Main Forms of the Disease
In pathology, two main forms of chronic pyelonephritis are distinguished:
- Chronic obstructive pyelonephritis — develops when mechanical urinary tract obstruction is the primary cause, against which an infectious process ensues.
- Chronic reflux pyelonephritis (or reflux nephropathy) — the most common variant of renal tissue scarring, debuting in early childhood due to congenital vesicoureteral and intrarenal reflux.
Pathogenesis and General Mechanisms
The foundation of chronic pyelonephritis involves local obstructive disorders or urine backflow. These factors trigger a cascade of pathological reactions:
- Recurrent inflammation of the tubulointerstitial zone.
- Gradual replacement of normal parenchyma with connective tissue (scarring).
- Involvement of the calyces and pelvis in the pathological process with their subsequent deformation.
Morphological Findings
Histological examination of renal tissue in Pyelonephritis chronica reveals characteristic changes across various structures:
- Tubules: purulent casts are found within the lumen.
- Vessels: in scarred zones, arterioles (arcuate and interlobular) undergo obliterating endarteritis. When arterial hypertension is superimposed, arteriolosclerosis and hyalinosis develop.
- Calyces: the mucous membrane is surrounded by a zone of fibrosis and a massive chronic inflammatory infiltrate.
- Glomeruli: frequently affected by periglomerular fibrosis, and in late stages, secondary focal segmental glomerulosclerosis (FSGS) develops within them.