Voiding Volumes in Diabetes Insipidus
Yes, people with diabetes insipidus routinely urinate well over 600 ml at one time, often experiencing what parents describe as "bed flooding" due to the massive urine volumes produced. 1
Typical Urinary Patterns in Diabetes Insipidus
Volume Characteristics
Children with diabetes insipidus demonstrate significantly increased voiding volumes compared to healthy children, with urodynamic studies showing markedly elevated single-void volumes as an early manifestation of the disease. 1
The condition causes excretion of abnormally large volumes of diluted urine (polyuria), with patients producing urine osmolality typically around 100 mOsm/kg H₂O—far below the normal concentrated urine. 1
Cystometric examination reveals increased bladder capacity in patients with diabetes insipidus, with urodynamic findings consistently showing increased cystometric capacity as a hallmark feature. 1
Clinical Manifestations of Large Voiding Volumes
Night incontinence is highly prevalent in children with nephrogenic diabetes insipidus, with some parents reporting "bed flooding" rather than typical bedwetting, reflecting the extraordinary urine volumes that exceed what standard diapers can contain. 1
Parents often resort to using "double nappies" (placing an adult diaper around the child's regular diaper) to manage the overflow from the massive urine volumes produced overnight. 1
Full continence is typically not achieved until the second decade of life in patients with diabetes insipidus, largely due to the challenge of managing such large urine volumes. 1
Urodynamic Evidence
Diabetic children show significantly increased average urinary flow and increased delay until first sensation of the need to void, consistent with both the large volumes produced and sensory nerve dysfunction. 1
Urodynamic testing demonstrates impaired bladder sensation and increased cystometric capacity as defining features, with these abnormalities appearing as early as within 1 year of diabetes insipidus diagnosis. 1
Physiological Basis for Large Voiding Volumes
The inability to concentrate urine results in continuous production of large volumes of dilute urine (typically <200 mOsm/kg), as the collecting duct cannot reabsorb water due to AVP deficiency or resistance. 1, 2
The tonicity of typical intravenous fluids (
300 mOsm/kg H₂O) exceeds the urine osmolality in diabetes insipidus (100 mOsm/kg H₂O) by approximately 3-fold, meaning around 3 liters of urine are needed to excrete the osmotic load from just 1 liter of isotonic fluid. 1
Clinical Implications
Urological complications occur in 46% of patients with nephrogenic diabetes insipidus, with nocturnal enuresis and incomplete voiding being the most frequently observed problems related to the large urine volumes. 1
Regular kidney ultrasound monitoring (at least every 2 years) is recommended to detect urinary tract dilatation and bladder dysfunction caused by the chronic polyuria, as the large volumes can lead to "flow uropathy." 1, 3
Bladder ultrasound should ideally be performed before and after emptying because in approximately one-third of patients, dilatation improves with double voiding, highlighting the mechanical challenges posed by large urine volumes. 1