ORMC Progressive Care Unit (PCU) Practice Test

In intrinsic AKI, the kidney’s tubular injury sharply reduces its ability to form urine. The oliguric phase is defined by a drastic drop in urine output, making oliguria the most characteristic sign. In adults, this means urine output typically falls to less than about 400 mL in 24 hours (often described as <0.5 mL/kg/hour). That reduced urine production directly reflects the damaged tubules and impaired filtration output.

As a result, waste products accumulate (azotemia) and fluid/electrolyte balance becomes uneasy, leading to issues like fluid retention and potential hyperkalemia. But these are consequences of the impaired kidneys; the defining feature of the oliguric phase remains the markedly decreased urine output. Note that some patients may have non-oliguric AKI, but when oliguric, the low urine output is the hallmark.