What causes chronic tubulointerstitial nephritis?

The main causes of chronic tubulointerstitial nephritis are:

• Medicines:
  • NSAIDs and non-narcotic analgesics;
  • 5-aminosalicylic acid;
  • lithium preparations;
  • immunosuppressants (cyclosporine, tacrolimus);
  • cytostatics (cisplatin);
  • diuretics (furosemide, ethacrynic acid, thiazides);
  • traditional medicine (Chinese herbs).
• Environmental factors:
  • lithium;
  • lead;
  • cadmium.
• Metabolic disorders:
  • uric acid metabolism disorders;
  • hypercalcemia;
  • hypokalemia;
  • hyperoxaluria.
• Systemic diseases:
  • sarcoidosis;
  • Sjogren's disease and syndrome.
• Other:
  • Balkan endemic nephropathy.

Chronic tubulointerstitial nephritis (drug variant), unlike many other variants of chronic nephropathy, is potentially preventable. Most cases are associated with long-term use of NSAIDs and non-narcotic analgesics; the term analgesic nephropathy is used to describe them.

The development of analgesic nephropathy is caused by chronic blockade of renal prostaglandin synthesis under the action of NSAIDs and non-narcotic analgesics, accompanied by a significant deterioration in renal hemodynamics with ischemia mainly of tubulointerstitial structures. Progressive tubulointerstitial inflammation and fibrosis lead to irreversible deterioration of renal function. In addition, a characteristic feature of analgesic nephropathy is calcification of the renal papillae. Pronounced carcinogenic action is attributed to N-hydroxylated metabolites of phenacetin.

The risk of analgesic nephropathy is increased with long-term use of drugs in high doses. Most NSAIDs and non-narcotic analgesics are sold without a prescription, which predisposes patients to their uncontrolled use. The combination of NSAIDs and non-narcotic analgesics with caffeine and codeine causes the development of psychological dependence. In addition, patients with chronic pain syndromes (osteoarthritis, lower back pain syndrome, migraine) often take drugs for prophylactic purposes, which leads to a significant increase in their dosages.

A history of renal impairment with penicillin antibiotics is a relative contraindication to the use of cephalosporins due to a certain commonality of their antigen structure. In patients who have had acute tubulointerstitial nephritis caused by NSAIDs, these drugs may be prescribed in the future, but the doses and duration of their use should be carefully monitored.

Long-term uncontrolled use of thiazide-like and loop diuretics, especially in large doses (for example, by women to reduce body weight) leads to the development of hyperkalemia, accompanied by potassium-penic nephropathy. Chronic potassium-penic tubulointerstitial nephritis is characterized by a decrease in renal blood flow and SCF; with a long course, cysts are formed.

The development of chronic drug-induced tubulointerstitial nephritis is also possible with the administration of aminosalicylic acid and its derivatives, used to treat chronic inflammatory bowel diseases, including Crohn's disease. Men are more often affected.

Chronic drug-induced tubulointerstitial nephritis occurs when taking cytostatics (platinum drugs), cyclosporine and tacrolimus.

When using some Chinese herbs, tubulointerstitial damage develops. The pool of proteins excreted in the urine consists of both albumin and low-molecular proteins normally reabsorbed by tubular epithelial cells; glucosuria develops. Aristolochic acid, contained in these herbs, predisposes to the development of malignant tumors of the urinary tract.

Chronic tubulointerstitial nephritis due to environmental factors

Environmental factors, including heavy metals, cause the development of chronic tubulointerstitial nephritis; lithium and lead nephropathy are the most common.

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Lithium nephropathy

The development of lithium intoxication occurs when salts of this substance accumulate in the environment, but most cases of kidney damage are associated with long-term use of lithium-containing drugs in the treatment of manic-depressive psychosis.

More than 50% of patients taking lithium-containing drugs develop distal renal tubular acidosis due to impaired proton secretion in the distal tubules under the influence of lithium. Lithium directly reduces the formation of cyclic AMP in the epithelial cells of the distal tubules, which leads to a significant decrease in the susceptibility of these cells to stimulation by antidiuretic hormone. Lithium has a direct toxic effect on the tubular cells, promoting their dehydration. An additional factor contributing to tubulointerstitial damage in patients taking lithium drugs is hypercalcemia.

Lead nephropathy

The development of tubulointerstitial nephropathy is characteristic of chronic lead intoxication. Currently, it is mainly household sources of lead that are dangerous (see "Lifestyle and Chronic Kidney Diseases"). Damage to the renal tubulointerstitium is caused by exposure to both lead and urates. The risk of lead intoxication is increased in the presence of predisposing factors, mainly metabolic:

• hypophosphatemia;
• iron deficiency states;
• excess vitamin D;
• insolation.

Cadmium nephropathy

Excessive cadmium intake results in chronic tubulointerstitial nephritis. Increased incidence of cadmium-induced kidney damage is observed when excess amounts of this element enter the environment: the largest outbreaks were observed in Belgium and Japan. Currently, cases of chronic tubulointerstitial nephritis associated with cadmium intoxication are rare.

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Radiation nephropathy

Ionizing radiation in doses exceeding 2000 rad causes the development of radiation tubulointerstitial nephritis. It is observed in patients suffering from malignant tumors and receiving radiation therapy, as well as in recipients of bone marrow transplants. In the latter, nephrotoxic effects of ionizing radiation develop at lower doses (1000-1400 rad).

Ionizing radiation affects predominantly the endothelial cells of the renal glomeruli. The death of endothelial cells in combination with intracapillary thrombosis leads to severe ischemia of the renal tubulointerstitium structures, accompanied by their atrophy. Inflammatory infiltrates are often absent, so it is recommended to use the term "nephropathy" rather than "nephritis" to describe radiation damage to the renal tubulointerstitium. As a rule, tubulointerstitial fibrosis develops.

The development of radiation nephropathy is predisposed by the combination of exposure to ionizing radiation with other factors capable of causing damage to renal tissue (some cytostatics, secondary hyperuricemia in patients with malignant tumors). Reducing the duration of radiation therapy sessions and increasing the duration of breaks between them reduces the risk of kidney damage.

Chronic tubulointerstitial nephritis in systemic diseases

Chronic tubulointerstitial nephritis often develops in systemic diseases (especially in sarcoidosis). An additional factor predisposing to the development of renal tubulointerstitium damage in sarcoidosis is the pathology of calcium metabolism caused by a violation of the transformation of vitamin D into the active form due to the fact that the macrophages of sarcoid granulomas contain the enzyme la-hydroxylase, and not 24-hydroxylase. As a result, hypercalciuria and hypercalcemia develop.

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