Perineal masses are rare in childhood. We present the case of a female neonate with a mass protruding from the perineum.

The pregnancy was normal, with provision of prenatal care, normal antenatal ultrasounds and blood tests. The patient was born to term, with an Apgar score of 9. Her anthropometric measurements were within the 50th to 75th percentile. No family history of interest. At birth, a bilobulated mass was detected that had an external portion measuring 4 × 2.5 cm, was lined with mucosa and had a distal orifice, set in the perineal region between a hypertrophic outer fold and the anus. There were no associated anomalies, the urethral meatus was patent, with passage of urine with normal appearance and normal labia minora and vaginal introitus, the anus in the right location slightly compressed by the mass that allowed passage of meconium without abdominal distension or perineal fistulas (Fig. 1). Imaging with ultrasound and magnetic resonance did not detect anomalies in any other organs (genitals, gastrointestinal tract/anal canal, urinary system, perineal muscle) or any fistulas. The base of the mass was located in the right ischioanal fossa, lateral to the anal canal and vagina, without communication between these two structures, and ending in a pouch that continued externally with an inner cavity of mucosal contents and an external orifice directed toward the skin. The mass was resected with an anterior sagittal approach without postoperative complications, save for wound dehiscence that ended up healing without sequelae. Biopsy: anorectal duplication (Fig. 2).

Figure 1.

Perineal mass that had undergone exstrophy between the right outer fold of the vulva, which was hypertrophic, and the anus: (A) appearance on initial examination; (B) improved visualization of its relationship with adjacent perineal anatomic structures; (C) surgical specimen.

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Figure 2.

Histological appearance of the inside-out mass with anal squamous epithelium (green arrow), transitional zone (black arrow) and rectal mucosa with two layers of muscle (yellow arrow) (×4), findings consistent with the diagnosis of anorectal duplication.

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Gastrointestinal tract duplications are infrequent congenital anomalies, and only 5% of them involve the rectum; they are usually cystic, as opposed to tubular, and can be found within, posterior to or anterior to the rectum.1 Duplications that protrude as a perineal mass and have undergone exstrophy are extremely rare and may be associated with other malformations, including anorectal, genitourinary or vertebral anomalies1–3 (none of which were present in this patient), so they should be ruled out.