Clinical Scenarios in Chronic Kidney Disease: Chronic Tubulointerstitial Diseases

Chronic tubulointerstitial diseases are a common final pathway toward chronic renal failure regardless the primary damage (glomerular, vascular or directly the tubulointerstitium). Chronic tubulointerstitial nephritis (CTN) is characterized by interstitial scarring, fibrosis and tubule atrophy, resulting in progressive chronic kidney disease. Most frequent causes of CTN are drugs, heavy metals, obstructive uropathy, nephrolithiasis, reflux disease, immunologic diseases, neoplasia, ischemia, metabolic diseases, genetics and miscellaneous. At ultrasound (US), kidneys' morphological aspect is similar in all forms of chronic interstitial nephropathy and only chronic pyelonephritis with or without reflux shows distinguishing characteristics. In interstitial nephropathy, kidneys' profiles are finely irregular and corticomedullary differentiation is altered because of a diffused hyperechogenicity. The only indirect sign of chronic interstitial damage can be derived from the value of intrarenal resistive indexes that hardly overcome 0.75. US is mandatory in clinical chronic pyelonephritis work-up because it provides information on kidney's diameter and on growth nomogram in children. Renal profiles can be more or less altered depending on the number of cortical scars and the presence of pseudonodular areas of segmental compensatory hypertrophy. In the early stages, US diagnosis of renal tuberculosis is difficult because parenchymal lesions are non-specific. US sensitivity in the diagnosis of hydronephrosis is very high, close to 100% and, finally, US is the first choice imaging technique in the diagnosis of urinary lithiasis.