Pediatric emergency medicine trisk 383

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


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


Frequency is often associated with urinary tract infection (UTI) and as such this
diagnosis should be of high suspicion (see Chapters 31 Fever , 94 Infectious
Disease Emergencies ). Accurate diagnosis of pediatric UTI is important to
ensure both appropriate initial treatment and follow-up evaluation. Viral (e.g.,
adenovirus) or fungal cystitis should be considered in patients with a negative
urine culture, especially those who are immunocompromised. Chemical cystitis
can occur, but is a rare diagnosis in pediatric populations. Partial distal urethral
obstruction, specifically posterior urethral valves, may cause frequency as
patients cannot empty the bladder and instead produce frequent small voids. The
urinary stream in the male child who presents with posterior urethral valves is
usually nonforceful and not sustained and may be associated with straining. The
enlarged bladder is sometimes palpable as a lower abdominal mass.

TABLE 78.1
DIFFERENTIAL DIAGNOSIS OF URINARY FREQUENCY
Intraurinary system

Extraurinary system

Renal
Renal parenchymal disease
Sickle cell disease
Nephrogenic diabetes
insipidus
Ureter
Ectopic ureter
Nephrolithiasis
Bladder
Urinary tract
infection/bacterial cystitis
Viral cystitis
Chemical cystitis
Posterior urethral valves
Urethra/Penis/Vagina
Urethritis
Vulvovaginitis (infectious,
foreign body, trauma)
Balanitis
Meatal ulceration
Urethral syndrome
Pinworms

Neurologic

Neurogenic bladder (spinal cord lesion, spina
bifida)
Central diabetes insipidus (head injury, brain
tumor, septo-optic dysplasia)
Uninhibited/unstable bladder
Abdominal
Abdominal/pelvic mass
Ovarian torsion/cyst
Appendicitis
Pregnancy
Constipation
Endocrine/Metabolic
Hyperglycemia/diabetes mellitus
Hypercalciuria
Salt-losing congenital adrenal hyperplasia
Drugs/Toxins
Caffeine
Ethanol
Lithium
Diuretics
Vitamin D
Psychogenic
Behavioral
Psychogenic polydipsia
Munchausen-by-proxy

Urethra, Penis, Vagina, and Anus
Frequency is a presenting symptom of urethritis, more specific to the adolescent
population. The most common etiologies of urethritis are Chlamydia trachomatis
and Neisseria gonorrhoeae. Balanitis and balanoposthitis in young males,