What is a serious condition indicated by the absence of urine production?

Anuria refers to the complete absence of urine production, typically defined as producing less than 100 milliliters of urine within a 24-hour period. This is a serious medical condition that usually indicates significant renal impairment or full renal failure, dehydration, severe obstruction of the urinary tract, or potential systemic issues such as shock. When the kidneys fail to produce urine, it can lead to the accumulation of waste products in the body, electrolyte imbalances, and can be life-threatening if not addressed promptly.

In contrast, oliguria denotes a reduced urine output of less than 400 milliliters per day but not a complete absence of urine, indicating some level of kidney function still exists. Polyuria involves excessive urine production, often seen in conditions like diabetes mellitus. Urinary retention signifies an inability to completely empty the bladder, which may lead to discomfort and other complications but does not necessarily imply the absence of urine production altogether.