Acute Appendicitis in Pregnancy

Even More Tummy Pain
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Diagnosis and reasoning

Abdominal pain is an extremely common complaint in pregnancy, with a broad array of potential physiological and pathological causes; a meticulous history and systematic examination is key towards determining which of these is more likely. Similar to non-pregnant individuals, the location of the pain is perhaps the strongest pointer towards the likely etiology; in this patient, the right-lower quadrant location immediately raises the spectre of acute appendicitis. Other potential considerations include nephrolithiasis, urinary tract infection (UTI), ovarian torsion, and pelvic inflammatory disease. The presence of tenderness and guarding in the right iliac fossa add fuel to the suspicion of appendicitis; further evaluation in this regard is essential. In children and male adults, the Alvarado score is a useful clinical tool for objectively determining the probability of acute appendicitis. However, it has been shown to be less accurate in women of reproductive age, and should probably not be used to guide therapy in this population. In addition, while her full blood count (FBC) shows a mild leukocytosis, this is within the normal range for this stage of pregnancy; note that that a normal FBC does not rule out the possibility of appendicitis. At this point, it is essential to appreciate that the diagnosis of appendicitis in pregnancy should never be made upon clinical findings or laboratory findings alone, as appendectomy during pregnancy is associated with a fetal loss rate ranging from 2.6% to 10.9%, and a premature labor rate of 3.5%. The American College of Radiology (ACR) recommends graded compression ultrasound (USS) as the first-line imaging study in these patients; unfortunately, this turns out to be inconclusive in this case. In patients in whom ultrasonography does not provide a diagnosis, further imaging of the abdomen and pelvis via magnetic resonance imaging (MRI) should be performed; this clinches the diagnosis by demonstrating changes suggestive of appendicitis. Note that diagnostic laparoscopy is not indicated in this patient, and in indeed should never be arbitrarily performed in pregnancy; as there little suspicion of pelvic inflammatory disease, gonococcal and chlamydial nucleic acid amplification testing (NAAT) cannot be justified. Appendectomy is emergently indicated once the diagnosis of appendicitis in pregnancy is made; these patients should also receive perioperative antibiotic therapy. Cesarean section is only indicated if the appendix is perforated (or for the usual obstetric indications); tocolytics are used if uterine contractions are present.


Discussion

Acute appendicitis complicates between 1 in 1500 to 1 in 2000 pregnancies, and accounts for approximately 25% of all non-obstetric operations conducted during pregnancy. While the prevalence of appendicitis is the same in both gravid and nongravid women, the incidence of appendiceal perforation is markedly higher in pregnancy (43%), as compared to a 4% to 19% rate in the nonpregnant population. For decades, the traditional teaching has been that the appendix migrates superiorly during pregnancy, due to displacement by the enlarging uterus; thus, clinicians were advised to look out for right upper quadrant pain as a manifestation of appendicitis (particularly in late pregnancy). However, several modern studies have shown that the location of the appendix does not change significantly in most women; in addition, the majority of patients in case literature have presented with right lower quadrant pain. Note that the pain may initially commence in the epigastric or periumbilical region, before subsequently localizing; perforation should be suspected if the pain becomes diffuse over time. Fever is present in 25% of affected women; anorexia, nausea and vomiting are also often seen. Examination reveals right-sided direct abdominal tenderness in almost all patients; around 70% may also demonstrate guarding and rebound tenderness, while around 50% to 65% manifest rigidity. It should be appreciated that the clinical diagnosis of appendicitis in pregnancy can be extremely tricky, as anorexia, nausea, vomiting and abdominal discomfort may be present in normal pregnant women. While computerized tomography (CT) has mostly transformed appendicitis from a clinical diagnosis into a radiological one, there are reservations about the use of CT in pregnancy, due to fetal exposure to ionizing radiation. That said, the dose thus afforded (≤3000 mrad) is less than the level believed to be harmful to the fetus (5000 mrad). The American College of Radiology (ACR) currently recommends ultrasonography with graded compression as the initial imaging study in this population; an abnormal appendix appears as a tubular, blind-ended, noncompressible structure occupying the right lower quadrant and measuring more than 6 mm in diameter. Unfortunately, the sensitivity of ultrasound ranges is only between 20% to 36%; thus, in most patients, this will be nondiagnostic or inconclusive. In such cases, magnetic resonance imaging (MRI) should be attempted next; findings consistent with appendicitis include an enlarged, fluid-filled appendix measuring more than 7 mm in diameter. Note that the overall sensitivity of MRI for diagnosing acute appendicitis has been reported to be between 90% to 100% with a specificity of 94% to 98%. If ultrasound is inconclusive and MRI scanning is unavailable, a diagnostic dilemma may result. While it might be tempting to immediately operate on such patients, it should be noted that surgical intervention for appendectomy is associated with a 3.5% incidence of premature labor, and a fetal loss rate ranging from 2.6% to 10.9%; in addition, the negative appendectomy rate in the absence of imaging ranges from 23% to 33%. Thus, CT scanning should be considered if MRI is unavailable, as the benefits most likely outweigh the risks; CT findings consistent with appendicitis include inflammation and an enlarged, nonfilling tubular structure with or without a fecalith. Immediate surgical intervention is indicated once the diagnosis of appendicitis is made; this may be via open appendectomy or laparoscopy; note that the incidence of preterm delivery and other complications are similar with both techniques. The only indication for delay of surgery is active labor; in such cases, appendectomy should be performed immediately postpartum. Cesarean delivery is indicated if appendiceal rupture occurs. All patients should receive perioperative antibiotics; these should cover anaerobic organisms, as 95% of patients grow Bacteroides fragilis on culture. Perioperative tocolytics are indicated only in patients with documented uterine contractions; they should not be used prophylactically. Overall, uncomplicated appendicitis in pregnancy has a 3% to 5% fetal loss rate, with negligible maternal mortality; however, with appendiceal perforation, these increase to a 20% to 35% fetal loss rate, and a 4% maternal mortality rate.


Take home messages

  1. Appendicitis in pregnancy can be extremely tricky to diagnose, unless a high index of suspicion is maintained.
  2. Contrary to traditional teaching, the appendix does not migrate to the upper abdomen in most women, while the majority of gravid patients with appendicitis present with right lower quadrant pain.
  3. The diagnosis of appendicitis in pregnancy should never be made upon clinical grounds alone, as abdominal surgery in this population is associated with a non-insignificant rate of fetal loss and premature labor.
  4. Compression graded ultrasound is the initial imaging modality of choice; MRI is indicated if ultrasound is inconclusive.

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