Causes of Right Adnexal Cystic Lesions in Infants
In infants, right adnexal cystic lesions are most commonly benign ovarian cysts of follicular origin, which may be simple or complicated by hemorrhage or torsion, often detected prenatally or in the neonatal period. 1
Primary Etiologies by Pathophysiology
Functional/Physiologic Cysts
- Follicular cysts are the most common cause of neonatal ovarian cysts and arise from maternal hormonal stimulation in utero 1
- These cysts are of follicular origin and can be detected on prenatal ultrasound, often appearing before birth 1
- Simple follicular cysts appear completely anechoic with an imperceptible wall on ultrasound 1
Complicated Cysts (Hemorrhagic or Torsed)
- Hemorrhagic or twisted cysts are the second most common presentation and occur frequently in utero 1
- Torsion commonly occurs prenatally and can be diagnosed on prenatal sonograms by characteristic appearance including a thin, highly echogenic wall 1
- Complicated cysts demonstrate various sonographic patterns: fluid-debris levels, retracting clots, septations with or without internal echoes, or solid-appearing masses containing liquid and/or organized hematoma 1
- Most infants with cysts that twisted in utero are asymptomatic after birth, though some with hemorrhagic or twisted cysts may be symptomatic 1
Other Benign Lesions
- Paraovarian cysts can occur in the pediatric population and represent extraovarian structures 2, 3
- Fallopian tube cysts are part of the differential diagnosis for adnexal masses in children 2, 3
Rare Causes
- Benign ovarian tumors including teratomas (dermoid cysts) are uncommon in infants but should be considered 2, 3
- Malignant ovarian tumors are extremely rare in the infant age group but are part of the comprehensive differential 2, 3
Diagnostic Approach
Ultrasound Characteristics
- Uncomplicated simple cysts: Completely anechoic, imperceptible wall, no internal echoes 1
- Complicated cysts: Thin highly echogenic wall (11 of 12 cases), with variable internal appearance ranging from fluid-debris levels to solid-appearing organized hematoma 1
- Prenatal detection is common, with many cysts identified before birth on maternal ultrasound 1
Natural History and Clinical Presentation
- Many simple cysts resolve spontaneously without intervention 1
- Complicated cysts (twisted or hemorrhagic) may persist without change in size over 1-8 months 1
- Most infants are asymptomatic, even with complicated cysts that twisted in utero 1
- Symptomatic presentation occurs in a minority of cases with hemorrhagic or twisted cysts 1
Critical Clinical Pitfalls
- Do not assume all cystic lesions require immediate surgery—many simple follicular cysts resolve spontaneously, and even some complicated cysts may be managed conservatively with observation 1
- Recognize that torsion can occur prenatally—the presence of a thin, highly echogenic wall with complex internal features suggests in utero torsion, but these infants are typically asymptomatic at birth 1
- Understand that solid-appearing masses may actually be organized hematoma—complicated cysts can appear solid on ultrasound but represent hemorrhagic or twisted cysts rather than true solid tumors 1
- Consider the age-specific differential—while functional cysts dominate in infants, the differential in older children and adolescents expands to include endometriomas, infectious lesions, and a broader range of benign and malignant tumors 2, 3