Cystitis: Definition, Epidemiology & Etiology

00:00 In our discussion of urinary tract infections, we turn to cystitis.

00:06 To define it we'd call it a clinical syndrome characterized by dysuria, frequency, urgency, and occasionally suprapubic tenderness caused by inflammation and infection of the bladder.

00:21 It's a disease that's much more common in women than men.

00:25 In fact, women have an incidence of asymptomatic bacteriuria of around 1 to 3%.

00:35 Up to 60% of women have had at least one episode of cystitis during their lifetime.

00:43 And 10% have it once a year.

00:46 The peak incidence is among young, sexually active women, 18-24 years of age and 2-5% have recurrent problems with cystitis.

01:00 Men, on the other hand, have a very low prevalence of cystitis -- less than 0.1 %.

01:09 And when a man has cystitis, we have to look for a complication because there's usually some kind of obstructive uropathy duplicating collecting system, some kind anatomical explanation for cystitis and we have to work them up for urologic abnormalities.

01:30 The lack of circumcision predisposes some men to cystitis and among men who have sex with men anal insertive sexual intercourse is a predisposing factor.

01:47 95% of the time, the cause is a single species of bacterium, so polymicrobial infections are unusual.

01:56 The most common bug is, as you might expect, Escherichia coli.

02:02 Now, we have lots of E. coli in our intestine -- lots of them.

02:07 But only about 20% of this E. coli are what we would call uropathogenic E. coli.

02:16 So these E. coli are different.

02:19 They possess virulence factors that the other E. coli do not have that allow them to colonize and invade the urinary tract.

02:28 Most of them have what we call Type 1 fimbriae -- this fringe that surrounds the surface.

02:34 And this group of fimbria can attach to mannose residues which we find commonly on the glycoproteins on urothelium.

02:44 And so they can attach to urothelium and they're not washed away in the urinary stream.

02:51 These are called mannose-sensitive E. coli, and the other E. coli's don't have them.

03:00 Furthermore, the normal urinary tract has a defense mechanism.

03:07 There is a glycoprotein present in trace amounts in urine.

03:12 It's called uromodulin.

03:14 The old name is Tamm-Horsfall protein, and this uromodulin has mannose residues on it.

03:23 So these mannose-sensitive E. coli will bind to the uromodulin and then be washed away in the urine stream.

03:33 So they never get a chance to attach because of the uromodulin that's present normally in urine.

03:42 Now recurrent and complicated cystitis leads to an increased incidence of more resistant organisms, that we don't usually find causing cystitis.

03:55 That would be, for example, Proteus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter species, and even some resistant E. coli, and among the Gram-positives -- Enterococcus.