Anal Canal Duplication With Abscess Formation and Associated Sacrococcygeal Hamartoma in an Adolescent: A Report of a Rare Case

Abstract

Anal canal duplication (ACD) is a rare congenital malformation, typically diagnosed in pediatric populations, and often associated with other anomalies. Due to its nonspecific symptoms, it may be misdiagnosed or diagnosed late, particularly in adolescents or adults. We report the case of a 17-year-old female patient who presented with rectal pain, fever, and purulent perianal discharge. Physical examination revealed an accessory anal opening posterior to the native anus. Magnetic resonance imaging (MRI) demonstrated a perirectal abscess, a duplicated anal canal, and a suspicious presacral mass. A colonoscopy revealed a bulging rectum with normal mucosa. Surgical excision was performed for both the accessory anal canal and the presacral mass, and histopathological analysis confirmed the diagnosis of ACD and identified the mass as a benign sacrococcygeal hamartoma. This case highlights the diagnostic challenge of ACD due to its clinical resemblance to other perianal pathologies. Imaging modalities, particularly MRI and endoscopy, are critical for excluding differential diagnoses, guiding surgical management, and confirming post-surgical histopathology. ACD itself is a rare condition, with abscess formation being a rarely reported complication. The co-occurrence of ACD and a sacrococcygeal hamartoma is exceptionally rare and, to our knowledge, has not been previously reported. This case underscores the importance of a multidisciplinary approach for accurately diagnosing and effectively treating rare anorectal anomalies such as ACD, particularly when complicated by infection or associated with other anomalies.

Keywords: acessory anal canal; anal abscess; anal canal duplication; hamartoma; sacrococcygeal hamartoma.

Figure 1. Image highlighting an accessory perianal orifice with dentate line-like features (arrow) suggestive of anal canal duplication

Figure 2. Sagittal 2D FIESTA MRI view demonstrating a well-defined perirectal collection with central necrosis, suggestive of perirectal abscess formation localized within an anal accessory canal (red arrow), without communication with the principal canal (blue arrow)

2D FIESTA MRI: two-dimensional fast imaging employing steady-state acquisition magnetic resonance imaging

Figure 3. Axial 2D FIESTA MRI demonstrating a mildly enhancing solid lesion anterior to the coccyx, measuring 2.5 × 2 × 1.8 cm (red arrow)

2D FIESTA MRI: two-dimensional fast imaging employing steady-state acquisition magnetic resonance imaging

Figure 4. Histological composition of the hamartoma composed of squamous and columnar epithelium with fibrous stroma, skeletal muscle, and secretory gland aggregates