Emergency general surgery in pregnancy

Introduction

There are more than 8000 urgent non-obstetrical surgical procedures performed each year, impacting up to 2% of all pregnancies.1 The evaluation of the pregnant patient must weigh the risks and benefits of diagnostic methodology and therapy on the mother, and the fetus as well. Complicating care is the fact that the normal physiologic and anatomic changes that occur in pregnancy may make it difficult to interpret signs usually used in early diagnosis of emergency conditions. The delay in diagnosis and treatment of the surgical abdomen in the pregnant patient because of fear of unnecessary procedures and tests contributes to the high complication rate in this patient population. Attention to detail, heightened suspicion, serial physical examination, clinical awareness and systematic evaluation can help avert unnecessary maternal complications and fetal loss from emergency surgical conditions. This review will highlight the more common causes of the acute abdomen in pregnancy with suggested treatment options. Appropriate diagnostic tests or procedures should never be avoided or delayed simply because of pregnancy; never penalize a patient for being pregnant.

Normal physiologic and anatomic changes in pregnancy

The physiologic changes that comprise maternal adaptation to pregnancy involve almost every organ system. The plasma volume in pregnancy increases by almost 50%, whereas the red cell mass increases by only 20%, resulting in the ‘physiologic anemia of pregnancy’. It is not uncommon to see a baseline hematocrit of 31%–33%.2 The increased plasma volume allows the pregnant patient to withstand a significant amount of blood loss before any overt manifestations of shock appear. Cardiac output increases beginning in the second trimester. Uterine blood flow also increases as the fetus grows, comprising 20% of cardiac output by term. This system is highly regulated and extremely sensitive to external agents such as catecholamine and maternal intravascular volume loss. Maternal hemorrhage can be compensated by decreased uterine flow. Maternal hypovolemia may be marked by fetal distress before any evidence of maternal tachycardia or hypotension is present.

Oxygen consumption and resting ventilation increase in pregnancy as a result of an increase in tidal volume caused by rising progesterone levels. This results in a respiratory alkalosis with a pCO₂ of approximately 30 mm Hg and a metabolic compensation with bicarbonate levels in the 19–20 mEq/L range.3 Gastrointestinal motility is decreased, and in addition to the reduction in resting lower esophageal pressure, pregnant patients are more likely to experience gastroesophageal reflux and have an increased risk of aspiration with general anesthesia.

Hematologically, in addition to the decrease in hemoglobin levels seen from the physiologic anemia, there is a relative leukocytosis. Typically, the white cell count will range from 12 000/mm³ to 15 000/mm³ and can reach as high as 25 000/mm³, often complicating the diagnosis of infection.3 The state of relative hypercoagulability in pregnant patients is well known to increase the risk for thromboembolic complications.4

Anatomically, the uterus becomes an intra-abdominal organ at approximately 12 weeks of gestation. At 20 weeks the uterus can be palpated at the umbilicus, and by 36 weeks the uterus reaches the costal margin. The growing uterus can complicate invasive procedures such as port placement in laparoscopic surgery. As the uterus enlarges, maternal organs are displaced upwards; in the late stages of pregnancy the majority of the gastrointestinal tract may be found above the inferior costal margins. The diaphragm may also be elevated by as much as 4 cm. Finally, as the pregnancy progresses, uterine compression of the vena cava decreases venous return, resulting in a 30% drop in cardiac output. This ‘supine hypotensive syndrome’ can be alleviated by displacing the uterus from the vena cava by positioning the patient in the left lateral decubitus position or at least placing pillows under the patient’s right side to elevate it slightly.4

Pregnancy is associated with reduced ureteral tone and peristalsis, which can lead to a dilated ureter and hydronephrosis. This is due in part to mechanical compression on the ureters as the uterus enlarges, with the rate of right-sided hydronephrosis significantly higher than the left side.5 These changes can lead to infection or urolithiasis.6

Radiological issues in the pregnant patient

The key concern regarding imaging during pregnancy is the effect of ionizing radiation on the growing fetus. The risks of radiation include fetal death, growth retardation, microcephaly, malformations, mental retardation and childhood cancers.7 Knowledge of the effects of radiation on fetal development has been extrapolated from animal studies and observations of exposed human populations, particularly those of Hiroshima and Nagasaki.8 9 While the American College of Obstetricians and Gynecologists states that exposure of <5 rads has not been associated with an increase in fetal anomalies or pregnancy loss,10 clinically, the fetal dose of concern for teratogenesis is probably in the range of 10–20 rads.11 When deciding on the appropriate workup for any pregnant patient, always remember the principle that a ‘pregnant patient should not be penalized for being pregnant’.

A typical ‘PanScan’ (CT imaging of the head, cervical spine, chest, abdomen and pelvis) usually delivers <5 rads. An abdominal CT scan can be performed to evaluate abdominal pathology with only 0.3 rads.7 Ultrasound is useful in identifying appendicitis, cholecystitis and free fluid after abdominal trauma, and poses no known risk to the growing fetus. MRI is emerging as a useful test to evaluate the abdomen in pregnant patients.12 13

Radiation exposure during endoscopic retrograde cholangiopancreatography (ERCP) can be reduced to a level significantly below 5 rads. In several series that measured the amount of radiation exposure during ERCP, pregnant patients were exposed to anywhere from 0.04 to 0.18 rads, without any short-term complications to the pregnancy and newborns.14 15 There has been noted to be a clear correlation between the lengths of fluoroscopy time with radiation exposure. Precautions such as using lead shielding (placed underneath the pregnant patient), maximizing distance between the patient and the X-ray source, and decreasing fluoroscopy times are recommended to minimize exposure.16 The technique of ERCP without using any radiation for pregnant patients has been described.17Magnetic resonance cholangiopancreatography (MRCP), choledochoscopy and endoscopic ultrasound have all been used to confirm clearance of the biliary system without the use of radiation following ERCP.18

Laparoscopy in pregnancy

Laparoscopy has emerged as a diagnostic and therapeutic tool in the care of the pregnant patient with abdominal pain.19 Laparoscopy is well tolerated by both mother and fetus with minimal adverse effects in all trimesters.20 21 Although a 2012 meta-analysis of 11 studies found low-grade evidence that laparoscopic compared with open appendectomy was associated with a higher rate of fetal loss,22 a more recent Nationwide Inpatient Sample study of 20 000 patients found a three times higher risk of an adverse obstetrical outcome associated with open surgery.23 Our preference is to favor the laparoscopic approach as long as it appears safe for trochar insertion depending on the body habitus and degree of pregnancy. Open trochar placement (Hasson technique) or insertion of the Veress needle into an alternate site (Palmer’s point) is recommended to avoid injury to the uterus during entry.24 25 Palmer’s point is described in the left upper quadrant, 3 cm below the costal margin in the midclavicular line.26 In the late second trimester and beyond, laparoscopy becomes technically difficult and an open incision (vertical or over the point of maximal tenderness) can be used. The surgeon should avoid manipulation of the uterus during the procedure. Immediate preoperative and postoperative fetal monitoring should be used in all viable pregnancies of 24 weeks and older.27 28

Acute abdomen in the pregnant patient

Approximately 1 in 635 women require non-obstetrical abdominal surgery during pregnancy.29 Making the diagnosis is often problematic for the following reasons: the expanding uterus, which displaces other intra-abdominal organs and thus makes physical exam difficult30; the high prevalence of nausea, vomiting and abdominal pain routinely encountered in the normal obstetric patient31 and the general reluctance to operate unnecessarily on a gravid patient.1 Acute appendicitis and cholecystitis are the most common non-obstetrical emergencies requiring surgery during pregnancy.24

Appendicitis

A case of acute appendicitis during pregnancy was first reported in the literature by Hancock in 1848.32 It is the most common non-obstetric surgical emergency during pregnancy.1 It occurs in about 1 in 1000–2000 pregnancies and may occur at any time during the pregnancy.33–35 The diagnosis is more frequently missed in pregnant than in non-pregnant patients, because signs and symptoms of appendicitis, such as leukocytosis, nausea and vomiting, are also commonly seen during pregnancy. There is a question of reliability of the abdominal examination in pregnant patients suspected of having appendicitis. The classical teaching is that the location of pain from appendicitis moves progressively upward as the pregnancy progresses based on Baer’s 1932 study of barium images of 78 pregnant patients.36 More recent retrospective studies have failed to corroborate this hypothesis showing roughly 90% of patients having pain in the right lower quadrant regardless of trimester.37 38 Maternal morbidity is usually the result of a delay in diagnosis. Fetal loss occurs in 3%–5% of pregnant patients without perforation but can be as high as 36% with perforation.35 This high risk of fetal loss with perforation along with the difficulty of diagnosing appendicitis in the pregnant patient explains the high rate (50% in many series) of normal appendices found at operation.39 Traditionally, this high rate of negative operation had not been found to increase maternal or fetal morbidity; however, recent data suggest that negative appendectomy may be associated with an increase in fetal loss.40 41 Therefore, it is important to confirm the diagnosis before heading to the operating room. Ultrasound, CT, MRI or diagnostic laparoscopy can confirm the diagnosis. Ultrasound should be the first-line study for abdominal pain in the pregnant female; however, the sensitivity ranges from only 20% to 36%. If ultrasound is indeterminate, the next study that should be ordered if available is an MRI. A review of imaging strategies for right lower quadrant pain in pregnant females performed a meta-analysis of six studies examining the role of MRI in diagnosing appendicitis in pregnant females. They found a pooled sensitivity of 0.91 and a specificity of 0.98.42 If MRI is unavailable, a CT may be ordered. While the diagnostic accuracy of CT for appendicitis in the non-obstetric population has been well demonstrated,43 there is a paucity of data for pregnant females. Two small studies looking specifically at pregnant patients demonstrated successful diagnoses of appendicitis in 5/7 patients and 12/13 patients.44 45 Protocols involving abdominal ultrasound followed by CT scan, if inconclusive, have been associated with a reduction of negative appendectomy rates.39 Our diagnostic algorithm for appendicitis is shown in figure 1. Appendectomy can be performed open or laparoscopically20 depending on the surgeon’s comfort level with the patient’s body habitus and degree of pregnancy. The laparoscopic approach has advanced to become the standard of care at many centers; this is the authors’ preference as well.

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Figure 1

This algorithm is our suggested diagnostic workup for a pregnant patient with a suspected diagnosis of appendicitis.

Conclusion

Pregnant patients are a specific population, where worry about the risk of harm to the fetus often overshadows clinical decision making when presented with a possible surgical diagnosis. While it is important to limit duration of exposure to radiation and unnecessary surgery in this population, delays in diagnosis and treatment can also harm both fetus and mother. Obtaining the correct diagnosis in the pregnant patient can be challenging because of the normal physiologic and anatomic changes that occur with pregnancy. While reduced radiation imaging such as MRI or radiation-free ERCP may allow limiting of radiation exposure to the fetus, availability and time involved may hinder use depending on one’s practice setting. Minimally invasive surgery may be performed safely depending on the surgeon’s comfort level with the duration of pregnancy. In cases of general surgical emergencies during pregnancy, a diagnosis should be rapidly sought and treatment offered, lest we should ever penalize a patient for being pregnant.