What is the term used to describe this type of renal calculus and what are they usually composed of?
Staghorn calculus. They are usually composed of struvite (magnesium ammonium phosphate) and are usually seen in the setting of infection with urease producing bacteria (e.g. Proteus, Klebsiella, Pseudomonas and Enterobacter)
What is the underlying process occurring in the kidney?
Multiple low density regions related to the calculus suggest xanthogranulomatous pyelonephritis.
A thick walled collection measuring 11 x 8 x 11.7cm extends from the perinephric space through the pararenal space and into the abdominal wall. The left kidney is displaced anteriorly and measures 12.2cm. It contains a large staghorn calculus. The parenchyma is thinned with decreased enhancement. Extensive rounded radiolucencies are seen in the parenchyma. Fat stranding is seen throughout the retroperitoneum, however no free fluid collections identified. There is mild dilatation and inflammatory stranding of the left ureter, however, no obstructing lesion is identified. The bladder is hyperdense, thought to relate to previous CT study.
The right kidney measures 12.5cm and contains simple cysts. Splenomegaly measures 17 x 6.5 x 11cm. No focal lesion. What appear to be loops of small bowel are seen in the pouch of Douglas.
The pancreatic duct is dilated (5 mm), however, no intra- or extra-hepatic biliary dilatation is seen. Pancreatic duct dilatation appears to extend to the ampulla without an obstructing lesion identified.
Gallbladder and adrenals are unremarkable. No free intraperitoneal gas or fluid. Lung
bases are clear.
No aggressive bony lesions. Right hip prosthesis with associated artefact noted. No CT evidence of osteomyelitis/discitis.
- CT (SCOUT):