Pediatric emergency medicine trisk 1529 1529
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CHAPTER 78 ■ URINARY FREQUENCY
DANIEL CORWIN, HEATHER L. HOUSE
INTRODUCTION
Urinary frequency is a symptom of several commonly encountered clinical
pediatric problems. Frequency may also be the presentation of life-threatening
conditions that require emergent diagnosis and management. Therefore, an
organized approach in the emergency department (ED) evaluation of this
symptom is important for any clinician providing acute care to children.
Urinary frequency (pollakiuria) is defined as an increase in the number of voids
per day. It is a symptom distinct from polyuria (excretion of excessive amounts of
urine). Although the two symptoms can be related, most children who present to
the ED with frequency have a normal daily urine output, although the individual
voids are frequent and small. Frequency is also distinct from enuresis, which is
defined as inappropriate urination at an age when bladder control should be
achieved.
PATHOPHYSIOLOGY
Almost all newborns void during the first day of life and infants void up to 30
times a day. Over the next 2 years, the number of voids per day decreases and the
volume of urine produced increases. Children between 3 and 5 years of ages
average 8 to 14 voids per day and by 5 years of age decreases to 6 to 12 times per
day. Adolescents average 4 to 6 voids per day. In the school-aged population,
urinary frequency is usually defined as voiding more often than every 2 hours.
Normal bladder mucosa responds to pressure and pain. When urine volume
approaches the bladder capacity it produces an uncomfortable sensation. Voiding
is initiated by relaxation of the striated muscles of the urinary sphincter. There is
an associated contraction of the smooth muscle of the bladder, resulting in
bladder emptying. This mechanism is mediated by sacral nerves II to IV.
Uncontrolled, uninhibited bladder contractions are the normal mechanism for
infant and toddler voiding. Uninhibited (parasympathetic-mediated) bladder
contractions do not normally occur after toilet training. By 5 years of age, 90% of
children have achieved direct voluntary mastery of the voiding reflex and exhibit
the adult pattern of urinary control.
Normal pediatric values for urine output are useful in determining the presence
of polyuria. The traditional definition of polyuria is a urinary output of more than
