Pediatric emergency medicine trisk 1530 1530
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900 mL/m2/day. An infant/toddler up to 2 years of age rarely exceeds 500 mL per
day. Children 3 to 5 years of age void up to 700 mL per day. Children 5 to 8 years
of age have an approximate maximum volume of 1,000 mL per day. Children 8 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 2 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 6 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
