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Anal canal duplication is a rare gastrointestinal malformation characterized by extra anal orifices at 6 o’clock in the lithotomy position. To date, there have been only 110 reported cases. The purpose of this study is to contribute two infant cases, one of which is associated with anorectal stenosis, which has never been described.
An 8-month-old baby was referred for refractory constipation. She was born full-term and fully breast-fed since birth, without other medical issues. As she began complementary food, she developed progressive constipation. Treatment such as laxatives and enema was given to aid in defecation, but the condition aggravated. A posterior anal orifice was identified on physical examination (). Barium fistulography and contrast enema revealed a narrowed distal rectum at the level of the fifth sacral vertebra. The proximal rectum and sigmoid colon were significantly dilated, with the widest part being about 44 mm (). No dilation was observed in the descending colon and transverse colon. Magnetic resonance imaging (MRI) demonstrated a bird’s beak-like appearance of the distal rectum and no presacral mass or spinal abnormality. The duplication appeared as a line of high-signal lesions communicating with the skin ().
An 11-month-old girl was found to have a posterior anal orifice since birth (). She was asymptomatic and had full-term birth, without other medical problems. Barium fistulography and contrast enema showed a 5-mm-long and 4-mm-diameter tubular area with no communication with the rectum (). No obvious abnormality was observed in the size and shape of the colon and rectum (). MRI revealed no spinal abnormalities or presacral mass.
Anal canal duplication is a rare malformation with poorly understood etiology and less defined clinical management criteria. Patients are always asymptomatic or just with local symptoms around the perianal region. Differential diagnosis should be carefully evaluated between ACD with perianal fistula and perianal abscess. Comorbidities were found in 25% of the patients, of which presacral masses were the most common, accounting for 50%, and anorectal malformations (ARMs) account for 5% (, ). We report a case associated with anorectal stenosis, accompanying secondary mega-rectosigmoid, which has never been described before.
Early diagnosis is crucial but easy to miss in neonates (). Our patient was suspected of having ACD and anorectal stenosis 8 months after birth; mega-rectosigmoid most likely occurred due to delayed diagnosis and treatment. The diagnosis should be made when a second perineal opening appears behind the normal anus at 6 o’clock. The diagnosis of concomitant malformations is also important because of their direct impact on the surgical strategy. Auxiliary examinations such as fistulography and MRI are useful tools for ACD diagnosis. Contrast enema can describe the diameter and length of the duplication and, more importantly, the communication with the rectum. MRI can inform the relationship between ACD and adjacent soft tissue like the anal sphincter and striated muscle. A key role of MRI is to find other abnormalities such as presacral mass, intrasacral meningocele, or duplicated rectum. Methylene blue detection can be performed to check whether there is communication between ACD and the anus.
