19. (Illustrated) Urinary tract disorders - UTI Flashcards
Urinary tract infection (UTI) - General information
What is Pyelonephritis and Cystitis?
Why is UTI in childhood important? (2)
About 3–7% of girls and 1–2% of boys have at least
one symptomatic UTI before the age of 6 years, and
12–30% of them have a recurrence within a year. UTI
may involve the kidneys (pyelonephritis), when it is
usually associated with fever and systemic involvement,
or may be due to cystitis, when there may be no
fever.
UTI in childhood is important because:
- Up to half of patients have a structural abnormality of their urinary tract
- Pyelonephritis may damage the growing kidney by forming a scar, predisposing to hypertension and to progressive chronic kidney disease if the scarring is bilateral.
The NICE (National Institute for Health and Care Excellence)
guidelines on UTI in children were published in
2007, although they have proved to be controversial
as they recommend fewer children being investigated
and the investigations are less extensive.
Clinical features
Difference between infants and children
Dysuria alone is usually due to…
Presentation of UTI varies with age (Box 19.1). In
infants, symptoms are nonspecific; fever is usually
but not always present, and septicaemia may develop
rapidly. The classical symptoms of dysuria, frequency,
and loin pain become more common with increasing
age. Serious illness from septicaemia is described in
Chapter 6. Dysuria alone is usually due to cystitis, or
vulvitis in girls or balanitis in uncircumcised boys.
Symptoms suggestive of a UTI may also occur following
sexual abuse.
Collection of samples
How can urine be collected in a child with “nappies”?
How can urine be collected in an older child?
What should be done with the urine samples in children under the age of 3?
What determines a 90% probability of infection? (for clean-catch and midstream samples)
The most common error in the management of UTI in
children, and especially in infants, is failure to establish
the diagnosis properly in the first place. If the diagnosis
of a UTI is not made, the opportunity to prevent renal
damage may be missed, or, if incorrectly diagnosed,
may lead to unnecessary invasive investigations.
For the child in nappies, urine can be collected by:
• a ‘clean-catch’ sample into a waiting clean pot
when the nappy is removed. This is the
recommended method
• an adhesive plastic bag applied to the perineum
after careful washing, although there may be
contamination from the skin
• a urethral catheter if there is urgency in obtaining
a sample and no urine has been passed
• suprapubic aspiration, when a fine needle
attached to a syringe is inserted directly into the
bladder just above the symphysis pubis under
ultrasound guidance; it may be used in severely ill
infants requiring urgent diagnosis and treatment,
but it is an invasive procedure, and is increasingly
replaced by urethral catheter sampling.
In the older child, urine can be obtained by collecting
a midstream sample. Careful cleaning and collection
are necessary, as contamination with both white cells
and bacteria can occur from under the foreskin in boys,
and from reflux of urine into the vagina during voiding
in girls.
Ideally, the urine sample should be observed under a
microscope to identify organisms and cultured straight
away. This is indicated in all infants and children under
the age of 3 years with a suspected UTI. If this is not
possible, the urine sample should be refrigerated to
prevent the overgrowth of contaminating bacteria.
Urinary white cells are not a reliable feature of a UTI,
as they may lyse during storage and may be present
in febrile children without a UTI and in children with
balanitis or vulvovaginitis. Dipsticks can be used as a
screening test. Urine culture should still be performed
unless both leucocyte esterase and nitrite are negative
or if the clinical symptoms and dipstick tests do not
correlate (Table 19.3).
A bacterial culture of more than 105 colony-forming
units (CFU) of a single organism per millilitre in a
properly collected specimen gives a 90% probability of
infection. If the same result is found in a second sample,
the probability rises to 95%. A growth of mixed organisms
usually represents contamination, but if there
is doubt, another sample should be collected. Any
bacterial growth of a single organism per millilitre in
a catheter sample or suprapubic aspirate is considered
diagnostic of infection.
Bacterial and host factors that predispose to infection
Infecting organism
UTI is usually the result of…
The most common organism/pathogen is…
Which organism/pathogen is more commonly diagnosed in boys and why?
UTI is usually the result of bowel flora entering the
urinary tract via the urethra, although it can be haematogenous,
e.g. in the newborn. The most common
organism is Escherichia coli, followed by Klebsiella,
Proteus, Pseudomonas, and Streptococcus faecalis.
Proteus infection is more commonly diagnosed in boys
than in girls, possibly because of its presence under the
prepuce. Proteus infection predisposes to the formation
of phosphate stones by splitting urea to ammonia, and
thus alkalinizing the urine. Pseudomonas infection may
indicate the presence of some structural abnormality in
the urinary tract affecting drainage and it is also more
common in children with plastic catheters.
Bacterial and host factors that predispose to infection
Antenatally diagnosed renal or urinary tract abnormality
Increases risk of infection and investigation of a UTI may
lead to urinary tract abnormality being detected if antenatal
diagnosis was not made or missed to follow-up.
Bacterial and host factors that predispose to infection
Incomplete bladder emptying
Contributing factors (6)
Contributing factors in some children are:
- Infrequent voiding, resulting in bladder enlargement
- Vulvitis
- Incomplete micturition with residual postmicturition bladder volumes
- Obstruction by a loaded rectum from constipation
- Neuropathic bladder
- Vesicoureteric reflux
Bacterial and host factors that predispose to infection
Vesicoureteric reflux
VUR is a developmental anomaly of the vesicoureteric junctions. The ureters are displaced laterally and enter directly into the bladder rather than at an angle, with a shortened or absent intramural course. Severe cases may be associated with renal dysplasia. It is familial, with a 30% to 50% chance of occurring in first-degree relatives. It may also occur with bladder pathology, e.g. a neuropathic bladder or urethral obstruction, or temporarily after a UTI. Its severity varies from reflux into the lower end of an undilated ureter during micturition to the severest form with reflux during bladder filling and voiding, with a distended ureter, renal pelvis, and clubbed calyces (Fig. 19.12). Mild reflux is unlikely to be of significance, but the more severe degrees of VUR may be associated with intrarenal reflux, which is the backflow of urine from the renal pelvis into the papillary collecting ducts and is associated with a particularly high risk of renal scarring if UTIs occur. The incidence of renal defects increases with increasing severity of reflux. There is considerable controversy as to whether renal scarring is a congenital abnormality already present in children with reflux and which predisposes to infection or if children with reflux have normal kidneys at birth which are damaged by UTIs and that preventing UTIs in these children prevents scars. VUR tends to resolve with age, especially lower grades of VUR.
VUR-associated ureteric dilatation is important as:
- Urine returning to the bladder from the ureters after voiding results in incomplete bladder emptying which encourages infection.
- The kidneys may become infected (pyelonephritis) especially if there is intrarenal reflux.
- Bladder voiding pressure is transmitted to the renal papillae which may contribute to renal damage if voiding pressures are high.
Infection may destroy renal tissue, leaving a scar, resulting in a shrunken, poorly functioning segment of kidney (reflux nephropathy). If scarring is bilateral and severe, progressive chronic kidney disease may develop. The risk of hypertension in childhood or early adult life is variously estimated to be up to 10%.
Management
All infants under 3 months of age…
Infants aged over 3 months and children with acute
pyelonephritis/upper UTI…
Children with cystitis/lower UTI…
All infants under 3 months of age with suspicion
of a UTI or if seriously ill should be referred
immediately to hospital. They require
intravenous antibiotic therapy (e.g. co-amoxiclav)
for at least 5–7 days at which point oral
prophylaxis can then be commenced (see
Case History 19.2).
Infants aged over 3 months and children with acute
pyelonephritis/upper UTI (bacteriuria and fever
≥38° C or bacteriuria and loin pain/tenderness
even if fever is <38° C) are usually treated with
oral antibiotics (e.g. trimethoprim for 7 days); or
else intravenous antibiotics, e.g. co-amoxiclav,
are given for 2–4 days followed by oral
antibiotics for a total of 7–10 days. The choice
of antibiotic is adjusted according to sensitivity
on urine culture.
Children with cystitis/lower UTI (dysuria but no
systemic symptoms or signs) can be treated with
oral antibiotics such as trimethoprim or
nitrofurantoin for 3 days.
Medical measures for the prevention of UTI (7)
The aim is to ensure washout of organisms that ascend
into the bladder from the perineum; and to reduce
the presence of aggressive organisms in the stool,
perineum, and under the foreskin:
- high fluid intake to produce a high urine output
- regular voiding
• ensure complete bladder emptying by encouraging
the child to try a second time to empty his bladder
after a minute or two, commonly known as double
voiding, which empties any urine residue or
refluxed urine returning to the bladder
- treatment and/or prevention of constipation
- good perineal hygiene
• Lactobacillus acidophilus, a probiotic to encourage
colonization of the gut by this organism and
reduce the number of pathogenic organisms that
might potentially cause invasive disease
• antibiotic prophylaxis, although this is
controversial. It is often used in those under 2 years
to 3 years of age with a congenital abnormality of
the kidneys or urinary tract or who have had an
upper UTI and those with severe reflux until out of
nappies. Trimethoprim (2 mg/kg at night) is used
most often, but nitrofurantoin or cephalexin may
be given. Broad-spectrum, poorly absorbed
antibiotics such as amoxicillin should be avoided.
Follow-up of children with recurrent UTIs, renal scarring, or reflux
In these children:
• urine should be dipsticked with any nonspecific
illness in case it is caused by a UTI and urine sent
for microscopy and culture if suggestive of UTI
• long-term, low-dose antibiotic prophylaxis can be
used. There is no evidence for when antibiotic
prophylaxis should be stopped
• circumcision in boys may sometimes be
considered as there is evidence that it reduces the
incidence of UTI
• anti-VUR surgery may be indicated if there is
progression of scarring with ongoing VUR but
it has not been shown to improve outcome in
mild VUR
• blood pressure should be checked annually if renal
defects are present
• urinalysis to check for proteinuria which is
indicative of progressive chronic kidney
disease
• regular assessment of renal growth and function
is necessary if there are bilateral defects because
of the risk of progressive chronic kidney
disease.
If there are further symptomatic UTIs in younger
children, investigations may be required to determine
whether there is new scar formation and if so
whether there is ongoing VUR, which may require
prophylactic antibiotic therapy or surgical anti-VUR
treatment.
