OEIS COMPLEX

- CLOACAL EXSTROPHY; VESICOINTESTINAL FISSURE

- SPLANCHNIC EXSTROPHY; EXSTROPHY-EPISPADIAS SEQUENCE

The cloaca is a temporary embryonic structure where the genital, urinary and digestive systems join caudally. Its correct development gives origin to the lower abdominal wall, bladder, intestine, anus, genitals and also part of the pelvis bones and lumbosacral spine.

Deviation of the normal development of the cloaca causes a series of phenotypes the most severe expression of which is the OEIS complex.

O	OMPHALOCELE
E	EXSTROPHY
I	IMPERFORATE ANUS
S	SPINAL DEFECT

· The fetal OEIS complex is a defect that affects the midline of the lower inferior hemibody.

· Incidence of 0.025-0.04:10.000 births.

· Etiology is unknown however several associations have been suggested:

o Teratogenic exposure like dixilamin succinate

o Genetic factor (i.e.: 47XXX)

o Sporadic familiar occurrence

o Possible multifactorial vascular embryonic disruption phenomena.

EMBRYOLOGY

Embryological it results from an arrest in the development of the urorectal septum in the 5-6 weeks embryo with inhibition of the later differentiation of the cloaca ). This result in:

1. default of the cloacal partition with common cloacal persistence and imperforate anus,
2. rupture of the cloacal membrane with cloacal exstrophy,
3. lack of fusion of the genital tubercles and the pubic ramus of the pelvis bones often associated with an omphalocele

incomplete development of the lumbosacral vertebras, spina bifida, lipomyelomeningocele or dilated central canal of the spine cord (hydromyelia).

ULTRASOUND

• Midline infraumbilical defect or a cystic structure (if there is cloacal membrane persistence) or a protuberant irregular mass in the inferior abdominal wall,
• Absent bladder in serial examinations,
• Lumbo-sacral myelomeningocele,
• Club feet,
• Wide pubic arch,
• Single umbilical artery,
• Genital anomalies,
• Anal atresia, and
• Omphalocele
• Elevated alpha-fetoprotein.

ASSOCIATED ANOMALIES

· Two or more cecal appendix,

· Males:

1. cryptorchidia,

2. penile agenesis or epispadias,

· Females:

1. bifid uterus,

2. vaginal duplication and

3. bifid clitoris.

REFERENCES

1. Austin PF.The prenatal diagnosis of cloacal exstrophy. J Urol 1998;160:1179-81.

2. Girz BA. First-trimester prenatal sonographic findings associated with OEIS (omphalocele-exstrophy-imperforate anus-spinal defects) complex: a case and review of the literature. Am J Perinatol 1998;15 :15

3. Hendren WH. Cloaca, the most severe degree of imperforate anus : expience with 195 cases. Ann Surg 1998;228:331-346

4. Wakim A. The pelvis of fetuses in the exstrophy complex. J Pediatr Orthop May-Jun 1997;17(3): 402.

5. Beaudoin S. Anatomical basis of a common embryological origin for epispadias and bladder or cloacal exstrophies. Surg Radiol Anat 1997;19:11

6. Weaver KB. Vertebral column and spinal cord malformation in children with exstrophy of the cloaca, with emphasis on their functional correlates. Teratology 1997;55(4):241-248

7. Bruch S. Challenging the embryogenesis of cloacal exstrophy. J Pediatr Surg 1996;31:768

8. Pinette MG. Prenatal diagnosis of fetal bladder and cloacal exstrophy by ultrasound. A report of three cases. J Reprod Med Feb 1996;41:132

9. Meizner I. Cloacal exstrophy sequence: an exceptional ultrasound diagnosis. Obstet Gynecol 1995;86(3):446

10. Lin H. Exstrophy of the cloaca in a 47,XXX child: review of genitourinary malformations in triple-X patients. Am J Genet 1993;45(6):761

11. Smith N. The OEIS complex (omphalocele-exstrophy-imperforate anus-spinal defects): recurrence in sibs. J Med Genet 1992;29:730