The Surgical Abdomen in Pregnancy
/A “surgical” or “acute abdomen” is a serious acute intra-abdominal condition accompanied by pain, tenderness, and muscular rigidity, for which emergency surgery should be contemplated.
This can be complicated by pregnancy because there are many physiologic and anatomic changes in pregnancy that can sometimes change the presentation of what we usually associate with acute abdomen
Anatomic and physiologic changes in pregnancy
Enlarging uterus
Uterus becomes intra-abdominal organ instead of pelvic organ at 12 weeks.
Can increase from 70g → 1110g and hold up to 5 L volume.
Uterus can compress ureters → can look like hydronephrosis and mimic urolithiasis.
Will displace other abdominal organs (mostly the viscera):
A relaxed and stretched abdominal wall can mask guarding.
Additional physiologic changes:
GI:
Delayed emptying of stomach, relaxed lower esophageal sphincter (remember: blame progesterone for everything!) → increase nausea/vomiting, bloating, GERD
Also decreased GI transit (slower motility d/t relaxed GI smooth muscles, again d/t progesterone) → Constipation
Nausea and/or constipation with associated symptoms can confound clinical gestalt when evaluating acute abdomen.
Heme:
Leukocytosis -standard in pregnancy, though can give impression of infection.
Recognizing the Acute Abdomen in Pregnancy
If someone comes with acute abdomen signs, you should treat them as if they have an acute abdomen until proven otherwise:
Abdominal rigidity, rebound, tenderness, guarding
Causes of acute abdomen in pregnancy:
Some clinical pearls for more common causes of acute abdomen in pregnancy:
Appendicitis: Classically taught that the appendix is displaced in pregnancy, BUT RLQ pain is still the most common symptom. Fever might be present in some patients.
Ultrasound has sensitivity of 67-100% and specificity of 83-96% in pregnancy (first line imaging).
CT has sensitivity of 86% and specificity of 97% - usually not used as much due to concerns for radiation.
MRI has high sensitivity and specificity - generally 2nd line, if if ultrasound is inconclusive.
Treatment: SURGERY!
Cholecystitis: Murphy’s sign is still typically positive.
Ultrasound is the investigation of choice with sensitivity >95%.
Treatment:
Admission, make NPO, give antibiotics.
Symptoms of cholecystitis may abate within 7-10 days of starting nonoperative treatment, but there is high risk of recurrence or serious complication.
In first and second trimester → good surgical candidates should undergo cholecystectomy.
In third trimester Nonoperative medical management with abx and fluid therapy should be tried first to allow delay of choley until postpartum, owing to technical difficulty in performing at this gestational age.
Remember, this is ONLY if it’s uncomplicated. If there is any sign of sepsis, perforation, or disease progression on antibiotics → immediate surgery.
A Word on Imaging
Recall our prior episode on imaging in pregnancy! The quick version:
Try ultrasound first for acute abdomen. Usually has high sensitivity and specificity, but the efficacy can decline after 32 weeks of gestation because of technical difficulties due to enlarging uterus
Next is MRI, generally.
For ionizing radiation:
Risk of radiation exposure on a developing fetus depends on both the dose of radiation and gestational age at which exposure occurs.
Fetal mortality is most significant in the first 2 weeks of conception (3-4 weeks pregnant).
Most vulnerable period for teratogenicity is during organ development (usually up to 12 weeks).
Risk of ionizing radiation-induced fetal harm is negligible at 50 mGy or less and risk of malformation increases only slightly with doses >150mGy.
Usual dose of CT abdomen/pelvis is about 25 mGy, and can be reduced to 13 mGy with automated exposure control facility in modern CT scanners.
A Word on Mode of Surgery
We are not general surgeons!
However, multiple studies show that laparoscopic surgery is less invasive and is feasible and safe in select pregnant patients.
If you can time surgery, the best time is 2nd trimester or very early 3rd tri
Pregnancy itself does not increase postoperative morbidity in pregnant women compared to nonpregnant women.
Timing works due to decreased exposure of fetus to anesthetic agents during organogenesis and decreased risk of SAB compared to 1st trimester.
In second trimester, uterus is not so big that it is hard to work around.
Obstetricians should be able to counsel/provide for intraoperative or peri-operative fetal monitoring if indicated and feasible — generally pre/post doptones pre-viability, and a discussion about continuous monitoring if after viability.
Postoperative care considerations:
If viable fetus, there should be additional monitoring of fetal heart rate and uterine activity post operatively.
If not viable, there should be dop tones obtained both before and after surgery
For post-op pain, usual post-op care is usually permissible.
Avoid NSAIDs if possible after 32 weeks due to concern for premature closure of the fetal ductus arteriosis.