In our discussions of urinary tract infections we turn now to pyelonephritis
and perinephric abscess.
So pyelonephritis would be a renal parenchymal infection
producing a clinical syndrome characterized by fever,
flank pain, and tenderness,
usually along with symptoms of urgency, dysuria, frequency,
the same symptoms of a lower urinary tract infection.
A perinephric abscess is an uncommon complication of urinary tract infection,
usually as a result of obstruction.
Occasionally, it's a complication of bacteremia
from a remote focus of infection.
And I want you to hold that thought until we get to staphylococcus.
Women are affected by pyelonephritis and perinephric abscess
far more than men.
200,000 adults are admitted for acute renal infection every year.
And as far as the epidemiology goes,
the risk factors for women are similar to the risk factors for acute cystitis.
And those are sexual intercourse,
a history of previous urinary tract infections,
the post-menopausal state
and that's because post menopausal women have prevalence
of carrying organisms in the urinary tract at about the level of 10%,
pregnancy, which is a normal type of urinary obstruction
and then other types of anatomic or functional abnormalities of the urinary tract
Among men, urinary tract infections are often quite complicated
and it's frequently associated with urologic abnormalities.
Men who have sex with men and anal insertive intercourse
are predisposed to kidney infections.
And then either gender are predisposed by urinary tract instrumentation
by having diabetes or by being immunosuppressed.
Once again, E. coli is responsible for most of this infection -- 80%.
But interestingly, we have many different strains of E.coli in our colonic flora,
yet only a few serogroups caused most of the infections,
and they are referred to as uropathogenic E. coli.
So what's different about them?
They possess virulence factors
that will enchance colonization
of not only the lower urinary tract
but they are able to invade the upper urinary tract.
Most other fecal E. coli do not have these virulence factors.
One of the most important are p-fimbriae.
This is the fringe around the organisms which attach to galactose
alpha (1-4) galactose-containing receptors on urothelial cells.
These sugars coat uroepithelial cells
and these are referred to also as mannose-resistant.
In other words, they may bind to Tamm-Horsfall or uromodulin,
but they're still able to attack the mucosa of the urinary tract.
Furthermore, this E. coli have cytotoxins like alpha-hemolysin
which can actually destroy or impair the function of urothelial cells.
And, of course, that's going to enhance the virulence of the organism
for not only cystitis but pyelonephritis
and extraintestinal manifestations of urinary tract infections
and can lead to hemolytic anemia as the name implies.
These organisms also have the ability to leech iron out of the sytem
by a protein called aerobactin which leeches away iron
and microorganisms need iron to reproduce.
There are some other causative organisms among the 20% that are not E. coli
Resistant E. coli,
Enterococci, especially in elderly men
and Group B streptococcus occasionally
especially in diabetics or immuno-compromised patients.