\"Cloaca\" is a term used to describe an anomaly in the female where a single orifice is located in the perineum draining both urogenital and gastrointestinal tracts. Few reports used the same term \"cloaca\" to describe the counterpart anomaly in the male. We present two \"male\" cases of anorectal anomalies associated with significant penile deformity (caudally displaced penis) that were managed during the period between January 2010 and September 2021. Characteristically, both cases had a single \"central\" perineal orifice. The latter was located anterior to the predestined site of the normal anus and just beneath a caudally positioned hypospadiac phallus. The caudal displacement of the penis was strikingly obvious by the presence of severe form of penoscrotal transposition. Both cases were associated with a perineal swelling (hamartoma) just beside the central perineal orifice. The urethra was very short (like that in the female), besides the single perineal orifice, which makes the presentation very similar to cloacal anomalies.

Subdivision of cloaca into urogenital and anorectal passages has remained controversial because of disagreements about the identity and role of the septum developing between both passages. This study aimed to clarify the development of the cloaca using a quantitative 3D morphological approach in human embryos of 4-10 post-fertilisation weeks. Embryos were visualised with Amira 3D-reconstruction and Cinema 4D-remodelling software. Distances between landmarks were computed with Amira3D software. Our main finding was a pronounced difference in growth between rapidly expanding central and ventral parts, and slowly or non-growing cranial and dorsal parts. The entrance of the Wolffian duct into the cloaca proved a stable landmark that remained linked to the position of vertebra S3. Suppressed growth in the cranial cloaca resulted in an apparent craniodorsal migration of the entrance of the Wolffian duct, while suppressed growth in the dorsal cloaca changed the entrance of the hindgut from cranial to dorsal on the cloaca. Transformation of this \'end-to-end\' into an \'end-to-side\' junction produced temporary \'lateral (Rathke\'s) folds\'. The persistent difference in dorsoventral growth straightened the embryonic caudal body axis and concomitantly extended the frontally oriented \'urorectal (Tourneux\'s) septum\' caudally between the ventral urogenital and dorsal anorectal parts of the cloaca. The dorsoventral growth difference also divided the cloacal membrane into a well-developed ventral urethral plate and a thin dorsal cloacal membrane proper, which ruptured at 6.5 weeks. The expansion of the pericloacal mesenchyme followed the dorsoventral growth difference and produced the genital tubercle. Dysregulation of dorsal cloacal development is probably an important cause of anorectal malformations: too little regressive development may result in anorectal agenesis, and too much regression in stenosis or atresia of the remaining part of the dorsal cloaca.

The raphe of the human penis and scrotum is considered to develop secondarily after disappearance of the initial midline seam by fusion of the bilateral genital folds. However, the fetal development was still obscure. We examined histological sections of 30 fetuses (17 males and 13 females) at 10-15 weeks. In male fetuses, the scrotum was not yet clearly identified because of no descent of testis. The perineal raphe was thin and wavy at 10 weeks, and it was continuous with and took a direction same as the inferior wall of the closed penile urethra after physiological hypospadias. Depending on growth of the bulbospongiosus muscle and corpus spongiosus penis, the midline intermuscular septum obtained a connection to the subcutaneous wavy raphe and made the latter thick and straight at 12-15 weeks. Notably, the perineal raphe extended posteriorly to attach to the external anal sphincter. In female fetuses, an epithelial fusion occurred along a short distance at the posterior end of the vestibule. However, in front of the external anal sphincter, a large midline mesenchymal tissue from the urorectal septum did not contain a raphe-like structure. Moreover, since the bilateral bulbospongiosus muscles were separated widely by the vestibule, they did not provide a midline septum. Fetal development of the perineal raphe was accelerated by reinforcement from the muscular septum. In contrast, without such a muscular support, the female raphe could not maintain its growth even if the seed appeared at the posterior end of the vestibule.