Main disease forms
In pathological anatomy, two main forms of chronic pyelonephritis are distinguished:
- Chronic obstructive pyelonephritis develops when the primary cause is a mechanical obstruction of the urinary tract, against which an infectious process develops.
- Chronic reflux pyelonephritis (or reflux nephropathy) is the most common variant of renal tissue scarring, debuting in early childhood due to congenital vesicoureteral and intrarenal reflux.
Pathogenesis and general mechanisms
The formation of chronic pyelonephritis is based on local obstructive disorders or urine reflux. 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 picture
Histological examination of the renal tissue in Pyelonephritis chronica reveals characteristic changes in various structures:
- Tubules: purulent casts are found in the lumen.
- Vessels: in the scarring zones, arterioles (arcuate and interlobular) undergo obliterating endarteritis. When arterial hypertension joins, arteriolosclerosis and hyalinosis develop.
- Calyces: the mucous membrane is surrounded by a zone of fibrosis and a massive chronic inflammatory infiltrate.
- Glomeruli: often suffer from periglomerular fibrosis, and in late stages, secondary focal segmental glomerulosclerosis (FSGS) develops in them.
Briefly: answers to topical questions
What macroscopic changes in the surface and size of the kidneys are characteristic of chronic pyelonephritis?
In chronic pyelonephritis, the kidneys undergo uneven shrinkage with the formation of a coarsely nodular and deformed surface. Coarse, discrete, corticomedullary scars with scar depressions are characteristic, predominantly localized in the region of the upper and lower poles of the kidneys. In bilateral process, the lesion is asymmetric, and the pelvicalyceal system appears deformed.
Which cells predominantly constitute the chronic inflammatory infiltrate in the renal stroma?
An infiltrate dominated by lymphoid and histiocytic elements forms in the renal stroma during the chronic inflammatory process. Morphologically, this cellular composition is characterized as lymphohistiocytic stromal infiltration, developing as a result of the chronization of productive inflammation.
What is the morphological phenomenon of the "thyroid kidney" (thyroidization) in chronic pyelonephritis?
The phenomenon of the "thyroid kidney" (thyroidization) is a structural reorganization of the parenchyma, in which individual tubules dilate and their lumens are filled with colloid or colloid-like masses. As a result, the histological picture of the affected renal tissue begins to outwardly resemble the structure of the thyroid gland.
What complications can develop with a prolonged course of chronic pyelonephritis?
The finale of the progressive course of the disease leads to kidney shrinkage, replacement of tubules with fibrous tissue, and the development of peritubular sclerosis. In addition, the pathological process causes secondary damage to the vascular bed and glomerular apparatus with the development of secondary focal segmental glomerulosclerosis.
Pyelonephritis is inflammation of the renal pelvis and interstitium (pyelos + nephros), leading to scars and casts in the tubules.
Class and exam questions
What are the main forms of chronic pyelonephritis distinguished in pathological anatomy?
Two main forms are distinguished: chronic obstructive pyelonephritis (against the background of urinary tract obstruction) and chronic reflux pyelonephritis, known as reflux nephropathy.
What happens to the renal vessels in scarring areas?
In areas of tissue scarring, obliterating endarteritis develops in arcuate and interlobular arterioles. With concomitant hypertension, arteriolosclerosis and hyalinosis are also observed.
What changes are detected in the glomeruli in the late stages of the disease?
In late stages of chronic pyelonephritis and reflux nephropathy, secondary focal segmental glomerulosclerosis (FSGS) develops in the glomeruli, and periglomerular fibrosis is also frequently present.
What else to study on this topic
- Clinical significance of chronic pyelonephritis and statistics among hemodialysis patients
- Mechanisms of vesicoureteral and intrarenal reflux formation
- Differential diagnosis of tubular and vascular renal alterations
- Stages of development of secondary focal segmental glomerulosclerosis
- Features of inflammatory infiltration around the renal calyx
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