The oliguric phase of acute tubular necrosis is characterized by fluid excess and electrolyte imbalance.
Explanation:
Death of epithelial cells of renal tubule is called tubular necrosis.
Tubular necrosis may result due to chronic low blood pressure or over use of nephrotoxic drugs.
Tubular necrosis is usually diagnosed by the presence of granular cast in the urine.
In oliguric phase the urine output significantly decreases due to the damaged renal tubules, resulting in fluid excess and  electrolyte imbalance.
