Special Feature

Appendicitis in Pregnancy

By Esther Chen, MD, and Stephanie B. Abbuhl, MD, FACEP

Acute appendicitis in pregnancy remains a diagnostic challenge. The most common non-obstetric surgical emergency in pregnancy, appendicitis occurs in approximately 1 in 1500 pregnancies,1 an incidence similar to that in the non-pregnant population.2 It also is slightly more prevalent in the second trimester of pregnancy. The differential diagnosis of abdominal pain in a pregnant patient is complicated by gynecologic and obstetric problems,3 resulting in diagnostic delay and subsequent higher maternal and fetal morbidity and mortality. In various studies, appendiceal rupture has been noted in 12-55% of pregnant patients at the time of surgery.1,4,5 A maternal mortality rate as high as 2.8%6 and a fetal mortality rate of 30%7 have been reported with appendiceal perforation, as compared to 0.1% and 2%, respectively, with uncomplicated appendicitis. Other complications such as preterm contractions and labor are common, especially in the third trimester; however, actual preterm delivery is rare.1,5

Clinical Presentation

Anatomic and physiologic changes during the normal pregnant state impact the evaluation of appendicitis. Anorexia, nausea, and vomiting are nonspecific symptoms common to both pregnancy and appendicitis and are less helpful than in non-pregnant patients. Abnormalities in vital signs suggestive of a surgical emergency, such as tachypnea (which is normal in pregnancy), can be difficult to interpret. Tachycardia, hypoxia, and hypotension may not be apparent until 30-50% of intravascular volume has been lost, due to physiologic "hypervolemia."8 In a recent series of 67 pregnancies with a preoperative diagnosis of probable appendicitis, the mean maximal temperature was not significantly different for the patients with proven appendicitis compared to those with normal findings (37.6°C vs 37.8°C).1 Pain location still is most common in the right lower quadrant (RLQ),1,5,6 despite classic obstetric teaching that appendiceal pain in the pregnant woman migrates laterally and superiorly toward the right upper quadrant with the growing uterus.9 The presence of leukocytosis also is difficult to interpret in pregnancy, where a white blood cell count of approximately 14,000 cells/mm3 may be normal in the second and third trimesters, with a range of 20,000-30,000 cells/mm3 during labor.8

Imaging Modalities

Conventional Radiography. Abdominal radiography has such low sensitivity and specificity for acute appendicitis that it plays a limited role in the diagnostic evaluation of suspected appendicitis.10 Its usefulness lies in detecting intestinal obstruction or perforation.

Ultrasonography. Ultrasonography (US) is the diagnostic test of choice in the initial evaluation of abdominal pain in pregnancy to exclude uterine and tubo-ovarian abnormalities and to rule out ectopic pregnancy. US offers several advantages: it is noninvasive, uses no radiation or contrast material, and can be used to detect certain alternative diagnoses. US diagnosis of appendicitis involves visualization of a noncompressible appendix that is greater than 6-7 mm in diameter with a dilated lumen, periappendiceal fluid, and lack of peristalsis. In a carefully performed study in nonpregnant adults, US has been shown to have a sensitivity of 75-90% and a specificity of 85-100%.2,10 However, the primary limitation of US is that the accuracy of the test requires visualization of the appendix, and the appendix frequently is not seen.

In fact, a normal or retrocecal appendix rarely is visualized.11 In addition, the quality of the examination is highly operator-dependent and the gravid uterus, bowel gas, and body habitus can interfere with the test. In a recent study of confirmed appendicitis in pregnant patients, ultrasound was nondiagnostic in 70% of the cases.5 It is even more limited when the appendix has perforated.

Although limited as a diagnostic modality, US provides essential fetal information during the management of the pregnant patient with an acute abdomen. It may be used to establish fetal well being when decisions need to be made regarding the use of tocolytics and delivery.12

Computed Tomography. In the emergency evaluation of RLQ pain in non-pregnant patients, abdominal computed tomography (CT) has become the diagnostic imaging study of choice, with a sensitivity of 90-100% and a specificity of 91-99%.10 Previous studies cite high diagnostic accuracy with improved clinical outcomes and cost savings.13 In the pregnant patient, the main disadvantage of CT is the exposure of ionizing radiation to the fetus, especially between 10 and 17 weeks of gestation when the central nervous system is most sensitive to teratogenesis. The currently accepted maximum cumulative fetal dose during pregnancy is 5 rad.14 An abdomnal/pelvic CT scan with 10 10-mm cuts causes an estimated fetal exposure of 2.6 rads. For comparison, a two-view chest x-ray exposes the fetus to about 0.00007 rad and a head CT of 10 10-mm cuts is 0.05 rad. Exposure to 1-2 rads has been associated with an increase in the incidence childhood leukemia, from a background rate of 3.6 per 10,000 to 5 per 10,000. Therefore, a fetus safely can be exposed to only one standard abdominal CT scan.15 Although it is within the acceptable published guidelines, there has been significant reluctance to use this imaging modality unless the benefit of diagnosis overwhelmingly exceeds the potential risks to the fetus. One small series has described the use of "limited helical scanning" where the radiation exposure was approximately 300 mrad.16

Magnetic Resonance Imaging. Magnetic resonance imaging (MRI), which uses no ionizing radiation, has received little attention as a potential diagnostic modality for the evaluation of appendicitis in pregnancy. Recently, fast MRI techniques have shortened the image acquisition time enough to examine patients with acute conditions without sedation and may be valuable when ultrasound findings are inconclusive.17

While there are no known biologic risks from MRI, there is no conclusive evidence for the safety of electromagnetic fields in animal or human embryos. Because of this uncertainty, MRI is not recommended in the first trimester unless the potential benefits outweigh the potential risks. In addition, gadolinium, which crosses the placenta into the fetal circulation, currently has unknown effects on the fetus and, therefore, is not recommended in pregnancy. Despite these unanswered questions, fast MRI without contrast has been shown to have some promise for the evaluation of the pregnant patient with suspected appendicitis as well as other gynecologic and obstetric pathology.17 More experience and data are needed to evaluate this modality as a possible alternative to CT in the pregnant patient.

Treatment

Antibiotics. Patients with acute appendicitis usually are given intravenous antibiotics with specific coverage for gram-negative aerobes and anaerobes. The patient with possible perforation, appendiceal abscess, or peritonitis definitely requires broad-spectrum antibiotics.3 Antibiotics that are considered safe in pregnancy are penicillins (including ampicillin/sulbactam), cephalo-sporins, clindamycin, and gentamicin. One relatively inexpensive, safe, and effective combination is clindamycin and gentamicin.

Surgery. Laparoscopy has been used for several years to rule out ectopic pregnancies in first trimester patients with abdominal pain. In the past, pregnancy was considered a relative contraindication to laparoscopic surgery because of possible deleterious effects of carbon dioxide, obstruction by the enlarged uterus, and the potential for fetal loss. Because the fundus rises to the umbilicus at approximately 20 weeks of gestation (the insertion site of the large port), an open appendectomy procedure usually is preferred in the late second trimester. A recent small study of laparoscopic procedures in pregnancy for nonobstetric emergencies showed that it was safe in the second and third trimesters, without complications of fetal distress, premature labor, or wound infection. The major modification of the procedure was alternative placement of the trocars with relation to the enlarged uterus.18

Conclusion

The signs and symptoms of normal pregnancy complicate the history and physical examination in the evaluation of suspected appendicitis, often resulting in diagnostic delay. Despite the presence of the growing uterus outside the pelvis after 10 weeks of gestation, RLQ pain is still the most common presenting symptom, even in late pregnancy. Although US is the imaging study of choice in pregnancy, it is non-diagnostic in the majority of cases. CT is more sensitive and specific than US, but concerns about radiation exposure significantly limit its use. To date, the safety and accuracy of MRI in the evaluation of appendicitis in pregnancy remains uncertain but has some promise and should be further studied. Most obstetricians will manage pregnant patients with suspected appendicitis conservatively with admission for serial abdominal exams in consultation with a general surgeon.

Dr. Chen is Assistant Professor of Emergency Medicine, University of Pennsylvania School of Medicine, Philadelphia. Dr. Abbuhl, Medical Director, Department of Emergency Medicine, The Hospital of the University of Pennsylvania; Associate Professor of Emergency Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, is on the Editorial Board of Emergency Medicine Alert.

References

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12. Perry R. Acute abdomen and pregnancy. Website: www.emedicine.com/med/topic3522.htm. (Accessed 8/18/2003.)

13. Torbati SS, et al. Impact of helical computed tomography on the outcomes of emergency department patients with suspected appendicitis. Acad Emerg Med 2003;10: 823-829.

14. American College of Obstetricians and Gynecologists, Committee on Obstetric Practice. Guidelines for diagnostic imaging during pregnancy. ACOG Committee Opinion no. 158. Washington, DC:ACOG, 1995.

15. Toppenberg KS, et al. Safety of radiographic imaging during pregnancy. Am Fam Phys 1999;59:1813-1819.

16. Castro MA, et al. The use of helical computed tomography in pregnancy for the diagnosis of acute appendicitis. Am J Obstetr Gynecol 2001;184:954-957.

17. Nagayama M, et al. Fast MR imaging in obstetrics. Radiographics 2002;22:563-580.

18. Rizzo AG. Laparoscopic surgery in pregnancy: long-term follow-up. J Laparoendosc Adv Surg Tech 2003; 13:11-15.9.