What Are the Chances of Developing a Non-obstetric（非产科） Abdominal Emergency During Pregnancy? What Risks Do Abdominal Emergencies Pose（产生） to the Developing Pregnancy?
Pearls and Pitfalls
• Up to 1 in 500 pregnant women develop an acute abdomen, and up to 1% of women need an operation during pregnancy for a non-obstetric abdominal emergency.
• Normal anatomic and physiologic changes during pregnancy can alter typical presentations of non-obstetric abdominal emergencies.
• Appendicitis is the most common non-obstetric surgical abdominal emergency during pregnancy.
• Non-obstetric abdominal emergencies during pregnancy may result in increased maternal and fetal（母婴） morbidity and mortality（发病率和死亡率）, especially if treatment is delayed.
What Are the Chances of Developing a Non-obstetric Abdominal Emergency During Pregnancy?
The differential diagnosis of abdominal pain in pregnancy is large, encompassing（包含） both obstetric and non-obstetric causes. Up to 1 in 500 pregnant women will develop an acute abdomen, and 0.2–1% of women will need an operation during pregnancy for a non-obstetric abdominal emergency.
Several factors may hamper（妨碍） the clinician’s ability to diagnose various abdominal emergencies. Physiologic and anatomic changes in pregnancy can change clinical presentations of various diseases, and clinicians often hesitate（犹豫） to perform radiographic tests because of risks from ionizing radiation.Delays in diagnosis, however, may harm both mothers and fetuses（胎儿）.
Non-obstetric abdominal emergencies in pregnancy may originate from the gastrointestinal, genitourinary（泌尿生殖系统）, and gynecologic（妇科） systems.
Anatomic and physiologic changes in pregnancy should be considered when evaluating pregnant women with abdominal pain. As the gravid uterus（妊娠子宫） grows, it displaces abdominal organs, such as the appendix, from their typical locations, leading to atypically localized pain. Peritoneal signs（腹膜体征） can be masked or delayed as the abdominal wall musculature（肌肉） is stretched. Using an elevated white blood cell count as a marker of pathology is unreliable, due to the physiologic leukocytosis（白细胞增多） of pregnancy.
Gastrointestinal causes of acute abdominal pain range from heartburn（胃灼热） and constipation to diverticulitis and worsening inflammatory bowel disease to surgical emergencies such as appendicitis and cholecystitis. Decreased gastric motility（胃动力） and compression of hollow（空洞的） viscous structures by the uterus（子宫） cause heartburn and constipation to occur more commonly during pregnancy. Gastroesophageal reflux disease（胃食管反流病） affects 30–85% of pregnant women, and constipation affects up to 40% of pregnant women.
Appendicitis is the most common non-obstetric surgical emergency in pregnancy and affects between 1 in 500 and 1 in 3000 pregnancies. It is responsible for one-quarter of the non-obstetric surgeries performed during pregnancy. Appendicitis is most common in the second trimester【妊娠期(以三个月为单位)】, with 40% of cases occurring during this time. The incidence of appendicitis in pregnancy is identical（完全相同的） to the incidence in nonpregnant women. A ruptured appendix, however, is two to four times more common in pregnant women. A perforated appendix increases fetal mortality from 0–1.5% to 20–35%. Delaying operative intervention leads to maternal complications such as septic shock, peritonitis, and venous thromboembolism（静脉血栓栓塞症）.
Cholecystitis affects approximately 1 in 1600 to 1 in 10,000 pregnancies. It is the second most common non-obstetric surgical emergency in pregnancy. Bile stasis（胆汁淤积症） occurs because of increased estrogen and progesterone levels（雌激素和孕激素） during pregnancy. The incidence of cholelithiasis and cholecystitis is higher in pregnant women. Cholecystitis may be managed conservatively with hydration（水化） and antibiotics; however, this increases the rate of spontaneous abortion（流产） from 0 to 2% with surgical management to 0–12% with conservative management.
Intestinal obstruction occurs in 1 in 1500 to 1 in 16,000 pregnancies. Obstruction may be caused by adhesions, intussusception（肠套叠）, hernia, carcinoma（癌）, or sigmoid volvulus（扭转）. It may also be caused by the rapidly growing uterus. Average maternal mortality is 6%, but it can be as high as 20% in the third trimester. Fetal mortality is 26%. Some cases may be managed conservatively, while other cases many require operative intervention, especially if perforation, bowel necrosis, or peritonitis is present. Obstruction is the third most common cause of non-obstetric surgical emergency during pregnancy.
Pancreatitis occurs in 1 in 1000 to 1 in 3300 pregnancies, with more than 50% of cases occurring in the third trimester. Pancreatitis is caused by gallstones in two-thirds of pregnant patients. Supportive care, including intravenous hydration, bowel rest, and analgesia, is the mainstay of management. Gallstone pancreatitis recurs in 70% of pregnant patients, as opposed to 20–30% of nonpregnant patients, so surgical consultation should be considered. Gallstone pancreatitis can lead to fetal death in 10–20% of cases.
Urinary Tract Causes
In the urinary tract, patients may suffer from urinary tract infection (UTI) and urolithiasis（尿石形成）. UTI in pregnancy ranges from asymptomatic bacteriuria（无症状菌尿） to cystitis（膀胱炎） to pyelonephritis（肾盂肾炎）. Asymptomatic bacteriuria can progress to pyelonephritis in 20–30% of pregnant women and should be treated when detected. Pyelonephritis occurs in 0.5–2% of pregnancies, with 80–90% of cases occurring in the second or third trimester.
The incidence of urolithiasis in pregnancy is equal to that in the general population. One in 200 to 1 in 2500 pregnancies are affected by urolithiasis, with 80–90% occurring in the second and third trimester. Diagnosis can be difficult, as hydronephrosis（肾积水） is a common finding in normal pregnancy. One potential algorithm for diagnosing urolithiasis is performing an initial renal ultrasound evaluating for unilateral hydronephrosis, followed by MRI or ultralow-dose（超低剂量） CT if the diagnosis is still unclear. Fifty to 80% of women will pass stones with conservative management. Surgery is required if there is intractable（顽固性） pain or persistent obstruction.
Adnexal torsion（附件扭转） is the most common non-uterine gynecologic emergency during pregnancy and occurs in up to 1 in 1800 pregnancies, most commonly in the first and second trimester. Assisted reproductive technologies often increase ovarian（卵巢） size. The incidence of torsion increases to 6–16% in these patients. Early operative intervention is crucial for preservation of both the pregnancy and future fertility（生育）.
Pelvic inflammatory disease（盆腔炎） (PID) is an inflammation and polymicrobial（多微生物） infection of the upper female genital tract（上生殖道）. Acute PID in pregnancy is rare, and it happens most frequently during the first trimester. PID may lead to maternal morbidity, preterm delivery（早产）, and fetal demise（胎儿死亡）.
Other causes of acute gynecologic abdominal pain during pregnancy include ovarian cysts and fibroids（卵巢囊肿和肌瘤）.
What Risks Do Abdominal Emergencies Pose to the Developing Pregnancy?
More than 8000 emergent surgical procedures are performed on pregnant patients annually in the United States. A 2009 review article by Cohen-Kerem et al. showed the overall rate of miscarriage following surgery was 5.8%, but the postoperative miscarriage（流产） rate during the first trimester was 10.6%. A large observational study of 47,000 patients who underwent non-obstetric surgery during pregnancy showed that surgery led to higher rates of stillbirth（死产） and preterm（早产） delivery. However, another recent study showed no significant difference in pregnancy outcomes in patients undergoing non-obstetric invasive procedures other than an increased rate of Caesarian（剖腹产） delivery.
What Are the Risks of Ionizing Radiation to a Developing Fetus（发育中的胎儿）?
Pearls and Pitfalls
• Ionizing radiation exposure is dependent on the type of study and the anatomic location being studied.
• Fetal exposure to ionizing radiation should be limited as much as possible, following the “as low as reasonably achievable” principle.
• The most vulnerable（脆弱的） period for the fetus is 8–15 weeks gestation（妊娠）.
• Fetal loss or teratogenesis（致畸） has not been shown after radiation exposure of <50 mSv.
• Ultrasound and MRI are the imaging modalities of choice for pregnant patients and should be used if the clinical scenario allows.
Ionizing radiation is commonly used in medical imaging, most frequently in the form of plain radiographs (X-ray) and computed tomography (CT). Studies that utilize ionizing radiation during pregnancy expose both the mother and the fetus. The degree of radiation exposure is dependent on the type of study and several other factors including the proximity（接近） of the uterus（子宫） to the anatomic location of the scan plane, patient size, study technique, and use of protective mechanisms such as lead to shield（盾） the abdomen and pelvis.
Ionizing radiation has various clinical effects on the fetus depending on gestational age（孕龄）. In very early pregnancy (less than 4 weeks), the embryo（胚胎） is partially protected from the effects of ionizing radiation due to the totipotent nature（全能性） of the cells. At this early stage, radiation exposure tends to result in death of the embryo or have no consequence. Between 4 and 8 weeks gestation（妊娠(期)）, there is risk to the developing fetal genitals（外生殖器）, organs, and the skeleton. The most vulnerable period for the fetus is between 8 and 15 weeks gestation. During this period of organogenesis（器官形成）, higher doses of radiation may cause more significant complications, including fetal demise（死亡） and microcephaly（小头）.
The amount of radiation also determines the clinical effect on the fetus. Above 100 mSv there is risk of teratogenesis（致畸） and pregnancy loss; however, medical diagnostic studies deliver radiation doses far below this threshold. Neither fetal anomalies nor fetal loss has not been reported below 50 mSv. X-ray is the most common form of ionizing radiation used in pregnancy. Most X-ray studies are very low-dose examinations (<0.1 mSv) and pose essentially（基本上） no risk to the fetus. The highest exposure to radiation comes from CT, particularly chest, abdomen, and pelvis scans (Table 105.1). Still, the radiation dose for most of these studies is well below 50 mSv.
The risk of future malignancy as a result of in utero（子宫） exposure to ionizing radiation is unknown but thought to be very small. When performing diagnostic imaging studies that utilize ionizing radiation, doses should be kept as low as reasonably achievable (ALARA principle).
Ultrasonography and magnetic resonance imaging are the imaging modalities of choice for pregnant patients, as these studies are not associated with ionizing radiation risk. However, The American College of Obstetricians（产科医师） and Gynecologists（妇科医生） emphasizes that a necessary diagnostic test should not be withheld（扣留） from a pregnant patient, even if the test utilizes ionizing radiation.
What Are the Risks of Doppler Ultrasound in Pregnancy?
Pearls and Pitfalls
• Ultrasound is safe and considered an imaging modality of choice for pregnant patients.
• Ultrasound waves do not produce ionizing radiation, but they do emit heat（放出热量）.
• There is a theoretical（理论上） risk of thermal（热） damage to fetal tissue if acoustic（超声波） output is too high.
• B-mode and M-mode ultrasound waves are recommended over Doppler waves for fetal assessment whenever possible.
Ultrasound is a safe, effective, and readily available tool for the assessment pregnant patients. It is often the only imaging tool used to diagnose unstable pregnancy conditions such as ruptured ectopic pregnancy（宫外孕破裂）. It is also the first-line modality for determining the location and assessing the viability（生存能力） of an early pregnancy.
Ultrasound uses high-frequency sound waves to produce images. Sound waves do not produce ionizing radiation but do emit heat, which can theoretically cause thermal damage to tissues if the acoustic output is too high. Although standard B-mode ultrasound waves have potential to cause thermal injury, Doppler imaging requires a higher acoustic output and therefore confers a higher risk of thermal damage.
In addition, Doppler imaging confers a potential risk of mechanical effects on fetal tissue. A pulsed Doppler ultrasound wave can produce contraction（收缩） or cavitation（空化） of bubbles（气泡） in the fetal lungs or bowels, which can theoretically damage fetal organs or disrupt loosely（松散地） tethered（系留的） embryonic tissues（胚胎组织）.
Despite these theoretical concerns, no studies have documented adverse fetal effects from Doppler imaging. That said, multiple professional societies, including the American Institute of Ultrasound Medicine and the International Society of Ultrasound in Obstetrics and Gynecology, recommend against the routine use of Doppler imaging in pregnancy.
It is important to mention that there are some cases where Doppler imaging in pregnancy is necessary. Ovarian torsion（卵巢囊肿蒂扭转） is an emergency diagnosis with high morbidity, and pregnancy is a risk factor for ovarian torsion. Pelvic ultrasound with color Doppler is the imaging modality of choice to diagnose ovarian torsion, as it helps determine the presence of blood flow to the ovary（卵巢）.
Ultrasound is safe and considered the imaging modality of choice for the pregnant patient. B-mode and M-mode ultrasound waves are recommended over Doppler waves for fetal assessment whenever possible.
What Are the Implications of Abdominal Pain in Preeclampsia（子痫前期） and HELLP Syndrome?
Pearls and Pitfalls
• Preeclampsia and HELLP syndrome are major causes of morbidity and mortality in pregnant patients. • Abdominal pain in a pregnant patient greater than 20 weeks gestation should raise suspicion for preeclampsia and/or HELLP syndrome.
• In patients with preeclampsia or HELLP syndrome, abdominal pain is an ominous（预兆的） sign signifying end-organ（终末器官） damage.
• Immediate obstetric consultation should be obtained in any pregnant patient with signs and symptoms of preeclampsia or HELLP syndrome, especially when presenting with abdominal pain.
Preeclampsia and HELLP syndrome are two leading causes of maternal（孕产妇） and perinatal（围产期） morbidity and mortality, and the incidence is rising. Preeclampsia is defined by the presence of new onset hypertension (systolic blood pressure ≥140 mmHg and/or diastolic ≥90 mmHg) after 20 weeks gestation with either proteinuria（蛋白尿） or other signs or symptoms of end-organ damage, listed in Table 107.1.
While the exact mechanism is still unclear, recent research suggests that abnormalities of early placentation（胎盘） can lead to placental（胎盘） insufficiency, triggering endothelial dysfunction（内皮功能障碍） and the resulting symptoms of preeclampsia. HELLP syndrome, an acronym（首字母缩略词） for its characteristic features of hemolysis（溶血）, elevated liver enzymes, and low platelets, is a syndrome related to preeclampsia but can be present with or without coexisting hypertension. Diagnostic criteria for HELLP syndrome are listed in Table 107.2.
Abdominal pain in the setting of preeclampsia can be an ominous（不祥的） sign. Persistent right upper quadrant or epigastric abdominal pain is a sign of end-organ damage. In HELLP syndrome, patients will often present with right upper quadrant or epigastric pain as well as nausea and vomiting. One study of women with HELLP syndrome reported that 90% had epigastric or right upper quadrant abdominal pain. The abdominal pain in HELLP syndrome is thought to be due to periportal necrosis（门静脉周围坏死）, microthrombi（微血栓）, and fibrin deposits in the sinusoids（血窦）, causing inflammation of the liver and subsequently stretch of Glisson’s capsule（肝纤维囊）. The pain can be intense（强烈） and unremitting（持续不断的）.
Any pregnant patient greater than 20 weeks gestational age presenting with epigastric or right upper quadrant abdominal pain should be evaluated for preeclampsia and HELLP syndrome. Minimum laboratory testing includes complete blood count, complete metabolic panel（完全代谢大检查）, and urinalysis（尿液分析） or urine protein/creatinine ratio. These tests evaluate for signs of endorgan damage associated with preeclampsia and HELLP syndrome. If the clinical picture or labs suggest possible HELLP syndrome (anemia, elevated liver enzymes, thrombocytopenia), lactate dehydrogenase can be included to assess for the possibility of hemolysis.
Emergency department treatment of preeclampsia is aimed at controlling blood pressure, initiating seizure prophylaxis(启动癫痫预防) to limit progression to eclampsia, and obtaining emergent obstetric consultation.
Blood pressure should be slowly stabilized around 140/90 mmHg rather than rapidly normalized. The most commonly used antihypertensive agents include labetalol（拉贝洛尔）, hydralazine（肼屈嗪）, and nifedipine（硝苯地平）. All are considered first-line therapy and are safe in pregnancy.
Prophylaxis（预防） against seizures should be given to any woman with preeclampsia and abdominal pain, as this constitutes a presentation of preeclampsia with severe features. Magnesium sulfate（硫酸镁） is the drug of choice and is given at a suggested dose of 4 g IV over 5 min, followed by a 1 g/h infusion. This treatment has been shown to decrease the risk of eclampsia（子痫） by 50%. If seizures develop, further magnesium（镁） administration is indicated with an additional 2–4 g IV over 5 min followed by a 2 g/h infusion.
Since the only definitive treatment for both preeclampsia and HELLP syndrome is delivery, emergent obstetric consultation should be obtained. Patients with preeclampsia and HELLP syndrome can deteriorate（恶化） rapidly and may require high level, multidisciplinary（多学科的） care. If the care setting is not equipped to handle both a patient with preeclampsia with severe features and a potentially preterm neonate（可能早产的新生儿）, transfer to another facility should be considered.