Iliopsoas Abscess: Role of Computed Tomography with Multiplanar Reformatted Images for Defining the Etiology

To the Editor:

Although ingestion of foreign bodies (FBs) is not uncommon in clinical practice, events such as gastrointestinal perforation, especially those involving the duodenum, are less frequent. Duodenal perforation leading to an iliopsoas abscess (IPA) has been reported rarely. Despite the low clinical suspicion in the context of unintentional ingestion of FBs, multi-detector-row computed tomography (MDCT) can play a valuable role in pre-operative diagnosis. We present herein a case of IPA secondary to duodenal perforation by an FB in which the diagnosis was made through MDCT reformatted images.

A 53-year-old man with no notable medical history presented to the emergency department with a one-week history of increasing right-sided abdominal and flank pain radiating to the right thigh, aggravated by walking and associated with limitation of right hip movement; a low-grade fever for the past two days also was reported. On physical examination, he was febrile (38.6°C), but hemodynamically stable, reporting right-sided pain during abdominal palpation, without guarding. Additionally, the patient was noted to have an antalgic groin and to maintain an antalgic posture, characterized by flexion of the right lower limb; no neurologic deficits were observed in the lower extremities. Laboratory studies revealed a white blood cell count of 14.6×10⁹/L and C-reactive protein concentration of 3.5 mg/dL; the remaining blood studies were unremarkable.

A CT scan of abdomen and pelvis showed enlargement of the right iliopsoas muscle associated with a 16.0×3.0-cm low-attenuation lesion exhibiting an air-fluid interface and rim enhancement after intravenous administration of contrast (Fig. 1). In this clinical setting, imaging findings were consistent with a right-sided IPA. In the multiplanar reconstructions, a linear and well-delimited low-attenuation object was depicted, extending from the interior of the duodenum and reaching the right iliopsoas collection (Fig. 2). A hypothesis was made of duodenal perforation by a FB causing an IPA.

OPEN IN VIEWER

FIG. 1.

Axial contrast-enhanced computed tomography scan through abdomen at two levels (A, B) shows enlargement of right iliopsoas muscle, determined by irregular low-attenuation lesion exhibiting air–fluid interface and rim enhancement.

OPEN IN VIEWER

FIG. 2.

Oblique sagittal contrast-enhanced reformatted images (A, B) through spatial orientation of thin and linear low-attenuation image, depicted in its entirety, extending from duodenum to right iliopsoas collection. A preoperative hypothesis of duodenal perforation by a foreign body causing a iliopsoas abscess.

Empiric antibiotic therapy with metronidazole and ceftriaxone was initiated, and the patient underwent laparotomy the next day to drain the abscess and remove the FB. Intra-operative findings confirmed the pre-operative hypothesis and revealed a wooden toothpick perforating the duodenum and extending into the right iliopsoas muscle with purulent collection (Fig. 3). Cultures of this material yielded Enterococcus faecalis (sensitive to penicillin, ampicilin, streptomycin, gentamicin, teicoplanin, vancomycin, and linezolid; resistant to ciprofloxacin), after which the antimicrobial regimen was switched to ampicillin-sulbactam. Postoperative recovery was uneventful, and the patient was discharged asymptomatically, without any complaints on routine outpatient follow-up.

OPEN IN VIEWER

FIG. 3.

Intraoperative findings (A, B) demonstrate foreign body (wooden toothpick) transfixing duodenum and right iliopsoas, with presence of a purulent fluid.

Iliopsoas abscesses can be classified as primary or secondary according to their etiology; whereas primary IPAs are rarer and usually idiopathic, affecting especially immunocompromised patients [1], secondary abscesses are more common and may be consequent to direct spread from infections of adjacent organs, such as the small and large bowel, kidneys and urinary tract, spine, and aorta [2]. An IPA secondary to a duodenal perforation by an FB is exceedingly rare, and, to the best of our knowledge, there is no report of imaging-based diagnosis in this setting.

Bowel perforations consequent to unintentional FB ingestion are difficult to diagnose pre-operatively [3] as a result of the low degree of clinical suspicion, the unavailability of a history of FB ingestion, and the lack of specificity of the clinical manifestations [4]. Therefore, the diagnosis is made commonly during laparotomy [3]. In our case, the IPA induced careful examination of the adjacent structures for an etiology that facilitated the diagnosis.

Multi-detector CT is an effective method for the evaluation of intestinal perforation caused by ingestion of a FB [5], as it enables high-quality multi-planar reconstructions with thin collimation and high resolution. Therefore, the gut can be assessed in all projections, and whatever the spatial orientation, a FB can be identified [5]. Although these affirmations generally are valid for calcified FBs [5], our case presented an additional difficulty, as the FB was a wooden toothpick and, therefore, appeared as a low-attenuation image on the MDCT scan.

Treatment of IPA consists of antibiotic therapy and open or percutaneous drainage, the latter having replaced surgical drainage as the method of choice. However, in patients such as ours, with suspicion of an underlying surgical gastrointestinal tract cause such as duodenal perforation, operative management is required. In addition, both the empiric and culture-driven antimicrobial therapy adopted in our case followed current international guidelines for the management of intra-abdominal infections of adults [6].