Skip to main content

The causes of thin stools in dogs can be various, but only a veterinary examination may reveal the underlying cause and get to the bottom of the problem. For sure, persistent thin stools are a sign of some ongoing issue versus a one-time thin stool ordeal.  Veterinarian Dr. Ivana shares some possible causes for thin stools in dogs.

The Importance of Inspecting Dog Stools

Being a responsible dog parent means dealing with disgusting situations on a daily basis. Checking the dog’s poop is one of those disgusting moments. Do not get me wrong, you are not a dog poop police and you do not have to check every single poop your dog makes, but checking every other day is highly advisable.

Having a pencil-thin poop is a problem dog owners frequently report. This sign, observed on its own does not mean much. First, the owner must determine whether the pencil-thin poop is a one-time occurrence or a frequently observed issue.

 Infrequent passing of skinny and long stools by dogs that are otherwise healthy is generally nothing to worry about. However, if the pencil-thin stools happen on a daily basis, and the dog is exhibiting additional abnormal signs and symptoms, it is highly advisable to schedule an appointment with your trusted vet. 

Early diagnosis and determination of the underlying cause increase the chances of efficient treatment and prevention of long-term consequences.

So if your dog produces a pencil-thin poop, observe it closely in the next few days. If the pencil-thin stools become a habit and/or if there are accompanying abnormalities – it is time to take the problem to the next level and call the vet. 

Normal Poop in Dogs

Once again, you are not poop police, but you do want to know how your dog’s poop looks like under normal circumstances. You need to know how normal poop looks so you can differentiate between normal and abnormal.

Normal, ideal dog poop should be shaped like a log (cylindrical), solid brown in color and easy to pick up (should not leave residues on the ground).

The log-like shape indicates the large intestines are in good shape.

The solid brown color indicates the dog is eating a healthy dog diet.

The easy-to-pick consistency indicates there are no motility and water retention issues on an intestinal level.

Therefore, producing pencil-thin stools is definitely not normal. This type of stool is often described as flat, thin, narrow and even ribbon-like. 

Why is My Dog's Poop Thin?

There are several possible underlying issues that may lead to pencil-thin stools. Some of them are frequent and others rarely seen. In this article we will investigate and review the most common underlying causes.

A Mass Present in the Rectum

If there is a mass in the rectum, the mass will apply some degree of pressure on the intestinal wall, thus changing its normal shape. When the shape of the intestine is altered, it is only logical that the poop’s shape will be altered as well.

Scroll to Continue

Discover More


What is Fear Generalization in Dogs?

Fear generalization in dogs is the process of a new stimulus or situation evoking fear because it shares similar characteristics to a another fear-eliciting stimulus or situation. This may sound more complicated that it is, so let's take a look at some examples of fear generalization in dogs.

What causes blood in a dog's stool?

Help, My Dog Hasn't Pooped in 3 Days!

If your dog hasn't pooped in 3 days, you may be worried about your dog and wondering what you can do about this problem. Dogs don't get constipated as often as humans, and therefore a lock of poop can make owners worry quickly. Veterinarian Dr. Ivana shares her thoughts.


Do Dogs Act Out of Spite? Here's What Science Says

Whether dogs act out of spite is an important question considering that spiteful behavior can put a big dent in your relationship with your dog. If your dog appears to pee, poop or destroy things out of spite, this is article is ultimately for you.

When a dog presents with pencil-thin poops in its history, the vet will start by performing a full physical examination. Then, the vet will perform a rectal exam (insert its finger inside the dog’s rectum while wearing special gloves). The goal is to find any abnormalities in the rectal area. 

For example, if there is an obstructive or compressive mass, the rectal exam will help the vet determine its size and locations. Both the size and the location are important and influence the future course of actions.

Dogs are prone to developing rectal masses. Some of them are benign and some are malignant. Frequently reported benign masses include perianal adenomas, anal cysts and polyps. Frequently reported malignant masses include several different types of rectal cancers – with the rectal adenocarcinoma being the most common.

 Sadly, the rectal exam only confirms the presence of a mass. Determining whether it is malignant or benign requires further testing such as biopsy.

The Dog's Prostate is Enlarged

As male dogs get older, the prostate gland naturally increases in size. More often than not, the prostate reaches its maximum size sometime between six and ten years of age. 

When the prostate enlarges it starts applying pressure on the rectal wall. If the enlargement is moderate, the applied pressure will be moderate too. However, in cases of significant enlargements, the rectal wall will be too compressed to produce normally shaped stools. In such cases, pencil-thin stools will start appearing.

The natural prostate enlargement does not usually affect the function of the urinary tract, although if pronounced, it occasionally produces constriction of the top of the urethra causing dribbling of urine and difficulty urinating.

This may also occur if the prostate is enlarged due to the presence of a cancerous tumor. Additionally, the prostate enlargement may be caused by a bacterial infection of the prostate.

Once again, the vet will perform a digital rectal exam. If necessary, based on the findings, the vet may require some additional diagnostic imaging and procedures. If the enlargement is caused by normal age-related changes there is not much the vet can do.

 If the dog's prostate enlargement is due to cancerous changes, a surgical removal of the gland and tumor are advisable. If the enlargement is due to infection, the vet will prescribe antibiotics.

Other Causes of Pencil-Thin Poop

Other, not so frequently reported causes of pencil-thin poop include the following:

  • Masses in other portions of the lower intestines (such as colon) and in anal glands area
  • Lower intestine obstructions caused by foreign bodies
  • Anal sac tumors, medically termed as anal sac apocrine adenocarcinomas, which tend to spread to the local lymph nodes
  • Enlarged lumbar lymph nodes

The Bottom Line 

From the above listed it can be concluded that dogs can produce pencil-thin stools due to several different reasons. Some reasons are temporary and harmless while others are persistent and dangerous.

 If your dog has pencil-thin poop, have it examined by a vet. Hopefully, everything will be alright and you can put your mind at ease. On the other hand, if there is something wrong, the vet will be able to make a treatment strategy in a timely manner. 

Related Articles