Xanthogranulomatous pyelonephritis

Key points

Nephrolithiasis leading to Pyelonephritis resulting in non-functioning kidney

E.Coli, Proteus infection

Focal or diffuse patterns

Is important differential for any presumed renal tumour - may require biopsy

Associated with Diabetes and Immunocompromise

Can present with mass, cutaneous fistulae

Histology

Lipid laden foamy macrophages - Xanthoma cells

XGP has positive periodic acid Schiff stain - differentiates from Renal Cell Carcinoma

Radiology

CT: ‘bear paw sign’, stag horn calculus

Management

Focal - drainage or partial nephrectomy

Diffuse - Radical transperitoneal nephrectomy

References

Jha SK, Leslie SW, Aeddula NR. Xanthogranulomatous Pyelonephritis. [Updated 2024 May 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557399/