What are the pathophysiology, diagnosis, management, and complications of conjoined twins?

From the Guidelines

Conjoined twins are rare anomalies resulting from incomplete division of a single fertilized ovum between days 13-15 of embryonic development, and their management requires a multidisciplinary approach with careful consideration of the extent of shared vital organs and the potential risks and benefits of separation surgery, as highlighted in the most recent study by 1.

Pathophysiology

The pathophysiology of conjoined twins involves the incomplete separation of the embryonic disc, leading to twins who remain physically connected at specific anatomical sites. The most common types include thoracopagus (joined at chest), omphalopagus (joined at abdomen), craniopagus (joined at head), and pygopagus (joined at buttocks), with the extent of shared organs varying by type.

Diagnosis

Diagnosis typically begins with prenatal ultrasonography, often as early as the first trimester, when fixed positioning of fetuses raises suspicion. Fetal MRI provides more detailed anatomical information about shared organs and vascular connections, while 3D imaging and echocardiography help evaluate cardiac involvement, as recommended by 1 and 1.

Management

Management requires a multidisciplinary approach involving maternal-fetal medicine specialists, neonatologists, pediatric surgeons, anesthesiologists, and ethicists. Delivery planning is crucial, with cesarean section typically necessary due to the mechanical difficulties of vaginal delivery. Postnatal evaluation includes detailed imaging to determine the feasibility of separation surgery, which depends on the extent of shared vital organs.

Complications

Complications include high mortality rates (40-60% overall), with prognosis depending on the type and extent of conjunction. Surgical separation may result in significant morbidity including organ dysfunction, neurological impairment, and psychological challenges. Long-term survivors often require multiple reconstructive surgeries and ongoing medical care. Ethical considerations are paramount, particularly when separation might sacrifice one twin to save the other, necessitating careful counseling for parents regarding realistic outcomes and quality of life considerations, as emphasized by 1 and 1.

Some key points to consider in the management of conjoined twins include:

• The importance of early diagnosis and prenatal planning, as highlighted by 1
• The need for a multidisciplinary approach to management, involving specialists from multiple fields, as recommended by 1
• The potential risks and benefits of separation surgery, and the importance of careful consideration of these factors in making decisions about treatment, as discussed by 1 and 1
• The need for ongoing medical care and support for long-term survivors, as emphasized by 1 and 1

From the Research

Pathophysiology of Conjoined Twins

• Conjoined twins are a rare complication of monozygotic twins, where the twins are joined in utero 2, 3, 4.
• The exact cause of conjoined twinning is not known, but it is thought to occur when a single fertilized egg fails to fully separate during the early stages of embryonic development 5.

Diagnosis of Conjoined Twins

• Early prenatal diagnosis of conjoined twins is increasingly made with transvaginal ultrasound and color Doppler studies 2.
• Ultrasound enables an early and accurate diagnosis of conjoined twins, which is vital for obstetric management 3, 4.
• Magnetic resonance imaging (MRI) may be used to identify intricate organ sharing and provide additional information for diagnosis and management 2, 3.
• Three-dimensional ultrasound (3DUS) may provide additional benefits in prenatal assessment, particularly in cases with atypical fetal union 2.

Management of Conjoined Twins

• Most prenatally diagnosed conjoined twins are terminated due to the high perinatal mortality 2.
• However, advancement in pediatric surgery has allowed for successful postnatal separation in a small number of cases 2, 6.
• Anesthetic management of conjoined twins' separation surgery is complex and requires careful planning and monitoring 6.
• Multidisciplinary cooperation is urgently needed for optimal obstetric management and perinatal preparation 4.

Complications of Conjoined Twins

• Conjoined twins are at high risk of perinatal mortality and morbidity 2, 3, 4.
• Complications of separation surgery may include massive blood loss, hemodynamic instability, desaturation, and hypothermia 6.
• Recent advances, such as 3D printing, may aid in surgical pre-planning and enable successful surgical separation of conjoined twins 3.