Kidney worm in dogs is caused by the giant kidney worm, Dioctophyme renale, a parasite that grows inside a dog’s kidney (usually the right one) and slowly destroys it. Dogs pick it up by eating raw frogs or fish, or by drinking water that’s carrying the larvae. It’s rare. It’s also the stuff of nightmares, because the females can reach about 100 cm long. So if you’ve just seen a video or a headline about it and you’re now side-eyeing your dog, here’s what’s actually worth knowing.
Quick note before we go on: this is general info, not a diagnosis. Blood in your dog’s pee or real tummy pain is a vet visit, today, whatever the cause turns out to be.
Kidney Worm in Dogs at a Glance
- Name: giant kidney worm, Dioctophyme renale
- Where it lives: usually inside the right kidney, sometimes loose in the belly
- How big: females up to about 100 cm (around 3 feet)
- How dogs catch it: eating raw frogs or fish, or drinking water with infected tiny aquatic worms in it
- Main warning sign: blood in the urine
- Treatment: surgery. Worming tablets don’t work on it
What Is the Giant Kidney Worm?
It’s a roundworm, a nematode, and it’s the biggest one known to infect land mammals. That’s according to a 2026 case write-up in Today’s Veterinary Nurse, which goes through a canine case step by step. It’s been found all over the world, in something like 49 mammal species, including dogs, cats and even people now and then.
Vets call the infection dioctophymiasis. Rolls off the tongue, right? You’ll mostly just hear “kidney worm”.
How Do Dogs Get Kidney Worms?
It’s a weird, roundabout life cycle, and your dog is kind of the last stop. Roughly:
- It starts with a grown female sitting in some animal’s kidney. Her eggs leave in the urine, and a lot of them wash into ponds and slow water.
- Little freshwater worms, oligochaetes if you want the fancy word, gobble the eggs. The larvae grow inside them.
- Frogs, fish or turtles eat those little worms. The larvae then encyst in their muscle and sit there.
- A dog eats the raw frog or fish, or drinks water with the infected little worms in it.
- Then it’s a slow trip. Something like 3.5 to 6 months for the larvae to wander through the body and land in a kidney. Nearly always the right one, for some reason.
Which dogs should you actually worry about? Frog hunters. Lake dogs who snack on fish guts. Ditch drinkers. Dogs on raw fish. Kidney worm in dogs that never leave the city sofa? Pretty unlikely.
Kidney Worm Symptoms in Dogs
The tricky thing is that early on there might be nothing to see. The worm chews the kidney up from the inside, bit by bit. Meanwhile the good kidney just quietly does double duty, and it can even grow bigger to keep up.
When signs do show up, vets list things like:
- blood in the urine (the big one, and often the first thing owners spot)
- straining or discomfort when peeing
- belly pain, a hunched back, not wanting to be picked up
- fever
- not eating, weight loss
Sometimes worms end up outside the kidney, floating in the abdomen. Then you might see more general belly trouble. And sometimes nobody knows until a vet stumbles on it during an unrelated surgery, which has happened more than once.
None of these signs are specific to kidney worms, by the way. Blood in the urine is much more often a bladder infection or stones. Which is exactly why you need the vet to look, not Google.
Here’s how kidney worm stacks up against the usual suspects when you see blood in the pee.
| Possible cause | How common | Typical clues | How vets check |
|---|---|---|---|
| Urinary tract infection | Very common | Peeing often, little bits, accidents | Urine test, culture |
| Bladder stones | Common | Straining, blood at the end of the stream | X-ray, ultrasound |
| Injury or trauma | Occasional | Recent fall, hit, rough play | Exam, imaging |
| Giant kidney worm | Rare | Frog or raw fish eater, pond drinker | Urine for eggs, ultrasound |
Real Cases Vets Have Reported
A few stories have done the rounds, and they’re useful because they show how this actually looks in real dogs.
In 2024, Michigan State University’s vet school described Maverick, a nine-month-old black Lab who loved hunting (and eating) frogs. His owner noticed blood in his urine. The regular vet found a lot of kidney worm eggs in his pee and sent him on, and an ultrasound found big worms in the right kidney. Surgeons took that kidney out with two adult worms inside, and MSU reported he went home a few days later, doing great.
Also in 2024, a hound called Twiggy at the Charleston Animal Society in South Carolina was in for a routine spay. The vet saw “a red tube-like object” through the incision. Turned out to be six giant kidney worms, per Veterinary Practice News. No one had a clue beforehand.
And in December 2025, researchers reported what Central America’s first confirmed case, in a French Bulldog in San José, Costa Rica, looked like: fever, vomiting, low platelets and serious kidney damage, with a worm of about 25 cm found in the kidney.
How Vets Diagnose It
Spotting kidney worm in dogs usually starts with a urine sample. Under the microscope, kidney worm eggs have a pretty distinctive look, barrel-shaped with a pitted shell. But a clear sample doesn’t rule it out, because if the only worms in there are male, immature, or sitting outside the kidney, there won’t be any eggs.
That’s why imaging is the real decider. An ultrasound can show the worms coiled up inside the kidney, and CT or MRI can be used too. Blood tests help vets see how well the kidneys are working overall, which matters a lot for what happens next.
Treatment: Why It’s Surgery, Not Tablets
This is the part about kidney worm in dogs that surprises people. No oral dewormer gets rid of a giant kidney worm. The fix is surgery.
Most often that means removing the worms along with the damaged kidney (a nephrectomy), because by the time it’s found the kidney is usually wrecked anyway. Dogs live fine with one healthy kidney. In some cases, when it’s caught early enough, vets can use keyhole-style techniques to pull the worms out and save the kidney, but that depends on the clinic and the dog.
If worms are loose in the abdomen, the surgeon removes those too and cleans up any damage. Recovery from a straightforward surgery is often quick, like Maverick going home in a few days, but every dog’s different.
How to Protect Your Dog
Good news: preventing kidney worm in dogs is mostly common sense.
- Don’t feed raw freshwater fish or frog. Cook it all the way through if it’s on the menu at all.
- Stop the frog hunting if you can. Easier said than done with some dogs, I know.
- Carry water on walks and hikes so they’re not drinking from ponds, ditches and slow streams.
- Watch the pee. Pink, red, brownish? Phone the vet.
- Don’t skip the yearly checkup. A quick urine test there can spot trouble before you do.
Feeding home-cooked? Our guide on whether homemade dog food is safe covers the raw-versus-cooked question in more detail.
Can Humans Get Kidney Worms From Dogs?
Not directly, no. Health officials in the Costa Rica report pointed out the parasite doesn’t pass straight from a dog to a person. People can be accidental hosts, but it’s through eating raw or undercooked freshwater fish, frogs or similar, the same route as dogs. Human cases are very rare.
Still, washing your hands after cleaning up after a sick dog is never a bad idea.
Kidney Worm in Dogs FAQ
Can a dog survive kidney worms?
Yes, plenty do. Out come the worms and the wrecked kidney, and the dog carries on with one good one. What really decides it is the other kidney, so vets run bloods on it before they operate.
Can dewormer kill kidney worms in dogs?
No. Regular worming tablets don’t treat the giant kidney worm. It needs surgery to remove the worms, and usually the affected kidney. Keep up normal worming anyway, it protects against plenty of other parasites.
How long does it take for a dog to show signs?
The larvae take roughly 3.5 to 6 months to reach the kidney and mature. After that it can be months longer before anything shows, and some dogs never show signs at all until the worms turn up on a scan or during surgery.
Which kidney do kidney worms affect?
Almost always the right one. Nobody’s totally sure why, but it’s thought to be down to where the larvae end up as they move through the body near the liver.
Are kidney worms common in dogs?
No, they’re rare. They show up most in dogs that eat raw fish or frogs or drink from natural water a lot. Blood in a dog’s urine is far more likely to be an infection or stones.
Can cats get giant kidney worms too?
They can, it’s been reported in cats as well as dogs and other mammals. Same route, raw fish or frogs. Indoor cats on normal food are at very low risk.
The Bottom Line
Kidney worms make great horror headlines, but for most dogs they’re not something to lose sleep over. Keep your dog off the raw frogs and pond water, keep an eye on their pee, and get any blood checked quickly.
Has your dog ever had a weird urinary scare? Tell us in the comments. And if it’s tummy trouble you’re dealing with instead, our guide on why your dog is throwing up explains which colours and signs mean an emergency.
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