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The Physiology Behind Puppy Accidents

Puppy accidents: no matter what your breeder and that promising book about potty training your dog in under a week have told you, they will occur in your home sooner than later. Potty training puppies as with potty training children, takes patience and time, so unless you won a stuffed puppy at some carnival game, those bladder and bowels will empty no matter how assiduously you stick to a puppy potty training program. As with many things in life, if it sounds too good to be true, it likely isn't true at all, and new puppy owners often learn this the hard (and often frustrating) way.

pupy accidents

Housebroken Puppies Ready for New Homes!

Yes, it's true that many breeders implement some preliminary potty training basics when the puppies are in their care, but don't expect to have all the homework done when your puppy comes home.

Puppies have a hard time generalizing what they have learned in the breeder's home.

Just because a puppy was housetrained in the breeder's place doesn't necessarily mean he'll be able to transfer the skill into a totally new context without help, explains Nicholas Dodman, in the book Puppy's First Steps.

It would be more realistic if certain breeders would explain that their puppies were introduced to potty training basics and that the new puppy owners must continue the training from day one, and that yes, they should expect some accidents along the way!

Potty Train Your Puppy in Under One Week!

Also, misleading is a new trend of books, e-books and videos making promising statements such as "How to potty-train a puppy under 7 days." Sure, this is an effective sales pitch, who wouldn't dream of a puppy who learned how to potty outside in just under a week?

So new puppy owners purchase the book, try to adhere to the program and then get upset when they notice it isn't working its magic. We can almost hear them say something in the terms of "What? It's day 8 and the puppy had an accident?" Turns out, titles like these will only lead to frustration.

Use this Formula for Success!

puppy accidents

Another common misleading statement that can lead to problems is suggesting the "puppy month's plus one rule." This is something we hear trainers often repeat "ad nauseam" to their clients.

The rule dictates the frequency a puppy should be taken out by calculating the puppy's age in months and then adding one. So if say the puppy was 3 months, you would add 1 and therefore the puppy should be taken out every four hours.

This formula only leads to frustrated puppy owners when they discover that their puppies are unable to make it for the whole four hours. Unfortunately, potty training is not math, and equations as such will not work their magic.

For instance, if the puppy had some rough play time, he'll likely guzzle down a lot of water, and then after several minutes, the Niagara falls will open, leading to "unexpected messes." Also, young pups need to be taken out after they wake up from a nap or during/after playing. 

Last time we checked, puppy bladders didn't have an incorporated counter, so it's not like the puppy's bladder is counting down the minutes with the predictability of a kitchen timer.

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Aunt Mary's Training Was Easy as Pie!

Last but not least, be wary of aunt Mary who says her puppy was so smart she was potty trained in under 10 days.

She may not truly recall how long it really took (things from the past often seem far easier than they really were) or she may have missed some piddles.

It's not uncommon to hear some people say "Oh, our Betsy was potty trained in what, 2 weeks?" and then the daughter remarks: " but mommy, did you forget all those accidents we found later when we moved the couch?"

It's quite easy to miss little sprinkles from pint-sized dogs like Chihuahuas and toy breeds, versus the Lake Michigan-like puddles of a mastiff or great dane!

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The Physiology Behind Puppy Accidents

Potty training puppies is not something that will happen overnight. Puppy owners need to be patient, understanding and learn effective methods to help their puppies succeed.

Understanding better the physiology behind puppy accidents, can help new puppy owners understand why it's so unrealistic to expect puppies to be potty trained in under a week and why certain mathematical formulas should be restricted to fixed variables that are constant versus things that are unpredictable and so variable such as puppy bladders and bowels!

puppy accidents

No Sphincter Control

In dogs, and any living being equipped with a bladder, urine is constantly accumulating. At a certain point, when the bladder is full and reaches its threshold, special stretch receptors in the bladder wall activate. This triggers the contraction of muscles of the bladder wall (detrusor muscles) which send to the dog's brain the sensation of having to urinate.

When dogs acknowledge this sensation, they may go to the door and bark to ask their owners to be let out. Control of the muscular sphincter found around the neck of the bladder allows them to hold the urine.

Then, once out, they can can relax the sphincter and urinate.

In young puppies, when the bladder wall contractions take place, they are unable to control their muscles of their sphincter so emptying of the bladder occurs at this point. So the moment they realize they need to go, their bladders are already emptying.

At what age do puppies attain sufficient muscle tone to allow them to control things a bit more? Stanley Coren, in his book "Born to Bark: My Adventures with an Irrepressible and Unforgettable Dog" claims that full control isn't reached until the puppy is 5 to 6 months.

So let's do some real math here. If most puppies are 8 weeks when they go to their new homes, how can they be already house trained? And how can they be possibly be house trained in under one week?

puppy food

Food equals poop!

The Gastrocolic Reflex

One main reason why the month plus one rule is faulty is the way a pup's gastrocolic reflex works. Right after a meal, a dog's gastrocolic reflex will increase the motility of the colon.

This causes the rectum to fill up which stimulates the smooth muscle of the internal anal sphincter and the striated muscle of the external anal sphincter, explains Katherine A. Houpt in the book "Domestic Animal Behavior for Veterinarians and Animal Scientists."

This means that shortly after eating, most puppies will have a need to defecate, which can set a puppy (whose owner adheres to the puppy month plus one rule) to failure.

You can almost hear frustrated new puppy owners make statements as such: "I just sent my puppy out at 5PM, my puppy had the opportunity to defecate, but he didn't. I then served him dinner when we came back in, and just an hour later, he had an accident on the carpet! Arrgh.. wasn't he supposed to be able to hold it for 4 hours?"

Being aware of the gastrocolic reflex can help new puppy owners attain success because they'll send their pups out after their pup's schedule meal times, which is when they're more likely to defecate. Other times pups should be taken out is after a nap, Soon, puppies will learn to associate going outside with the act of eliminating, a win-win situation for all!

Did you know? The veterinary term for the excretion of urine is "micturition."

idea tip


  • Katherine A. Houpt, Domestic Animal Behavior for Veterinarians and Animal Scientists
  • Thomas Colville DVM MSc, Joanna M. Bassert, VMD Clinical Anatomy & Physiology for Veterinary Technicians, Mosby 2002
  • Nicholas Dodman, Puppy's First Steps, Houghton Mifflin Company, Boston New York, 2007

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