Abdominal Pain in Early PregnancyCommentary by Charlie C. Kilpatrick, MD
Case & Commentary—Part 1
A 34-year-old woman who was 14 weeks pregnant presented to the emergency department (ED) with 5 days of nonspecific abdominal pain, nausea, and vomiting. On examination, she appeared well with normal vital signs and had some mild diffuse abdominal tenderness. Her white blood cell count was 19,000 cells/μL, and a urinalysis was positive for nitrates and leukocyte esterase (indicating possible infection). She was diagnosed with a urinary tract infection and was discharged on antibiotic therapy. No imaging was performed at this initial visit.
The patient returned the following day with unchanged abdominal pain and more nausea and vomiting. A fetal ultrasound was performed and found normal fetal heart activity. No further testing was done, and she was discharged home with instructions to continue the antibiotics.
Abdominal pain remains the most common reason for emergency department (ED) visits, comprising more than 11% of all visits in 2008.(1) In 2011, 54% of patients that presented to the ED were female, more than 25% were of childbearing age, and the pregnancy rate in the United States is approximately 10% at any given time.(2,3) For these reasons, clinicians that evaluate patients with abdominal pain in the ED should be familiar with common causes of abdominal pain in pregnant women and appreciate when nausea and vomiting in pregnancy is abnormal.
Nausea, vomiting, and abdominal pain are very common in pregnancy. Up to 80% of pregnant women experience nausea and vomiting, most commonly in the first trimester. Symptoms and signs that may indicate another cause include nausea and vomiting persisting past mid-pregnancy (approximately 20 weeks) and associated abdominal pain, fever, or diarrhea. In these instances, a more thorough evaluation is indicated.(4) Due to the enlarging uterus and fetal position/movement, abdominal pain is also common in pregnancy. Warning signs include pain that is localized, abrupt, constant, or severe, or pain that is associated with nausea and vomiting, vaginal bleeding, or fever. With any of these, further investigation into nonpregnancy-related causes is warranted. If any of the warning signs above is present, consultation with an obstetric specialist is recommended.
Women of childbearing age who present to the ED with abdominal pain at minimum should receive a urine pregnancy test, and the location and gestational age of the pregnancy should be determined with ultrasound. Miscarriage and ectopic pregnancy are the most frequent causes of abdominal pain in early pregnancy and are often accompanied by vaginal bleeding.(5,6) Once an early gestational age and intrauterine location is confirmed and miscarriage is ruled out, nonobstetric causes of abdominal pain should be explored, especially if any of the warning signs above are present.
With the exception of ovarian torsion, which is more common in the first trimester, the cause and incidence of non-obstetric abdominal pain in pregnancy varies little by gestational age of the fetus. The following are approximate incidences of some causes of acute abdomen in pregnancy: appendicitis (1/1500 pregnancies), cholecystitis, nephrolithiasis, pancreatitis, and small bowel obstruction (each occur in approximately 1/3000), with ovarian pathology (torsion or symptomatic masses) and uterine leiomyomas less common.(7)
After a history, physical examination, and the pregnancy test and ultrasound, laboratory tests that can assist in narrowing the differential diagnosis—including a complete blood count, liver and pancreatic enzymes, and urinalysis—should be reviewed. The white blood cell count increases to 10,000–14,000 cells/μL in normal pregnancy (and as high as 30,000 cells/μL in labor). However, a left shift in the differential and the presence of bands are abnormal and require further investigation.(8) If clinical signs and symptoms accompanied by laboratory data are not conclusive, prompt imaging may be necessary.
Imaging in pregnancy should begin with ultrasound or magnetic resonance imaging (MRI) as they have no ionizing radiation and have not been linked with fetal harm. Compression ultrasound may be useful in the evaluation of suspected appendicitis, cholecystitis, nephrolithiasis, and ovarian pathology in this setting. However, compression ultrasound becomes less sensitive and specific in pregnancy and relies heavily on the skill of the technician or radiologist. If the ultrasound is nondiagnostic, MRI can be considered as its lack of ionizing radiation also makes it safe for the fetus. MRI can aid in diagnosing acute appendicitis, cholecystitis, bowel obstruction, and ovarian pathology. If MRI is unavailable and there is serious concern for a nonpregnancy-related cause for the abdominal pain, computed tomography (CT) scanning can be performed.
If diagnostic tests that contain ionizing radiation (e.g., CT scanning) are deemed to be clinically necessary, they should not be withheld in the pregnant patient even with the concerns for an increased risk of fetal harm. Although a fetus can be harmed by radiation (including miscarriage, fetal anomalies, fetal growth restriction, intellectual disability, and future childhood cancer), the risk is low, especially at lower radiation doses. During the first 2 weeks of pregnancy, ionizing radiation is associated with an all-or-none type effect (miscarriage or intact survival) based on the radiation dose. After this time period, a dose less than 5 rads is recommended in order to decrease the chances of fetal harm.(9) A normal CT scan of the abdomen and pelvis delivers approximately 1 rad of radiation. As a rule, the least amount of ionizing radiation in necessary diagnostic tests should be utilized in the pregnant patient, and consultation with a radiologist and obstetrician is often helpful to achieve this goal.(9) A full discussion of the fetal risks associated with CT scanning is beyond the scope of this commentary, but a CT scan in this setting should only be obtained after obstetrical consultation.
In this case, at the first visit to the ED, the combination of abdominal pain, nausea, and vomiting appropriately raised concern for a nonpregnancy-related cause and triggered further investigations. The patient was found to have a leukocytosis and a positive urinalysis and was treated for urinary tract infection (UTI). At that first visit, she also should have had a urine pregnancy test and an ultrasound to establish the location and gestational age of the pregnancy. In addition, it would have been reasonable for the providers to have considered imaging, since the symptom constellation—5 days of constant abdominal pain, nausea, vomiting, abdominal tenderness on exam, and an elevated white blood cell count—were incompletely explained by a simple UTI. An ultrasound was performed when the patient returned to the ED and indicated a normal viable pregnancy. However, no further imaging was pursued. Given the severity and persistence of her symptoms despite treatment, a complete abdominal ultrasound (looking for nonpregnancy-related intra-abdominal pathology) would have been appropriate.