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Caudal duplication, (or caudal duplication syndrome) is a rare congenital disorder in which various structures of the caudal region, embryonic cloaca, and neural tube exhibit a spectrum of abnormalities such as duplication and malformations.<ref name=":3">,
Caudal Duplication Syndrome, Archives of Pediatrics & Adolescent Medicine, Vol. 147(Issue: 10), pp. 1048–52, DOI: 10.1001/archpedi.1993.02160340034009, PMID: 8213674,</ref> The exact causes of the condition is unknown,<ref name=":3" /> though there are several theories implicating abnormal embryological development as a cause for the condition.<ref name=":4" /> Diagnosis is often made during prenatal development of the second trimester through anomaly scans or immediately after birth.<ref name=":6" /> However, rare cases of adulthood diagnosis has also been observed. Treatment is often required to correct such abnormalities according to the range of symptoms present,<ref name=":6" /> whilst treatment options vary from conservative expectant management to resection of caudal tissue to restore normal function or appearance.<ref name=":7">, Caudal 'duplication' or 'split' syndrome: Is there a misnomer?, Journal of Pediatric Surgery Case Reports, Vol. 1(Issue: 10), pp. 351–356, DOI: 10.1016/j.epsc.2013.09.007,</ref> As a rare congenital disorder, the prevalence at birth is less than 1 per 100,000 <ref name=":4">, Caudal duplication syndrome, Journal of Clinical Neonatology, Vol. 2(Issue: 2), pp. 101–2, DOI: 10.4103/2249-4847.116412, PMID: 24049755, PMC: 3775131,</ref> with less than 100 cases reported worldwide.<ref name=":5">, A Rare Presentation of Caudal Duplication Syndrome in an Adult with No Functional Impairment, Journal of Case Reports, Vol. 4(Issue: 2), pp. 324–327, DOI: 10.17659/01.2014.0081,</ref>
The term "caudal duplication syndrome" has been coined since 1993<ref name=":3" /> to describe caudal abnormalities and conditions. However, there has been recent debate into the appropriateness of the term being "caudal split syndrome" instead of caudal duplication due to the "splitting" nature of the abnormalities, rather than "duplication".<ref name=":7" />
Signs and symptoms
The condition’s symptoms vary greatly due to the diverse spectrum of gastrointestinal (GI), urogenital (genitourinary, GU), spinal, and limb anomalies.<ref name=":0">,
Caudal duplication syndrome-report of a case and review of literature, The Indian Journal of Surgery, Vol. 75(Issue: Suppl 1), pp. 484–7, DOI: 10.1007/s12262-013-0838-z, PMID: 24426655, PMC: 3693374,</ref> Common examples include anorectal malformation, and duplication of the external genitalia,<ref name=":0" /> while other symptoms include incomplete duplication of the lower spine, spinal cord, (diastematomyelia) <ref name=":1">, Caudal duplication syndrome, Arquivos de Neuro-Psiquiatria, Vol. 67(Issue: 3A), pp. 695–6, DOI: 10.1590/S0004-282X2009000400023, PMID: 19722052,</ref> partial fusion of complete duplication of the uterus, vagina, colon, and bladder.<ref>Online Mendelian Inheritance in Man (OMIM) Caudal Duplication Anomaly -607864
</ref>
Malformations of the spine have indicated to cause varying levels of neurological impairment.<ref name=":1" /> Although the level of neurological impairment is dependent upon the severity and type of spinal abnormality, most reported cases of spinal cord duplication exhibit severe neurological impairment,<ref name=":1" /> though cases of mild or absent neurological impairment has also been observed.<ref name=":1" />
Though patients often present a diverse variety of symptoms, a case was observed in which a female adult with duplication of the colon, rectum, anus, urinary bladder, urethra, uterus, cervix, vagina, and external genitalia exhibited no detrimental effects.<ref name=":6">,
Caudal Duplication Syndrome: the Vital Role of a Multidisciplinary Approach and Staged Correction, European Journal of Pediatric Surgery Reports, Vol. 4(Issue: 1), pp. 001–005, DOI: 10.1055/s-0035-1570370, PMID: 28018799, PMC: 5177553,</ref> This suggests that rarely seen cases of complete duplication of the urogenital and gastrointestinal tract are often asymptomatic.<ref name=":2">, Complete genitourinary and colonic duplication: a rare presentation in an adult patient, Journal of Ultrasound in Medicine, Vol. 25(Issue: 3), pp. 407–11, DOI: 10.7863/jum.2006.25.3.407, PMID: 16495506,</ref>
As patients often present a multitude of differing symptoms within the caudal region, each patient exhibits a unique, characterised symptom which may or may not be cosmetically or physiologically detrimental to the individual.<ref name=":3" />
| Classification<ref name=":3" /> | Anomalies and salient clinical features<ref name=":3" /> |
|---|---|
| Gastrointestinal tract anomalies |
|
| Genitourinary tract anomalies | |
| Spinal anomalies (includes lower limb anomalies) |
|
Causes
The exact cause of the condition is unknown.<ref name=":3" /> Although various theories indicate incomplete separation of monozygotic twins as an etiological factor,<ref name=":4" /> abnormal adherence between the ectoderm and endoderm during gastrulation,<ref name=":0" /> polytopic primary developmental field defects,<ref>,
Two cases of the caudal duplication anomaly including a discordant monozygotic twin, American Journal of Medical Genetics, Vol. 112(Issue: 4), pp. 390–3, DOI: 10.1002/ajmg.10594, PMID: 12376942,</ref> somatic and germ line mutations in developmental genes,<ref name=":4" /> and damage to the caudal cell mass and posterior gut have also been linked to cause structural anomalies in the caudal region.<ref name=":0" />
It is speculated that the condition is related to the HOX gene,<ref name=":4" /> namely HOX10 and HOX11. Normally coding for the mammalian appendicular and axial skeleton, misexpression of the genetic factors could lead to abnormal proliferation of the caudal mesenchyme.<ref name=":4" />
Embryology is suggested to have an intimate association with the development of caudal duplication syndrome.<ref name=":3" /> At day 15 after fertilisation, the notochord grows from the primitive knot, in which it invaginates and forms the notochord canal within.<ref name=":3" /> Progressively, on day 20, the ventral wall of the notochord dissolves, while communications are formed between the amniotic and yolk sac.<ref name=":3" /> One such connection is the Kovalevsky’s canal. From the 23rd to 25th day of gestation, the spinal cord develops except for its distal-most aspect where the notochord and neural tube are joined to form the caudal cell mass.<ref name=":3" /> The canal of Kovalevsky crosses the caudal cell mass, while endoderm located anteriorly to the cell mass develops into the hindgut, various insults towards the cell mass and hindgut during the stage of development may lead to the development of caudal anomalies, one of which is caudal duplication syndrome.<ref name=":3" />
The incomplete regression of Kovalevsky’s canal may also lead to formations of fibrous bands joining the hindgut to the spinal canal,<ref name=":7" /> possibly leading to the onset of diastemetaomyelia.<ref name=":6" /> These bands may divide the notochord, developing into duplications of the lower spine and spinal cord, the adjacent mesoderm is also divided, resulting in duplicates of GI and GU tracts.<ref name=":6" /> Subsequently, the duplications can also lead to the presence of a range of anomalies including dorsal enteric fistulas, enteric cysts, spina bifida, malformed or duplicated colon, bladder, sacrum, and lower spinal cord.<ref name=":3" /><ref name=":9" />
Moreover, a midline pelvic mass defect during gestation could be an obstacle to caudal migration of paramesonephric structures (Müllerian duct), which could lead to duplication of the genital tract.<ref name=":3" /> Whilst failures of migration or fusion of those structures is one of the more prevalent embryological theories for duplication of lower genitourinary organs such as the bladder.<ref name=":3" /> Intestinal duplications extending into the rectum or anus is often rare.<ref name=":3" /><ref name=":5" /> However, if the caudal cell mass is divided early, duplications of the distal bowel may still occur.<ref name=":3" />
In gastrointestinal abnormalities, a mechanism known as “caudal twinning”<ref name=":4" /> is proposed in which during the 23th to 25th day of gestation, the intestinal tract is filled by rapid proliferation of endothelial cells, as the gut increases in size, vacuoles appear within the cell masses to constitute a single lumen.<ref name=":3" /><ref name=":6" /> However, in abnormal cases where a vacuole is pinched off, a second lumen is created.<ref name=":6" /> The second lumen is then proposed to magnify in size in proportion to the growth of the colon, effectively duplicating all caudal structures distal from the point of separation.<ref name=":3" /><ref name=":2" />
Diagnosis
The condition can often be seen as malformations that can be diagnosed by a prenatal anomaly scan in the second trimester, while progressively detailed examinations can be conducted after the first day of life of the baby.<ref name=":4" /> If an abnormality is detected early on, psychological and surgical preparation may be required to resort to a cesarean section to prevent obstructed labour, in which medical paediatric and surgical care soon follows after delivery.<ref name=":10">,
Caudal duplication syndrome: imaging evaluation of a rare entity in an adult patient, Radiology Case Reports, Vol. 11(Issue: 1), pp. 11–5, DOI: 10.1016/j.radcr.2015.12.001, PMID: 26973727, PMC: 4769617,</ref><ref>, Prenatal diagnosis of congenital renal and urinary tract malformations, Facts, Views & Vision in ObGyn, Vol. 3(Issue: 3), pp. 165–74, PMID: 24753862, PMC: 3991456,</ref><ref name=":12" />
Diagnosis during adulthood is extremely rare<ref name=":3" /> in cases where abnormalities are asymptomatic or are not visible upon physical inspection upon prenatal or birth inspections.<ref name=":5" /> Similarly to paediatric and prenatal diagnosis, an adulthood diagnosis can be made through various imaging modalities<ref name=":6" /> such as computed tomography (CT) scans to explicitly define the range of symptoms present in caudal duplication.<ref name=":10" />
Treatment
The rare, complex syndrome includes a wide spectrum of malformations ranging from partial or isolated to complete duplication of caudal organs in GI, GU, and neural systems.<ref name=":10" /> The syndrome may cause functional impairments such as an imperforate anus and hernia which may lead to death due to shock and organ failure and require prompt surgical intervention,<ref>,
A newborn with caudal duplication and duplex imperforate anus, Journal of Pediatric Surgery, Vol. 48(Issue: 5), pp. E37-43, DOI: 10.1016/j.jpedsurg.2013.03.068, PMID: 23701807,</ref> but most presented symptoms are not life-threatening and duplicated organs are in fact functional in many cases.<ref name=":3" /><ref name=":5" /> For instance, patients with genital duplication are mostly expected to have normal menstruation, sexual intercourse, and even pregnancy,<ref>, Female genital anomalies affecting reproduction, Fertility and Sterility, Vol. 78(Issue: 5), pp. 899–915, DOI: 10.1016/S0015-0282(02)03368-X, PMID: 12413972,</ref> although their self-esteem and quality of life may be influenced.<ref name=":7" /> Since the clinical presentation of each patient and its complexity vary greatly, the management which usually includes surgery are carefully planned and individualised based on the extent of duplication and functionality of the involved organs.<ref name=":6" />
An extensive medical work-up is required primarily before prognosis to understand the anatomy of patients and to decide appropriate treatment. Imaging modalities such as echocardiography, conventional X-ray, magnetic resonance imaging (MRI), ultrasonography, barium enema, computed tomography (CT) scan, and voiding cystourethrography (VCU) can be used to examine anomalies in detail.<ref name=":4" /><ref name=":6" /><ref name=":10" /> Exploratory laparotomy can also be conducted when needed.<ref name=":0" /> In most cases, surgical approach is utilised to excise or fuse the duplicated organs;<ref name=":4" /><ref name=":0" /><ref name=":8">,
Caudal 'duplication' or 'split' syndrome: Is there a misnomer?, Journal of Pediatric Surgery Case Reports, Vol. 1(Issue: 10), pp. 351–356, DOI: 10.1016/j.epsc.2013.09.007,</ref> however, surgical intervention is not a compulsory procedure for patients that do not exhibit functional deterioration and symptoms.<ref name=":6" /> Based on the work-up results, a multidisciplinary team consisting of a (paediatric) surgeon, a urologist, and a neurosurgeon plans individualised, staged correction.<ref name=":11">, Caudal duplication syndrome, Journal of the College of Physicians and Surgeons--Pakistan, Vol. 24(Issue: 1), pp. 64–6, PMID: 24411548, Full text,</ref>
If a prenatal or after birth diagnosis is made, medical paediatric and surgery care are organised soon after delivery.<ref name=":12">,
Challenges in the management of a rare case of caudal duplication syndrome in a poor resource setting, Journal of Pediatric Surgery Case Reports, Vol. 3(Issue: 11), pp. 508–511, DOI: 10.1016/j.epsc.2015.10.003,</ref> Adults with the syndrome, however, usually do not require surgical treatment unless accompanied by symptoms or psychological issues.<ref name=":6" /><ref name=":5" /> Reconstructive surgeries are performed to resolve the issue of functional impairments such as obstruction of colon, anatomic anomalies that hinder movement or cause infertility, and to improve cosmetic appearances in the case of genital duplication.<ref name=":6" />
Gastrointestinal tract
Treatments for colonic duplication varies from conservative management for asymptomatic cases to excision of duplicated colon to avoid potential issues such as colon structure and obstruction.<ref name=":6" /><ref name=":0" /> Resection is possible when each duplicated colon has a complete blood supply. If the duplicated colons share a wall, a septotomy can be performed to create a small hole to connect two colons.<ref name=":6" /><ref name=":0" /> In cases where rectum is also duplicated, either the rectums should be converted into one reservoir through septotomy followed by anorectoplasty or the duplicated colon and rectum should be removed and colostomies should be constructed.<ref name=":6" /> For patients with poor prognosis for bowel control, a Malone procedure can be utilised during the colostomy.<ref name=":6" /> Alternatively, in cases of renal duplication, the Mitrofanoff procedure is performed instead.<ref name=":6" />
Genitourinary tract
Duplication of genital tract that does not involve functional impairment does not require surgical intervention; however, plastic surgery can be carried out to improve patients’ self-esteem and social status.<ref name=":8" /> For duplication of female genital tract, the septum between duplicated organs such as vagina, cervix, and vulva are resected to combine two duplicated organs into one or one duplicated organ could be detached and excised.<ref name=":8" /> For male patients, one duplicated genitalia can be removed, and duplicated scrotum and testis can be either combined or excised.<ref name=":12" /> The external genitalia of both male and female can be reconstructed by midline apposition of tissues.<ref name=":8" /> For duplication of urinary tract, bladders can be combined to form a single larger bladder without altering the duplicated ureters.<ref name=":8" />
Spinal and lower limb tract
In cases of spine duplication, prophylactic surgery can be done to remove one duplicated spine, although it depends on the severity of duplication.<ref>,
Complete lumbar spine duplication in a neurologically intact man, The Journal of Spinal Cord Medicine, Vol. 32(Issue: 1), pp. 99–102, DOI: 10.1080/10790268.2009.11760759, PMID: 19264056, PMC: 2647508,</ref> In cases of malformation of the neural cord such as myelomeningocele and tethered cord which accompanies severe symptoms, preserving neurological function is the utmost importance by closing myelomeningocele and detethering the neural cord.<ref name=":6" /> This is a highly complex procedure that requires extreme caution not to injure the rectum in which case can cause a cerebrospinal fluid infection.<ref name=":6" /> For duplication of lower limb which not only hinders patients’ gait but also is highly visible and may affect patients’ self-esteem, excision of the supernumerary, non-functional pair of limb is often carried out.<ref name=":12" />
Due to the spectrum of symptoms present within caudal duplication, there is no uniform surgical treatment in relieving symptoms.<ref name=":11" /> The type and severity of surgical intervention is often dependent upon the type and complexity of symptoms presented.<ref name=":11" /> Thus, the primary goal of surgical treatment for the syndrome is to relieve symptoms, not to restore normal anatomy, and hence, potentially life-threatening malformations are addressed first and often followed by other anatomic or aesthetic reconstructions in later stages.<ref name=":6" /><ref name=":5" /> After the medical treatment, the patients are periodically monitored.<ref name=":8" /><ref name=":12" />
Epidemiology
Caudal duplication syndrome is a rare condition with only less than 100 patients in literature worldwide as of 2014 with only 2 patients diagnosed in adulthood.<ref name=":5" /> The prevalence of the syndrome is less than one per 100,000 births.<ref name=":7" /> The sex ratio of male to female patients is about 1:2, with no familial or racial predisposition has been found.<ref name=":11" />
History
The first systematic review for caudal duplication symptoms was done and the term "caudal duplication syndrome" was first proposed in 1993.<ref name=":3" /> The term was coined to describe rare anomalies associated with complete or partial duplication of caudal structures resulted from insults during embryogenesis to distinguish symptoms of spinal duplication syndrome which only involves spinal duplicity, only when there is associated complete or partial duplicity of vascular structures and/or organs such as bladder and distal gastrointestinal tract the term caudal duplication syndrome can be used.<ref name=":9">,
Split cord malformation: Part I: A unified theory of embryogenesis for double spinal cord malformations, Neurosurgery, Vol. 31(Issue: 3), pp. 451–80, DOI: 10.1227/00006123-199209000-00010, PMID: 1407428,</ref>
However, recently in 2013, it was suggested that “duplication” is a misnomer based on an analysis of two cases and literature review in which researchers found “hemi” organs was “split” not duplicated, proposing caudal “split” syndrome may be a more appropriate title.<ref name=":7" />
References
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