900 mL/m2/day An infant/toddler up to years of age rarely exceeds 500 mL per day Children to years of age void up to 700 mL per day Children to years of age have an approximate maximum volume of 1,000 mL per day Children to 14 years of age void up to 1,400 mL per day When polyuria is the cause of urinary frequency, the urine volume per void generally is more than mL per kg DIFFERENTIAL DIAGNOSIS A differential diagnosis of urinary frequency is outlined in Table 78.1 Many of these diagnoses are reviewed in more depth in other chapters of this textbook (in particular, see Chapters 31 Fever , 37 Hypertension , 57 Pain: Dysuria , 64 Polydipsia , 89 Endocrine Emergencies , 92 Gynecology Emergencies , 100 Renal and Electrolyte Emergencies , 119 Genitourinary Emergencies , 126 Behavioral and Psychiatric Emergencies ) The following discussion reviews the differential diagnosis by organ system and focuses on selected high-yield topics Renal and Urinary System Intrarenal Certain diseases of the renal parenchyma (e.g., renal tubular acidosis, Fanconi syndrome, and Bartter syndrome) lead the renal tubules to lose their ability to concentrate urine Subsequently, patients develop polyuria and frequency related to dilute urine and large urinary volumes Similarly, patients with sickle cell disease or sickle trait may have difficulty with urine concentration and develop urinary frequency as early as months of age Diabetes insipidus (DI) is a rare but life-threatening cause of frequency in the ED Clinically, patients present with polydipsia and resultant polyuria and frequency related to an inability of the kidneys to concentrate urine Nephrogenic DI is the kidney’s inability to respond to antidiuretic hormone The most common type of nephrogenic DI in childhood is the X-linked recessive type, which presents in males during early infancy If fluids are not accessible or if the thirst sensation is impaired, hypernatremic dehydration can develop Ureter Anatomic anomalies of the urogenital tract, such as ectopic ureter, may result in a chronic leakage of urine Patients with nephrolithiasis may experience urinary frequency, with or without dysuria, if the renal calculus migrates into the ureter Hematuria (other gross or microscopic) is often present with nephrolithiasis or urolithiasis Bladder