Conjoined Twins Workup

  • Author: Khalid Kamal, MD, FAAP, MBBS, FCPS, MCPS; Chief Editor: Marleta Reynolds, MD   more...
 
Updated: Apr 6, 2010
 

Laboratory Studies

  • Chromosomal studies are inconclusive. An abnormal X-chromosome inactivation has been proposed, but this has not been proven.
  • Amniocentesis with an estimation of the lecithin-sphingomyelin ratio is performed to assess fetal lung maturity and to determine the optimal time for a cesarean delivery.
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Imaging Studies

  • Prenatal ultrasonography can reveal conjoined twinning as early as 8 weeks' gestation. Conversely, twins with extreme fusion may be mistaken for a singleton. The twin fetuses do not move apart with fetal movement. Polyhydramnios is frequent (75%). A monoamniotic cavity is present, and more than 3 umbilical vessels may be observed. Fusion sites include the thorax (thoracopagus), abdomen (omphalopagus), pelvis (ischiopagus), sacrum (pygopagus), or skull (craniopagus). Extensive zones of fusion may be named by the prefix di- (meaning 2), followed by the portion of the twins that is unfused. Examples include dicephalus (2 heads on one body), and dipygus (double buttocks; single head and torso with separate pelves and 4 legs). Serial scans may be required to monitor for hydrops.
  • Prenatal echocardiography has better yield than postnatal echocardiography in thoracopagus twins, because surface scanning may be difficult.
  • MRI of the brain is performed along with magnetic resonance angiography and magnetic resonance venography to delineate structures and blood supply in the craniopagus variety.
  • Radionuclide angiography is performed to calculate the extent of cross-circulation. Selective angiography is usually not necessary in twins with a shared liver.
  • Sonography allows for a complete anatomic examination and search for associated lethal malformations. A detailed ultrasound examination to exclude the possibility of conjoined twins is mandatory in all multiple pregnancies. Two-dimensional ultrasonography is instrumental in prenatally diagnosing conjoined twins, but precise classification is difficult because of 3-dimensional structures. Three-dimensional ultrasound has shown promise in improving the visualization of complex anatomic spatial relationships. Abdominal ultrasonography is performed to determine how many gallbladders are present (1 or 2) and to determine the polarity of the liver and pancreas if these organs are also conjoined. Often, however, this determination may not be precise.
    • Advantages of sonography include the following:
      • Images other structures (eg, aorta, pancreas, liver)
      • Identifies complications (eg, stenosis, obstruction)
      • Can be rapidly performed at the bedside
      • Does not involve radiation (important in pregnancy)
    • Disadvantages of sonography include the following:
      • Dependent on the type and extent of fusion, as well as the operator's abilities
      • Inability to image the ductal system proximal to the common bile duct
      • Decreased sensitivity for the site and extent of duplication or fusion compared with CT scanning or MRI.
  • Fetal MRI can identify shared anatomy of twins with precise detail. However, this test is not 100% accurate.
  • CT scanning has been used in some studies.[22] However, the yield for complex anatomy is lower than that obtained from MRI. CT scanning may be helpful in shared bony pelvis and shared pelvic perineal muscles.
  • Contrast studies are performed to evaluate the extent of GI (see the image below), genitourinary, and reproductive system fusions. Esophagram showing union at the level of stomach. Esophagram showing union at the level of stomach.
  • Diisopropyl iminodiacetic acid (DISIDA) scanning is a nuclear medicine study performed to visualize the biliary tract. Technetium-labeled analogue of DISIDA is administered intravenously (IV) and is secreted by hepatocytes into bile, enabling visualization of the gall bladder and biliary tree in 30 minutes.
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Other Tests

  • On ECG, a single QRS indicates that cardiac separation is not possible. However, the presence of 2 separate patterns does not guarantee a successful separation.
  • EEG may be performed to evaluate baseline brain activity in craniopagus twins.
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Diagnostic Procedures

  • Cardiac catheterization is performed to determine the nature of complex cardiac anomalies. An accurate estimation of all major inflow and outflow vessels should be made.
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Contributor Information and Disclosures
Author

Khalid Kamal, MD, FAAP, MBBS, FCPS, MCPS  Staff Physician, Department of Pediatrics, Children's Hospital of Michigan

Khalid Kamal, MD, FAAP, MBBS, FCPS, MCPS is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, and Michigan State Medical Society

Disclosure: Nothing to disclose.

Coauthor(s)

Abdullah Al Rabeeah, MD, FRCSC  Minister of Health, Kingdom of Saudi Arabia

Disclosure: Nothing to disclose.

Ibrahim Abdulhamid, MD  Associate Professor of Pediatrics, Wayne State University School of Medicine; Director of Pediatric Pulmonary Medicine, Clinical Director of Pediatric Sleep Laboratory, Children's Hospital of Michigan

Ibrahim Abdulhamid, MD is a member of the following medical societies: American Academy of Pediatrics, American Academy of Sleep Medicine, and American Thoracic Society

Disclosure: Nothing to disclose.

Renato Roxas Jr, MD, FAAP, FACP  Assistant Professor, Departments of Internal Medicine and Pediatrics, Associate Program Director, Combined Internal Medicine and Pediatrics Residency Program, Wayne State University, Detroit Medical Center

Disclosure: Nothing to disclose.

C M Shahbaz Sarwar, MD  Resident Physician, Department of General Surgery, University of Pennsylvania

Disclosure: Nothing to disclose.

Specialty Editor Board

Robert K Minkes, MD, PhD  Professor of Surgery, University of Texas Southwestern Medical Center at Dallas, Southwestern Medical School; Medical Director and Chief of Surgical Services, Children's Medical Center of Dallas-Legacy Campus

Robert K Minkes, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American College of Surgeons, American Medical Association, American Pediatric Surgical Association, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Pharmacy Editor, eMedicine

Disclosure: Nothing to disclose.

Nicholas A Shorter, MD  Professor of Clinical Surgery and Clinical Pediatrics, State University of New York-Downstate University; Division Chief, Department of Surgery, Division of Pediatric Surgery, State University of New York-Downstate Medical Center

Disclosure: Nothing to disclose.

H Biemann Othersen Jr, MD  Professor of Surgery and Pediatrics, Emeritus Head, Division of Pediatric Surgery, Medical University of South Carolina

H Biemann Othersen Jr, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Association for the Surgery of Trauma, American Burn Association, American Cancer Society, American College of Surgeons, American Medical Association, American Pediatric Surgical Association, American Society for Parenteral and Enteral Nutrition, American Surgical Association, American Thoracic Society, British Association of Paediatric Surgeons, Society for Surgery of the Alimentary Tract, Society of Critical Care Medicine, South Carolina Medical Association, Southeastern Surgical Congress, Southern Medical Association, Southern Society for Pediatric Research, and Southern Thoracic Surgical Association

Disclosure: Nothing to disclose.

Chief Editor

Marleta Reynolds, MD  Professor of Surgery, Feinberg School of Medicine, Northwestern University; Head, Department of Surgery and Surgeon in Chief, Head, Division of Pediatric Surgery, Children's Memorial Hospital of Chicago

Marleta Reynolds, MD is a member of the following medical societies: American Pediatric Surgical Association

Disclosure: Nothing to disclose.

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This set of conjoined twins was a stillbirth. Prenatal ultrasonography failed to reveal the second head. An emergent cesarean section was performed after failure to progress.
This is an example of double-headed (bicephalus) conjoined twins, a rare occurrence.
Even though conjoined twinning is more common in female fetuses (75% of cases), most stillborn conjoined twins are male. A single penis and 2 testes were present in this case.
This is a much more rare occurrence termed heteropagus twinning. One twin is not fully formed (parasitic twin) and is dependent on the well-formed one. A malformed head, upper limb, and large ears are present in the parasitic twin. Three legs (tripus) are present.
Ethical issues arose in this set. The parents refused separation on the basis that the nonviable twin was still breathing. The wishes of the parents were respected. This set of twins was lost to follow-up.
Conjoined twins unified at the thorax and abdomen.
Another view of the same set of twins as shown in the previous image.
A superior radiographic view of the same set of twins as shown in the previous 2 images. The twins have 2 hearts that are not conjoined, making this a possible operation.
Esophagram showing union at the level of stomach.
Ischiopagus tetrapus twins.
Ischiopagus tripus twins.
Thoracoomphalopagus twins.
Pygopagus twins.
Ischiopagus tetrapus twins.
Craniopagus twins.
Craniopagus twins.
Rachipagus twins.
Parapagus twins.
Pygopagus twins.
Cephalothoracopagus twins.
Ischiopagus tetrapus twins.
Omphalopagus twins.
Thoracopagus twins.
Parasitic twinning.
 
 
 
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