The long-term renal effects of short periods of unilateral ureteral obstruction

The response of the kidney and its recovery following unilateral ureteral obstruction (UUO) depend on several factors including the duration of obstruction, the species involved and the age of the individual. In neonates, there is compelling evidence to indicate that even short periods of reversible UUO might lead to long-term renal impairment. In adults, the glomerular filtration rate returns to baseline values soon after the release of short periods of UUO. Despite this return to normal, experimental data have demonstrated that short periods of reversible UUO could lead to long-term renal functional alterations including tubular atrophy, interstitial fibrosis and urinary albumin leakage in addition to alterations in pro-inflammatory and pro-fibrotic cytokines. The concentrating ability of the kidney and its response to stimuli such as renal nerve stimulation and physiological doses of angiotensin-II were also shown to be affected at least in the intermediate-term following UUO reversal. In humans, epidemiological studies have also demonstrated a clear association between long-term renal impairment and ureteral obstruction. However, in clinical studies, it is usually difficult to precisely determine the degree and the time of onset of ureteral obstruction and more studies are required in this field. In conclusion, the available experimental and clinical data indicate that even short periods of UUO can cause long-term renal dysfunction. These findings might have clinical implications related to the early intervention following acute onset of UUO and to the need for long-term monitoring of renal functions particularly in patients with underlying chronic renal disease.