What is Pyelonephritis?
Pyelonephritis is a type of urinary tract infection (UTI) that affects the kidneys. It usually begins as a lower urinary tract infection and ascends to the kidney. In terms of histology, it involves inflammation of the kidney parenchyma, calyces, and pelvis.
Histological Features
In acute pyelonephritis, histological examination reveals infiltration of polymorphonuclear leukocytes (PMNs) in the interstitial tissue. There may also be the presence of
microabscesses in the renal parenchyma. The tubules often show signs of necrosis and contain neutrophils and cellular debris.
Chronic Pyelonephritis
Chronic pyelonephritis shows different histological features compared to the acute form. There is interstitial fibrosis and tubular atrophy. The glomeruli may also exhibit sclerosis. The
interstitial fibrosis is indicative of long-standing inflammation and damage.
Diagnosis
Histological examination is crucial for diagnosing pyelonephritis. Biopsy samples are stained using various techniques to highlight different cellular and extracellular components. Hematoxylin and eosin (H&E) staining is commonly used to identify
PMNs and tissue architecture. Special stains like Periodic acid-Schiff (PAS) can help in identifying the basement membrane and fibrotic changes.
Pathophysiology
The pathophysiology of pyelonephritis involves the ascent of bacteria from the bladder through the ureters to the kidneys. The infection triggers an immune response, leading to the infiltration of inflammatory cells like
neutrophils. The release of enzymes and reactive oxygen species by these cells causes tissue damage.
Complications
Untreated pyelonephritis can lead to complications such as renal abscess formation,
sepsis, chronic kidney disease (CKD), and hypertension. Chronic pyelonephritis can cause extensive renal scarring, leading to a non-functional kidney.
Therapeutic Implications
The histological findings in pyelonephritis have significant therapeutic implications. Acute pyelonephritis is usually treated with antibiotics, and the choice of antibiotic can be guided by the histological findings and sensitivity tests. Chronic pyelonephritis may require more complex management, including addressing the underlying causes such as
vesicoureteral reflux or obstruction.
Conclusion
Histology plays a crucial role in the diagnosis and management of pyelonephritis. Understanding the histological features of both acute and chronic forms helps clinicians in making informed decisions regarding treatment and management. Early diagnosis and appropriate treatment are essential to prevent complications and preserve kidney function.
