Cloaca - Prental Imaging & Diagnosis - Counseling

Genital urinary anomalies and anorectal malformations represent a broad spectrum; the more severe the malformations, the higher the chances that amniotic fluid volume will be abnormal

Cincinnati Children's uses a combined approach with ultrasound and fetal MRI because they are complementary techniques

On ultrasound, the first structure seen from the abdominal cord insertion is the bladder, outlined by umbilical arteries (three-vessel cord) or single artery (two-vessel cord)

Echogenic concretions (meconium) in the hydrocolpos or bladder are clues for rectourinary fistula and anorectal malformation

Ultrasound has technical limitations: it does not provide good imaging with poor amniotic fluid, is not good at detecting early stages of cystic renal dysplasia, and not all anorectal malformations will be detected even when searching for them

In the fetal bowel, the stomach and proximal bowel contain mostly fluid (bright on T2-weighted MRI), while distal bowel contains meconium (dark on T2-weighted imaging, bright on T1-weighted imaging)

Meconium is not expected to reach the rectum until 20 weeks gestation and will fill the entire colonic column by 26 weeks

In a Cincinnati Children's review of prenatal MRI of cloacal malformations, long common channel cloacas presented with high position of the rectum and dilatation

Cloacas and imperforate anus with rectourinary fistula can have fluid distention of the rectum and enterolith-like material

Increased fluid content in the rectum (bright signal instead of dark on T2-weighted MRI) is a clue for rectourinary fistula

Long common channel cloacas can present with hydrocolpos and urinary ascites

Urogenital sinus can present with urinary hydrocolpos and obstructive uropathy and/or ascites, but the rectum follows a normal course posterior to the bladder and is not dilated

Cloacal exstrophy patients typically present with persistent absent visualization of the bladder and normal amniotic fluid, indicating urine is making its pathway out

Cloacal exstrophy babies frequently have an omphalocele that is typically lower in position and can have spinal defects, typically skin-covered

The prolapsed terminal ileum in cloacal exstrophy appears as a tubular structure protruding and floating in amniotic fluid, called the 'elephant trunk sign'

In Cincinnati Children's review, cloacal exstrophy patients did not present meconium signal in the bowel in the expected distribution of the rectum, which is completely different from bladder exstrophy

Bladder exstrophy should have a normal rectum with bright T1 and dark T2 signal, absent bladder visualization, protruding structure in infraumbilical abdominal wall, and unusual external genitalia with epispadias

Dr. Peña reviewed mothers of babies born with cloacas who did not have prenatal diagnosis; when he obtained their ultrasounds, many had abnormalities but radiologists misdiagnosed them as urethrocele, double bladder, ovarian cysts, or bladder diverticulum instead of recognizing hydrocolpos

If a female fetus has a prenatal diagnosis of ovarian cyst, double bladder, or urethrocele, suspect the patient may have a cloaca; if the patient also has abnormal vertebrae, hydronephrosis, and dilated bowel, that confirms the diagnosis

Advantages of prenatal diagnosis include transferring the patient to a specialized center for proper colostomy and hydrocolpos drainage, and preparing the mother so she has time to digest the news and can enjoy the birth knowing the baby will go to surgery 24 hours later

For proper prenatal counseling of cloaca patients, surgeons want to know the common channel length and sacrum status, but this information is still limited in prenatal imaging

At 20 weeks gestation when most ultrasounds are done, cloacal findings may be very subtle with nothing that tips the community obstetrician off that there's anything wrong