conjoint twins

Conjoined Twins-A Case ReportSK SETHI, RS SOLANKI, U HEMALInd J Radiol Imag 2004 14:1:67-69
Key words: Conjoined Twins

One of the most interesting congenital malformations is a conjoined twin. Conjoined twins are a rare occurrence in obstetric practice. More commonly known as Siamese twins, this phenomenon is shrouded in mystery and considered a curiosity by general public. Current technology is providing a basis for earlier diagnosis and a better prognosis. Frequently, the twins are born dead, but there are few cases in which the twins survive. We present a case of Dicephalus Dipus Conjoined Twins; a rare type of conjoined twins.CASE REPORT
A 29 year old women, gravida3, para 2 Last childbirth - FTNVD male baby. She had regular menstrual periods before getting pregnant. Her grandmother had a history of twins. She was an unbooked case with no antenatal Ultrasound report. She presented to our hospital at term in the second stage of labour and underwent a vaginal delivery. Twins were delivered as breech. Twins had single male external genitalia, weighing 3 kg together. Placenta was single. On clinical examination it was noted that the twins were conjoined from level of xiphisternum downwards. The twins had two heads, two pairs of upper limbs, a shared pelvis and a single pair of lower limbs (dicephalus, tetrabrachius, dipus twins). Twins had single male external genitalia. Two separate heartbeats were auscultated with heart rate of around 146/min, respiratory rate being 45 for right twin and 52 for the left twin. No murmur was evident clinically. An infantogram was done to further assess the twins; findings of clinical examination were confirmed. Twins had a two heads, two thoraces, two pair of upper limbs and a shared abdomen, pelvis and a single pair of lower limbs. X-ray revealed the twins had two separate thoraces, two hearts and two vertebral columns. Echocardiography revealed that both the hearts were morphologically grossly normal, with no evidence of any gross cardiac anomaly. Ultrasonography of the abdomen revealed a shared liver, a single spleen on the left side and a single pair of kidneys. There was no evidence of any hydronephrosis. Twins were referred to a higher center for surgical management.
DISCUSSION
EMBRYOLOGICAL BASIS
Four days after fertilization the trophoblast (chorion) differentiates. If the split occurs before this time the monozygotic twins will implant as separate blastocysts each with their own chorion and amnion. Eight days after fertilization the amnion differentiates. If the split occurs between the 4th and 8th days, then the twins will share the same chorion but have separate amnions. If a split occurs after the 8th day and before the 13th day, then twins will share the same chorion and amnion. This is a very rare condition and accounts for 1-2% of monozygotic twins. The embryonic disk starts to differentiate on the 13th day. If the split occurs after day 13, then the twins will share body parts in addition to sharing their chorion and amnion. [1]
The classification of conjoined twins is based on the site of union. The suffix-pagus is used meaning fastened. Thoracopagus - shared thorax. 90% have a shared heart. Omphalopagus - shared abdomen. Thoraco-omphalopagus - one of the most common types. Ileopagus - connected at the iliac bone. When the twins are extensively connected then the duplicated part is named. For example, dicephalus refers to two heads with one body. [1]
An attempt to standardise and classify conjoined twins according to the external forms of conjunction has been proposed by Leacham (Table 1) [2]
Table1. Classification of conjoined twins
Designation
Description
Thoracopagus Cephalo-thoracopagus Dicephalus Craniopagus Omphalopagus Rachipagus Thoraco-omphalopagus
Joined at chestJoined at head and chestSingle trunk and two headsJoined at headJoined at abdomenDorsal union of head and trunkJoined at chest and abdomen
Regardless of the site of union, variations occur with regard to the internal organs. Certain organs may be common to both twins or these may be separate. In the thoracophagus, the heart is often conjoined with associated cardiac anomalies, and in omphalopagus the liver is often conjoined. Prognosis, obstetric management, and treatment planning are determined by degree of fusion and extent of joining of fetal organs. Cesarean section is recommended in most third-trimester deliveries because of the high incidence of dystocia and resultant fetal damage. [3]
Antenatal diagnosis by ultrasound is possible in modern day obstetrics. Ultrasonographic identification of any of the following classical signs may suggest the diagnosis: both fetal heads in the same plane, unusual backward flexion of the cervical spine, no change in the relative position after maternal movement and manual manipulations and inability to separate fetal bodies after careful observation. [4]
Dicephalus Dipus Conjoined Twins form a rare variant of conjoined twins. Such variants are usually stillborn or die immediately after birth, but some including the Scottish brothers of James III have lived for a number of years. As most of the studies concentrate on the obstetrical problems, the anatomical description of the dicephalus twins is often incomplete. A conjoint twin is frequently the mirror image of its partner and this is particularly true in dicephalus twins. The right set of lungs may be a mirror image of the normal and the right aorta usually has a right aortic arch. The liver is always single and there is usually one spleen and that is on left. The right stomach may be atrophic but is usually present, and the intestines almost always join either just distal to the duodenum or at the level of Meckel's diverticulum. Diaphragmatic hernia are also frequent. The right sided twin of the dicephalus dipus twin will usually have complex cardiovascular anomalies not amenable to surgical correction. This should be taken into account if the surgical separation of this variant of conjoined twins is planned. [5]
Separation of conjoined twins is complicated procedure. The importance of multidiscipline team with rehearsal of all aspects (surgical, anesthetic and nursing) of the operative procedure cannot be overemphasized. Although the outcome is influenced by careful planning and organization from all participants, the prognosis is often predetermined by the underlying anatomy which may preclude successful separation. [6]
Although, conjoined twins are rare, occurring in approximately 1 per 50,000 to 1 per 100,000; it should be suspected in all monochorionic, monoamniotic twin pregnancies, and careful sonographic assessment should be performed to identify the presence of shared fetal organs. [7]
Siamese twins or double monsters have always been a subject of curiousty and mystery for the general public. The present case highlights morphological features of an antenataly undiagnosed Dicephalus Dipus Conjoined Twins, a rare form of conjoined twins. Indirectly emphasizing the importance of careful antenatal sonographic assessment in all monochorionic, monoamniotic twin pregnancies to rule out conjoined twins. Early prenatal diagnosis and precise characterization of conjoined twins are essential for optimal obstetric, interventional and postnatal management as well as to reduce psychological trauma to the parents.REFERENCES
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