Conjoined Twins Treatment & Management

Once the diagnosis has been confirmed, the parents should be counseled on the possible outcomes. The team that will attempt the possible separation should provide this advice. The delivery should take place close to the surgical unit where the separation will be performed. With prenatal diagnosis, the delivery should always be by caesarean section. An elective cesarean delivery should be performed near term after confirmation of fetal lung maturity. Twin delivery may otherwise lead to overdistension and uterine atony.

The following are indications for emergent separation:

• One or both twins are in a life-threatening situation.
• A correctable, life-threatening associated congenital anomaly (eg, intestinal atresia, malrotation with midgut volvulus, ruptured exomphalos, anorectal agenesis) is present.

If the condition of the twins is stable and early separation is not indicated, the surgery is usually delayed until age 6-12 months. At that age, the twins are larger and better able to tolerate surgery. Rapid expansion of the body wall can occur to close substantial defects. The anatomy of the junction and the shared organs and structures dictate the technical details of the procedure.

A systematic approach to the workup is necessary in conjoined twins. The type of conjoined twinning present determines the specific studies needed; the possible areas of fusion are predictable in each type. Three-dimensional models^[23] should be built to depict the shared anatomy. The shared structures must be divided, if possible, so as to maintain functional integrity for each twin. Some shared organs (eg, a single rectum) may not be divisible.

• Cardiovascular system: Prenatal and postnatal echocardiography must be performed to accurately define the extracardiac and intracardiac anomalies. Catheterization should be performed in complex cardiac anomalies. Obtaining an ECG and radionucleotide angiogram may be helpful in deciding whether a separation operation can be carried out. A single QRS complex is an ominous sign.
• Hepatobiliary tree: The number of gallbladders, livers, and pancreata should be known. The conjoined liver may be oriented in an oblique plane to the axis of the twins. Hepatic venous drainage for each twin must be ascertained. A portoenterostomy or even a cutaneous biliary fistula in one of the separated twins may be required if only a single extrahepatic biliary tree exists.
• GI system: This should be evaluated from top to bottom because fusion may occur at any point. An imperforate anus may be present.
• Urinary tract: Imaging studies are performed to assess the status (eg, number, reflux, anatomy) of the kidneys, ureters, urinary bladders, and urethras.
• Genital system: In pygopagus and ischiopagus twins, the number, duplicity of vaginas, presence of a cervix, and urogenital sinus must be noted. In males, penile and scrotal status must be established.
• CNS: The nature and extent of nervous system junction needs to be established in pygopagus twins, who may also have associated hemivertebrae.
• Skin: Vascular territories of the skin must be mapped. The amount of skin needed to close the wound after separation must be evaluated. Skin and tissue expanders may be required to allow subsequent wound closure.
• Muscle and bone: All postoperative defects of the muscle and bone need to be covered.

Preoperative team conferences should be held, reviewing all the details and models. Moral, ethical, and legal issues need to be fully addressed before surgery.

Two complete anesthesia teams are required. Two surgical teams are necessary after the twins are apart. Full monitoring is necessary. All administered drugs and IV fluids are calculated on a total-weight basis, with half being delivered to each twin. The IV drugs administered may have an unpredictable effect because of the cross-circulation. Thus, particular care is needed when drugs are administered.

During the surgery, abnormal vascular communications and previously unidentified anomalies (eg, intestinal and genitourinary malformations) may be encountered. Unexpected findings are common even after an extensive preoperative evaluation. The surgical team should be aware of this and should be prepared to vary the operative procedure accordingly.

Where primary skin closure of the defect would otherwise be impossible, silastic skin expanders have been used to subsequently achieve tension-free closure. A tight thoracic wall closure can lead to cardiac tamponade. Absorbable synthetic mesh has been used with success to close thoracic and abdominal gaps. A porous polyethylene implant and a monofilament polypropylene patch have been suggested to reconstruct the sternum and abdominal wall, respectively.^[24] A skin graft from a nonviable twin may be used in certain cases.

Monitoring must be continued postoperatively in the ICU. Because surgery is prolonged, infants are mechanically ventilated for a variable period. Fluid and electrolyte balance should be closely monitored. Sepsis is a major cause of morbidity and mortality, and precautions must be exercised, particularly when large skin defects are present.

Reconstructive surgery is important in ischiopagus twins, who require GI, genitourinary, reproductive, or skeletal reconstruction. One twin keeps the shared anus and rectal canal, and the other receives reconstructed ones. Reconstruction is easier in twins with tetrapus than in twins with tripus.

Complications are common and may include the following:

• Congestive cardiac failure: This is observed when a conjoined heart is divided.
• Inadequate or incomplete organ systems: This complication occurs when the twins have unequal distribution of their organs (eg, one shared biliary tract). Adequate preplanning in these cases is essential.
• Enormous skin defect: This may result following separation of a large bridge and can often be avoided by delaying the surgery until age 1 year. Preseparation tissue expanders may be useful to avoid this problem. The expanders are essentially pouches, which are gradually filled with saline solution. This stretches the skin, allowing the surgeons to close the wounds after separation surgery.
• Infection: Strict infectious precautions are required for 2 days following the surgical procedure, and patients are kept in the ICU. If they do well, routine precautions are adequate for follow-up care.
• Hemorrhage: Life-threatening exsanguination can result, especially in craniopagus twins who have a large communicating venous sinus.

Several factors may predict or influence outcome, including the following:

• Prenatal MRI and ECG: These techniques can be performed to accurately define the conjoined anatomy, and an outcome can be predicted. However, the echocardiogram can underestimate the complexity of the cardiac anatomy. Currently, 9 weeks is the earliest gestational age at which conjoined twins have been detected. However, false-positive cases are common before 10-11 weeks, as the fetal movements are limited. Monoamniotic twins may appear conjoined.
• Postnatal surgery: Generally, the twins are separated at age 6-12 months. The prognosis improves with elective surgery and meticulous preoperative planning. Cardiac anatomy occasionally necessitates urgent separation at birth. However, urgent operations carry a high (40-80%) mortality rate.
• Skin closure material: Use of skin expanders and prosthetic mesh has improved outcome through providing better wound closure. However, prosthetic mesh used for abdominal closure often results in fistula formation.
• Thoracopagus with cardiac conjunction: The prognosis for separating twins with conjoined ventricles remains poor, unless two cadaveric cardiac transplants were made available. Only one case of successful separation of conjoined atria has been reported.
• Craniopagus: Usually, the twins have 2 largely separate brains; however, the venous sinus may be shared. Division of this sinus carries a high risk for life-threatening exsanguination.

Separating twins with a conjoined heart remains a challenge. In certain circumstances, separating conjoined twins presents ethical, legal,^[25] and religious issues. A choice sometimes has to be made to sacrifice one twin to give the other one a chance of survival. In these instances, consultation with the hospital ethics committee prior to going to the courts has helped. In these cases, a legal ruling must be made before proceeding with surgery.