Interstitial Nephritis - Histology

Introduction

Interstitial nephritis is an inflammation of the renal interstitium which is the space surrounding the renal tubules. This condition can be acute or chronic and it significantly impacts kidney function. Understanding its histological features is crucial for accurate diagnosis and effective treatment.

Histological Features

In the context of histology, interstitial nephritis is characterized by the presence of inflammatory cells such as lymphocytes, plasma cells, and macrophages in the renal interstitium. There is often associated edema and fibrosis. The tubules may show signs of damage, including atrophy and dilation.

Causes

Various factors can lead to interstitial nephritis. These include:

Drug-induced (e.g., antibiotics, NSAIDs)
Infections (e.g., bacterial, viral)
Autoimmune disorders (e.g., systemic lupus erythematosus)
Idiopathic (unknown causes)

Acute vs. Chronic Interstitial Nephritis

Acute interstitial nephritis (AIN) is often sudden in onset and commonly reversible if identified early and the causative agent is removed. Histologically, AIN shows a prominent infiltration of inflammatory cells, particularly eosinophils, and tubular injuries.
Chronic interstitial nephritis (CIN), on the other hand, develops over a longer period and often leads to irreversible damage. Histological features of CIN include interstitial fibrosis, tubular atrophy, and a more mononuclear cell infiltrate.

Diagnosis

The diagnosis of interstitial nephritis is largely dependent on a kidney biopsy. Histological examination of biopsy samples reveals the characteristic inflammatory infiltrate and tubular damage. Immunohistochemistry can further help in identifying specific inflammatory cells and the presence of immune complexes.

Treatment

Treatment of interstitial nephritis involves addressing the underlying cause. For drug-induced cases, discontinuation of the offending drug is crucial. In cases involving infections, appropriate antibiotics are used. For autoimmune disorders, immunosuppressive therapy may be needed. Supportive treatment to maintain kidney function, including hydration and avoidance of nephrotoxic agents, is also important.

Conclusion

Understanding the histological features of interstitial nephritis is essential for its diagnosis and management. The condition can range from reversible, acute forms to chronic, irreversible damage, highlighting the importance of early detection and appropriate treatment.