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Ultrastructural demonstration of intracellular bacteria in xanthogranulomatous pyelonephritis
Abstract:
Xanthogranulomatous pyelonephritis is considered to be an unusual cellular response to bacterial invasion. This assumption is based on circumstantial evidence and experimental studies. In our electron microscopic study of five cases of xanthogranulomatous pyelonephritis demonstrated a stratification of the cellular components, somewhat resembling that described in the experimental lesions. The center of the xanthogranulomas was occupied by purulent exudate. Bacteria were identified mainly in polymorphonuclear leukocytes and extracellularly in four cases in which central area were available for electron microscopic studies. Many bacteria were located in cytoplasmic vacuoles. more peripherally, histiocytes predominated, and their cytoplasm contained numerous lipid droplets with and without limiting membranes and phagolysosomes. The latter contained electron dense, granular, and membranous structures. The outermost layer of the lesion demonstrated macrophages with a decreased number of lipid droplets and larger intralysosomal particles. Lymphocytes, plasma cells, and fibroblasts represented an increasing proportion of the infiltrate in this layer. Our study suggests that xanthogranulomatous pyelonephritis is a bacteria induced process. Its histological appearance may be related to incomplete bacterial degradation and altered host response.
Insights
Xanthogranulomatous pyelonephritis is a rare kidney inflammation caused by bacteria. Electron microscopy reveals distinct cellular layers, suggesting an altered host response to bacterial invasion.
Area of Science:
- Nephrology
- Pathology
- Microbiology
Background:
- Xanthogranulomatous pyelonephritis (XGP) is an uncommon renal inflammatory condition.
- Its etiology is often attributed to bacterial infection, but direct evidence is limited.
Purpose of the Study:
- To investigate the cellular and bacterial components of XGP using electron microscopy.
- To elucidate the pathogenesis of XGP by examining host response to bacterial invasion.
Main Methods:
- Electron microscopic examination of five cases of XGP.
- Identification and localization of bacteria within cellular components.
- Analysis of cellular stratification and morphology.
Main Results:
- Bacteria were identified within polymorphonuclear leukocytes and extracellularly, often in cytoplasmic vacuoles.
- Xanthogranulomas showed a layered structure with distinct cellular populations (purulent exudate, histiocytes, macrophages, lymphocytes, plasma cells, fibroblasts).
- Histiocytes and macrophages contained lipid droplets and phagolysosomes with bacterial remnants, indicating altered degradation.
Conclusions:
- The findings support the hypothesis that XGP is a bacteria-induced inflammatory process.
- The unique histological appearance may result from incomplete bacterial clearance and a modified host immune response.