Clinical History
A 76-year-old male patient with an extensive past medical history was hospitalized for bradycardia and respiratory failure. The patient’s nurse reported continuous foul-smelling mucus around the patient’s groin and noted an opening on his scrotum. During the previous hospital stay, a peri-rectal abscess was noted that drained spontaneously without intervention.
Imaging Findings
A hysterosalpingogram catheter was inserted into the scrotal fistula and approximately 15mL of Omnipaque 240 was injected into the fistula for multiple spot fluoroscopic and radiographic images, obtained in multiple obliquities.
Injection of Omnipaque 240 contrast material through the catheter at the scrotal fistula site demonstrates a fairly long fistulous tract communicating with the rectum. Contrast fills into a pouch-like structure, which is felt to represent the rectal pouch. There is no extravasation of contrast material. The contrast appears to be retained in this visualized pouch.
Discussion
An enterocutaneous fistula is the chronic manifestation of the acute perirectal process that forms an anal abscess. The incidence of an anal fistula developing from an anal abscess ranges from 26 to 38 percent [1]. Radiological imaging such as endosonography, computed tomography, magnetic resonance imaging or fistulography can be used to assess and confirm the presence of a fistula [2].
The utility of CT for perianal fistulas is less clear. The limited resolution of CT makes it difficult to differentiate between inflammatory soft tissue streaking and a fistula tract [3]. MRI provides a reliable alternative for diagnosing fistulas. In one study, the results of a MRI were compared with the surgical evaluation in 35 patients. The overall concordance between the MRI and surgery was 85 percent [4].
Although rectocutaneous fistulas are a common complication of the perirectal abscess, the scroto-rectal subtype is very rare and an uncommon presentation of this complication. This case is presented due to its rarity in presentation.
Treatment of the fistula depends on the site, extent of involvement, and the organs involved. In general, the need for surgery in fistulas involving the rectum is determined 6 to 12 weeks after treatment of the initial anorectal abscess. If drainage persists after the initial incision and drainage, and a fistula is suspected, surgery is indicated [5]. Superficial, low transsphincteric, and low intersphincteric fistulas are usually treated with fistulotomy. High transsphincteric, suprasphincteric, and extrasphincteric fistulas are usually treated with noncutting setons and antibiotics [6].
A peri-rectal opening was documented in the patient’s chart before prior discharge and the patient was scheduled for outpatient follow-up and possible intervention. The patient reported pelvic pain and drainage from the site of the initial rectal abscess for several months after discharge from the hospital. He continued to experience pelvic and groin pain for which the patient took pain medication, and he did not follow up with surgery. Before starting our fistulogram, the peri-rectal region and the previous area of the peri-rectal abscess were thoroughly investigated and no opening or evidence of a peri-rectal fistula was noted. These finding suggest that the initial ano-rectal fistula and irritation and infectious processes within the pelvis initiated a second fistula tract between the rectum and scrotum with resultant closure of the primary tract. We believe that appropriate and timely follow-up as well as surgical intervention, if needed, can prevent such drastic complications.
Differential Diagnosis List
Scrotal enterocutaneous fistula
Inguinal fecal fistula secondary to inguinal hernia
Rectocutaneous fistula secondary to inflammatory bowel disease
Final Diagnosis
Scrotal enterocutaneous fistula
