Mechanisms of toxic and drug-induced injury
Iatrogenic renal injuries develop through several scenarios. The first is an acute interstitial immunologic reaction (a typical example is the response to methicillin administration). The second pathway is associated with the development of acute kidney injury (AKI). The third variant represents cumulative, i.e., progressive tubular injury. It is insidious because it clinically manifests only years after continuous toxin exposure and inevitably leads to chronic kidney disease (CKD). A classic example of this scenario is analgesic nephropathy, which is often diagnosed only at the end-stage CKD phase.
Acute drug-induced interstitial nephritis
This disease proceeds as a hypersensitivity reaction. Triggers include synthetic penicillins (ampicillin, methicillin), other antibiotics (rifampicin), diuretics (thiazides), nonsteroidal anti-inflammatory drugs (phenylbutazone), and other medications such as cimetidine.
The pathogenesis is based on two immune mechanisms:
- IgE-mediated mechanism: serum IgE levels increase, and basophils and plasma cells containing this immunoglobulin accumulate in the lesion site.
- Delayed-type hypersensitivity (DTH): a mononuclear or granulomatous infiltrate forms, and skin tests for haptens yield positive results.
Morphological picture:
- Macroscopically: the kidneys appear slightly enlarged.
- Microscopically: pronounced edema is revealed in the interstitium. The inflammatory infiltrate consists predominantly of mononuclear cells (macrophages and lymphocytes), but the presence of eosinophils and a large number of neutrophils is also extremely characteristic of this pathology. Basophils and plasma cells are less common. Under the action of methicillin or thiazides, interstitial granulomas with giant cells may form. Various degrees of necrosis and regeneration are observed in the tubules. Glomeruli are generally spared. The exception is cases triggered by NSAID intake: minimal change disease with nephrotic syndrome may develop as a competing condition.
Analgesic nephropathy
The disease is associated with excessive and prolonged use of analgesics. This is one of the most frequent causes of CKD, especially in Western European countries. Morphologically, the process represents chronic tubulointerstitial nephritis accompanied by renal papillary necrosis (tips of the pyramids).
Macroscopically, the kidneys retain normal dimensions or are slightly reduced. Alternating areas of bulging and depression are noticeable on the cortical surface. Depressions correspond to zones of cortical atrophy located strictly above the necrotic papillae. The pyramids themselves are at different stages of destruction: from fresh necrosis to calcification, fragmentation, and complete sloughing.
Histological picture:
- Papillae: areas of necrosis are visible. In severe cases, the papilla undergoes complete necrosis, turning into amorphous masses where only the contours of former tubules can be discerned. Foci of dystrophic calcification appear. Segments of papillae can desquamate and be excreted in the urine.
- Cortex: tubules disappear or undergo marked atrophy. Fibrosis and chronic inflammation develop in the interstitium. The main mechanism of these changes is obstructive atrophy arising from the destruction of tubules in the underlying papillae. Secondary pyelonephritis frequently complicates the process.
- Blood vessels: specific analgesic microangiopathy develops. It affects small blood vessels of the papillae and the submucosa of the urinary tract. Its characteristic marker is basement membrane thickening that gives a positive PAS reaction.
Briefly: answers to topical questions
What changes in the urinary sediment are characteristic of acute tubulointerstitial nephritis?
Eosinophils (eosinophiluria), erythrocytes, protein, casts, and leukocytes may be detected in the urine in acute tubulointerstitial nephritis.
- Eosinophiluria is a specific finding observed in 95% of patients with acute allergic interstitial nephritis.
- Hematuria is one of the possible signs of acute interstitial nephritis.
- Proteinuria, cylindruria, and leukocyturia may be combined with renal hematuria.
Which infectious agents can cause acute tubulointerstitial nephritis?
Acute tubulointerstitial nephritis can be caused by viral infections. In particular, a specific renal involvement in the form of acute interstitial nephritis is characteristic of hemorrhagic fever with renal syndrome (HFRS).
- HFRS virus: causes an acute viral zoonotic natural focal disease accompanied by systemic damage to small blood vessels, leading to the development of acute kidney injury.
To quickly recall the main groups of drugs causing acute interstitial nephritis, use the acronym PAND: Penicillins, Antibiotics (others, e.g., rifampicin), NSAIDs, Diuretics (thiazides).
Class and exam questions
How to differentiate papillary necrosis in analgesic nephropathy from diabetic papillary necrosis?
With analgesic abuse, changes in the pyramids are staggered in time: some papillae are just undergoing necrosis while others are already calcifying or sloughing. In diabetes mellitus, all papillae are at the same stage of acute necrosis.
Are glomeruli affected in acute drug-induced nephritis?
As a rule, glomeruli remain intact. An exception is cases caused by NSAID intake — in such instances, the development of minimal change disease with nephrotic syndrome is possible.
Are changes reversible in acute drug-induced renal injury?
Yes, if the trigger is identified in time and the drug is discontinued, kidney function usually recovers within several months. However, in elderly patients, damage is more often irreversible.
What else to study on this topic
- Mechanisms of IgE-mediated renal tissue injury
- Delayed-type hypersensitivity reactions in the interstitium
- Morphogenesis of interstitial granulomas upon thiazide administration
- Pathogenesis of obstructive cortical atrophy
- Analgesic microangiopathy and basement membrane alterations
Master the entire topic in the "Pathological Anatomy" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Tubulointerstitial nephritis" and 4,414 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 153 video lessons on the subject
Other topics in the section "Diseases of the Kidneys and Urinary Tract"
Free video lessons: pathological anatomyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.