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Imaging of an unusual case of parasitic twinning
Computerized Medical Imaging and Graphics PERGAMON
Computerized Medical Imaging and Graphics 23 (1999) 219–222 www.elsevier.com/locate/compmedimag
Imaging of an unusual case of parasitic twinning E. Chun a, A. Vade a,*, M.D.Z. Rizvi b, H. Elsayed b a
Department of Radiology, Loyola University Medical Center, 2160 S. First avenue, Maywood, IL 60153, USA Department of Pediatrics, Loyola University Medical Center, 2160 S. First avenue, Maywood, IL 60153, USA
b
Received 9 December 1997; accepted 27 March 1998
Abstract Conjoined twins are rare in the literature and parasitic conjoined twins are rarer still. To our knowledge no cases of parasitic conjoined twins have previously been reported in the radiology literature. We present a case of parasitic conjoined twins in which radiographic findings played an important role in management. q 1999 Elsevier Science Ltd. All rights reserved. Keywords: Conjoined; Parasite; Twin
1. Case report A 29-year-old Hispanic G2P1001 woman had good prenatal care and had a non-contributory maternal history. An obstetric ultrasound at an outside hospital revealed foetal abnormalities (coarctation of aorta, hydrocephalus and nonvisualization of urinary bladder). A 3320 g female was delivered vaginally with Apgars of 9 and 9 at 1 and 5 min, respectively. The infant was clinically stable and had no evidence of cardiac anomalies on echocardiogram. The infant had bladder extrophy and two umbilical cords (each with two vessels), one inserted just above and the other just below the bladder extrophy. The infant stooled from an opening just inferior and to the right of the bladder extrophy. The infant had a soft tissue mass attached to its pelvis and a third well formed spontaneously moving lower extremity attached to the posterior pelvis. The right side of the soft tissue mass contained partially herniated fluid filled bowel loops. There was a significant amount of hair noted over the posterior aspect of the soft tissue mass. Plain abdominal film (Fig. 1) revealed a widened pubic symphysis and angulation of the distal spine to the left at the S2-3 level. The pelvis had two acetabulae, each with a normal relationship to a normal lower extremity. Inferior to this pelvis, within the extraneous soft tissue mass, was another bony hemipelvis, with its acetabulum related to an extraneous lower extremity. The soft tissue mass contained a few malformed ribs and two vertebrae. These vertebrae
* Corresponding author. Tel.: 1 708-216-8626; fax: 1 708-216-8394. E-mail address: [email protected] (A. Vade)
were aligned with the proximal sacrum of the infant. Air filled bowel loops were visualized within the complete pelvis of the infant and in the center of the soft tissue mass. MRI revealed normal abdominal anatomy in the infant. However, the infant’s sigmoid colon was seen leading into the rectum posteriorly and the bowel in the soft tissue mass entering the same rectum anterolateral and to the right side of the sigmoid opening (Fig. 2). MRI showed continuity of the infant’s spinal canal with that of the soft tissue mass, at S2–S3 level and spinal dysraphism of the two vertebrae in the soft tissue mass with the neural tube exposed to the external surface at this level. The spinal cord of the infant showed hydromyelia in its entirety and was tethered to the sacrum at S1–S2 level. At this level the nerve roots from the spinal cord were seen to diverge into the distal sacral canal of the infant on the left and into the vertebral canal present in the soft tissue mass inferiorly (Fig. 3). MRI also revealed hydrocephalus and an Arnold Chiari Type 2 malformation in the infant and two hydronephrotic kidneys in the soft tissue mass. CT scan demonstrated an opacified small bowel loop entering the spinal canal at L5 –S1 level through the left neurovertebral foramen (Fig. 4). The infant became febrile at one week of age and was found to have E. coli meningitis with negative blood cultures. At this time the infant was lethargic, had seizures and loss of movement of the extraneous limb. These symptoms improved with antibiotic therapy. Based on the imaging findings and after conference with the parents, a decision was made to discontinue antibiotic treatment and discharge the child home where she died shortly thereafter of sepsis. No postmortem was performed.
0895-6111/99/$ - see front matter q 1999 Elsevier Science Ltd. All rights reserved. PII: S0895-611 1(99)00011-7
220
E. Chun et al. / Computerized Medical Imaging and Graphics 23 (1999) 219–222
Fig. 1. Plain radiograph reveals widened pubic symphysis (black arrows) and angulation of the spine at S2-3 level (open arrow). Curved arrow shows hemipelvis with single acetabulum and an extraneous lower extremity. White arrow delineates the soft tissue mass which contains ribs and air filled bowel loops. Bladder extrophy is seen as a soft tissue density overlying the pelvis (long arrows).
2. Discussion Throughout the years there have been multiple reports of abnormal twinning from conjoined twins to parasitic twins
to fetus in fetu. The reported incidence of conjoined twinning varies from 1 in 50 000 to 1 in 100 000 and 10% are parasitic [1,2]. Conjoined parasitic twin pregnancy occurs with monovular, monoamniotic multiple pregnancy, and is
Fig. 2. Coronal T2 MR (TR 2000 ms, TE 80 ms) shows two hydronephrotic kidneys (straight arrows) in the parasite and a single distended rectum (R) which is shared by both parasite and autosite. Fluid filled (solid curved arrow) and air filled (curved open arrow) partially herniated bowel loops are seen in the parasite.
E. Chun et al. / Computerized Medical Imaging and Graphics 23 (1999) 219–222
Fig. 3. Coronal T2 MRI (TR 4700 ms, TE 95 ms) of lumbosacral spine shows hydromyelia (open arrows) extending up to the sacrum and bifurcation of spinal contents (straight arrow). Some nerves are seen entering the vertebral axis of the parasite and some entering the distal sacral spine of the autosite (arrow heads).
associated with a viable twin (the autosite) who is histologically and developmentally appropriate for gestational age, and an incompletely developed parasite [3,4]. Parasitic conjoined twins are also referred to as unequal or asymmetrical conjoined twins or heteropagus twins. The parasite may be attached to the visible surface (heteropagus twins) or inside of the autosite (fetus in fetu). In heteropagus
Fig. 4. Axial CT of the pelvis shows opacified bowel loops (straight arrow) entering the vertebral canal at lumbosacral level (I ischium, P pubis, V vertebra and curved arrow bladder extrophy).
221
twinning the site of the parasite will indicate the type of original conjunction [4]. When the parasite is attached to the posterior pelvis of the autosite, it is a pygopagus type. The pyopagi parasite is usually posterolateral to the autosite. The twins never share the anterior trunk and therefore have separate umbilical cords [4]. The union involves primarily the bones and meninges but sometimes neural tissue as well. There is usually a shared spinal cord, meninges, bladder, anus and rectum [5]. All these features were seen in our case. The pyopagi parasites rarely contain recognizable parts [3]. In our case few recognizable internal organs were present in the parasite. The presence of some spinal axis in the parasite may have been responsible for the presence of some internal organs in the soft tissue mass [6]. There is a marked trend for acephalic parasitic conjoined twins to form legs [7]. Cases of acephalous parasites with ectopic legs reported in the literature had no vertebrae [7]. Moreover the ectopic legs in these acephalous parasites showed paucity or absence of muscles and nerves. Stephens et al postulated that this was due to absence of vertebral and axial structures in these parasites [7]. Our case which had both vertebral axis and a well-developed leg was unusual from those reported in the literature [7]. The presence of well developed skeletal muscles in the ectopic extremity of the parasite in our case may have been due to adequate innervation of the myeloblast from the parasites or autosites neuroaxial structures since some of the nerve roots of the autosite were seen on MRI to diverge into the parasites spinal canal. Drutt et al. reported two cases where assessments of the interrelationship between the autosite and the parasite were made by the deficits discovered in the autosite post resection of the parasitic masses on the backs of the autosites [8]. These cases involved unusual heteropagus twins with spines and spinal cords in the acephalic parasites and two normal appearing lower extremities in the autosite. After resection of the parasitic masses from the backs of these autosites, neurologic deficits occurred in the left lower limb in both cases. The consensus was that the well developed left leg and hemipelvis were part of the parasite in both cases. These cases are similar to our case except that the autosite in our case had two complete lower extremities. The autosite in this case had hydrocephalus and hydromyelia of the entire spinal cord. The neural tube structures of the autosite and the parasite were continuous. Herniation of bowel loops into the spinal canal with a probable neurenteric fistulous connection in the autosite or direct stool contamination of the CSF space at the spinal dysraphism site in the parasite may have led to E. coli meningitis. The radiologists role in this case was very important in deciding on discontinuance of any therapy on this infant, who may have otherwise undergone multiple futile corrective surgical procedures resulting in prolonged stress to the infant and parents.
222
E. Chun et al. / Computerized Medical Imaging and Graphics 23 (1999) 219–222
3. Summary Complex anatomical information on parasitic conjoined twins can be obtained by various imaging procedures. This information on the parasite may not be considered important because corrective surgical procedure for parasitic conjoined twin consists of complete separation and removal of the parasite from the autosite. However, imaging of parasitic conjoined twins is important to make ethical decisions regarding the implementation of corrective surgery or continuance of palliative medical therapy.
References [1] Edmonds LD, Layde PM. Conjoined twins in the United States 1970– 1977. Teratology 1982;25:301–308. [2] Zimmermann AA. Embryologic and anatomic consideration of conjoint twins. Birth Defects 1967;3:18–21. [3] Potter EI. Pathology of the fetus and the infant, 2. Chicago, IL: Year Book Medical Publishers, 1961:216–233. [4] Spencer R. Conjoined twins: theoretical embryologic basis. Teratology 1992;45:591–602. [5] O’Neill Jr. JA, Holcomb GW, Schnaufer L, Templeton Jr. JM, et al. Surgical experience with thirteen conjoined twins. Ann Surg 1988;208(3):299–310. [6] Ursell PC, Wigger HJ. Asplenia syndrome in conjoined twins: a case report. Teratology 1983;27:301–304. [7] Stephens TD, Siebert JR, Graham Jr, J M, Beckwith JB. Parasitic conjoined twins, two cases and their relation to limb morphogenesis. Teratology 1982;26:115–121. [8] Drutt R, Garcia C, Drutt RM. Poorly organized parasitic conjoined twins: report of four cases. Pediatric Pathology 1992;12:691–700.
Aruna Vade, M.D. is a board-certified radiologist with CAQ (Certificate of Added Qualification) in Pediatric Radiology. She is full Professor of Radiology and Pediatrics at Loyola University Medical Center, Maywood, IL, USA. She has 48 publications in peer reviewed journals on various topics related to pediatric radiology. She has presented papers at national and international levels and had several poster exhibits on topics related to pediatric radiology at numerous scientific meetings. She is an active member in several radiological societies and executive member in Chicago Radiological Society. She is a member of hospital pediatric sedation committee at LUMC and also Society of Pediatric Radiology Sedation Committee.
Elizabeth Chun, M.D. was first year radiology resident at Loyola University Medical Center from July 1995 to June 1996.
Zehra Rizvi, M.D. is an Associate Professor of Pediatric and Attending Neonatologist at Loyola University Medical Center in Maywood, IL, USA. She is also an Attending Neonatologist at Elmhurst Hospital in Elmhurst, IL.
H. Elsayed, M.D. is a Neonatologist at Loyola University Medical Center.
Computerized Medical Imaging and Graphics 23 (1999) 219–222 www.elsevier.com/locate/compmedimag
Imaging of an unusual case of parasitic twinning E. Chun a, A. Vade a,*, M.D.Z. Rizvi b, H. Elsayed b a
Department of Radiology, Loyola University Medical Center, 2160 S. First avenue, Maywood, IL 60153, USA Department of Pediatrics, Loyola University Medical Center, 2160 S. First avenue, Maywood, IL 60153, USA
b
Received 9 December 1997; accepted 27 March 1998
Abstract Conjoined twins are rare in the literature and parasitic conjoined twins are rarer still. To our knowledge no cases of parasitic conjoined twins have previously been reported in the radiology literature. We present a case of parasitic conjoined twins in which radiographic findings played an important role in management. q 1999 Elsevier Science Ltd. All rights reserved. Keywords: Conjoined; Parasite; Twin
1. Case report A 29-year-old Hispanic G2P1001 woman had good prenatal care and had a non-contributory maternal history. An obstetric ultrasound at an outside hospital revealed foetal abnormalities (coarctation of aorta, hydrocephalus and nonvisualization of urinary bladder). A 3320 g female was delivered vaginally with Apgars of 9 and 9 at 1 and 5 min, respectively. The infant was clinically stable and had no evidence of cardiac anomalies on echocardiogram. The infant had bladder extrophy and two umbilical cords (each with two vessels), one inserted just above and the other just below the bladder extrophy. The infant stooled from an opening just inferior and to the right of the bladder extrophy. The infant had a soft tissue mass attached to its pelvis and a third well formed spontaneously moving lower extremity attached to the posterior pelvis. The right side of the soft tissue mass contained partially herniated fluid filled bowel loops. There was a significant amount of hair noted over the posterior aspect of the soft tissue mass. Plain abdominal film (Fig. 1) revealed a widened pubic symphysis and angulation of the distal spine to the left at the S2-3 level. The pelvis had two acetabulae, each with a normal relationship to a normal lower extremity. Inferior to this pelvis, within the extraneous soft tissue mass, was another bony hemipelvis, with its acetabulum related to an extraneous lower extremity. The soft tissue mass contained a few malformed ribs and two vertebrae. These vertebrae
* Corresponding author. Tel.: 1 708-216-8626; fax: 1 708-216-8394. E-mail address: [email protected] (A. Vade)
were aligned with the proximal sacrum of the infant. Air filled bowel loops were visualized within the complete pelvis of the infant and in the center of the soft tissue mass. MRI revealed normal abdominal anatomy in the infant. However, the infant’s sigmoid colon was seen leading into the rectum posteriorly and the bowel in the soft tissue mass entering the same rectum anterolateral and to the right side of the sigmoid opening (Fig. 2). MRI showed continuity of the infant’s spinal canal with that of the soft tissue mass, at S2–S3 level and spinal dysraphism of the two vertebrae in the soft tissue mass with the neural tube exposed to the external surface at this level. The spinal cord of the infant showed hydromyelia in its entirety and was tethered to the sacrum at S1–S2 level. At this level the nerve roots from the spinal cord were seen to diverge into the distal sacral canal of the infant on the left and into the vertebral canal present in the soft tissue mass inferiorly (Fig. 3). MRI also revealed hydrocephalus and an Arnold Chiari Type 2 malformation in the infant and two hydronephrotic kidneys in the soft tissue mass. CT scan demonstrated an opacified small bowel loop entering the spinal canal at L5 –S1 level through the left neurovertebral foramen (Fig. 4). The infant became febrile at one week of age and was found to have E. coli meningitis with negative blood cultures. At this time the infant was lethargic, had seizures and loss of movement of the extraneous limb. These symptoms improved with antibiotic therapy. Based on the imaging findings and after conference with the parents, a decision was made to discontinue antibiotic treatment and discharge the child home where she died shortly thereafter of sepsis. No postmortem was performed.
0895-6111/99/$ - see front matter q 1999 Elsevier Science Ltd. All rights reserved. PII: S0895-611 1(99)00011-7
220
E. Chun et al. / Computerized Medical Imaging and Graphics 23 (1999) 219–222
Fig. 1. Plain radiograph reveals widened pubic symphysis (black arrows) and angulation of the spine at S2-3 level (open arrow). Curved arrow shows hemipelvis with single acetabulum and an extraneous lower extremity. White arrow delineates the soft tissue mass which contains ribs and air filled bowel loops. Bladder extrophy is seen as a soft tissue density overlying the pelvis (long arrows).
2. Discussion Throughout the years there have been multiple reports of abnormal twinning from conjoined twins to parasitic twins
to fetus in fetu. The reported incidence of conjoined twinning varies from 1 in 50 000 to 1 in 100 000 and 10% are parasitic [1,2]. Conjoined parasitic twin pregnancy occurs with monovular, monoamniotic multiple pregnancy, and is
Fig. 2. Coronal T2 MR (TR 2000 ms, TE 80 ms) shows two hydronephrotic kidneys (straight arrows) in the parasite and a single distended rectum (R) which is shared by both parasite and autosite. Fluid filled (solid curved arrow) and air filled (curved open arrow) partially herniated bowel loops are seen in the parasite.
E. Chun et al. / Computerized Medical Imaging and Graphics 23 (1999) 219–222
Fig. 3. Coronal T2 MRI (TR 4700 ms, TE 95 ms) of lumbosacral spine shows hydromyelia (open arrows) extending up to the sacrum and bifurcation of spinal contents (straight arrow). Some nerves are seen entering the vertebral axis of the parasite and some entering the distal sacral spine of the autosite (arrow heads).
associated with a viable twin (the autosite) who is histologically and developmentally appropriate for gestational age, and an incompletely developed parasite [3,4]. Parasitic conjoined twins are also referred to as unequal or asymmetrical conjoined twins or heteropagus twins. The parasite may be attached to the visible surface (heteropagus twins) or inside of the autosite (fetus in fetu). In heteropagus
Fig. 4. Axial CT of the pelvis shows opacified bowel loops (straight arrow) entering the vertebral canal at lumbosacral level (I ischium, P pubis, V vertebra and curved arrow bladder extrophy).
221
twinning the site of the parasite will indicate the type of original conjunction [4]. When the parasite is attached to the posterior pelvis of the autosite, it is a pygopagus type. The pyopagi parasite is usually posterolateral to the autosite. The twins never share the anterior trunk and therefore have separate umbilical cords [4]. The union involves primarily the bones and meninges but sometimes neural tissue as well. There is usually a shared spinal cord, meninges, bladder, anus and rectum [5]. All these features were seen in our case. The pyopagi parasites rarely contain recognizable parts [3]. In our case few recognizable internal organs were present in the parasite. The presence of some spinal axis in the parasite may have been responsible for the presence of some internal organs in the soft tissue mass [6]. There is a marked trend for acephalic parasitic conjoined twins to form legs [7]. Cases of acephalous parasites with ectopic legs reported in the literature had no vertebrae [7]. Moreover the ectopic legs in these acephalous parasites showed paucity or absence of muscles and nerves. Stephens et al postulated that this was due to absence of vertebral and axial structures in these parasites [7]. Our case which had both vertebral axis and a well-developed leg was unusual from those reported in the literature [7]. The presence of well developed skeletal muscles in the ectopic extremity of the parasite in our case may have been due to adequate innervation of the myeloblast from the parasites or autosites neuroaxial structures since some of the nerve roots of the autosite were seen on MRI to diverge into the parasites spinal canal. Drutt et al. reported two cases where assessments of the interrelationship between the autosite and the parasite were made by the deficits discovered in the autosite post resection of the parasitic masses on the backs of the autosites [8]. These cases involved unusual heteropagus twins with spines and spinal cords in the acephalic parasites and two normal appearing lower extremities in the autosite. After resection of the parasitic masses from the backs of these autosites, neurologic deficits occurred in the left lower limb in both cases. The consensus was that the well developed left leg and hemipelvis were part of the parasite in both cases. These cases are similar to our case except that the autosite in our case had two complete lower extremities. The autosite in this case had hydrocephalus and hydromyelia of the entire spinal cord. The neural tube structures of the autosite and the parasite were continuous. Herniation of bowel loops into the spinal canal with a probable neurenteric fistulous connection in the autosite or direct stool contamination of the CSF space at the spinal dysraphism site in the parasite may have led to E. coli meningitis. The radiologists role in this case was very important in deciding on discontinuance of any therapy on this infant, who may have otherwise undergone multiple futile corrective surgical procedures resulting in prolonged stress to the infant and parents.
222
E. Chun et al. / Computerized Medical Imaging and Graphics 23 (1999) 219–222
3. Summary Complex anatomical information on parasitic conjoined twins can be obtained by various imaging procedures. This information on the parasite may not be considered important because corrective surgical procedure for parasitic conjoined twin consists of complete separation and removal of the parasite from the autosite. However, imaging of parasitic conjoined twins is important to make ethical decisions regarding the implementation of corrective surgery or continuance of palliative medical therapy.
References [1] Edmonds LD, Layde PM. Conjoined twins in the United States 1970– 1977. Teratology 1982;25:301–308. [2] Zimmermann AA. Embryologic and anatomic consideration of conjoint twins. Birth Defects 1967;3:18–21. [3] Potter EI. Pathology of the fetus and the infant, 2. Chicago, IL: Year Book Medical Publishers, 1961:216–233. [4] Spencer R. Conjoined twins: theoretical embryologic basis. Teratology 1992;45:591–602. [5] O’Neill Jr. JA, Holcomb GW, Schnaufer L, Templeton Jr. JM, et al. Surgical experience with thirteen conjoined twins. Ann Surg 1988;208(3):299–310. [6] Ursell PC, Wigger HJ. Asplenia syndrome in conjoined twins: a case report. Teratology 1983;27:301–304. [7] Stephens TD, Siebert JR, Graham Jr, J M, Beckwith JB. Parasitic conjoined twins, two cases and their relation to limb morphogenesis. Teratology 1982;26:115–121. [8] Drutt R, Garcia C, Drutt RM. Poorly organized parasitic conjoined twins: report of four cases. Pediatric Pathology 1992;12:691–700.
Aruna Vade, M.D. is a board-certified radiologist with CAQ (Certificate of Added Qualification) in Pediatric Radiology. She is full Professor of Radiology and Pediatrics at Loyola University Medical Center, Maywood, IL, USA. She has 48 publications in peer reviewed journals on various topics related to pediatric radiology. She has presented papers at national and international levels and had several poster exhibits on topics related to pediatric radiology at numerous scientific meetings. She is an active member in several radiological societies and executive member in Chicago Radiological Society. She is a member of hospital pediatric sedation committee at LUMC and also Society of Pediatric Radiology Sedation Committee.
Elizabeth Chun, M.D. was first year radiology resident at Loyola University Medical Center from July 1995 to June 1996.
Zehra Rizvi, M.D. is an Associate Professor of Pediatric and Attending Neonatologist at Loyola University Medical Center in Maywood, IL, USA. She is also an Attending Neonatologist at Elmhurst Hospital in Elmhurst, IL.
H. Elsayed, M.D. is a Neonatologist at Loyola University Medical Center.