Imaging the pregnant patient with right lower quadrant pain

Julia R. Fielding, M.D.

Julia_fielding@med.unc.edu

RSNA 2010

Ultrasound is test of choice• First trimester

– With bleeding

exclude ectopic pregnancy

renal stones

-Without bleeding

ovarian pathology

Ectopic Pregnancy• No IUP and positive pregnancy test• 1/3 of those with ectopic pregnancy will have a normal

US exam• Those with a simple adnexal cyst have a 10% likelihood

of ectopic pregnancy• A complex non-ovarian mass has a sensitivity of 84%,

specificity 99% and positive predictive value of 96% for ectopic pregnancy

• Complex fluid/blood is often presentDighe M et al, J Clin Ultrasound 2008;36:352-366

ECTOPIC PREGNANCY

Courtesy Dr. D. Brown, Mayo Clinic

Renal stones

Incidence of 1/1500 pregnancies

Stones that are >5mm, located in the proximal ureter and of irregular shape usually will require treatment

US will identify hydronephrosis

Ureteral jets indicate an incompletely obstructed ureter and may spare the patient a stent

HYDRONEPHROSIS

BLADDER STONE

SCOUT 10 MINUTE

Right mid ureteral stone

Differential diagnosis ovarian pathology

• Corpus luteum cyst – Usually 2-5cm, can be up to 10cm in size– Regresses week 11-16 as placenta develops

• Simple cyst/hemorrhagic cyst/endometrioma/dermoid

• Torsion – 70% cases with abnormal adnexa• Cancer very rare

Simple Cyst

Courtesy Dr. D. Brown, Mayo Clinic

Ovarian torsion

Use of CT increasing

N Engl J Med 2007;357:2777-84

What are the numbers?• 62 million CT scans annually, 4 million in children• University of North Carolina ER data:• 2000-2005, pediatric admissions increased 2%, chest CT

increased by 435%, abdominal CT by 49% (Emerg Radiol 2007;14:227-32)

• Brown University, Rhode Island Hospital data:• Number of pregnant women scanned increased 89% in

10 years with only a 7% increase in admissions (RSNA 2007)

Why do we worry?• In general, fetal absorption is 40% that of

maternal abdomen• Ex: Maternal pelvic CT dose is 4cSv, fetal dose

is 1.6 -1.8 cSv (1cSv =1 rem)• This is well below the 10cSv level for teratogenic

effects• However….

Invest Radiol 2000;35:527-533

Why do we worry?• Young children (and presumably those in

utero) are most susceptible to radiation damage and therefore at higher risk for development of cancers later in life

• Organs involved are brain, digestive tract, bone marrow (leukemia)

N Engl J Med 2007;357:2277-84

N Engl J Med 2007;357:2277-84

What can we do?Have a plan!

1.Balance risks/benefits – talk over the procedure with the referring physician and make sure CT is needed and is the test of choice.

2. Let the referring physician discuss and document the need for the CT scan in the medical record

What can we do?

3.Get written and oral informed consent for use of radiation (see new ACR guidelines)

4.Avoid multiple CT scans – radiation effects are cumulative

5.Use best scanning techniques – automatic dose reduction is useful, beware dropping the maS so low that the scan is not diagnostic

What are the indications for CT scan in pregnancy?

• 1. Renal stones when US is indeterminate particularly in 2nd/3rd trimester

• 2. Appendicitis – MR is now test of choice, CT appropriate for IBD, obstruction

• 3. Cancer staging – substitute MR if possible• 4. Lung disease – PE studies and V/Q scans yield

similar radiation doses• 5. Trauma – use your routine protocol, most common

cause of fetal death is maternal death• 6. Intracranial hemorrhage

What is the radiation dose to the fetus?

• For CT examination of head, extremities and chest, minimal <10 mSv

• For CT of the abdomen/pelvis, moderate 1.6-1.8 cSv

Is there a risk to the use of IV contrast agent?

• Very minimal risk of depression of fetal thyroid function by free iodide

• Water-soluble contrast agents (100cc) contain 5 micrograms of free iodide, less than 1/10th the level known to cause thyroid dysfunction in neonates

• Exception would be maternal renal failure when free iodide not excreted back across placenta

Eur Radiol 2005;15:1234-1240

Radiology 2010;256:744-750

Flank pain/obstructing ureteral stone

• Choice 1: Ultrasound with hydronephrosis, severe pain, stent placed prophylactically under ultrasound guidance

• Choice 2: <24 weeks, limited IVU• Choice 3: >24 weeks, helical CT

HYDRONEPHROSIS

SINGLE LEFT JET

RIGHT HYDRONEPHROSIS

DIILATED URETER

COMPRESSED URETER

Lower abdominal pain with suspicion of appendicitis

• Ultrasound, followed by• Choice 1: MRI of the abdomen and pelvis• Choice 2: Contrast-enhanced helical CT

27 year old woman, 33 weeks pregnant with negative ultrasound

Courtesy Dr. E. Lazarus, Rhode Island Hospital

Cancer staging of the abdomen and pelvis

• Choice 1: MRI of the abdomen and pelvis, judicious use of Gd-DTPA

• Choice 2: Contrast-enhanced CT of the abdomen/pelvis

I+ CT

Jejunal adenoCA with SBO

Recurrent gastric cancer

TRAUMA• Use your routine protocol• Intravenous contrast agent always

necessary, oral contrast agent varies by institution

Ruptured splenic artery aneurysm

When do we use MRI in pregnancy?

• 1. The information requested from the MR study cannot be acquired using US

• 2. The data are needed to affect the care of the patient or fetus during the pregnancy

• 3. The referring physician does not feel is is prudent to wait until the patient is no longer pregnant to obtain these data.

When do we use MRI during pregnancy?

• In general, when the information to be obtained is absolutely essential to the well being of the mother or child

• Specifically, – RLQ pain, suspicion of appendicitis/bowel disease– Characterization of an adnexal mass– Cancer staging– Choledocholithiasis– Head and back injuries– Fetal/placental abnormalities

Safety issues• Present data have not conclusively

documented any deleterious effects of MR imaging exposure on the developing fetus

• All pregnant women should understand and sign a consent for the performance of MRI

What about Gd chelates and fetal renal development?

• Gd chelates do pass through the placenta and remain in the amniotic fluid

• Because of our lack of knowledge regarding contrast/fetal kidneys, avoid Gd chelates in pregnant women unless absolutely necessary - cancer staging/vascular issues such as aneurysm, AVM

Basic protocol for maternal abd/pelvis

• Sagittal/axial/coronal ultrafast T2 weighted images (HASTE/SSFSE) using large FOV and torso coil if possible. Axial T2W series performed with fat saturation.

• Ax T1 weighted image with fat sat through pelvis (to locate blood)

• Patient supine or in left lateral decubitus position

Appendicitis• Incidence 1:1500 pregnancies• Graded compression US is impractical after the first

trimester• MRI is test of choice – excellent NPV for

appendicitis in those patients with a normal US (94%)

• Alternative is CT (fetal dose 1.8cGy)• Appearance on T2WI: Tube >6mm, often vertical,

just below TI with adjacent high signal edema

Case 1

Case 2

TERMINAL ILEUM

APPENDIX

Acute appendicitis with perforation

Low signal appendicolith adjacent to appendix

Case 3

Bowel inflammation/obstruction

• Incidence SBO in pregnancy is 1 in 1500 to 1 in 66,500.

• Majority due to adhesions, volvulus, internal hernias and inflammatory bowel disease

• MRI has a 95% sensitivity for obstruction, while location of transition point can be identified in 70-90%

Small bowel adhesions• Third trimester pregnancy• s/p total colectomy for UC with formation

of J pouch• Small bowel obstruction to right of uterus

POINT OF TRANSITION

Uterine leiomyomata• Leiomyoma is the most common adnexal mass

with an prevalence of 40%• These masses grow during pregnancy• May torse, bleed or interfere with fetal

development or delivery (LUS fibroid)• Bridging vessels from the uterus and/or

continuirity of the serosa are diagnostic of a fibroid

Uterine leiomyomata• Round, well-demarcated• Variable T2 signal intensity • High T1 signal intensity indicated bleeding,

“red degeneration”

Fibroid in patient with lupus

First trimester pregnancy

Pancreatitis• Pregnant female, 2nd trimester with

abdominal pain and elevated amylase• Diagnosis – pancreatitis• Are there stones involved?

YES!

T2-weighted/fat sat images - PANCREATITIS

CHOLEDOCHOLITHIASIS

Renal mass identified on US

Placenta previa

Does this work with AIP?• Usually not• Percreta may sometimes be identified if

there is extension of placenta into bladder or when the placenta is posterior

• Accreta and increta can rarely be identified

References• Pedrosa I, et al. Magnetic resonance imaging of

right lower quadrant pain in pregnant and non-pregnant patients. Radiographics 2007; 27:721-743

• Fielding JR, et al. Magnetic resonance imaging of abdominal pain during pregnancy. Top Magn Reson Imaging 2006;17:409-416

References• Wieseler KM, Imaging in pregnant

patients: Examination appropriateness. Radiographics 2010; 30: 1215-1229

Thank you