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Tubulointerstitial inflammation, cast formation, and renal parenchymal damage in experimental pyelonephritis
Abstract:
Some basic changes in experimental pyelonephritis were studied by transmission and scanning electron microscope. Initially, bacteria settled and multiplied in capillaries and venules. Leukocytes first marginated and then escaped from the capillaries, particularly to the wide peritubular interstitium. After opening the tubular basement membrane, the infiltrating leukocytes were immediately localized in the tubular wall between epithelial cells but were never seen between the epithelial cells and the underlying basement membrane. The inflammatory cells seemed not to be able to pass through the tight junctions of the nonnecrotic tubular epithelium. As a consequence of severe inflammatory injury, the tight junctions exhibited alterations of intermediate junction type. Where circumscribed necrosis of the tubular walls occurred, leukocytes appeared in the lumen. Thus, pus casts originated from these sites, apparently as drainage of interstitial abscesses. The secondary/regressive and regenerative/tubular changes were similar to those occurring after various tubular lesions.
Insights
In experimental pyelonephritis, bacteria initially colonize capillaries. Leukocyte infiltration into kidney tubules occurs via interstitial spaces and leads to pus cast formation.
Area of Science:
- Nephrology
- Microbiology
- Pathology
Background:
- Experimental pyelonephritis involves bacterial infection of the kidney.
- Understanding leukocyte migration is crucial for kidney inflammation.
Purpose of the Study:
- To investigate the ultrastructural changes during experimental pyelonephritis.
- To elucidate the mechanisms of leukocyte infiltration and pus cast formation.
Main Methods:
- Transmission electron microscopy (TEM) was used.
- Scanning electron microscopy (SEM) was employed.
Main Results:
- Bacteria initially multiplied in capillaries and venules.
- Leukocytes infiltrated the peritubular interstitium and tubular walls.
- Pus casts formed from leukocytes in tubular lumens following necrosis.
Conclusions:
- Leukocyte transmigration occurs through interstitial spaces and tubular walls.
- Tight junction integrity is compromised during severe inflammation.
- Pus cast formation is linked to interstitial abscess drainage into tubules.