Endgames Picture Quiz

Abdominal pain in pregnancy

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e6818 (Published 17 October 2012) Cite this as: BMJ 2012;345:e6818
  1. D Jones, foundation year 1 doctor,
  2. J Wilson, surgical registrar,
  3. NG Warnock, consultant radiologist,
  4. D J Alexander, consultant surgeon
  1. 1York Hospital, York YO31 8HE, UK
  1. Correspondence to: D Jones ugm4djj{at}gmail.com

A 39 year old primigravid woman who was 36 weeks pregnant presented to the maternity unit with a one day history of worsening intermittent abdominal pain and vomiting. The pain was colicky in nature, with no radiation, and it was worse when she was lying flat. There had been no vaginal bleeding, no change in bowel habit, and no urinary symptoms. She had been previously well and had no medical history of note. She was tachycardic (117 beats/min), but respirations, blood pressure, and temperature were normal. On examination she was tender in the right upper quadrant and epigastrium, with no guarding. Before the general surgeons were contacted, the obstetric team had taken a history and carried out an examination, including a speculum examination, assessment of fetal heart sounds, and cardiotocography monitoring. All fetal assessments were normal and speculum examination excluded preterm labour.

Routine haematological and biochemical investigations showed a raised alkaline phosphatase, consistent with pregnancy, and a raised amylase (113 U/L; reference range 30-100). Abdominal ultrasound showed a normal single fetus and no intraperitoneal free fluid or gallstones. Despite regular analgesia and antiemetics the pain worsened gradually over the next 48 hours, with constant bilious vomiting.

After discussion with the general surgeon on call, it was decided that the possibility of bowel obstruction needed to be investigated, so abdominal radiography was performed (fig 1).

Questions

  • 1 What are the important differential diagnoses for abdominal pain during pregnancy?

  • 2 Is it safe to perform abdominal radiography during pregnancy? What other forms of imaging could be used?

  • 3 What can be seen on the abdominal radiograph?

  • 4 How should the patient be managed?

Answers

1 What are the important differential diagnoses for abdominal pain during pregnancy?

Short answer

Initial differential diagnosis includes gastroenteritis, cholecystitis, appendicitis, acute pancreatitis, ureteric colic, bowel obstruction, and placental abruption.

Long answer

It is difficult to make a clinical diagnosis in pregnant women with abdominal pain because of the multiplicity of potential causes from many different body systems. In addition, the history and examination are often obscured by the ongoing anatomical and physiological changes of pregnancy.1 2 A gravid uterus may compress or displace abdominal organs, guarding may not occur in peritonitis because the abdominal wall muscles are stretched, and markers of infection such as the white blood cell count are less helpful because leucocytosis is common during pregnancy.1 2

Obstetric causes of abdominal pain in pregnancy vary with the stage of pregnancy. In the third trimester, causes include preterm labour, placental abruption, and uterine rupture.1 In this case preterm labour was excluded by a speculum examination. Placental abruption often presents with vaginal bleeding, so was less likely, and uterine rupture would have been seen on ultrasound as a herniation of gestational sac contents.

Gynaecological causes include ovarian torsion and leiomyomas, both of which often present in the first trimester of pregnancy owing to rapid fetal growth, and were therefore unlikely in this case.1

Gastrointestinal causes are not unique to pregnancy but the common symptoms of abdominal pain, nausea, and vomiting are non-specific during pregnancy. Potential gastrointestinal causes in this case include appendicitis, cholecystitis, acute pancreatitis, gastroenteritis, and bowel obstruction.2 Appendicitis is the most common non-obstetric reason for surgery in pregnant women, occurring in one in 1500 pregnancies.2 In this case a normal ultrasound scan made the diagnoses of appendicitis, cholecystitis, and acute pancreatitis less likely.

Bowel obstruction in pregnancy is rare, with a reported incidence of one in 1500-66 431 pregnancies.3 4 Volvulus is reported to account for 24-44% of cases of obstruction, with other causes including adhesions, intussusception, carcinoma, hernias, and appendicitis.4 5 6 7 Pregnancy itself can be a risk factor for volvulus because of displacement and compression of the colon by the gravid uterus. A volvulus is most likely to occur between 16 and 20 weeks’ gestation, when the fetus grows most rapidly, and between 32 and 36 weeks’ gestation as the fetus enters the pelvis.6 Caecal volvulus is a surgical emergency that is caused by an axial twist of the caecum, distal ileum, and proximal colon in the absence of normal caecal fixation.8 The symptoms of volvulus include abdominal distension, abdominal pain, constipation, nausea, and vomiting.1 Bowel obstruction could not be ruled out by the history, examination, and investigations performed at this stage. The remaining causes of abdominal pain in pregnancy were unlikely given the history, but include cystitis and vascular causes, such as splenic artery aneurysm and venous thrombosis, and ureteric colic.

2 Is it safe to perform abdominal radiography during pregnancy? What other forms of imaging could be used?

Short answer

Plain abdominal radiographs in pregnancy carry a very low risk to the fetus and are vital to prevent diagnostic delay when ultrasound has failed to establish the diagnosis. Other imaging modalities that could be used to investigate abdominal pain in pregnancy include computed tomography, magnetic resonance imaging, and colonoscopy.

Long answer

In the United Kingdom, guidance from the Health Protection Agency, the Royal College of Radiologists, and the College of Radiographers states that normal medical exposure to ionising radiation at any stage of pregnancy presents no risk of threshold related deleterious effects. Such effects would be caused only by very high doses of radiation on fetal tissues and include death, malformation, growth retardation, and abnormal brain development.9 This conclusion is supported by the American College of Radiology, which states that no single diagnostic procedure results in a radiation dose that threatens the wellbeing of the developing fetus.10 However, the stochastic effects (risk that is proportional to dose received with no minimum threshold), particularly of induced cancer in childhood, need to be considered and carefully balanced against the risks to maternal and fetal health of alternative diagnostic and therapeutic strategies.

The UK guidance aids this by stratifying diagnostic imaging procedures into groups according to the radiation dose absorbed by the fetus (measured in mGy) and associated risk of induced childhood cancer.9 Such ranges are wide approximations because of variations in examination equipment and technique (which should always be adjusted to minimise exposure), maternal size, and the imprecision of estimates of fetal dose and cancer risk. For an abdominal radiograph, the typical fetal dose in early pregnancy is 0.1-1.0 mGy, with an associated risk of induced childhood cancer of one in 100 000 to one in 10 000. In the later stages of pregnancy, the fetal dose may be towards or beyond the upper end of this range. Even the next tier of examinations (typical early fetal dose 1.0-10 mGy), which includes computed tomography of the upper abdomen (but not pelvis), has an associated childhood cancer risk to the early fetus of only one in 10 000 to one in 1000. These ranges have to be set in the context of a natural risk of childhood cancer of about one in 500 and the dangers to mother and baby of a delayed or missed diagnosis.7 9 In support of this, guidelines from the Society of American Gastrointestinal and Endoscopic Surgeons state that computed tomography delivers a low radiation dose and may be used judiciously in pregnancy, and that expeditious and accurate diagnosis should take precedence over concerns about ionising radiation. The same guidelines add that the risks and benefits should be discussed with the patient before any diagnostic study.11

Previously documented cases report the safe use of both computed tomography and magnetic resonance imaging in the investigation of abdominal pain in pregnancy when plain abdominal radiography has been unhelpful or to rule out a true caecal volvulus.5 6 A recent prospective review of 40 cases of abdominal pain in pregnancy with indeterminate ultrasound found that magnetic resonance imaging led to an accurate diagnosis in every case.12 This suggests that magnetic resonance imaging is accurate and may be preferable to computed tomography because of the lack of ionising radiation.10 12 13

Finally, although not first line investigations, there is some evidence to support the use of colonoscopy and diagnostic laparoscopy for diagnosing lesions not apparent on radiography. The literature suggests both are safe in pregnancy and may even be therapeutic if colonoscopic decompression or laparoscopic surgery can be performed.10 11 14 15

3 What can be seen on the abdominal radiograph?

Short answer

Plain abdominal radiography shows a third trimester fetus, in a cephalic presentation, with pronounced distension of the maternal caecal pole and a caecal diameter of 15 cm, features consistent with caecal volvulus and mechanical bowel obstruction.

Long answer

The radiograph shows a third trimester fetus in a cephalic (head down) presentation (fig 2). The spine of the fetus can be seen curving across the mother’s lumbar spine and the fetal lower limbs are projected over the maternal left upper quadrant. In the right upper quadrant lies the inverted grossly distended caecum, with very little colonic gas beyond. This picture is consistent with obstruction as a result of caecal volvulus.

Figure2

Fig 2 Abdominal radiograph showing a distended caecal pole (A) and a third trimester fetus in a cephalic presentation: (B) fetal lower limbs, (C) fetal vertebrae, (D) fetal skull

4 How should the patient be managed?

Short answer

Successful treatment involves imaging and acting early with emergency caesarean section and surgical intervention. Conservative management with intravenous fluids, nasogastric tube, and urinary catheter should be performed while preparing for theatre.

Long answer

The chance of death for both mother and fetus is high when obstruction occurs during pregnancy,4 so it is important to consider this diagnosis. When obstruction is suspected, early diagnosis and prompt treatment are vital. An accurate assessment of risk is difficult because of the lack of research. However, a review of the 20 most recent reported cases of obstruction in pregnancy found that four mothers and eight fetuses died. In all of these cases there was a delay between presentation and surgical intervention of more than 48 hours.4 This review highlights the importance of imaging and acting early. The diagnosis is often missed or delayed, however, because similar symptoms are common in pregnancy and doctors are reluctant to use imaging in pregnancy.

If intestinal obstruction is suspected, a conservative approach should start immediately, but it must be used only during investigation and preparation for theatre. This involves instituting a nil by mouth policy, placing a nasogastric tube and urinary catheter, promptly instigating fluid resuscitation, and correcting electrolyte abnormalities.3 Surgical intervention is inevitable in pregnant patients, and prolonged conservative management can increase morbidity and mortality. Conservative management should be attempted only if the diagnosis is uncertain and for a maximum of 48 hours. Perinatal death both from fetal hypoxia secondary to maternal shock and from preterm labour secondary to peritonitis have been reported.16

Recent guidelines state that although any operative procedure has associated risks, abdominal surgical intervention is safe in all trimesters of pregnancy.11 17 In cases of large bowel obstruction after 30 weeks’ gestation, caesarean section is appropriate because fetal survival rates are high and fundal height may necessitate caesarean section before laparotomy. In early pregnancy, however, the risk to the fetus is higher, and laparotomy or laparoscopy and caecopexy or resection may be possible without delivering the baby. Evidence suggests that laparoscopy can be performed safely during any trimester of pregnancy and has the same indications in pregnant and non-pregnant patients when treating acute abdominal processes.11 Recent guidelines state that the laparoscopic approach should be used for most abdominal operations during pregnancy rather than laparotomy.11 Although in the past it was recommended that surgery be delayed until the second trimester to reduce rates of spontaneous abortion and preterm labour, it is now recognised that postponing necessary operations may increase complication rates for both mother and fetus.11

Patient outcome

The patient was diagnosed as having a large bowel obstruction due to caecal volvulus. The obstetrics team had begun conservative management with intravenous fluids, nasogastric tube, and urinary catheter while investigations were being undertaken. After discussion between the patient, general surgeon, and obstetrician it was decided that a caesarean section followed by laparotomy was the best course of action. Some diagnostic delay had been caused by the raised alkaline phosphatase and amylase values, which led to a negative ultrasound for suspected gallstones.

The baby was born at 36 weeks’ gestation, two days after presentation to the maternity unit. After caesarean section a laparotomy was performed through a lower midline scar. A clear caecal volvulus with a distended caecum was seen, with no evidence of ischaemia, gangrene, or perforation. The volvulus was reduced and caecopexy performed. The decision to perform caecopexy was controversial because recurrence rates for this condition are high. However, the caecum was healthy and the recommended treatment of right hemicolectomy is not without risks, so because of the unusual circumstances, a pragmatic decision was made to fix the caecum. The patient made an uneventful postoperative recovery and was discharged home.

Notes

Cite this as: BMJ 2012;345:e6818

Footnotes

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Patient consent obtained.

References