Interstitial nephritis (tubulointerstitial nephritis)

Interstitial nephritis (tubulointerstitial nephritis) in children is an acute or chronic non-specific, abacterial, non-destructive inflammation of the interstitial tissue of the kidneys, accompanied by involvement of the tubules, blood and lymphatic vessels of the renal stroma in the pathological process.

The importance of the problem of tubulointerstitial nephritis in children is determined by the fact that the absence of pathognomonic clinical syndromes and similarities with other nephropathies are the reason for its rare diagnosis, especially acute tubulointerstitial nephritis.

According to ICD-10 (1995), the group of tubulointerstitial nephritis also includes pyelonephritis, which is considered a bacterial (infectious) variant of tubulointerstitial nephritis. Such a combination of pyelonephritis and tubulointerstitial nephritis is based on the commonality of morphological changes with predominant damage to the tubules and interstitium. However, the etiology of these diseases is different, each of them has its own pathogenesis features, which determines a fundamentally different approach to therapy. Moreover, with pyelonephritis, in addition to the tubulointerstitium, lesions of the pelvis and fornical apparatus of the kidney are noted. These differences do not allow us to consider tubulointerstitial nephritis and pyelonephritis as variants of the same disease.

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Epidemiology of interstitial nephritis in children

The prevalence of interstitial nephritis has not been precisely established, which is largely due to the rare use of kidney biopsy. According to autopsy data, the frequency of tubulointerstitial nephritis ranges from 1.47 to 5%. When performing kidney biopsy in children with nephropathy, tubulointerstitial nephritis is detected in 5-7% of cases, and in children with acute renal failure - in 2%. According to a number of morphologists, tubulointerstitial diseases are much more common (4.6%) than glomerular diseases (0.46%). There are also indications that tubulointerstitial nephritis is observed in 14% of children with nephropathy who are registered with a dispensary.

According to some data, in more than 30% of cases tubulointerstitial nephritis is not clinically diagnosed, but is detected only during morphological examination of kidney biopsies. Thus, there is no doubt that tubulointerstitial nephritis occurs more often than it is diagnosed.

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Causes of Interstitial Nephritis in Children

The etiology of tubulointerstitial nephritis is varied. Acute tubulointerstitial nephritis can develop with various infections, as a result of the use of certain medications, poisoning, burns, injuries, acute hemolysis, acute circulatory disorders (shock, collapse), as a complication of vaccination, etc.

Chronic tubulointerstitial nephritis is also a heterogeneous polyetiological group of diseases in which, in addition to the above factors, hereditary predisposition and renal dysembryogenesis, metabolic disorders, chronic infection and intoxication, immunological diseases, unfavorable environmental factors (heavy metal salts, radionuclides), etc. are of great importance. Chronic tubulointerstitial nephritis can develop as a continuation of acute nephritis.

What causes interstitial nephritis?

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Pathogenesis of interstitial nephritis in children

The diversity of etiologic factors makes the pathogenesis of tubulointerstitial nephritis ambiguous.

The development of postinfectious tubulointerstitial nephritis is associated with the impact of microorganism toxins and their antigens on the endothelium of interstitial capillaries and the basement membrane of the tubules. This leads to direct cell damage, increased capillary permeability, and the inclusion of nonspecific inflammatory factors. In addition to direct toxic effects, immunologically mediated damage to the endothelium and tubules develops.

Chemicals, heavy metal salts, and medications, when eliminated by the kidneys, can also have a direct damaging effect on the tubular epithelium. However, the development of immune reactions, in which medications act as allergens or haptens, will be of primary importance for the development and maintenance of inflammation, especially in drug-induced tubulointerstitial nephritis.

Pathogenesis of interstitial nephritis

Symptoms of interstitial nephritis in children

Symptoms of interstitial nephritis are non-specific and often oligosymptomatic, which determines the difficulties of its diagnosis. In acute tubulointerstitial nephritis, the clinical picture of the underlying disease (ARI, sepsis, shock, hemolysis, etc.) dominates, against the background of which oliguria, hyposthenuria, moderate tubular proteinuria (up to 1 g/l), hematuria are detected, which is often interpreted as acute renal failure.

Symptoms of interstitial nephritis

Diagnosis of interstitial nephritis in children

Tubular dysfunction syndrome is manifested by decreased titratable acidity, decreased excretion of ammonia and concentration capacity. Possible disruption of reabsorption and transport processes in the tubules (aminoaciduria, glucosuria, acidosis, hyposthenuria, hypokalemia, hyponatremia, hypomagnesemia).

The study of enzymes - markers of mitochondrial activity - reveals mitochondrial dysfunction. The study of urine enzymes in the active phase of acute tubulointerstitial nephritis shows, first of all, an increase in y-glutamyl transferase, alkaline phosphatase, as well as beta-galactosidase, N-acetyl-O-glucosaminidase and cholinesterase, which emphasizes the interest in the pathological process of the glomerular apparatus.

According to ultrasound and DG data, half of the patients with acute tubulointerstitial nephritis show increased echogenicity of the renal parenchyma, and 20% show an increase in their size. In the CDC mode, no signs of intra-arterial blood flow disturbance are detected. Pulse Doppler imaging reveals a decrease in the resistance index at the level of the interlobar and arcuate arteries in 30% of patients.

Diagnosis of interstitial nephritis

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Treatment of interstitial nephritis in children

The polyetiological nature of tubulointerstitial nephritis requires a differentiated approach to its therapy in each specific case. However, it is possible to identify general principles of tubulointerstitial nephritis therapy, which should include:

• cessation of the influence of the etiological factor (chemical, physical, infectious, autoimmune, toxic-allergic, etc.) on the interstitium of the renal tissue;
• organization of general and motor regimes aimed at reducing the functional load on renal tissue;
• rational, gentle diet therapy, the purpose of which is to reduce the metabolic load on renal tissue;
• elimination of abacterial inflammation in renal tissue;
• elimination of metabolic disorders;
• prevention of interstitial sclerosis;
• restoration of kidney function.

How is interstitial nephritis treated?