What are the differential diagnoses for nausea, vomiting, diarrhea, and left-sided abdominal pain in a woman diagnosed with intrauterine fetal demise at 7 weeks 5 days gestation one week ago, with no vaginal bleeding?

Differential Diagnosis for Post-IUFD Gastrointestinal Symptoms with Left-Sided Abdominal Pain

The most critical diagnosis to exclude is ectopic pregnancy, particularly given the left-sided abdominal pain and absence of vaginal bleeding, as this represents a life-threatening condition that can present with gastrointestinal symptoms and may coexist with or be misdiagnosed as intrauterine pregnancy. 1

High-Priority Life-Threatening Diagnoses

Ectopic Pregnancy (Including Heterotopic Pregnancy)

• Ectopic pregnancy must be ruled out first despite the prior diagnosis of intrauterine fetal demise, as heterotopic pregnancy (simultaneous intrauterine and ectopic pregnancy) can occur, and the initial ultrasound may have missed an ectopic gestation 2
• Left-sided pain is particularly concerning for tubal ectopic pregnancy, which classically presents with unilateral pain 1
• Gastrointestinal symptoms (nausea, vomiting, diarrhea) are common presenting features of ectopic pregnancy and may be mistaken for gastroenteritis 2
• The absence of vaginal bleeding does NOT exclude ectopic pregnancy—many ectopic pregnancies present without bleeding 1
• Transvaginal ultrasound showing a "tubal ring" has high specificity for ectopic pregnancy, and the absence of adnexal abnormalities decreases likelihood with a negative likelihood ratio of 0.12 1

Retained Products of Conception with Infection

• Following intrauterine fetal demise at 7 weeks 5 days, retained products can lead to endometritis or sepsis 2
• Presents with abdominal pain, gastrointestinal symptoms, and potentially fever
• Can progress to septic shock if untreated

Ovarian Torsion

• Unilateral (left-sided) abdominal pain with nausea and vomiting is classic for adnexal torsion 1
• Pregnancy increases risk due to corpus luteum cysts and ovarian enlargement
• Requires urgent surgical intervention to preserve ovarian function

Moderate-Priority Diagnoses

Incomplete or Missed Abortion with Complications

• The diagnosed intrauterine fetal demise may be progressing to spontaneous abortion 2
• Gastrointestinal symptoms can accompany the process
• Left-sided pain may indicate asymmetric uterine cramping or referred pain

Hyperemesis Gravidarum (Persistent)

• Although typically associated with viable pregnancy, nausea and vomiting can persist after fetal demise due to continued hCG production 3, 4
• Severe cases present with dehydration, electrolyte abnormalities, and ketonuria 5
• The PUQE (Pregnancy-Unique Quantification of Emesis) score can classify severity 5

Gastrointestinal Pathology (Non-Obstetric)

• Acute appendicitis: Can present with left lower quadrant pain if the appendix is retrocecal or if there is referred pain; pregnancy increases risk 1
• Gastroenteritis: Viral or bacterial infection causing the classic triad of nausea, vomiting, and diarrhea
• Diverticulitis: Left-sided colonic inflammation (though less common in reproductive age)
• Inflammatory bowel disease flare: Can be exacerbated by pregnancy

Urinary Tract Pathology

• Pyelonephritis: Left-sided kidney infection presenting with flank/abdominal pain, nausea, vomiting 1
• Nephrolithiasis: Kidney stones causing colicky left-sided pain with gastrointestinal symptoms

Lower-Priority but Possible Diagnoses

Corpus Luteum Cyst Rupture or Hemorrhage

• Can cause acute unilateral pelvic pain with peritoneal signs 1
• May present with nausea and vomiting

Gestational Trophoblastic Disease

• Rare but can present with hyperemesis and abnormal hCG patterns 2
• Usually diagnosed on ultrasound showing characteristic "snowstorm" pattern

Critical Diagnostic Approach

Immediate Laboratory Evaluation

• Serial quantitative β-hCG levels: Essential to determine if levels are rising (suggesting ectopic or molar pregnancy), plateauing (pregnancy of unknown location), or falling (resolving pregnancy) 1
• Complete blood count: Assess for infection (leukocytosis) or hemorrhage (anemia)
• Comprehensive metabolic panel: Evaluate for dehydration, electrolyte abnormalities, renal function, and liver function 6
• Urinalysis and urine culture: Rule out urinary tract infection or pyelonephritis

Imaging Studies

• Transvaginal ultrasound is the single best diagnostic modality for evaluating early pregnancy complications and ectopic pregnancy 1
• Assess for:
  • Confirmation of intrauterine fetal demise
  • Presence of adnexal masses or "tubal ring" suggesting ectopic pregnancy 1
  • Free fluid in pelvis (suggesting rupture or hemorrhage)
  • Ovarian appearance (torsion, cysts)
• If β-hCG >3,000 mIU/mL and no intrauterine pregnancy visible, ectopic pregnancy is strongly suggested 1

Clinical Examination Pearls

• Peritoneal signs (rebound tenderness, guarding) suggest surgical emergency (ruptured ectopic, appendicitis, torsion)
• Cervical motion tenderness on pelvic exam suggests ectopic pregnancy or pelvic inflammatory disease
• Fever points toward infectious etiology (endometritis, pyelonephritis, appendicitis)
• Orthostatic vital signs indicate significant volume depletion from vomiting/diarrhea

Common Pitfalls to Avoid

• Do not assume the prior IUFD diagnosis excludes ectopic pregnancy—heterotopic pregnancy occurs, and initial imaging may have been incomplete 2
• Do not rely on vaginal bleeding as a necessary criterion—many ectopic pregnancies present without bleeding 1
• Do not use ketonuria alone to assess severity of hyperemesis—it does not indicate dehydration 5
• Do not dismiss gastrointestinal symptoms as simple gastroenteritis in the setting of recent pregnancy complications without thorough evaluation 2