What is the differential diagnosis for a pregnant female with abdominal pain after blunt trauma?

Differential Diagnosis for Pregnant Female with Abdominal Pain After Blunt Trauma

In a pregnant patient with abdominal pain following blunt trauma from a dog jumping on her abdomen, the differential diagnosis must prioritize life-threatening maternal and fetal complications, with placental abruption, uterine rupture, and direct fetal injury being the most critical diagnoses to exclude immediately. 1

Obstetric Trauma-Related Diagnoses (Highest Priority)

Placental Abruption

• Most common serious complication of blunt abdominal trauma in pregnancy, occurring even with seemingly minor trauma 2
• Presents with abdominal pain, uterine contractions, vaginal bleeding (though bleeding may be concealed), and uterine tenderness 2
• Ultrasound sensitivity for detecting abruption is only 40-50%, meaning normal imaging does NOT exclude this diagnosis 1
• Associated with preterm birth and adverse peripartum outcomes in 46.2% of cases with trauma 2

Uterine Rupture

• Life-threatening emergency that can occur from blunt abdominal trauma, particularly in the gravid uterus which is at increased risk 1, 3
• Presents with severe abdominal pain, peritoneal signs, hemodynamic instability, and loss of fetal heart tones 3
• Requires immediate surgical intervention to prevent maternal and fetal death 1

Direct Fetal Injury

• Includes fetal intracranial injury, fractures, and direct trauma to fetal structures 4
• More common in later pregnancy when the fetus is larger and less protected by amniotic fluid 4
• Assessed via ultrasound evaluation of fetal anatomy and biophysical profile 1

Fetomaternal Hemorrhage

• Can occur with any abdominal trauma, leading to fetal anemia and potential fetal demise 4
• Diagnosed with Kleihauer-Betke stain to detect fetal cells in maternal circulation 2

Non-Obstetric Trauma-Related Diagnoses

Intra-Abdominal Solid Organ Injury

• Splenic or hepatic injury from blunt trauma, which may present with delayed bleeding 1
• Requires contrast-enhanced CT for definitive diagnosis if clinically indicated 1

Bowel or Mesenteric Injury

• Can occur with blunt abdominal trauma, presenting with peritoneal signs and free fluid 1
• May have delayed presentation as bowel perforation develops 1

Retroperitoneal Hemorrhage

• Especially high incidence with blunt trauma in pregnancy due to increased pelvic vascularity 4
• May present with flank pain, hemodynamic instability, and falling hematocrit 4

Non-Traumatic Obstetric Causes (Must Still Consider)

Preterm Labor

• Uterine contractions are common after trauma (occurring in 19-53% of cases) but do not predict preterm birth 2
• Persistent contractions despite tocolysis suggest more serious underlying pathology 2

Ruptured Ectopic Pregnancy (if early gestation)

• Critical diagnosis in early pregnancy with abdominal pain 5
• Presents with hemodynamic instability and positive β-hCG 5

Non-Traumatic Non-Obstetric Causes

Appendicitis

• Most common cause of abdominal pain requiring emergency surgery in pregnant patients 5, 6
• Can present atypically in pregnancy due to anatomical displacement of the appendix 5
• MRI has 97% sensitivity and 95% specificity for diagnosis in pregnancy 1
• Critical pitfall: Normal imaging does NOT exclude appendicitis—diagnosis can be made on clinical grounds alone 6

Urolithiasis/Pyelonephritis

• Common causes of abdominal pain during pregnancy 5
• Diagnosed with ultrasound initially, MRI if needed 1

Ovarian Torsion

• Can cause acute abdominal pain in pregnancy 5
• Diagnosed with ultrasound showing enlarged ovary with decreased or absent Doppler flow 1

Cholecystitis

• Pregnancy increases risk of gallstone formation 7
• Ultrasound shows gallbladder wall thickening >3mm, pericholecystic fluid, and sonographic Murphy sign 7

Critical Clinical Approach

Immediate Assessment Priorities

• Hemodynamic status: Tachycardia is a significant predictor of serious complications in pregnant trauma patients 5
• Fetal heart rate monitoring: Continuous monitoring is essential as uterine contractions and fetal distress may indicate abruption 2
• Peritoneal signs: Rigidity, guarding, and rebound suggest surgical emergency 1
• Vaginal bleeding: May indicate abruption or other obstetric complication 2

Essential Laboratory Studies

• Complete blood count to assess for hemorrhage 2
• Coagulation profile (abruption can cause DIC) 2
• Kleihauer-Betke stain to detect fetomaternal hemorrhage 2
• Urinalysis 5

Imaging Algorithm

• FAST ultrasound: Initial triage tool to detect free fluid and assess fetal status, though less sensitive in pregnancy than non-pregnant patients 1
• Obstetric ultrasound: Assess fetal viability, biophysical profile, amniotic fluid, and retroplacental hemorrhage (though sensitivity for abruption is limited) 1
• MRI abdomen/pelvis without contrast: Preferred advanced imaging to avoid radiation, with excellent sensitivity for appendicitis and other pathology 1
• CT abdomen/pelvis with IV contrast: Should NOT be withheld if life-threatening pathology is suspected and other modalities are inconclusive—maternal survival takes priority 1

Critical Pitfalls to Avoid

• Do not assume normal vital signs exclude serious injury: Pregnant patients have increased blood volume and may not show hypotension until significant blood loss has occurred 4
• Do not rely solely on imaging to exclude abruption: Clinical diagnosis with continuous fetal monitoring is essential 1, 2
• Do not assume absence of abdominal tenderness excludes injury: Findings of abdominal tenderness are NOT predictive of preterm birth or adverse outcomes 2
• Do not delay imaging in high-risk scenarios: The risk of a single CT to the fetus is very low compared to missing a life-threatening diagnosis 1
• Do not discharge without adequate observation period: Admit for continuous uterine and fetal monitoring for at least 4-24 hours depending on severity 2