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Chronic tubulointerstitial nephritis: diagnosis
Last reviewed: 23.04.2024
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Diagnosis of chronic tubulointerstitial nephritis is very complicated. When analgesic nephropathy is still at the preclinical stage, in most patients, when performing Zimnitsky's trial, a depression of the relative density of urine is detected. A moderate urinary syndrome is characteristic (microhematuria, moderate proteinuria). A significant increase in the excretion of proteins with urine indicates the development of severe glomerular lesions (more often - focal segmental glomerulosclerosis), predicting the development of terminal renal failure. Accession of the macrohematuria is a sign of developing necrosis of the renal papillae; at its preservation it is necessary to exclude uroepithelial carcinoma, the risk of which with analgesic nephropathy is very high, especially in smokers. Analgesic nephropathy is characterized by aseptic ("sterile") leukocyturia.
In chronic tubulointerstitial nephritis caused by lithium preparations, an increase in serum creatinine concentrations is observed, more often moderate. Urinary syndrome and hypertension are rare.
When nephropathy caused by Chinese herbs, detect proteinuria, usually not exceeding 1.5 g / day.
Patients with chronic tubulointerstitial nephritis due to the action of lithium are prone to the development of acidosis in the presence of predisposing factors (sepsis, hypercatabolic syndromes), despite the normal pH of the blood.
With lead nephropathy, proteinuria values do not exceed 1 g / day, characterized by an increase in the content of tubular proteins - beta 2- microglobulin and retinol-binding protein. Determine the concentration in the blood of lead, as well as protoporphyrin (markers of impaired heme synthesis) in erythrocytes. To confirm the diagnosis of chronic intoxication with small doses of lead, a lead mobilization test with ethylenediaminetetraacetyl acid (EDTA) is used: 1 g of EDTA is administered intramuscularly twice at an interval of 8-12 hours, then the content of lead in a daily portion of urine is determined. If daily excretion of lead exceeds 600 μg, chronic intoxication with small doses is diagnosed.
Signs of chronic cadmium tubulointerstitial nephritis:
- tubular proteinuria (increased excretion of beta 2- microglobulin);
- glucosuria;
- aminoaciduria;
- hypercalciuria;
- hyperphosphaturia.
With radiation nephropathy, proteinuria is rarely diagnosed, but cases of a significant increase in urinary protein excretion after decades after exposure to ionizing radiation are described.
For sarcoidosis, hypercalcemia, hypercalciuria, "sterile" leukocyturia, and insignificant proteinuria are characteristic.
[Instrumental diagnosis of chronic tubulointerstitial nephritis
Chronic drug tubulointerstitial nephritis
Histological examination of the kidney tissue in NSAIDs with nephropathy reveals signs similar to nephropathy of minimal changes; in the podocytes, the loss of most of the legs is observed.
With ultrasound, a decrease in the size of the kidneys and the unevenness of their contours are revealed. Calcification of the renal papillae is detected with greater certainty in CT, which does not require the introduction of contrast and is currently considered as a reference visualizing method for diagnosing analgesic kidney damage. A kidney biopsy is inexpedient.
Additional arguments in favor of the diagnosis of analgesic nephropathy are obtained with cystoscopy: the characteristic pigmentation of the triangle of the bladder is observed. At a biopsy of this site of a mucosa of a bladder find out a microangiopathy.
Diagnosis of tubulointerstitial nephritis with the intake of Chinese herbs is confirmed by biopsy: a distinctive feature of the morphological picture is the severity of fibrosis tubulointerstitium and atrophy of the tubules developed in a relatively short time from the beginning of the intake of Chinese herbs. With a biopsy of the kidneys and the mucous membrane of the urethra, a cellular atypia is often observed.
Chronic tubulointerstitial nephritis due to environmental factors
In the morphological study of kidney tissue, relatively specific signs are detected-edema and vacuolization of the epitheliocytes of the distal tubules and collecting tubules, in the PAS reaction they note the accumulation of glycogen. Glycogen granules in these cells arise within a short time from the beginning of the intake of lithium-containing drugs and, as a rule, disappear when they are withdrawn. Tubulointerstitial fibrosis of varying degrees is also observed. As the progression of the disease is characterized by the formation of tubular microcust. With biopsy, nephropathy is most often detected with minimal changes, less often focal segmental glomerulosclerosis.
In chronic lead intoxication, the kidneys are symmetrically reduced in size, no specific morphological signs of lesion are described.
Chronic tubulointerstitial nephritis in systemic diseases
Morphological signs in sarcoidosis are macrophage infiltration of renal tubulointerstitium with formation of typical sarcoid granules. Involving the glomeruli is not typical.