Wednesday, May 21, 2014

Things I learned about ectopic ureters in dogs and cats

Louis doesn't have ectopic ureters. But he is a handsome devil.
Here at SAT we have something of a soft spot for the urinary tract. It is deceptively simple in design. Urine travels from the upper urinary tract (the kidneys and ureters) into the lower urinary tract (the bladder and urethra). This one-way flow [everytime I type that word I think about Shaggy singing "Hey sexy lady, I like your flow" and can't help wondering if he too is enamoured with the design of the urinary tract?] helps get rid of waste and ensure bacteria is flushed out (imagine E.coli and other pathogens arming itself with crampons and climbing up the distal urethra like a determined mountaineer, only to be washed out by a waterfall of healthy urine).

But it doesn’t always happen that way.

Last week we attended a fascinating talk by University of Sydney surgeon Mark Newman about ectopic ureters. This is a congenital abnormality of the distal ureter – normally they enter the bladder in a “J” curve” (except in a dog or cat, just turn the J on its side), and enter at an angle such that as the bladder fills it closes the ureters and prevents reflux (backflow).

(Interesting fact – the internal diameter of the dog ureters is around 2-2.5mm in diameter, and in cats it’s just 0.4mm).

Instead of J-curving, extramural ectopic ureters course right on past the bladder and empty into the urethra. This is the most common type of ectopic ureter found in cats (you can see some diagrams here).

In dogs, the most common form is intramural ectopic ureters – they enter the bladder wall but can course along through the wall with the opening more distal (or closer to the trigone of the bladder) than usual. In fact sometimes they can open into the urethra or seminal vesicles in males, while in females they can open into the urethra, vagina or vestibule.

Females are more commonly affected than males, and some breeds are more likely to be affected than others (Skye terriers, Labradors, huskies, bulldogs, Newfoundlands, West Highland White Terriers, fox terriers and poodles.

Animals with intramural ectopic ureters often have abnormalities of the trigone of the bladder or the internal urethral sphincter as well.

So what does this mean clinically? Affected animals often present with incontinence – it can be continual urine leakage, or it can be intermittent. But some can void (pee) normally. These animals are prone to urinary tract infections and development of uroliths (bladder stones). That’s more than a mere inconvenience – patients can develop multi-drug resistant bacterial infections and succumb to these before there’s a chance to repair the underlying defect.

Queue for the loo: whilst neither Phil or Bosca have ectopic ureters, affected dogs can still appear to void normally.
The other problem is that often these animals have concurrent abnormalities such as urethral sphincter mechanism incompetence, a hypoplastic bladder, renal aplasia or hypoplasia and so forth. Thus just fixing the ectopic ureters doesn’t eliminate the incontinence or predisposition to infection.

It doesn’t end there. Affected animals can acquire secondary conditions – hydroureter, hydronephrosis or pyelonephritis (makes sense right – if urine can reflux or travel retrograde from the lower to the upper urinary tract, problems will occur upstream). This can lead to irreversible damage to the ureters or kidneys.

Ectopic ureters can be tricky to diagnose but these days contrast CT and cystourethroscopy (essentially passing a scope into the urethra and bladder) are the methods of choice, though work up should include urine culture and sensitivity (usually more than once) and abdominal ultrasound.

Surgical treatment involves re-implantation of the ureters into the bladder wall. In vetland, this is typically a specialist procedure and with good reason. It takes a delicate, experienced surgeon to maintain the patency of tiny dog and cat ureters (it can be performed in general practice, although less commonly now that specialists abound). 

Dr Newman cited studies reporting surgical cure rates of 22-67% - that’s a big range but depends on the type of ectopic ureter, presence of concurrent conditions and complications. Obviously a very good argument for early detection.

If you've read this far down here is a pic taken on Saturday night. I'd just been nerding it up at a meeting at the airport, of all places, because it was my only opportunity to pin-down the co-author of a paper who lives interstate. I dropped into a housewarming party afterwards and blow me down, Louis the chihuaua was wearing practically the SAME JUMPER. 

Nerdsville, Population 2?

Argyle is SOOOOO hot this season. I swear there was no collusion about outfits.