):743-749.
http://www.ncbi.nlm.nih.gov/pubmed/9849946 (Accessed on June 12, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 459-460, 463-464, 468.
Comment
Enlarged Fetal Bladder
Detection of an enlarged fetal bladder immediately raises suspicion for an obstructive etiology. The bladder lls and empties every 15 to 45 minutes; the fetus should be imaged over
time to determine if the bladder empties. Bladder dilation
can be caused by obstructive etiologies (e.g., PUVs in males,
urethral atresia in females) or nonobstructive etiologies (e.g.,
prune-belly syndrome, megacystis-megaureter syndrome).
Dilation of the pelvicaliceal system (hydronephrosis) and
ureter (hydroureter) can be caused by obstructive etiologies
(e.g., PUVs, urethral atresia, ectopic ureterocele) or by nonobstructive etiologies (e.g., prune-belly syndrome, megacystismegaureter syndrome, vesicoureteral reux).
Bladder Abnormality and Fetal Gender
Determining fetal gender is important in cases of urinary tract
obstruction. In a male fetus, the most likely diagnosis is an
obstructive uropathy secondary to PUVs, which occurs exclusively in males (Figures A to C). A keyhole appearance of the
urinary bladder is classic for PUVs (Figure D). In one study
of male fetuses, the presence of oligohydramnios, progressive
bladder wall thickening, and dilated posterior urethra was most
suggestive of PUVs, whereas the presence of a patent urachus
was most suggestive of prune-belly syndrome. The presence
of pyelectasis and megacystis without additional amniotic uid,
bladder, urethral, or renal abnormalities was most suggestive
of vesicoureteral reux, ureterovesical junction obstruction, or
nonreuxing, nonobstructive megacystis-megaureter.
Timing of Detection of Obstruction and Fetal
Outcome
The timing of detection and the degree of obstruction have
been shown to be predictors of outcome in fetuses with
PUVs. An obstructed bladder detected before 28 weeks’ gestation is associated with a poor prognosis. Obstruction of
the urinary tract that results in dilation detected at this early
age often results in intrauterine death or poor renal function
in infants who survive. With moderate to severe upper tract
dilation, the prognosis is signicantly worse than with isolated bladder distention or mild upper tract dilation. Moderate to severe dilation is dened as an anteroposterior diameter
of the renal pelvis of 10 mm or greater with caliectasis.
Detection of echogenic kidneys or cystic renal parenchymal
changes indicates renal dysplasia, which is also associated
with a poor prognosis. In utero, decompression can be performed with vesicoamniotic shunt placement. However, this
procedure has not been shown to improve outcome. Nonetheless, detection of PUVs and characterization of the degree
of obstruction may be helpful in counseling parents about
the prognosis.
118
CASE 58
A
CRL = crown rump links.
B
D
History: A patient with a positive beta–human chorionic
gonadotropin (β-hCG) and pelvic pain presents to be examined for the presence of a normal gestational sac.
1. What criteria are used to aid in distinguishing a normal
intrauterine pregnancy (IUP) from an abnormal one?
(Choose all that apply.)
A. A gestational sac seen on transvaginal ultrasound with
a mean sac diameter (MSD) of 25 mm or more should
contain a visible embryo.
B. A yolk sac should be visible when the MSD seen on
transvaginal ultrasound is 25 mm or more.
C. Fetal heart motion is usually detected when the fetal
pole is equal to or greater than 2 mm.
D. Visualization of an amnion and the yolk sac but not an
embryo when the gestational sac is 25 mm or more in
mean sac diameter raises the question of pregnancy loss.
2. What does the most recent data suggest about the use of
an absolute isolated quantitative beta hCG to determine the
timing of the appearance of a gestational sac in the uterus
on transvaginal ultrasound?
A. The absolute value of the quantitative beta hCG should
not be used to determine whether a true intrauterine
gestational sac could be seen.
B. 1000 mIU/mL is the threshold to see a gestational sac.
C. 5000 mIU/mL is the threshold to see a gestational sac
in the uterus.
D. 10,000 mIU/mL is the new threshold to see a gesta-
tional sac in the uterus.
3. What is the signicance of an abnormal or absent yolk sac?
A. Poor pregnancy outcome
B. No signicance
C. Certain mortality
D. Rarely deleterious
4. Why is it so important to evaluate early intrauterine sacs
C
very carefully?
A. Methotrexate is being used with increased frequency if
an ectopic pregnancy is suspected.
B. A sac often represents decidual reaction of an ectopic
pregnancy.
C. Twins or triplets are likely.
D. A miscarriage is likely.
119
ANSWERS
CASE 58
Early Intrauterine Gestational Sac
1. A, B, and D
2. B
3. A
4. A
References
Chiang G, Levine D, Swire M, et al: The intradecidual sign: is it reliable for
diagnosis of early intrauterine pregnancy? AJR Am J Roentgenol 2004;
183(3):725-731.
http://www.ncbi.nlm.nih.gov/pubmed/15333362 (Accessed on June 12, 2012.)
Dogra V, Paspulati RM, Bhatt S: First trimester bleeding evaluation. Ultrasound
Q 2005; 21(2):69-85.
http://www.ncbi.nlm.nih.gov/pubmed/15905817 (Accessed on June 12, 2012.)
Kurtz AB, Needleman L, Pennell RG, et al: Can detection of the yolk sac
in the rst trimester be used to predict the outcome of pregnancy? AJR
158:843 -847, 1992.
http://www.ncbi.nlm.nih.gov/pubmed/1546604 (Accessed on June 12, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 342, 347, 352, 353, 359.
Comment
Normal versus Abnormal Intrauterine Pregnancy
Many ultrasound imaging criteria have been described to aid in
distinguishing a normal IUP from an abnormal IUP or anembryonic gestation. A gestational sac with an MSD of 16 mm
or more without an embryo is an ultrasound sign of anembryonic gestation. When any early pregnancy is being evaluated,
it is essential to know the quantitative β-hCG level and which
international standard (IS) is being performed in the laboratory. There are three different tests: rst, second, and third IS.
The rst IS is twice the second IS. The third IS is 1.8 times the
second IS (similar to the rst).
Significance of Beta–Human Chorionic
Gonadotropin Level
Data have suggested that an intrauterine sac should be visible
with a β-hCG level of 1000 mIU/mL using the rst and third
IS. In cases in which the β-hCG level is 1000 to 2000 mIU/mL
and no IUP is seen with transvaginal ultrasound, ectopic pregnancy becomes a concern. However, a study showed that in
cases in which no denite IUP was visible by transvaginal
ultrasound with a β-hCG level of 2000 mIU/mL, normal
pregnancies subsequently developed in one third of cases.
Careful interpretation of these studies is essential because
obstetricians are administering methotrexate with increasing
frequency if they suspect an ectopic pregnancy when no IUP
is visible on ultrasound. Close follow-up should be considered
if clinically appropriate.
Gestational Sac
When an early sac is identied in the uterus, transvaginal
scanning is often required to visualize a yolk sac or a small
fetal pole. A yolk sac should be visible when the MSD is
25 mm or greater; the fetal pole should be visible when the
MSD is 25 mm or greater. However, follow-up should be
recommended in 7 to 10 days because a normal IUP may be
identied later even when these criteria are not met (some
embryos are not visualized until the MSD is greater than
25 mm). If a fetal pole is seen (Figure A), fetal heart motion
is usually detected when the pole is 6 mm or greater. The size
of the fetal pole in relation to the sac is also predictive of outcome. If the fetal pole is too small for the sac or too large for
the sac, fetal demise often results. Visualization of an amnion
(and the yolk sac) but not an embryo (empty amnion) when
the gestational sac mean diameter is 25 mm or greater is associated with pregnancy loss. However, it is essential to be careful when interpreting these studies, because methotrexate is
being administered with increasing frequency by obstetricians
if an ectopic pregnancy is suspected when no IUP is visible on
ultrasound. Close follow-up should be considered if clinically appropriate. New data have shown that the β-hCG absolute quantitative value should no longer be used to determine
a cutoff value for ability to see an early intrauterine gestational
sac in transvaginal ultrasound.
Yolk Sac
The yolk sac (actually the secondary yolk sac) becomes visible before the fetal pole (Figure C). The yolk sac is responsible for nutritional, endocrine, metabolic, immunologic, and
hematopoietic functions in organ formation before placental
circulation has been completed. An abnormal or absent yolk
sac is associated with poor pregnancy outcome. However,
the presence of a normal-appearing yolk sac is not consistently predictive of a normal early pregnancy. A large yolk sac
(9 to 10.8 mm; Figure D) is a sign of possible impending fetal
demise, and close follow-up is indicated. Also, normal yolk
sacs are smooth, spherical, lucent, and not calcied. However,
transient abnormally shaped yolk sacs have resulted in normal
pregnancies.
120
CASE 59
A
B
History: A patient has an ultrasound scan that raises a ques-
tion of a fetal intracranial abnormality.
1. What should be included in the differential diagnosis for
Figure A? (Choose all that apply.)
A. Alobar holoprosencephaly
B. Agenesis of corpus callosum
C. Hydranencephaly
D. Severe hydrocephalus
E. Schizencephaly
2. All of the following are typical ndings of hydranencephaly
except:
A. The cerebral hemispheres are absent.
B. Thalami usually are present and not fused.
C. There is a midline falx.
D. Ependyma is present in the CSF cavity.
C
3. Which of the following conditions is not considered to be
potentially associated with hydranencephaly?
A. Trisomy 21
B. Toxoplasmosis
C. Intrauterine demise of one twin of a monochorionic
pregnancy
D. Fetal hypoxia
4. Which of the following statements concerning hydranencephaly is false?
A. Hydranencephaly is associated with renal dysplasia.
B. Hydranencephaly is associated with polyvalvular devel-
opment of fetal heart defects.
C. Long-term survival is poor.
D. Hydranencephaly is commonly associated with an
increased rate of fetal facial anomalies.
121
ANSWERS
CASE 59
Hydranencephaly
1. C
2. D
3. A
4. D
References
Hahn JS, Lewis AJ, Barnes P: Hydranencephaly owing to twin-twin transfu-
sion: serial fetal ultrasonography and magnetic resonance imaging ndings.
J Child Neurol 2003; 18(5):367-370.
http://www.ncbi.nlm.nih.gov/pubmed?term=12822826 (Accessed on June
13, 2012.)
McGahan JP, Ellis W, Lindfors KK, et al: Congenital cerebrospinal uid-
containing intracranial abnormalities: a sonographic classication. J Clin
Ultrasound 1988; 16(8):531-544.
http://www.ncbi.nlm.nih.gov/pubmed?term=3152397 (Accessed on June
13, 2012.)
Winter TC, Kennedy AM, Byrne J, et al: The cavum septi pellucidi: why is it
important? J Ultrasound Med 2010; 29(3):427-444.
http://www.ncbi.nlm.nih.gov/pubmed?term=20194938 (Accessed on June
13, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 382-383.
Comment
Differential Diagnosis
The differential diagnosis in this case of a massive cerebrospinal uid collection is straightforward. Massive hydrocephalus
may occur, but usually a small mantle of brain tissue is present.
Midline structures and the brainstem structures, including thalami and choroid plexus, are present. Alobar holoprosencephaly
is associated with midline defects of the brain and of the face,
including fused thalami, lack of a falx, and a monoventricular cavity surrounded by cerebral tissues. Hydranencephaly is
associated with near-complete absence of the cerebral hemispheres, nonpaired thalami, and presence of the falx. It is the
most correct diagnosis in this case.
Ultrasound Findings
Ultrasound features of hydranencephaly include the absence of
the cerebral hemispheres (Figure A). The falx is often present as
shown on postnatal MRI (Figures B and C). Brainstem structures
are present, including the thalami, which are usually not fused.
Hydranencephaly is thought to be due to a destructive
process of the brain that leads to liquefactive necrosis of the
cerebral hemispheres. This necrosis is usually thought to be
secondary to occlusion of the carotid arteries. Any potential
etiology that would cause massive cerebral infarction, including fetal hypoxia, in utero demise of one twin, and severe in
utero infection, can lead to necrotizing vasculitis resulting in
hydranencephaly.
Prognosis and Management
The prognosis for hydranencephaly is dismal. Most fetuses
affected with hydranencephaly do not survive the rst year of
life. There is probably little recurrent risk for hydranencephaly;
the exception would be a persistent infectious disorder that would
cause recurrent uterine infection and destruction of the fetal
brain owing to necrotizing vasculitis or other cerebral destruction.
122
CASE 60
A
D
History: A 24-year-old woman presents with persistent
abnormal vaginal bleeding postpartum.
1. What should be included in the differential diagnosis?
(Choose all that apply.)
A. Pelvic inammatory disease
B. Retained products of conception (POC)
C. Endometritis
D. Endometrial polyp
2. What is the normal endometrial thickness after a spontaneous abortion or a dilatation and curettage?
A. No greater than 5 mm
B. Greater than 10 mm
C. Less than 3 mm
D. There is no normal value.
B
3. What is the role of Doppler ow in this case?
A. It is denitive for retained POC.
B. It is rarely helpful to make the diagnosis of retained
POC.
C. The low-resistance arterial ow is seen in trophoblastic
tissue.
D. High-resistance arterial ow is seen in trophoblastic
tissue.
4. Which of the following is not a presenting nding in retained
POC?
A. Fever after incomplete pregnancy loss or abortion
B. Uterine tenderness
C. Vaginal bleeding
D. Urinary frequency
C
123
ANSWERS
CASE 60
Retained Products of Conception
1. B and C
2. A
3. C
4. D
References
Durfee SM, Frates MC, Luong A, et al: The sonographic and color Dop-
pler features of retained products of conception. J Ultrasound Med 2005;
24(9):1181-1186.
http://www.ncbi.nlm.nih.gov/pubmed/16123177 (Accessed on June 13, 2012.)
Kaakaji Y, Nghiem HV, Nodell C, et al: Sonography of obstetric and gyneco-
logic emergencies: part 1, obstetric emergencies. AJR Am J Roentgenol 2000;
174(3):841-849.
http://www.ncbi.nlm.nih.gov/pubmed/10701602 (Accessed on June 13,
2012.)
Sadan O, Golan A, Girtler O, et al: Role of sonography in the diagnosis of
retained products of conception. J Ultrasound Med 2004; 23(3):371-374.
http://www.ncbi.nlm.nih.gov/pubmed/15055784 (Accessed on June 13, 2012.)
Cross-Reference
Ultrasound: The REQUISITES, 2nd ed, pp 540-541.
Comment
Clinical Presentation
Retained POC manifest with bleeding, uterine tenderness, and
fever in the rst 10 days after incomplete pregnancy loss, spontaneous or elective abortion, or full-term pregnancy. Complications of a delayed diagnosis may include peritonitis, septic
and hypovolemic shock, disseminated intravascular coagulopathy, and, rarely, osseous endometrial metaplasia.
Ultrasound Imaging
On ultrasound examination, retained POC may be difcult to distinguish from intrauterine decidua, hemorrhage,
and endometrium. After a spontaneous abortion or after a
dilatation and curettage, an endometrial stripe of less than 5
mm in thickness is an excellent, but not absolute, predictor of
the absence of retained POC. Any endometrial collection or
endometrial thickening greater than 5 mm suggests retained
POC (Figures A to D). The endometrial contents may appear
as hypoechoic or hyperechoic solid material, with or without a
mass; heterogeneous uid with solid material; or a solid mass
with calcication. A hyperechoic mass (>15 mm) that expands
the endometrial canal is the best predictor (Figures A to D).
A study determined that an endometrial mass is the most sensitive nding for retained POC; if no mass or uid is seen and
the endometrial thickness is less than 10 mm, retained POC
are unlikely. The presence of color ow on Doppler was not
helpful in that series, but in other studies, Doppler ow has
been more helpful (Figures B to D). Retained trophoblastic
tissue has low-resistance arterial ow, which is uncommonly
seen with endometritis. A more recent study found the reliance
on common signs and symptoms and the use of ultrasound to
diagnose retained POC to be associated with an unacceptably
high false-positive rate.
Differential Diagnosis
The differential diagnosis should include molar pregnancy
(hydatidiform mole), which may manifest with vaginal bleeding.
On ultrasound examination, this tissue may be hyperechoic, as
in this case; however, owing to the multiple uid-lled spaces,
the tissue has good through-transmission. The uterus is usually
greatly enlarged. Active trophoblastic tissue from any source
produces arterial waveforms with elevated diastolic ow (low
impedance) (Figure B). When detected, these waveforms distinguish retained POC from decidua and hemorrhage. However, similar waveforms can be seen with a hydatidiform mole.
If doubt remains between POC and molar pregnancy, evaluation of the serum beta–human chorionic gonadotropin levels
should be diagnostic because a molar pregnancy would have
persistently elevated levels, whereas POC would have low levels that often continue to decline.
124
CASE 61
History: A patient presents with a third-trimester, large-for-
dates gestation.
1. What should be included in the differential diagnosis for
the ultrasound ndings in Figure A? (Choose all that apply.)
A. A large amount of peritoneal uid from fetal hydrops
B. A large amount of peritoneal uid from cystic hygroma
L
with diffuse lymphatic obstruction
C. A large amount of peritoneal uid from obstruction by
a mass not seen in these images
D. A large amount of peritoneal uid from a sacrococcy-
geal teratoma, which leads to hydrops from high vascular outow from the tumor
AA
L = liver.
BB
2. What is one of the earliest ultrasound ndings of nonimmune hydrops?
A. A large amount of peritoneal uid
B. Oligohydramnios
C. Enlarged nuchal translucency at 9 weeks’ gestation
D. Pericardial uid
3. How does the Doppler tracing of the umbilical artery (Figure B) help in the diagnosis of this case of nonimmune
hydrops?
A. Fetal tachyarrhythmia (trigeminy)
B. Fetal bradycardia
C. Fetal tardus parvus waveform
D. A Doppler tracing does not help narrow the cause of
nonimmune hydrops.
4. What is the outcome of a fetus with severe nonimmune
hydrops?
A. Good
B. 50% do very well
C. Poor, with mortality greater than 70%
D. Almost always fatal
125