Images in medicine: Diagnosis and pre-surgical triage of transanal rectal injury using multidetector CT with water-soluble contrast enema

Abstract

Transanal rectal injuries caused by foreign body insertion, sexual abuse, or iatrogenic procedures represent a very uncommon surgical emergency. Morbidity may be further increased by patient's embarrassment and delayed presentation. Since management decisions largely depend on anatomic and severity assessment, multidetector Computed tomography with rectally administered water-soluble iodinated contrast medium is highly valuable to accurately depict traumatic rectal injuries, and to distinguish between intraperitoneal vs extraperitoneal injuries that require different surgical approaches.

A 38-year-old male presented to emergency department complaining of rectal bleeding accompanied by dull pelvic and perineal pain. On further questioning, he admitted recreational self-insertion of a hard-consistency, unsharp foreign object six hours before, and appearance of hemorrhage following its withdrawal. Physical examination revealed pelvic tenderness at palpation, with appreciable peristalsis and absent peritonism. External inspection of perineal region was normal. Digital examination revealed continent anal sphincter, rectal blood, no palpable foreign material or masses. With the exception of unspecific increase of acute-phase reactants, laboratory assays were within normal limits.

At emergency admission, plain radiographs of thorax and abdomen yielded unremarkable findings, excluding residual radio-opaque foreign bodies, intraperitoneal air indicating free perforation, and gross extraluminal gas collections in the pelvic inlet [Figure 1a]. Because of persistent symptoms, painful digital exploration, and abnormal C-Reactive Protein (43 mg/l), urgent unenhanced abdomino-pelvic multidetector computed tomography (MD-CT) was requested to rule out abscess collections: As the only finding, minimal fluid and tiny gas bubbles were detected in the peritoneal cul-de-sac, abutting the anterior aspect of the rectum [Figure 1b]. The attending surgeon opted for a conservative management including food withdrawal.

Figure 1.

Plain radiographs exclude opaque foreign bodies, intraperitoneal air, and gross extraluminal pelvic gas (a). Unenhanced CT (b, viewed at lung window) detected minimal fluid and gas bubbles (arrows) in the peritoneal cul-de-sac, abutting the rectum. Follow-up CT (c) detected increasing pre-rectal collection (*) with gas-fluid level. Repeated CT with water-soluble contrast enema showed distended rectum (d), air-fluid collection opacified through ventral extraluminal leak from the proximal rectum (arrowheads in e and f) indicating intraperitoneal rectal perforation, patent upstream sigmoid colon (f)

Twenty-four hours later, follow-up MD-CT detected increasing abnormal pre-rectal collection with prominent gas-fluid level [Figure 1c]. Further investigation was proposed by the attending radiologist with repeated MD-CT acquisition following water-soluble contrast enema (sodium-megluminediatrizoate, Gastrografin^®) slowly administered through a thin, soft rectal tube. Intravenous contrast medium was not used. CT findings included well-distended rectum with preserved upstream opacification of the sigmoid colon. A single extraluminal contrast leak was identified in the ventral aspect of the proximal rectum, causing opacification of the above-mentioned air-fluid collection [Figure 1d-f]. Intraperitoneal rectal perforation was diagnosed and the patient underwent primary surgical repair. The patient was discharged from hospital after a brief, uneventful postoperative stay.

Most usually resulting from penetrating rather than from blunt trauma, transanal rectal injuries represent a relatively uncommon but clinically critical diagnosis in emergency practice, and are associated with significant morbidity and mortality. Causes include fall on sharp objects, criminal assault or sexual violence, foreign body insertion through the anus, and rectal cleansing enema. Most often related to auto-eroticism, a surprisingly wide list of reported foreign bodies may be introduced into the rectum, predominantly in men.[1]

Clinical manifestations may range from asymptomatic cases, to rectal bleeding, and sometimes peritonitis. Not unusually, presentation and diagnosis are delayed because of patient's embarrassment and denial, resulting in increased morbidity. Most often, rectal trauma is clinically assessed by physical examination, digital exploration, and proctoscopy. Alternatively, anorectal injuries may be diagnosed intraoperatively or by means of diagnostic peritoneal lavage. The rectosigmoid junction is the most frequently injured site. Lesions predominantly involve the anterior rectal wall because of the anatomical postero-anterior direction of the anorectal canal.[1]

Although some controversy persists regarding the optimal management of full-thickness penetrating rectal injuries, it is important to bear in mind that accurate recognition and precise anatomic characterization of lesions are essential to allow a correct therapeutic choice and successful outcome. In the past, colostomy was largely adopted in trauma care, to divert the fecal stream, and prevent or arrest fecal contamination of the peritoneal cavity. From the surgical perspective, the key issue is the distinction between intraperitoneal and extraperitoneal rectal lesions. Injuries to the serosalized anterior and lateral sidewalls of the upper two-thirds of the rectum are classified as intraperitoneal, that should undergo primary repair. Conversely, lesions involving the distal one-third of the rectum circumferentially and the upper two-thirds of the rectum posteriorly are considered extraperitoneal. Extraperitoneal injuries to the upper two-thirds and accessible distal one-third of the extraperitoneal rectum are treated with repair and fecal diversion, whereas wounds to the lower one-third, which are not explored should be managed with presacral drainage.[2,3]

Usually adopted as the first diagnostic approach, plain radiographs may prove useful to detect residual endoluminal foreign bodies, signs of bowel obstruction, and overt perforation identified by free intraperitoneal air.[4]

Currently, MD-CT represents the mainstay technique to image spontaneous and post-traumatic abdomino-pelvic disorders, as it may identify even minimal amounts of extraluminal gas indicating hollow viscus perforation. Appropriate use of oral, rectal, and intravenous contrast, as necessary, is helpful to maximize the diagnostic accuracy of MDCT in the evaluation of bowel injuries. Barium sulfate preparations are contraindicated when perforation is considered.[5] As this case exemplifies, optimal distal bowel distension and opacification by means of retrogradely administered water-soluble iodinated contrast allows to directly visualize and locate rectal perforations, indicated by extraluminal contrast leakage, thereby providing correct injury diagnosis and presurgical classification.[3,4,5]