RX Patient Tools
Use these quick guides before reading the article, or return to them when you need help preparing questions for a doctor.
Dipygus is an extremely rare birth defect where the lower part of the body is partly or completely doubled, usually with two pelvises and extra legs that grow from the hips or lower back region. It is considered a very severe form of caudal duplication syndrome, a condition in which the structures in the lower (caudal) part of the embryo, such as the spine, intestines, urinary organs, and genital organs, are duplicated. Wikipedia+1
In dipygus, the baby usually has one head and one upper body, but the body splits lower down, so there may be two bottoms, two sets of external genital organs, and four or even more legs. Because it is so rare, most of what doctors know comes from single case reports and small case series rather than large studies. PMC+1
Dipygus belongs to the broader group of conjoined twin conditions. In these conditions, a single fertilized egg does not completely separate into two identical twins, or the early embryos fuse again, so some parts of the body are shared and some are duplicated. In dipygus, this duplication mainly affects the lower spine, pelvis, and legs, and sometimes the intestines, bladder, and reproductive organs. PubMed+1
Because caudal duplication as a whole is estimated to occur in less than 1 in 100,000 births and fewer than 100 cases have been reported worldwide, classic dipygus is even rarer. Many affected babies also have other serious problems such as spinal defects or abnormal anus and bladder openings, so care requires a specialized team. Wikipedia+1
Other names for dipygus
Dipygus has been described in the medical literature using several related names. Each name highlights a different part of the same problem. PMC+1
Some authors call it “caudal duplication with classic dipygus deformity”, to show that it is the most extreme end of the caudal duplication spectrum, with almost complete duplication of the body at the lower end. Wikipedia+1
The term “double buttocks deformity” or “double pelvis malformation” has also been used, especially in older reports, because the most striking feature is the presence of two pelvis regions and two sets of buttocks. These are descriptive terms rather than strict diagnostic labels. PMC+1
In the classification of conjoined twins, some cases are described as “monocephalus dipygus parapagus” – “monocephalus” meaning one head and “parapagus” meaning fusion along the side, with the lower body duplicated. This terminology places dipygus within conjoined twin categories used by pathologists and surgeons. PMC+1
Types of dipygus
Because dipygus is so rare, there is no single universal classification, but case reports and reviews describe several patterns or “types” that help doctors understand the anatomy and plan treatment. PMC+1
-
Complete (classic) dipygus – In this type, the body axis splits completely at the lower end. The child has one head and chest, but two pelvises, two sets of external genital organs, and four well-formed legs. Internal organs such as the colon, bladder, and uterus may also be fully duplicated. PMC+1
-
Partial dipygus – Here the duplication is incomplete. There may be an extra pelvis fragment or an extra leg attached to an accessory small pelvis between the normal thighs, while the rest of the body is single. Some internal organs may be duplicated, and others may be single. Academia+1
-
Symmetrical dipygus – In symmetrical cases, both sides of the lower body are similar in size and shape. The legs may all be nearly normal, and both sets of pelvis and genital organs may look similar. Function of limbs and organs can sometimes be surprisingly good, although complex surgery is usually needed. PMC+1
-
Asymmetrical (parasitic) dipygus – In this type, one lower body segment is well developed and functional, and the other is smaller, malformed, and often called a parasitic twin. The extra pelvis and legs may not move properly or may be missing bones or joints. Surgeons often remove the parasitic part to improve function and appearance. Iran Journals+1
-
Dipygus with mainly internal duplication – In some patients with classic external dipygus, the duplication of internal organs such as colon, bladder, uterus, or vagina is more severe than the visible external splitting. Detailed imaging often shows double colons, double bladders, or double reproductive tracts that must be mapped before surgery. PMC+1
Causes of dipygus
The exact cause of dipygus is not fully known. Most information comes from theories about caudal duplication syndrome and conjoined twins in general. Researchers believe many steps in early embryo development must go wrong at the same time. Wikipedia+1
-
Incomplete separation of monozygotic twins – Many authors think dipygus is a form of conjoined twinning where a single fertilized egg starts to split into identical twins but does not finish the separation, so only the lower part of the body is duplicated. PubMed+1
-
Abnormal “caudal twinning” of the hindgut region – Another theory suggests that only the tail end of the embryo “twins,” leading to duplication of the hindgut, spine, and urogenital structures without full twin formation. Academia+1
-
Abnormal interaction of ectoderm and endoderm during gastrulation – In very early pregnancy, the germ layers (outer ectoderm and inner endoderm) must separate and fold correctly. Abnormal sticking or splitting at this stage may cause split notochord and duplication of caudal organs. Wikipedia+1
-
Defects in the caudal cell mass – The caudal cell mass is a group of cells at the tail end that forms the lower spinal cord and sacral structures. Damage or abnormal division of this mass can produce duplicated spine and bowel segments. Wikipedia+1
-
Misexpression of HOX genes – Distal HOX genes such as HOX10 and HOX11 help pattern the lower spine and limbs. Research suggests misexpression of these genes could cause abnormal growth and duplication of caudal structures. ResearchGate+1
-
Mutations in other developmental genes – Some authors propose that yet-unknown somatic or germline mutations in genes controlling body patterning might contribute, but no specific gene for dipygus has been confirmed so far. ResearchGate+1
-
Failure of regression of embryonic canals – Incomplete regression of structures such as Kovalevsky’s canal can produce fibrous bands that split the notochord and hindgut, leading to double spinal cords and duplicated bowel and bladder. Wikipedia+1
-
Abnormal development of the cloaca – The embryonic cloaca is a common cavity for the urinary, genital, and intestinal tracts. Errors while it divides into the rectum and urogenital sinus can lead to duplicated colons, bladders, and genital organs. PMC+1
-
Midline pelvic mass or defect – A mass or failure in the midline pelvis region during embryo growth can block normal migration of Müllerian ducts (future uterus and vagina) and urinary structures, resulting in duplicated genital and urinary tracts. Wikipedia+1
-
General errors in neurulation and secondary neurulation – Problems while the spinal cord tube closes and extends may split or duplicate the lower neural tube and adjacent tissues, helping to create dipygus patterns. Wikipedia+1
-
Maternal insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes (indirect risk) – Pregnancies complicated by insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।" data-rx-term="diabetes" data-rx-definition="Diabetes is a condition where blood sugar stays too high because insulin is low or not working well. সহজ বাংলা: রক্তে চিনি বেশি থাকার রোগ।">diabetes have higher rates of serious birth defects, including neural tube and caudal malformations. While not proven to cause dipygus directly, poor glucose control may increase the overall risk of complex defects. PMC+1
-
Maternal obesity and high blood sugar – High body weight and high blood sugar in early pregnancy are linked to neural tube defects and other major malformations, which may overlap with mechanisms that can result in caudal duplication. PMC+1
-
Exposure to teratogenic medicines or chemicals – Some drugs and chemicals (teratogens) are known to raise the risk of severe birth defects and may play a role in abnormal twin splitting or caudal development in rare cases. PMC+1
-
Alcohol and substance use in early pregnancy – Alcohol, some illicit drugs, and certain toxic exposures have been associated with higher rates of congenital anomalies, including complex body-wall and spinal defects, though specific links to dipygus are not proven. Dove Medical Press+1
-
Lack of folic acid supplementation – Not taking folic acid before conception and in early pregnancy increases the risk of neural tube defects. Because caudal duplication involves severe disturbances of the lower neural tube and spine, low folate may contribute in some pregnancies. PMC+1
-
Advanced maternal age – Monozygotic twinning, and therefore conjoined twinning, appears slightly more common with increasing maternal age, suggesting that older egg cells may be more susceptible to abnormal splitting. UTMB WWW (ROOT)+1
-
Family history of congenital malformations – Some studies show that families with a history of major birth defects may have a higher background risk, possibly due to shared genes or environmental exposures, although dipygus itself is not usually familial. JSTOR+1
-
Random developmental error – Many authors emphasize that most conjoined and caudal duplication cases seem to arise sporadically, without any clear risk factor, suggesting that random errors during very early embryonic development may be enough to cause the condition. Mayo Clinic+1
-
Combination of genetic susceptibility and environment – It is likely that, in some pregnancies, a combination of subtle genetic sensitivity and external exposures leads to abnormal splitting or duplication of the caudal area rather than a single cause. ResearchGate+1
-
Shared mechanisms with other caudal anomalies – Dipygus shares features with other caudal conditions (like caudal regression and spinal duplications), so common pathways such as vascular disruption, abnormal mesoderm formation, or defective signaling molecules may underlie several different but related malformations. PMC+1
Symptoms and clinical features of dipygus
The symptoms of dipygus depend on how much of the body is duplicated and how well the duplicated organs work. Some problems are obvious at birth, while others appear later as the child grows. Wikipedia+1
-
Visible duplication of pelvis and legs – The most striking sign is the presence of two pelvis regions and extra legs, sometimes with four legs or more. The extra legs may be smaller or twisted, or they may look almost normal. PMC+1
-
Double buttocks and perineum – There may be two sets of buttocks, and the area between the thighs (perineum) may be divided, with two clefts and unusual skin folds. PMC+1
-
Duplication of external genital organs – Some children have two penises or duplicated vulva and clitoris, often with two separate vaginal openings in females. Appearance can vary from almost normal to very complex. Wikipedia+1
-
Two anal openings or anorectal malformations – There may be two anus openings, a single abnormal opening, or an imperforate anus (no opening). These problems can cause difficulty passing stool and require early surgery. Wikipedia+1
-
Duplicated colon or small intestine – Imaging may show two colons or duplicated segments of the bowel, which can lead to constipation, abdominal pain, bleeding, or intestinal obstruction in later infancy or childhood. PubMed+1
-
Duplicated bladder and urethra – Some patients have two bladders and two urethras, leading to urinary incontinence, frequent infections, or difficulty emptying the bladder. PMC+1
-
Kidney and ureter anomalies – There may be duplicated ureters, abnormal kidney position, or kidney underdevelopment, which can cause urine back-flow, infections, or reduced kidney function. PMC
-
Uterus and vaginal duplication in females – Girls may have a double uterus, double cervix, and double vagina (uterus didelphys), which can later affect menstruation, pregnancy, and delivery, although some women with caudal duplication have given birth successfully. Wikipedia+1
-
Spinal abnormalities – Duplication of lower vertebrae, spinal cord splitting, or spina bifida may be present, raising the risk of weakness, numbness, leg deformities, or bladder and bowel control problems. Wikipedia+1
-
Difficulty walking or abnormal gait – Extra or malformed legs and pelvic deformities can make standing and walking difficult. Children may walk with a limp, need assistive devices, or need surgery to remove non-functional limbs. ispub.com+1
-
Chronic constipation or bowel obstruction – Duplicated or narrowed bowel segments can slow the passage of stool, leading to chronic constipation, bloating, vomiting, or even life-threatening obstruction if not treated. Dove Medical Press+1
-
Urinary incontinence or retention – The abnormal anatomy of bladder and urethras, together with possible nerve problems, can cause leakage of urine or inability to empty the bladder completely. PMC+1
-
Recurrent urinary or bowel infections – Structural problems and incomplete emptying of the bladder or bowel make infections more common, which can damage organs if they keep happening. PMC+1
-
Pain or discomfort in the lower back or abdomen – As the child grows, abnormal alignment of the spine, pelvis, and internal organs can lead to long-term pain, especially if there are hernias or tethered spinal cord. PMC+1
-
Psychological and social impact – Even when physical function is fairly good, having a very unusual body shape can lead to low self-esteem, social anxiety, or bullying, so psychological support is an important part of care. Wikipedia+1
Diagnostic tests for dipygus
Because anatomy is so complex and unique in each person with dipygus, doctors use many tests to map the skeleton, nerves, and internal organs before deciding on treatment. Wikipedia+1
1. Full newborn and childhood physical examination – At birth and later check-ups, doctors carefully observe the shape of the pelvis, legs, genital area, anus, and back. They note the number and position of limbs and openings to plan urgent and later surgeries. Wikipedia+1
2. Focused perineal and genital inspection – A detailed look at the perineum, external genital organs, and anus helps identify duplicated structures, abnormal openings, and signs of imperforate anus or fistulas (abnormal connections). PMC+1
3. Neurological examination of lower limbs – Doctors test muscle strength, tone, reflexes, and sensation in the legs and feet to see if the spinal cord and nerves are working properly or if there is weakness from spinal duplication or tethering. Wikipedia+1
4. Abdominal and spinal palpation and inspection – The abdomen and back are felt and inspected to look for masses, hernias, spinal defects, and abnormal curves. This exam can suggest hidden duplications of bowel or bladder and guide imaging choices. PMC+1
5. Digital rectal examination – In older infants and children, a gentle finger exam of the rectum checks for duplicated or narrow rectal channels, abnormal direction of the bowel, or masses that could explain constipation or obstruction. Dove Medical Press+1
6. Pelvic examination (in older patients) – For adolescents and adults, especially females, manual pelvic exam helps identify double vagina, double cervix, or abnormal uterine position, which may affect menstruation and fertility. Wikipedia+1
7. Range-of-motion testing of hips and legs – Doctors move each hip, knee, and ankle to see how well joints in all legs move, which limbs are functional, and which are stiff or malformed, helping plan limb-saving or limb-removal surgery. ispub.com+1
8. Manual muscle strength testing – Simple tests like asking the child to push or pull against resistance show which muscle groups are strong or weak on each side. Patterns of weakness may point to spinal cord splitting or nerve damage. PubMed+1
9. Basic blood tests (CBC, kidney function, infection markers) – Blood tests check for anemia, infection, and kidney stress. They are important before and after surgery and help monitor the effects of chronic infections or kidney problems linked to urinary anomalies. Dove Medical Press+1
10. Urine analysis and culture – Routine urine tests look for blood, protein, and signs of infection. Urine cultures show which bacteria are causing infections so doctors can choose the right bacterial infections. সহজ বাংলা: ব্যাকটেরিয়ার সংক্রমণের ওষুধ।" data-rx-term="antibiotic" data-rx-definition="An antibiotic is a medicine used to treat bacterial infections. সহজ বাংলা: ব্যাকটেরিয়ার সংক্রমণের ওষুধ।">antibiotic and assess the effect of duplicated urinary tracts. PMC+1
11. Genetic testing (karyotype or chromosomal microarray) – Although no single “dipygus gene” is known, chromosomal tests help rule out other syndromes and may detect large genetic changes that could affect prognosis or family counseling. ResearchGate+1
12. Pathologic examination of removed tissues – When extra limbs, pelvis segments, or duplicated organs are surgically removed, a pathologist studies them under a microscope to confirm their structure, look for tumors, and document the duplication pattern. ispub.com+1
13. Nerve conduction studies (NCS) – In older children or adults with leg weakness or numbness, electrodes placed on the skin are used to measure how quickly and strongly nerves send signals, helping detect nerve damage from spinal anomalies. PubMed+1
14. Electromyography (EMG) – A fine needle electrode in muscles measures their electrical activity during rest and movement. Abnormal patterns may show long-standing nerve injury or imbalance between the two halves of the lower body. PubMed+1
15. Somatosensory evoked potential (SSEP) tests – Mild electrical or sensory stimuli to the legs are recorded over the brain to see how well signals travel through the spinal cord. This test helps assess function in duplicated or tethered spinal cords. PubMed+1
16. Prenatal ultrasound (second-trimester anomaly scan) – Many cases of caudal duplication and dipygus can be suspected before birth when routine ultrasound shows extra legs, abnormal pelvis, or duplicated organs. This allows early counseling and delivery planning. Wikipedia+1
17. Fetal MRI – When ultrasound finds a suspicious malformation, fetal MRI gives clearer images of soft tissues and organs and helps define the extent of duplication, similar to its role in other complex conjoined twin malformations. ScienceDirect+1
18. X-rays of pelvis and spine – Plain radiographs show the number and shape of pelvic bones, vertebrae, and limb bones. They are a first step in mapping the bony structure before more detailed imaging and surgery. eurjanat.com+1
19. Computed tomography (CT) scans – CT provides cross-sectional images of bones and soft tissues, allowing doctors to see extra pelvises, limb attachments, and relationships between bowel and bladder. CT angiography can show important blood vessels before surgery. PubMed+1
20. Magnetic resonance imaging (MRI) of spine and abdomen – MRI is crucial for showing the spinal cord, nerves, and internal organs without radiation. It helps identify spinal cord duplication, tethered cord, duplicated colons and bladders, and their exact connections, which is vital for safe surgical planning. PMC+1
