Persistent cloaca of the fetus

Synonyms
Cloacogenic bladder; ano-rectal malformation; extensive cloacal malformation; sinus urogenitalis; urogenital sinus.

Etymology

Singular: cloaca (noun); plural: cloacae

• Modern Latin: cloaca - euphemism for "sewer" or "latrine"; from cluo (cluere) "to cleanse";
• Zoology: a common cavity into which the intestinal, genital, and urinary tracts open in vertebrates such as fish, reptiles, birds, and some primitive mammals.

History
The cloaca maxima was the sewer system built in the sixth or seventh century B.C. by one of the kings of Rome, probably Tarquinius Priscus (although Livy attributes it to Tarquin the Proud), to drain the marshes in the valleys between the hills into the Tiber River. Some archaeologists date it later.
Incidence
Occurs in 0.3-0.5 : 10,000 births, the vast majority in girls.
Etiology
Cloaca is a single canal into which the urinary, genital and intestinal tracts lead at about 5th - 6th week of gestational weeks. Persistent cloaca is a consequence of failure of the urogenital septum to divide rectum from urogenital sinus. It may be related to B-class Eph/ephrin signaling [1].
Sonographic diagnosis of  the whole spectrum of the ano-rectal malformations
One of the best recent articles which summarizes the literature focused on the topic of the prenatal diagnosis of ano-rectal malformations was published in 2010 by Bischoff et al [2].
"A retrospective review of the medical records of 489 patients born with cloaca was performed; 95 of them had prenatal ultrasound reports that represent the material analyzed for this study. A literature review was performed, finding 31 publications, with 68 cloaca patients detected by prenatal images. The abnormal findings of our patients were compared with those described in the literature to determine the most common abnormal prenatal images found in patients with cloaca.
The 95 ultrasound reports found in our patients described 270 abnormalities, the most frequent were: abdominal/pelvic cystic/mass (39), hydronephrosis (36), oligohydramnios (23), distended bowel/bowel obstruction (19), ascites (15), 2 vessel cord (14), dilated bladder (14), dilated ureter (14), polyhydramnios (10), echogenic bowel (8), multicystic kidney (8), "ambiguous genitalia" (7), hydrops fetalis (7), hydrocolpos (4), absent kidney (3), abnormal spine (3), and anorectal atresia (3). In spite of these findings, the radiologists who interpreted the studies only suspected a cloaca in 6 cases (6%). The literature review showed 212 abnormalities in 68 demonstrated cloaca patients. The most frequent were: abdominal/pelvic cystic/mass (46), hydronephrosis (44), ascites (21), oligohydramnios (20), distended bowel (11),multicystic dysplastic kidney (7), ambiguous genitalia (6), non-visualization of the bladder (6), two-vessel cord (5), dilated bladder (5), intraabdominal calcification (4), polyhydramnios (4), enterolithiasis (4), hydrometrocolpos (3), and dilated ureter (3)".
As the above mentioned article shows, there is an increased suspicion of the persistent cloaca, when the cystic abdominal masses, gastrointestinal, and urological abnormalities are present.
Early sonographic diagnostic of the persistent cloaca - implications for targeted examination
Major signs
1.  Enterolithiasis. "Fecal stones" observed during ultrasound examination as a round, well bordered intraluminal structures with an acoustic shadowing behind them (Images 1, 2, 11, 12, and Videos 1, 2). The enterolithiasis is a result of the intraluminal mixture of the meconium and alkaline fetal urine. This is the main and pathognomonic sign of a fistulation between enteric and urinary system [3-5].
2. Abnormal external genitalia. Complete fusion of the labio scrotal folds creating a dome of the testicular sacks occurs around 13 weeks of gestational age. Absence of this fusion, associated with cranial direction of the phallus, is an early pathognomonic sonographic sign of hypospadias [6,7]. A "pseudo-phallus" in early pregnancy may appear sonographically as a hypospadias in chromosomally female fetuses (Images 3, 4, 7, 8 and Video 3).
Minor signs
1. Urinary abnormalities especially double collecting system  (Image 5, Video 4), multicystic dysplastic kidney, and dilated non-emptying urinary bladder.
2. Intestinal anomalies - dilated, urine-filled intestines, malrotation of the intestines (Images 6, 9, 10, and Video 5).
3. Abnormal Mullerian system - hydrometrocolpos with secondary ascites, uterus didelphys.
Optimal "time-window" for ultrasonographic examination of the ano-rectal malformations:
We had 3 cases of ano-rectal malformations where abnormal enlargement of distal colon appeared at 14 and 16 weeks of pregnancy followed by normal appearance of the colon at 20 weeks. In two of those cases the dilated colon appeared again during the third trimester of pregnancy.
In one case abnormal pseudo-phallus turned out to be normal after 22nd week and the neonate was born with normal clitoris (to our surprise).
We conclude that some of the sonographic features of the ano-rectal malformation (fluid dilated colon and pseudo-phallus) may disappear in the mid-gestation and though the optimal time to diagnose these anomalies is during the first and early second trimesters [7-9].
Retrospective view on the COW 112
In 2004 theFetus.net website posted an interesting Case of the week number 112 by Maher Sarraf. The case shows thoracopagus twins with persistent cloaca and different genders. Although there are some "chromosomal explanations" as confirmed by Pr. Opitz and Pr. Benirschke, seeing the case in the view of our current case, the "male" external genitalia may also represent a pseudo-phallus of the chromosomally female twin with the anorectal malformation.