Harnvolumen

Harnvolumen refers to two related but distinct concepts in urinary physiology. One is the amount of urine produced and excreted by the kidneys over a period, most commonly a 24-hour interval. The other is the bladder’s storage capacity, i.e., the maximum volume the bladder can hold before the urge to void becomes noticeable. Both measures are used to assess kidney function, fluid balance, and lower urinary tract health.

Normal ranges vary by context. Daily urine volume in adults is typically about 800 to 2000 milliliters, influenced by fluid intake, diet, and medications. Functional bladder capacity usually lies in the range of roughly 300 to 500 milliliters, with maximum capacities often cited around 600 to 700 milliliters. Individual values differ, and aging can affect both production and storage capacity.

Measurement and assessment methods include a 24-hour urine collection to determine total daily volume, and bladder diaries that record voided volumes and times. Post-void residual ultrasound assesses how much urine remains in the bladder after urination. Urodynamic studies may evaluate storage and outlet functions when more detail is needed.

Clinical relevance: very low volumes (oliguria, typically <400 mL/day) can indicate dehydration or impaired kidney function, while very high volumes (polyuria, >3000 mL/day) may point to diabetes mellitus, diabetes insipidus, or diuretic use. Abnormal bladder capacity can contribute to symptoms such as urinary frequency, urgency, or incontinence, and is considered alongside other urinary tract findings in diagnosis and management.

See also: oliguria, polyuria, nocturia, diuresis, micturition, bladder capacity.