How should a 36‑week primigravida with abdominal pain, one episode of vomiting and loose stools, who is not in active labor, be evaluated and managed?

Management of 36-Week Primigravida with Abdominal Pain, Vomiting, and Loose Stools

This patient requires urgent evaluation to exclude serious pregnancy-specific complications (HELLP syndrome, acute fatty liver of pregnancy, intrahepatic cholestasis) and surgical emergencies (appendicitis, bowel obstruction), while recognizing that isolated gastroenteritis is the most likely diagnosis given she is not in labor.

Immediate Clinical Assessment

Critical Red Flags to Evaluate

• Assess for peritoneal signs (guarding, rebound tenderness, rigidity) which would indicate surgical emergency requiring immediate laparotomy 1, 2
• Check vital signs meticulously: tachycardia is a significant predictor of serious complications in pregnant patients and demands immediate attention 2
• Evaluate for signs of preeclampsia/HELLP syndrome: right upper quadrant pain, headache, visual changes, or edema, as HELLP presents with abdominal pain and nausea/vomiting in 0.2-0.6% of pregnancies 1
• Look for jaundice and hypoglycemia which would suggest acute fatty liver of pregnancy (AFLP), a life-threatening condition occurring in 0.005-0.010% of pregnancies 1
• Assess hydration status: orthostatic hypotension, decreased skin turgor, dry mucous membranes 1

Essential Laboratory Studies

• Complete blood count: platelets <150 × 10⁹/L suggests HELLP syndrome 1
• Comprehensive metabolic panel: elevated AST/ALT (>300-1,000 U/L suggests AFLP; 2-30× ULN suggests intrahepatic cholestasis) 1
• Coagulation profile: low antithrombin III, elevated PT, low fibrinogen point to AFLP 1
• Urinalysis: to exclude urinary tract infection/pyelonephritis 2
• Lactate and D-dimer: elevated levels may assist in identifying bowel ischemia, though not sufficiently accurate alone 1

Differential Diagnosis Priority

Life-Threatening Pregnancy-Specific Conditions (Rule Out First)

1. HELLP Syndrome: Presents with abdominal pain, nausea/vomiting, commonly with preeclampsia; requires immediate delivery if diagnosed 1
2. Acute Fatty Liver of Pregnancy: Presents with abdominal pain, nausea/vomiting, jaundice, hypoglycemia; requires immediate delivery 1
3. Intrahepatic Cholestasis of Pregnancy: Less likely given acute presentation, but check total bile acids >10 μmol/L 1

Surgical Emergencies

1. Appendicitis: Most common cause of abdominal pain requiring emergency surgery in pregnant patients; location may be atypical due to anatomical displacement 2, 3
2. Bowel obstruction/volvulus: Severe pain out of proportion to examination findings should raise suspicion 1, 4
3. Cholecystitis: Pregnancy increases gallstone formation risk 3

Most Likely Diagnosis (If Above Excluded)

Viral gastroenteritis: Single episode of vomiting with loose stools, no labor, suggests self-limited gastroenteritis 1, 5

Imaging Strategy

Start with ultrasound as the primary imaging modality for all pregnant patients with abdominal pain 2, 3

• Obstetric ultrasound: Assess fetal well-being, amniotic fluid, placental position 2
• Abdominal ultrasound: Evaluate gallbladder (wall thickening >3mm, pericholecystic fluid), appendix if visualized, kidneys for hydronephrosis 3
• If ultrasound inconclusive and surgical pathology suspected: Proceed to MRI without contrast (97% sensitivity and 95% specificity for appendicitis in pregnancy) 2, 3
• Reserve CT with IV contrast for life-threatening situations only when diagnosis cannot be made by ultrasound or MRI and immediate intervention is needed 2

Management Algorithm

If Peritoneal Signs Present or Hemodynamically Unstable

• Immediate surgical consultation 2
• Broad-spectrum antibiotics 1
• Prompt laparotomy for overt peritonitis 1
• Multidisciplinary approach involving acute care surgeons, obstetricians, and anesthesia 1

If Stable Without Peritoneal Signs (Presumed Gastroenteritis)

• IV hydration with isotonic saline to correct volume depletion 5
• Antiemetics: Metoclopramide or ondansetron (both safe in pregnancy; metoclopramide has less drowsiness and dystonia than promethazine) 1
• Correct electrolyte abnormalities 1, 5
• Thiamine 100 mg daily if prolonged vomiting to prevent Wernicke encephalopathy 1
• Serial abdominal examinations every 4-6 hours to detect peritoneal signs, increasing pain, or guarding 5
• Monitor vital signs closely, particularly for tachycardia 5

Disposition Criteria

Admit for observation if 5:

• Unable to tolerate oral intake
• Persistent vomiting
• Significant pain requiring IV analgesia
• Abnormal laboratory findings suggesting HELLP/AFLP

Discharge with 24-48 hour follow-up if 2, 5:

• Tolerating oral intake
• Pain controlled with oral analgesia
• Vital signs stable
• No peritoneal signs
• Laboratory studies exclude pregnancy-specific liver disease

Critical Pitfalls to Avoid

• Do not attribute all abdominal pain to normal pregnancy changes without excluding serious pathology first 2
• Do not delay surgical intervention when appendicitis is diagnosed; maternal and fetal outcomes worsen with delayed treatment 2
• Do not withhold CT imaging in life-threatening situations due to radiation concerns; single-acquisition CT delivers <25 mGy with minimal fetal risk 2
• Persistent liver chemistry abnormalities despite symptom resolution should prompt investigation for another etiology beyond simple gastroenteritis 1