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hello and welcome back to the nephrology
curriculum
today we're going to be talking about
urinary tract infection or uti
let's start out with a clinical case the
29 year old woman
comes to the clinic complaining of a
three-day history of burning with
urination
and increased in urinary frequency she
has suprapubic discomfort but no new
vaginal discharge
she's in a monogamous relationship with
her husband and she's been sexually
active with her last sexual encounter
three days ago
her last menstrual period was about one
week prior
on exam she's a febrile her blood
pressure is 118 over 72
pulse is 70. her exam is relatively
remarkable
unremarkable except for mild suprapubic
tenderness to palpation
but no cost of vertebral or cva
tenderness to palpation or percussion
the remainder of the exam is normal her
labs demonstrate on urine analysis a
specific gravity of 1.02
she's got trace blood and leukocyte
estrase positive
and nitrite positive as well so the
question is what is the most likely
cause
of this woman's symptoms let's go
through our case and see if we can find
out
so i think what's important in looking
at the history she's complaining of
dysuria that's burning with urination
frequency and urgency along with
suprapubic discomfort
very suggestive of cystitis
she also had sexual intercourse which
has been associated with utis
in women and on exams she's got mild
suprapubic tenderness without having
actual cva tenderness
suggestive of an isolated cystitis
on urine analysis we can see that having
leukocyte esterase
indicates the presence of white cells
and nitrites indicate the presence of
a gram-negative organism such as e coli
so the question is what is the most
likely cause of this patient symptoms
an uncomplicated urinary tract infection
or to be more specific
cystitis so
what would be most appropriate in terms
of the next step in management of this
particular patient
given her symptoms and given her urine
analysis
i think it's most appropriate to start
empiric therapy so we can use empiric
antibiotic therapy with nitrofurantoin
or trimethoprim sulfamethoxazole so
before we move on i think it's important
to review some terminology and
definitions
let's start with cystitis cystitis is
infection of the bladder
or lower urinary tract pylonephritis is
infection
of the kidney or the upper urinary tract
you'll also hear people talk about
uncomplicated urinary tract infections
this is infection in the urinary tract
where there's no functional or
anatomical abnormality
there's no functional impairment or
concomitant disease that would promote
the uti a complicated uti on the other
hand
is when infection is associated with a
structural or functional abnormality in
the genital urinary tract
or the presence of an underlying disease
that increases risk of acquiring an
infection
you'll also hear the term asymptomatic
bacteria
that means that you have presence of two
separate consecutive clean voided urine
specimens
where there's 10 to the fifth or more
colony forming units per milliliter
of the same bacteria in the absence of
symptoms
okay so let's move on when we think
about who's vulnerable to utis there's
five different demographic populations
that we really need to consider
first urinary tract infection in
children
second women in uncomplicated cystitis
third is women with recurrent cystitis
and then fourth
complicated urinary tract infections and
then finally
asymptomatic bacteria so when we think
about the pathogenesis of uti
in an uncomplicated infection
neuropathogens are present in the rectal
flora
they can enter the bladder by the
urethra
we do see an increase in frequency in
women and that's because of the smaller
distance between the anus and the
urethral meatus
there are also host determinants that
are involved in promoting an
uncomplicated infection
behavioral this includes sexual
intercourse recent
anti-microbial use or sub-optimal
voiding habits so if people
incompletely void their genetic
determinants as well
the innate and adaptive immune response
is going to be important
increased epithelial adherence of some
of the bacteria and a prior history of
recurrent cystitis will also play a role
and finally there are biological
determinants the postmenopausal state or
glycosyria particularly in diabetics
how about in a complicated infection in
terms of pathogenesis the same risk
factors in host determinants from
uncomplicated uti play a role here as
well
but in addition these patients will
often have a structural
or functional abnormality of the
genitourinary tract
they can have obstruction or stasis of
urine outflow
or they might have impaired host defense
this might be a patient who's
immunosuppressed
there's also an association with
diabetes mellitus
people with diabetes are going to be
more prone to things like renal abscess
emphysematous pyelonephritis and
xanthogranulomatous palaeonephritis
which we'll be talking about later
so let's get back to our original
clinical case that we were talking about
remember our 29 year old woman who came
into the clinic complaining of
cystitis her symptoms of disuria
frequency and urgency were very
suggestive of cystitis
she had the right behavioral
determinants she had recently
had intercourse with her husband and on
physical exams she had
signs of cystitis by having suprapubic
tenderness
we knew without having cva tenderness
and fever
that she likely did not have
pyelonephritis or infection of her
kidney
and her urine certainly looked as if
there was
infection with cystitis she had
leukocyte estrase that was positive as
well as nitrates
which were indicative of gram-negative
organisms
so our question is what microbial agent
would most likely be the cause of her
cystitis
the answer is e coli
what if the patient though instead was a
68 year old gentleman
who was hospitalized with a urinary
catheter would e coli still be the
number one cause
we have to think about in that
population nosocomial or hospital
acquired infections
those particular patients may need
coverage for organisms such as
methicillin resistant staphylococcus
aureus or mrsa
so let's review the bacterial etiologies
of urinary tract infections
i want you to pay attention to these two
tables that we have here
the table on the left are gram-negative
organisms associated with utis
the table on the right are gram-positive
organisms
and what i'd like you to note is that
look at that first line
e coli by far and away is the number one
cause
of urinary tract infections and
uncomplicated urinary tract infections
it's to a lesser extent we see e coli
and complicated utis
but one thing that you should note with
complicated utis we tend to see some of
the more
obscure organisms like pseudomonas
abiginosa
and some of the other enterobacter
species as well
for our gram-positive organisms the most
common that we see are going to be
coagulase negative staph
like staph saprophyticus and about five
to twenty percent of uncomplicated utis
less so in our complicated utis but we
have an increase in
enterococcal infections and complicated
utis
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you