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Nov 18, 2011

The list of potential badness in the pregnant patient with right lower quadrant pain is long and distinguished, but it often comes down to a simple question, "Does this patient have appendicitis?" The subtext of this question is, "Is this patient going to need a CT scan?" Nobody likes ordering am abdominal CT on a pregnant patient because, no matter how low the statistical risk of damage to the fetus, there is still potential harm from ionizing radiation. As you will see below, the risk of immediate  maternal and fetal harm is far greater than the long term risk of ionizing radiation exposure.

Interview with Ingrid Lim MD at ACEP 2011

Risk of mortality with appendicitis in pregnancy:

In a pregnant patient with unperforated appendicitis, fetal loss is 3-5%. With perforation, fetal loss skyrockets: -30% in trimesters 1 and 2 -70% in trimester 3

Maternal mortality is 1% without  perforation and 4% with perforation

Diagnosis:

Step 1: Ultrasound- more sensitive in the 1st vs. 3rd trimester. Even though it may be inconclusive as far as appendicitis, ultrasound can give valuable information about the fetus, uterus, ovaries, kidneys and gallbladder. If ultrasound doesn't give the answer....

Step 2: MRI without contrast DO NOT USE GADOLINIUM:CONTRAINDICATED IN PREGNANCY If no MRI available...

Step 3: CT with or without contrast depends on your local radiologist. Contrast (IV or PO) is considered safe in pregnancy. Research has shown that contrast does not harm fetal thyroid

RADIATION PRIMER for CT Appy protocol 

Fetal background radiation exposure during 9 months of pregnancy 0.1 rad (1mGy) Teratogenesis threshold: 5 rad (50mGy)

Estimated fetal radiation exposure from CT Appy protocol:

Trimester 1: 2.4 rad (24mGy)

Trimesters 2 and 3: 3 rad (30mGy)

Teratogenesis - fetal death. malformation or developmental delay from in utero radiation exposure. The threshold for a <1% teratogenesis risk is 5 rad (50mGy). The highest risk period is 3-15 weeks. The amount of radiation absorbed from a CT appy protocol is less than the 5 rad teratogenic threshold.   Even with exposure to 10 rads,  there is a 99% chance of no fetal teratogenic effects.

Carcinogenesis-    Most worrisome for childhood cancers such as leukemia. The baseline risk of dying from childhood cancer is  1 in 2000. A 5 rad exposure is believed to increase that risk to 2 in 2000. While that is a doubling of the relative risk, it is still small compared the rate of fetal loss from a ruptured appendix.

Bonus section: Ectopic Pregnancy and HCG levels

Traditional teaching holds that if the HCG does not double in the first 48 hours, consider ectopic. But many patients do not follow this curve. With  the development of more sensitive assays, a minimum rise of 53% over 48 hrs is acceptable. 3% of ectopic pregnancies can have a negative serum HCG

Two theories: 1.     Have to have a viable trophoblast to produce HCG, no trophoblast…no HCG    2.  Ectopic died then ruptured

Bottom line, if patient looks sick and there is a lot of free fluid in the pelvis –go to surgery

Written Summary:  Justin Arambasick MD  Akron General  Medical Center and Rob Orman MD

A good article on MRI uses in pregnancy

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