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Lucy B. Spalluto, MD • Courtney A. Woodfield, MD2 • Carolynn M.
DeBenedectis, MD • Elizabeth Lazarus, MD
Clinical diagnosis of the cause of abdominal pain in a pregnant patient
is particularly difficult because of multiple confounding factors related
to normal pregnancy. Magnetic resonance (MR) imaging is useful in
evaluation of abdominal pain during pregnancy, as it offers the benefit
of cross-sectional imaging without ionizing radiation or evidence of
harmful effects to the fetus. MR imaging is often performed specifi-
cally for diagnosis of possible appendicitis, which is the most common
illness necessitating emergency surgery in pregnant patients. However,
it is important to look for pathologic processes outside the appendix
that may be an alternative source of abdominal pain. Numerous enti-
ties other than appendicitis can cause abdominal pain during pregnancy,
including processes of gastrointestinal, hepatobiliary, genitourinary,
vascular, and gynecologic origin. MR imaging is useful in diagnosing
the cause of abdominal pain in a pregnant patient because of its ability
to safely demonstrate a wide range of pathologic conditions in the ab-
domen and pelvis beyond appendicitis.
©RSNA, 2012 • radiographics.rsna.org
MR Imaging Evaluation
of Abdominal Pain during
and Other Nonobstetric
FOR TEST 1
After completing this
will be able to:
■Describe the nor-
mal abdominal and
pelvic anatomy of
the pregnant patient
at MR imaging.
■List the MR im-
aging findings of
■Recognize the MR
of entities beyond
appendicitis that can
cause abdominal or
pelvic pain in preg-
Abbreviations: ACR = American College of Radiology; FISP = fast imaging with steady-state precession; GRE = gradient-echo; HELLP = hemoly-
sis, elevated liver enzyme levels, and low platelet count; IBD = inflammatory bowel disease; SSFSE = single-shot fast spin-echo
RadioGraphics 2012; 32:317–334 • Published online 10.1148/rg.322115057 • Content Codes:
1From the Department of Diagnostic Imaging, Warren Alpert Medical School of Brown University, Women and Infants Hospital, Rhode Island
Hospital, Providence, RI. Presented as an education exhibit at the 2010 RSNA Annual Meeting. Received March 18, 2011; revision requested May
12 and received July 5; accepted July 20. For this journal-based CME activity, the authors, editor, and reviewers have no relevant relationships to
disclose. Address correspondence to L.B.S., Department of Radiology, Vanderbilt University Medical Center, 1161 21st Ave S, Nashville, TN 37232
2Current address: Diagnostic Imaging, Trevose, Pa.
318 March-April 2012 radiographics.rsna.org
Pregnant patients frequently present with non-
specific abdominal pain that requires medical at-
tention. Diagnosis of abdominal pain in pregnant
women is confounded by several factors found in
a normal pregnancy. Such confounding factors
include nonspecific leukocytosis, displacement
of abdominal and pelvic structures from their
normal locations by the gravid uterus, a difficult
abdominal examination, and nonspecific nausea
and vomiting (1,2). Yet, accurate and efficient di-
agnosis of the source of abdominal pain is impor-
tant, as a delay in diagnosis can be detrimental to
the condition of both the mother and fetus (3).
Often, when a pregnant patient presents with
abdominal pain, the diagnosis of appendicitis
must be considered, as it is the most common ill-
ness necessitating emergency surgery in pregnant
patients (4). Magnetic resonance (MR) imaging
allows determination of the presence or absence
of appendicitis without the drawback of expos-
ing pregnant patients to the ionizing radiation of
computed tomography (CT) (5). In addition, the
excellent soft-tissue contrast resolution of MR
imaging has the added benefit of allowing evalu-
ation of numerous additional structures within
the field of view that may be the source of the
patient’s abdominal pain.
In this article, we briefly review the MR imag-
ing technique used for evaluating abdominal pain
in the pregnant patient. We then illustrate the nor-
mal anatomy of the pregnant female pelvis at mul-
tiplanar MR imaging and review the findings of
acute appendicitis in the pregnant patient. Finally,
we discuss the appearances of numerous entities
other than appendicitis that can be a source of
abdominal pain in the pregnant patient, including
processes of gastrointestinal, hepatobiliary, genito-
urinary, vascular, and gynecologic origin.
MR Imaging Technique
Given that no study, to our knowledge, has dem-
onstrated deleterious effects on the fetus second-
ary to MR imaging, the American College of
Radiology (ACR) approves of MR imaging of the
pregnant patient in any trimester, including the
first (6). The ACR does continue to reinforce the
need to assess the potential risk versus benefit of
MR imaging in the pregnant patient and also the
need to determine whether the MR imaging may
be delayed until after pregnancy.
Although the radiofrequency energy used
in MR imaging is nonionizing, it does deposit
energy in the patient in the form of heat. In addi-
tion, the pulse sequences generally used for fast
fetal imaging, such as single-shot fast spin-echo
(SSFSE) sequences, deposit more radiofre-
quency energy in the body than do the standard
gradient-echo (GRE) sequences owing to the
multiple radiofrequency pulses used in succes-
sion (6). Although the predicted fetal tempera-
ture rises associated with MR imaging are below
the expected teratogenic levels, the potential risk
of heating the fetus and amniotic fluid should be
The amount of energy deposited in the
patient, or the specific absorption rate, is
monitored by all modern MR imaging systems
to ensure compliance with safety guidelines, al-
though the guidelines are generally designed for
the nonpregnant patient. However, studies that
used a realistic model of the pregnant patient
have demonstrated that the maximum localized
specific absorption rate resides in the mother,
not the fetus (6). The ACR does not recommend
the administration of gadolinium contrast mate-
rial to pregnant women, as gadolinium-based
contrast agents have been shown to cross the
placental barrier (8).
At our institution, a 1.5-T MR imaging
system is used for abdominal imaging in preg-
nant patients. MR imaging for appendicitis can
be performed with or without an oral contrast
material preparation similar to that used for
CT (eg, 600 mL of barium sulfate administered
2 hours before the examination). We initially
used oral contrast material for our MR imag-
ing examinations for appendicitis but recently
transitioned to performing them without oral
contrast material. The patient is imaged in the
RG • Volume 32 Number 2 Spalluto et al 319
Figure 1. Normal appearance of the pregnant pelvis at 12 weeks gestation. (a) Sagittal T2-weighted SSFSE image
shows the gravid uterus during a myometrial contraction (arrows). (b) Axial T2-weighted SSFSE image shows the
normal appendix in the right lower quadrant (arrow).
supine position with a surface phased-array coil
covering the abdomen and pelvis.
A comprehensive multiplanar imaging proto-
col is used for evaluating the appendix and other
potential sources of abdominal pain. The field of
view for the examination extends from the dome
of the liver superiorly through the symphysis pu-
bis inferiorly. The protocol includes axial, sagittal,
and coronal T2-weighted SSFSE sequences; axial
true fast imaging with steady-state precession
(FISP) sequences; axial in-phase and out-of-
phase T1-weighted GRE sequences; and axial
short tau inversion-recovery sequences.
The multiplanar T2-weighted SSFSE im-
ages allow imaging of the bowel in a relatively
motionless state and help confirm the location
of the appendix in more than one plane. The
axial T1-weighted GRE images are obtained to
confirm appendiceal patency by demonstrat-
ing blooming artifact from air or oral contrast
material in the appendix lumen from out-of-
phase to in-phase imaging. The axial true FISP
images help differentiate high-signal-intensity
adnexal vessels from the lower signal intensity
of a normal appendix, and the axial short tau
inversion-recovery sequence is used to highlight
any periappendiceal edema or fluid associated
of the Pregnant Patient
Before interpreting images for pathologic find-
ings in the pregnant patient, it is necessary to
understand the normal anatomy of the preg-
nant pelvis at multiplanar MR imaging and
pregnancy-associated anatomic changes. In early
pregnancy, the uterus maintains its normal ver-
sion and flexion, which is usually anterior and is
best illustrated on sagittal images (Fig 1). The
bladder lies immediately anterior and inferior to
the uterus. The vagina is posterior to the blad-
der and urethra and anterior to the rectum and
anus. The ovaries lie within the pelvis lateral to
the midline uterus and are suspended by the
mesovarium, broad ligaments, and suspensory
infundibulopelvic ligaments (9). The ovaries
are easily recognized because of the high signal
intensity of the follicles.
RG • Volume 32 Number 2 Spalluto et al 333
Figure 19. Ovarian edema in a pregnant patient at 12
weeks gestation. Axial T2-weighted fat-saturated SSFSE
image shows an enlarged, edematous right ovary (arrow)
and a normal left ovary (arrowhead).
teratoma or enlarged corpus luteal cyst remains a
more common scenario. Early diagnosis is crucial
to allow ovary-sparing surgery (41).
MR imaging features of ovarian torsion during
pregnancy include an enlarged ovary and a thick-
ened, twisted fallopian tube (Fig 18) (31). On
T1-weighted images, the signal intensity varies
according to the age of internal blood products.
Late torsion demonstrates increased signal inten-
sity on T2-weighted images owing to necrosis.
A rare entity that may cause pain in pregnancy is
ovarian edema secondary to compression of the
ovarian vasculature between the enlarging gravid
uterus and anterior pelvic wall. Ovarian edema
may also arise secondary to partial or intermit-
tent ovarian torsion (35). At MR imaging, ovar-
ian edema appears as ovarian enlargement, ho-
mogeneous low signal intensity on T1-weighted
images and high signal intensity on T2-weighted
images in the ovarian stroma, and peripheral
displacement of ovarian follicles (Fig 19). This
entity occurs most often on the right side.
Abdominal pain in pregnant women can be dif-
ficult to diagnose secondary to multiple con-
founding factors found in normal pregnancy. MR
imaging is often performed as a safe and accurate
method to exclude appendicitis, the most com-
mon cause of abdominal pain necessitating sur-
gery in pregnant women. MR imaging also allows
evaluation of numerous additional structures
in the abdomen and pelvis that may be the true
source of abdominal pain in the pregnant patient.
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This journal-based CME activity has been approved for AMA PRA Category 1 Credit
TM. See www.rsna.org/education/rg_cme.html.
Teaching Points March-April Issue 2012
MR Imaging Evaluation of Abdominal Pain during Pregnancy: Appendicitis
and Other Nonobstetric Causes
Lucy B. Spalluto, MD • Courtney A. Woodfield, MD • Carolynn M. DeBenedectis, MD • Elizabeth Lazarus, MD
RadioGraphics 2012; 32:317–334 • Published online 10.1148/rg.322115057 • Content Codes:
Diagnosis of abdominal pain in pregnant women is confounded by several factors found in a normal
pregnancy. Such confounding factors include nonspecific leukocytosis, displacement of abdominal and
pelvic structures from their normal locations by the gravid uterus, a difficult abdominal examination, and
nonspecific nausea and vomiting (1,2).
Page 321 (Figure on page 321)
MR imaging features of appendicitis include an appendiceal diameter greater than 7 mm, an appendiceal
wall thickness greater than 2 mm, high-signal-intensity luminal contents on T2-weighted images due to
fluid or edema, and hyperintense periappendiceal fat stranding and fluid (Fig 3).
The terminal ileum is the most commonly affected portion of the gastrointestinal tract (~80% of cases),
making IBD a good mimic of appendicitis (14).
Page 326 (Figure on page 327)
Features of obstructive hydronephrosis at MR imaging include renal enlargement, perinephric fluid, and an
abrupt change in ureteral caliber above or below the uterus (Fig 10).
Most adnexal masses are asymptomatic during pregnancy, but they may cause pain if they rupture,
rapidly enlarge, or serve as a lead point for torsion (2,35). MR imaging allows differentiation of extra-
ovarian masses such as an exophytic fibroid or ectopic pregnancy from an actual ovarian mass.