Presentation
Left gluteal swelling and left sciatica pain for past 1 week after trivial injury.
Patient Data
Extensive large hypoechoic collections are seen at the left gluteal region and left retroperitoneal regions. Mobile internal debris is seen within these collections. On color Doppler, no significant internal vascularity.
Large multi-loculated peripherally rim enhancing collection at the subcutaneous tissue of left gluteal region with extension to involve the left gluteal medius, left gluteal minimus, left illiacus, lateral aspect of abdominal wall muscles and superiorly into the left psoas muscle. Extension into the left posterior pararenal space which causes significant anterior displacement of other left retroperitoneal spaces. Anterosuperiorly, the collection extends into the left perinephric space, abutting and displacing the left kidney. No air pocket, fat component, solid component or calcification within collection.
Marked fat streakiness surrounding this collection as well as thickening of left pararenal fascia and perinephric fat.
A few enlarged abdominal lymph nodes at the preaortic and left paraaortic region,
The adjacent bone (pelvis bone and vertebrae) are intact, without bony erosion or aggressive periosteal reaction. No intraspinal extension of this collection.
Left moderate hydronephrosis and proximal hydroureter secondary to proximal ureteric calculus. The left kidney is small and hypoenhancing suggestive of chronicity of obstructive uropathy. The proximal left ureteric wall is thickened and enhancing.
Long segment of central filling defects (20-40HU) at the right lower lobe pulmonary artery and its segmental branches, as well as subsegmental branches of posterobasal segment left lower lobe pulmonary artery. Minimal subpleural atelectasis at the posterobasal segment of right lower lobe. No pleural effusion bilaterally.
Case Discussion
With multi-spatial rim enhancing collections with intramuscular extension correlating with raised infective markers and newly diagnosed diabetes mellitus, an abscess is the top differential diagnosis. It is unlikely to be a retroperitoneal malignancy in view of the lack of aggressive features such as bony erosion and enhancing solid components.
Incidental findings of filling defects in the right lower lobe pulmonary artery and subsegmental branches of the posterobasal segment left lower lobe pulmonary artery are in keeping with acute pulmonary embolism (PE).
The abscess was drained with an ultrasound-guided pigtail drainage catheter. The acute PE was treated with anticoagulants.
Klebsiella pneumoniae was isolated from the drained pus, while Candida albicans was isolated from the urine. K. pneumoniae is the second most frequent bacterial organism in urinary tract infection, after Escherichia coli, and the close relation between the chronically obstructed left kidney and the large left retroperitoneal/gluteal abscesses, the etiology of the abscess is likely arising from a left infected obstructed kidney.
This case depicts the importance of having a systematic review of all areas in CT scan, though the main indication for this CT scan is for assessing the extension of the retroperitoneal/subcutaneous collection, the incidental finding of acute pulmonary embolism is very crucial for the patient's management. In view of the patient's risk factor of immobility due to sciatica for the past 1 week, this has increased the chances of pulmonary embolism, the assessment of the imaged pulmonary arteries should be included in routine assessment.
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