Chronic tubulointerstitial nephritis

Chronic tubulointerstitial nephropathies (CTINs) are a group of renal diseases, characterized by variable interstitial inflammation and fibrosis and tubular atrophy, and a slow course towards end-stage renal disease (ESRD). The causes of CTIN are numerous, including nephrotoxic drugs and chemicals, infections, autoimmune diseases, obstructive uropathies, and metabolic disorders. Taken together, CTIN are responsible for less than 10% of all ESRD cases requiring renal replacement therapy. The clinical manifestations of CTIN typically comprise low-grade proteinuria, leucocyturia, and variably reduced glomerular filtration rate (GFR), whereas the blood pressure is usually normal or moderately increased. Tubular abnormalities are common, including type 2 (proximal) renal tubular acidosis, Fanconi syndrome, nephrogenic diabetes insipidus, and type 1 (distal) renal tubular acidosis, with hypokalaemia and nephrolithiasis. Radiology exams reveal shrunken kidneys, sometimes with irregular outlines. A renal biopsy is often required for the diagnosis of CTIN and its aetiology. The treatment of CTIN mainly involves discontinuation of exposure to nephrotoxins and specific therapy of renal infections, urinary tract obstruction, or underlying systemic diseases. Agents like ACE inhibitors and pirfenidone, which might reduce interstitial inflammation and fibrosis, are still under clinical evaluation.