There is a large 6.8 cm (AP) x 6.4 cm (Trans) x 10.8 cm (CC) irregular, heterogeneous hypodensity centered in the right psoas muscle, which extends inferiorly to involve the ipsilateral iliacus muscle as well. This is representative of a right psoas muscle abscess.
Associated mass effect is also seen, as evidenced by proximal right hydroureter. There is also a 12 mm x 10 mm obstructive staghorn calculus in the inferior major calyx of
the right kidney. No significant hydronephrosis/ peri-renal fat stranding.
The left kidney and ureter are normal in size and appearance.
The appendix is not visualized in this study in keeping with known history of appendicectomy; however, the right iliac fossa has secondary signs of inflammation including fat stranding and hyperenhancement, which may represent a peri-appendiceal abscess and possible explanation for the aetiology of the psoas muscle abscess.