What are the implications and management options for a fetus with multiple cystic spaces on the right lung diagnosed at 30 weeks gestational age (GA) on fetal ultrasound?

Multiple Cystic Spaces in Right Fetal Lung at 30 Weeks: Diagnosis and Management

Most Likely Diagnosis

This presentation is most consistent with Congenital Pulmonary Airway Malformation (CPAM), formerly called congenital cystic adenomatoid malformation (CCAM), which accounts for 25% of congenital lung lesions and typically presents as multiple cystic spaces on prenatal ultrasound. 1, 2

Immediate Diagnostic Steps

Calculate CPAM Volume Ratio (CVR)

• Measure the lesion using the formula for a prolate ellipse (length × width × height × 0.52) divided by head circumference to calculate CVR. 1
• CVR >1.6 cm² predicts high risk for hydrops fetalis and intrauterine death 2, 3
• At 30 weeks, this calculation is critical for risk stratification 1

Comprehensive Ultrasound Assessment

• Evaluate for mediastinal shift, which was present in 45% of cases and correlates with need for postnatal surgery. 4
• Assess contralateral lung compression 1
• Measure amniotic fluid volume to detect polyhydramnios 2
• Screen for hydrops fetalis (pleural effusion, ascites, skin edema, pericardial effusion), which occurred in only 7% of cases but carries significantly worse prognosis. 4
• Perform detailed anatomic survey to exclude associated structural anomalies 1

Consider Fetal MRI

• MRI is especially helpful for thoracic anomalies and airway management planning in fetuses with masses, and should ideally be performed at or after 22 weeks gestation, making it appropriate at 30 weeks. 1
• Use MRI if ultrasound findings are incomplete or additional anatomic detail is needed for delivery planning 1

Differential Diagnosis to Consider

Bronchopulmonary Sequestration (BPS)

• Typically appears as solid echogenic mass rather than multiple cysts 3
• May have identifiable systemic arterial feeding vessel on Doppler 5

Hybrid Lesions

• Hybrid features of both CPAM and BPS were seen in 11 of 42 surgically excised cases, demonstrating overlap between these entities. 4

Congenital Lobar Emphysema

• Usually presents as hyperinflated lobe rather than discrete cysts 3

Ongoing Surveillance Protocol

Serial Ultrasound Monitoring

• Perform weekly or biweekly ultrasounds to monitor for development of hydrops, changes in mass size, mediastinal shift, and amniotic fluid volume. 1
• CVR can increase progressively with gestational age, as demonstrated in one case where CVR grew from 0.88 cm² at 19 weeks to 5.2 cm² at 35 weeks. 2
• Monitor for spontaneous regression, which can occur but does not eliminate need for postnatal surgery 4

Multidisciplinary Team Involvement

• During pregnancy, a multidisciplinary team should join in the management of CPAM patients, with prenatal visits increased to weekly from 31 weeks of gestation in high-risk cases. 2

Indications for Fetal Intervention

Criteria for In Utero Therapy

• Fetal intervention is indicated for large lesions causing hydrops fetalis, with ultrasound-guided laser coagulation of feeding artery (for BPS) being superior to pleuroamniotic shunting, achieving complete regression in 80% of cases. 5
• Thoracoamniotic shunts were used in 3 of 4 cases requiring antenatal intervention 4
• All cases requiring intervention should be referred to a tertiary fetal treatment center with expertise in fetal therapy. 5

Prognosis Without Hydrops

• Antenatally diagnosed cystic lung disease has an excellent prognosis in the absence of signs of severe fetal distress, with 96% of fetuses born alive. 4
• Only 2 of 64 liveborn infants died, both with large microcystic lesions and severe fetal distress 4

Delivery Planning

Timing and Location

• Administer antenatal corticosteroids for fetal lung maturation between 24-34 weeks if preterm delivery is anticipated. 5
• Delivery should occur at a tertiary center with neonatal intensive care and pediatric surgical capabilities. 5
• During cesarean section, neonatologists and pediatric surgeons should be present for timely evaluation of newborns. 2

Airway Management Preparation

• Fetal MRI findings guide airway management planning for delivery 1
• Have EXIT (ex utero intrapartum treatment) procedure capability available if massive lesion threatens airway 3

Postnatal Management

Immediate Neonatal Period

• Close monitoring in the first 24-48 hours is critical, as complications can occur rapidly even after complete prenatal regression. 5
• The neonate should be admitted to the neonatal intensive care unit for monitoring immediately after birth, even if asymptomatic. 2
• Obtain postnatal chest CT scan to confirm diagnosis and characterize lesion 6, 4

Surgical Intervention

• Surgical excision was required in 45% of lesions showing late-gestation "resolution," indicating that antenatal regression does not eliminate need for postnatal evaluation. 4
• The need for surgery should be based on appropriate postnatal investigations (CT scans) rather than on antenatal behavior. 4
• Sixty-three percent of infants underwent thoracotomy and appropriate excisional surgery at a median of 7.5 months (range 1 day to 34 months). 4
• Early removal of congenital cystic lesions achieves good outcomes and prevents potential complications including repeated lung infection and malignant change. 6

Timing of Surgery

• Emergency surgery required if respiratory distress develops 7
• Elective lobectomy typically performed between 10 days and 7 months of age 7
• Timely intervention should be made at the onset of respiratory symptoms. 2

Key Prognostic Factors

Favorable Indicators

• Absence of hydrops fetalis 4
• Macrocystic rather than microcystic pattern 4
• Unilateral lesion 4
• CVR <1.6 cm² 2

Poor Prognostic Signs

• Hydrops fetalis (7% incidence but high mortality) 4
• Large microcystic lesions 4
• CVR >1.6 cm² 2, 3
• Bilateral involvement 4