Case of the Week #593

Shilpa Chaitanya Reddy
Bangalore, India

Posting Dates: Oct 31, 2023 - Nov 14, 2023

Answer

We present a case of OEIS complex (Omphalocele, Exstrophy of bladder, Imperforate anus and spinal defect) also known as Cloacal exstrophy.

Ultrasound revealed the following findings:

Video 1, Image 1: lower abdomen and pelvic region shows low exompholus
Image 2: Non-visualization of bladder between the two umbilical veins with normal kidneys. Exstrophy of bladder should be considered.
Video 2: Absence of the perianal muscular complex concerning for imperforate anus
Video 3: Terminal myelocystocele
Image 3: 3D reconstruction of cloacal extrophy

The pregnancy was terminated and abortus examination confirmed our findings.

**Image 1** Low exomphalos with cloacal exstrophy.

**Image 2** Terminal myelocystocele - closed neural tube defect

DISCUSSION

Introduction: Cloacal exstrophy is also called OEIS complex [1] and is a midline defect that consists of omphalocele, bladder exstrophy, imperforate anus, spinal and genital abnormalities, and occasionally limb defects [2]. The incidence is not known, though has been estimated between 1 in 200 000 to 1 in 250 000 live births [3]. Fetuses with OEIS have both neural tube defects and omphalocele, thus can present with high maternal serum alpha-fetoprotein (AFP) on screening. However, the neural tube defect is often covered with skin and the omphalocele can be covered with a thick membrane, therefore, maternal serum AFP cannot be used to detect all cases of OEIS. Detailed fetal ultrasound examination remains the best tool with which to detect this condition prenatally [4-10].

Embryology: The cloaca is divided into a urogenital sinus anteriorly and hindgut posteriorly at six weeks of pregnancy. The failure of lateral to medial mesoderm extension to form an infraumbilical abdominal wall causes cloacal membrane rupture. Cloacal exstrophy is caused by the rupture of the cloacal membrane before the complete descent of the urogenital septum, causing herniation of the bladder and bowel that can be detected using prenatal ultrasound [11].

Epidemiology: OEIS complex is a heterogeneous condition and in almost all cases is sporadic. There are few cases reported in association with chromosomal abnormalities including a deletion in chromosome 1p36 [12] and a deletion of 3q12.2-q13.2, which may help in mapping the gene or genes associated with the complex [13]. Additionally, there have been cases of OEIS associated with exposure to diphenylhydantoin [2] and diazepam [14].

Ultrasound findings: The primary ultrasound findings in OEIS include omphalocele, low insertion of the umbilical cord, large midline infra-umbilical anterior wall defect, lumbosacral myelomeningocele which is usually covered with skin, failure to visualize the urinary bladder, failure to visualize the external genitalia, and limb defects including abnormal position, such as clubfeet, or a missing limb [15]. Early diagnosis may be challenging, however low insertion of the cord may help in early diagnosis of bladder exstrophy [16] and diagnosis can be confirmed by MRI [17].

Prenatal Counselling: A prenatal diagnosis of OEIS complex can help counsel the parents and their families regarding the choice to terminate or continue the pregnancy [1]. Cloacal exstrophy is a surgically correctable anomaly with a survival rate of almost 100% [16], thus it is important to diagnose during the prenatal period in order to have resources available in the postnatal period.

Management: Management of cloacal exstrophy requires a multidisciplinary team, which includes a neonatologist, pediatric surgeon, urologist, radiologist, and colorectal surgeon. One surgical approach is to close the abdominal wall defect, repair the bladder defect, perform pelvic osteotomies, and create a colostomy. Alternatively, the surgical repair can be performed in several stages [18].

REFERENCES

[1] Dorjey Y. Role of ultrasound scan in prenatal diagnosis of cloacal exstrophy. Clin Case Rep. 2023 Mar; 11(3): e7072.
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[3] Kallen K, Castilla EE, Robert E, et al. OEIS complex–a population study. Am J Med Genet 2000 May 1;92(1):62-8.
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