How to Express Anal Glands in Dogs: A Science-Based Guide
Learn the science behind canine anal glands, when to express them, how the process works, and what research reveals about this often-misunderstood anatomy.
Quick Answer: Expressing anal glands in dogs means manually emptying the two small sacs located at the 4 o'clock and 8 o'clock positions around the anus. Most dogs empty these glands naturally during defecation, but some require manual assistance when the glands become impacted. The Merck Veterinary Manual notes that anal sac disease is among the most common perianal disorders in dogs. You can have this done by a veterinarian or trained groomer, typically costing $15–$50 per session, or learn to do it at home with proper technique. Always consult your veterinarian before attempting home expression, especially if your dog shows signs of pain, swelling, or discharge.
The Anatomy and Physiology of Canine Anal Glands
The term "express anal glands" (often searched as "express analysis glands dog" due to autocorrect) refers to the manual drainage of the anal sacs — two small, pea-to-grape-sized pouches embedded in the internal and external anal sphincter muscles. Each sac is lined with sebaceous and apocrine glands that produce a pungent, oily secretion ranging in color from pale yellow to brownish-gray.
According to the Merck Veterinary Manual, these sacs normally empty during defecation when the firm stool presses against them as it passes through the anal canal. The resulting secretion is deposited onto the feces, serving as a chemical signature unique to each individual dog.
The Physiological Mechanism
The anal sacs connect to the exterior through small ducts that open at the mucocutaneous junction of the anus. During normal defecation, the contraction of the external anal sphincter and the physical pressure of formed stool compress the sacs, forcing secretion through these ducts. The secretion contains a complex mixture of:
- Volatile fatty acids — including acetic, propionic, and butyric acids
- Trimethylamine — responsible for the characteristic fishy odor
- Squalene and cholesterol — lipid components from sebaceous glands
- Individual-specific proteins — creating a unique scent profile
When stool is consistently soft or the ducts become narrowed due to inflammation, the sacs fail to empty properly, leading to impaction, infection, or abscess formation.
Evolutionary Basis: Why Dogs Have Anal Glands
An Ancestral Communication System
In wild canids — wolves, coyotes, and foxes — anal sac secretions serve as a sophisticated chemical communication system. When a wolf defecates on a territorial boundary, the anal sac secretion deposited on the feces conveys information about identity, reproductive status, social rank, and individual health to any conspecific that investigates the marking.
Research published in the AVMA's canine behavior resources confirms that scent-marking behaviors in domestic dogs are direct evolutionary holdovers from these wild ancestors. The "scooting" behavior some dogs display — dragging their hindquarters along the ground — may be a vestigial scent-marking behavior, though it more commonly signals anal sac discomfort in modern dogs.
Among wild canids, the anal sac also serves a defensive function similar to that of skunks (though far less potent). When startled or threatened, some wild canids can involuntarily release the entire contents of their anal sacs as a deterrent. Domestic dogs have largely lost this reflex, though some fearful dogs may express their glands during extreme stress — a phenomenon commonly observed in veterinary clinics.
How Is Anal Gland Expression Different From Humans?
Humans possess anal crypts (small recesses in the anal canal) but lack true anal sacs entirely. This anatomical difference reflects divergent evolutionary pressures: primates rely heavily on visual and vocal communication rather than olfactory signaling, making scent-gland-based identity markers unnecessary.
Dogs, by contrast, have approximately 300 million olfactory receptors (compared to roughly 6 million in humans), and their vomeronasal organ (Jacobson's organ) is specifically adapted to process the complex pheromonal information contained in anal sac secretions. When dogs greet each other by sniffing the rear end, they are gathering detailed chemical data about the other individual — a behavior that has no human equivalent in scope or function.
| Feature | Dogs | Humans |
|---|---|---|
| Anal sacs present | Yes — bilateral, 4 & 8 o'clock positions | No |
| Scent-marking function | Primary chemical communication | Not applicable |
| Secretion composition | Volatile fatty acids, trimethylamine, squalene | N/A |
| Natural emptying mechanism | Pressure during defecation | N/A |
| Common disorders | Impaction, sacculitis, abscess, adenocarcinoma | Hemorrhoids, fissures, cryptitis |
When and Why Anal Glands Need Manual Expression
Not every dog requires manual anal gland expression. Many dogs — particularly those eating high-fiber diets that produce firm stools — empty their anal sacs naturally with every bowel movement. However, the American Kennel Club notes that certain dogs are predisposed to anal sac issues and may need regular professional expression.
Signs Your Dog's Anal Glands Need Attention
- Scooting — dragging the hindquarters along carpet or grass
- Excessive licking — focused on the perianal area or base of the tail
- Foul, fishy odor — noticeable even from a distance, especially when the dog sits on furniture
- Difficulty defecating — straining or producing small, ribbon-like stools
- Swelling — visible lumps at the 4 or 8 o'clock positions around the anus
- Blood or pus — in the stool or on bedding where the dog has been sitting
- Pain response — yelping or snapping when the hindquarters are touched
When to Call the Vet Immediately
If you notice a ruptured abscess (open wound near the anus with bloody or purulent discharge), fever, lethargy combined with perianal pain, or your dog is unable to defecate at all, seek veterinary care within 24 hours. Anal sac abscesses can tunnel into surrounding tissue and require surgical drainage and antibiotics. Emergency visits typically cost $150–$400, while planned expression runs $15–$50 at a grooming salon or $30–$75 at a veterinary clinic.
Breed Variations and Risk Factors
While any dog can develop anal sac problems, research and clinical observation have identified clear patterns in predisposition:
| Category | Higher Risk | Lower Risk |
|---|---|---|
| Size | Small & toy breeds (under 25 lb / 11 kg) | Large & giant breeds (over 60 lb / 27 kg) |
| Breed examples | Chihuahuas, Toy Poodles, Cocker Spaniels, Dachshunds, Beagles | German Shepherds, Labrador Retrievers, Great Danes |
| Body condition | Overweight dogs (BCS 6-9/9) | Lean, fit dogs (BCS 4-5/9) |
| Diet type | Low-fiber, highly processed diets producing soft stool | High-fiber diets producing firm, well-formed stool |
| Allergies | Dogs with chronic atopic dermatitis or food allergies | Dogs without allergic skin disease |
| Chronic GI issues | Dogs with chronic diarrhea or loose stools | Dogs with normal, consistent stool quality |
The link between small breeds and anal sac disease is partly anatomical: smaller dogs have narrower anal sac ducts that are more easily obstructed by thickened secretions or inflammatory swelling. Obesity compounds the problem because excess perianal fat reduces the natural compression of the sacs during defecation.
Common Misconceptions Debunked
| Myth | Fact |
|---|---|
| "Every dog needs monthly anal gland expression." | Most dogs never need manual expression. Routine expression of healthy glands can actually weaken the natural emptying mechanism and create dependency. |
| "Scooting always means full anal glands." | Scooting can also indicate intestinal parasites (especially tapeworms), perianal fistulas, allergies, or skin infections. A veterinary exam is needed to determine the cause. |
| "Anal gland expression is extremely painful for all dogs." | When performed correctly on non-inflamed glands, expression causes brief discomfort at most. However, impacted or infected glands are genuinely painful and may require sedation for treatment. |
| "Adding pumpkin to food eliminates the need for expression." | Fiber supplementation (1–4 tablespoons of canned pumpkin depending on dog size) can help firm stools and promote natural emptying, but it won't resolve already-impacted glands or anatomical duct problems. |
| "Only groomers can express anal glands." | Owners can learn external expression at home with veterinary guidance. Internal expression (inserting a gloved finger into the rectum) should be performed by trained professionals due to the risk of tissue damage. |
Practical Implications: What Owners Need to Know
Day-to-Day Management Strategies
- Prioritize stool quality. Aim for a Body Condition Score-appropriate diet that produces firm, well-formed stools (score 2–3 on the Purina Fecal Scoring System). If your dog's stool is consistently soft, discuss fiber supplementation with your vet — common options include canned pumpkin (not pie filling), psyllium husk at 1/4 teaspoon per 10 lb (4.5 kg) body weight, or prescription high-fiber diets like Royal Canin Gastrointestinal High Fibre or Hill's Prescription Diet w/d.
- Monitor for early warning signs. Check your dog's perianal area weekly during grooming. Note any asymmetry, swelling, or unusual odor. Catching impaction early (before it progresses to sacculitis or abscess) means a $30–$75 vet visit instead of a $300–$800 surgical procedure.
- Maintain a healthy weight. For a 20 lb (9 kg) dog, even 2 extra pounds significantly increases perianal fat deposits. Use the WSAVA Body Condition Score chart to assess your dog monthly.
- Address underlying allergies. Dogs with chronic atopic dermatitis have higher rates of anal sacculitis because perianal inflammation narrows the duct openings. Effective allergy management (Apoquel, Cytopoint, or elimination diet trials) often reduces anal gland problems as a secondary benefit.
- Establish a professional relationship. If your dog needs regular expression, find a groomer or veterinary technician who uses gentle technique and keeps records of secretion consistency, color, and volume — this information helps your vet track developing problems.
External vs. Internal Expression: A Technical Distinction
External expression involves placing a tissue or cloth over the anal area and applying gentle, firm pressure from outside the body, milking the sacs toward the duct openings. This method is less invasive, suitable for routine maintenance, and can be learned by owners.
Internal expression requires a gloved, lubricated index finger inserted into the rectum while the thumb applies external pressure. This technique allows more complete emptying and is necessary for thick, pasty impactions that cannot be expressed externally. It should only be performed by veterinarians, veterinary technicians, or experienced groomers — improper technique can rupture the sac internally or damage the rectal mucosa.
When Anal Gland Behavior Signals a Deeper Problem
Recurrent anal sac disease (more than 3–4 episodes per year) warrants investigation beyond simple expression. Underlying conditions that can drive chronic anal sac problems include:
- Hypothyroidism — reduces skin and gland turnover, thickening secretions. A full thyroid panel (T4, free T4, TSH) costs $80–$200.
- Chronic gastrointestinal disease — IBD, exocrine pancreatic insufficiency (EPI), or food-responsive enteropathy causing persistent soft stools.
- Perianal fistulas — an immune-mediated condition especially common in German Shepherds, requiring immunosuppressive therapy (cyclosporine or tacrolimus).
- Anal sac adenocarcinoma — a malignant tumor more common in older dogs (especially Spaniels and Dachshunds). Presents as a firm, unilateral swelling. This cancer often causes paraneoplastic hypercalcemia (elevated blood calcium), detectable on a $50–$120 chemistry panel.
In cases of chronic, refractory anal sac disease, surgical removal of both anal sacs (anal sacculectomy) may be recommended. This procedure typically costs $800–$2,500 depending on complexity and geographic region, and carries a small risk of post-operative fecal incontinence (reported in approximately 3–5% of cases according to surgical outcome studies).
Related Canine Behaviors and Scent Communication
Understanding anal glands connects to several other aspects of canine behavior and physiology:
- Urine marking — another scent-depositing behavior driven by similar evolutionary pressures; intact males lift legs to place urine at nose-height for other dogs.
- Rear-end sniffing during greetings — dogs gather anal sac secretion data to assess identity, sex, and reproductive status. This is normal, functional behavior, not "bad manners."
- Raising the tail when meeting other dogs — elevating the tail exposes the anal sac openings, facilitating scent dispersal. A tucked tail may indicate a dog attempting to suppress scent signaling (submissive or fearful state).
- Rolling in strong-smelling substances — while not directly related to anal sacs, this behavior may function as scent camouflage or scent enhancement, complementing the dog's own chemical signature.
Frequently Asked Questions
Why do dogs need their anal glands expressed?
Dogs need expression only when the glands fail to empty naturally during defecation. This typically occurs when stools are too soft to provide adequate pressure, when the duct openings are narrowed by inflammation, or when the secretions have thickened beyond what can pass through the ducts. Not all dogs ever require manual expression.
Can dogs express their own anal glands?
Yes — most dogs express their anal glands naturally every time they produce a firm stool. Some dogs can also involuntarily express their glands during moments of extreme fear or excitement (the sudden "fishy smell" you might notice at the vet clinic). However, dogs cannot voluntarily choose to express their glands on command the way skunks can.
How do dogs process scent information from anal glands?
When a dog sniffs another dog's anal region, scent molecules from the anal sac secretions travel to the vomeronasal organ (Jacobson's organ) located in the roof of the mouth. This organ has direct neural connections to the amygdala and hypothalamus — brain regions governing emotion, social behavior, and hormonal responses. The dog processes information about the other individual's identity, sex, hormonal status, and potentially diet and health state.
What does it mean when my dog scoots on the carpet?
Scooting most commonly indicates anal sac discomfort — the dog is trying to relieve pressure or irritation by applying friction to the area. However, scooting can also signal tapeworm segments irritating the perianal skin, allergic dermatitis, a foreign body (such as a grass awn) lodged near the anus, or perianal tumors. A veterinary examination is the only way to determine the exact cause.
Is it normal for my dog's anal glands to leak?
Occasional small amounts of anal sac secretion on bedding or furniture can be normal, particularly in small breeds or dogs with slightly relaxed sphincter tone. However, frequent leaking, large volumes of discharge, or discharge that contains blood or pus is not normal and warrants a veterinary evaluation.
How often should anal glands be expressed?
There is no universal schedule. Some dogs never need expression; others require it every 4–8 weeks. The correct frequency depends on your dog's diet, breed, body condition, and individual anatomy. Over-expressing healthy glands can stretch the sacs and weaken natural emptying, so only express when clinical signs indicate a need.
Tom Renshaw
All our authors care for dogs every day — read more of their work on the authors page.
