Interstitial kidney damage is characterized by inflammatory cell infiltration, interstitial edema, and varying degrees of tubular damage with renal insufficiency occurring within a short period of time due to a variety of causes. The pathological manifestations of chronic interstitial nephritis are characterized by interstitial fibrosis, interstitial single nucleated cell infiltration and tubular atrophy. Interstitial kidney damage examination has the following items: 1. Urine examination Generally a small amount of small molecule proteinuria, urine protein quantification is mostly in 0.5 to 1.5 g/24 hours, rarely >2.0 g/24 hours; urine sediment examination may have microscopic hematuria, leukocytes and tubular urine, occasionally visible eosinophils. Abnormal renal tubular function varies according to the site and degree of tubular involvement, and may include renal diabetes, tubular acidosis, hypotonic urine, Fanconi syndrome, etc. 2.Blood test Some patients may have hypokalemia, hyponatremia, hypophosphatemia and hyperchloremic metabolic acidosis. Blood uric acid is often normal or mildly elevated. Chronic interstitial nephritis has a high incidence and degree of anemia, often orthocytic orthochromic anemia. In acute interstitial nephritis, the percentage of peripheral blood eosinophils is elevated and may be accompanied by elevated IgE. Idiopathic interstitial nephritis may have anemia, eosinophilia, rapid sedimentation, and elevated CRP and globulin. The B ultrasound of acute interstitial nephritis may show normal size or enlarged kidneys with enhanced cortical echogenicity. In chronic interstitial nephritis, ultrasound, radionuclide, CT and other imaging tests usually show that both kidneys are shrunken and the kidneys are not well defined. Imaging is also helpful in determining certain specific causes, such as urinary tract obstruction, vesicoureteral reflux, and cystic kidney disease. Intravenous urography (IVU) can show signs of renal papillary necrosis characteristic of analgesic nephropathy. Because contrast agents are tubularly toxic, they should be used with caution in cases of renal tubular injury. 4, renal biopsy pathology Pathological examination is important to confirm the diagnosis. Except for infection-associated acute interstitial nephritis, all other types should be actively performed by renal puncture to distinguish the type of interstitial infiltrating cells and the degree of fibrosis, thus helping to determine the prognosis after the development of treatment plan.