What are the differential diagnoses for upper abdominal pain and vomiting in a 20‑week pregnant woman?

Differential Diagnosis of Upper Abdominal Pain and Vomiting at 20 Weeks Gestation

In a 20-week pregnant patient with upper abdominal pain and vomiting, you must immediately assess for pre-eclampsia with epigastric pain, acute appendicitis (the most common non-obstetric surgical emergency in pregnancy), and hyperemesis gravidarum, while also considering biliary disease, peptic ulcer disease, and pancreatitis. 1, 2

Life-Threatening Obstetric Causes (Assess First)

Pre-eclampsia with Severe Features

• Epigastric pain and vomiting are independent risk factors for serious morbidity in women with severe pre-eclampsia 1
• Check blood pressure immediately—new hypertension (≥140/90 mmHg) with new proteinuria (≥1+ on dipstick) after 20 weeks defines pre-eclampsia 1
• Measure proteinuria via dipstick or protein:creatinine ratio (≥30 mg/mmol indicates significant proteinuria) 1
• Note that 34% of eclamptic women have diastolic BP ≤100 mmHg, so normal blood pressure does not exclude the diagnosis 1
• Headache combined with epigastric pain significantly increases eclampsia risk 1

HELLP Syndrome

• Obtain liver function tests—elevated transaminases with thrombocytopenia and hemolysis suggest HELLP syndrome 1
• Right upper quadrant or epigastric pain is the presenting symptom in 30-90% of HELLP cases 3

Non-Obstetric Surgical Emergencies

Acute Appendicitis

• Appendicitis is the most frequently encountered non-obstetric surgical condition in pregnant women, occurring in 1 per 500-2000 pregnancies, and most commonly manifests in early to mid-pregnancy 1, 2
• Pregnant women are more likely to present with perforated appendicitis, and perforation carries higher risk of fetal loss 1, 2
• Pain may be atypical in location due to upward displacement of the appendix by the gravid uterus 3, 4
• Check for fever, leukocytosis (though pregnancy normally elevates WBC to 6,000-16,000/μL), and peritoneal signs 1, 2
• Ultrasound combined with MRI is the most commonly used imaging approach (41%), followed by MRI alone (29%) 1
• Delayed diagnosis leads to perforation rates of 25-50% in pregnancy versus 4-19% in non-pregnant patients 2

Cholecystitis and Biliary Colic

• Pregnancy increases cholesterol saturation of bile and gallbladder stasis, making biliary disease common 3, 4
• Right upper quadrant pain radiating to the right shoulder or scapula suggests biliary origin 3
• Obtain right upper quadrant ultrasound to assess for gallstones, gallbladder wall thickening, and pericholecystic fluid 3, 4

Peptic Ulcer Disease and Gastritis

• Epigastric pain 1-3 hours postprandially suggests peptic ulcer disease 3
• Pregnancy typically improves peptic ulcer symptoms due to decreased gastric acid secretion, so new or worsening symptoms warrant investigation 3

Pancreatitis

• Obtain serum lipase and amylase—levels >3 times upper limit of normal suggest pancreatitis 3, 4
• Epigastric pain radiating to the back is characteristic 3
• Pregnancy-related hypertriglyceridemia and gallstones are common causes 4

Pregnancy-Related Non-Emergent Causes

Hyperemesis Gravidarum

• Persistent vomiting beyond first trimester affecting 0.3-2% of pregnancies 5, 6
• Check electrolytes for hypokalemia and metabolic alkalosis, which occur in 40-50% of severe cases 7, 6
• Assess for ketonuria, weight loss >5% of pre-pregnancy weight, and dehydration 6
• Thyroid function tests should be checked, as hyperthyroidism causes similar symptoms 7, 6

Physiologic Nausea and Vomiting of Pregnancy

• Elevated hCG and estrogen combined with progesterone-induced delayed gastric emptying cause symptoms 5
• Typically improves after first trimester, so persistence at 20 weeks suggests alternative diagnosis 6

Other Important Considerations

Urinary Tract Pathology

• Pyelonephritis presents with flank pain, fever, and costovertebral angle tenderness 1, 4
• Nephrolithiasis causes colicky flank pain radiating to groin 1, 4
• Obtain urinalysis and urine culture 4

Ovarian Pathology

• Ovarian torsion presents with sudden-onset severe unilateral lower abdominal pain, though pain can radiate upward 1
• Hemorrhagic corpus luteum cyst can cause acute pain 1
• Ultrasound with Doppler assesses ovarian blood flow 1

Critical Diagnostic Approach

Obtain these immediately:

• Blood pressure and urine protein to exclude pre-eclampsia 1
• Complete blood count, comprehensive metabolic panel, liver function tests 7, 4
• Lipase if pancreatitis suspected 4
• Urinalysis 4

Imaging strategy:

• Start with abdominal ultrasound—safe, no radiation, evaluates gallbladder, appendix, kidneys, and ovaries 1, 3, 4
• Add MRI if ultrasound inconclusive for appendicitis or other surgical pathology 1
• CT should not be withheld when serious pathology is suspected despite pregnancy 8

Common Pitfalls to Avoid

• Do not attribute symptoms to "normal pregnancy" without excluding dangerous causes first—25-55% of pregnant women with severe hypertension and new proteinuria require delivery within 48 hours 1
• Do not delay imaging or surgical consultation in pregnant patients—perforation rates increase dramatically with diagnostic delays in appendicitis 2
• Do not assume normal vital signs exclude serious pathology—pre-eclampsia can occur with relatively normal blood pressures 1
• Do not forget that laboratory values have different normal ranges in pregnancy—WBC up to 16,000/μL is normal 2, 4