Tubulointerstitial diseases are clinically heterogeneous disorders that share similar features of tubular and interstitial injury. In severe and prolonged cases, the entire kidney may become involved, with glomerular dysfunction and even renal failure. The primary categories of tubulointerstitial disease are
Contrast nephropathy Contrast Nephropathy Contrast nephropathy is worsening of renal function after IV administration of radiocontrast and is usually temporary. Diagnosis is based on a progressive rise in serum creatinine 24 to 48 hours... read more is acute tubular necrosis caused by an iodinated radiocontrast agent.
Analgesic nephropathy Analgesic Nephropathy Analgesic nephropathy is chronic tubulointerstitial nephritis caused by cumulative lifetime use of large amounts (eg, ≥ 2 kg) of certain analgesics. Patients present with kidney injury and usually... read more is a type of chronic interstitial nephritis, and reflux nephropathy Vesicoureteral Reflux and Reflux Nephropathy Reflux nephropathy is renal scarring presumably induced by vesicoureteral reflux of infected urine into the renal parenchyma. The diagnosis is suspected in children with urinary tract infections... read more 
and myeloma kidney Myeloma-Related Kidney Disease Patients with multiple myeloma overproduce monoclonal Ig light chains (Bence Jones proteins); these light chains are filtered by glomeruli, are nephrotoxic, and, in their various forms (free... read more 
can involve chronic tubulointerstitial nephritis.
Tubulointerstitial disorders can also result from metabolic disturbances Metabolic Nephropathies Tubulointerstitial disorders can result from several metabolic disturbances. (See also Overview of Tubulointerstitial Diseases.) Several metabolic disturbances can cause tubulointerstitial nephritis... read more 
and exposure to toxins Heavy Metal Nephropathy Exposure to heavy metals and other toxins can result in tubulointerstitial disorders. (See also Overview of Tubulointerstitial Diseases.) Heavy metals (eg, lead, cadmium, copper) and other toxins... read more .
Pathophysiology
The kidneys are exposed to unusually high concentrations of toxins. The kidneys have the highest blood supply of all tissues (about 1.25 L/min or 25% of cardiac output), and unbound solutes leave the circulation via glomerular filtration at ≥ 100 mL/min; as a result, toxic agents are delivered at a rate 50 times that of other tissues and in much higher concentrations. When urine is concentrated, the luminal surfaces of tubular cells may be exposed to molecule concentrations 300 to 1000 times greater than those of plasma. The fine brush border of proximal tubular cells exposes an enormous surface area. A countercurrent flow mechanism increases ionic concentration of the interstitial fluid of the medulla (and thereby increases urine concentration) up to 4 times the plasma concentration.
In addition, factors can affect cellular vulnerability after exposure to toxins:
Tubular transport mechanisms separate drugs from their binding proteins, which normally protect cells from toxicity.
Transcellular transport exposes the interior of the cell and its organelles to newly encountered chemicals.
Binding sites of some agents (eg, sulfhydryl groups) may facilitate entry but retard exit (eg, heavy metals).
Chemical reactions (eg, alkalinization, acidification) may alter transport in either direction.
Blockade of transport receptors may alter tissue exposure (eg, diuresis from blockade of adenosine A1 receptors, such as with aminophylline, may decrease exposure).
The kidneys have the highest oxygen and glucose consumption per gram of tissue and are therefore vulnerable to toxins affecting cell energy metabolism.
