Poisoning and kidney damage in dogs – dangerous substances

Overview

A toxin can damage the kidneys before clear signs appear

Acute kidney injury means sudden kidney tissue damage, reduced kidney function or both. It can range from mild injury to kidney failure. Reduced blood filtration by the kidneys causes uraemic waste products to accumulate in the body. Fluid, salt and acid balance may also be disrupted.

Kidney injury can exist before blood creatinine rises clearly. Urine output may initially increase or later become very low. Continuing to urinate therefore does not exclude damage.

Ethylene glycol-induced acute kidney injury has also been confirmed in canine post-mortem examinations reported from northern Europe.

Causes

Ethylene glycol in engine coolant

Ethylene glycol is used in car engine coolants. Its sweet taste can attract an animal to drink it. Breakdown products formed in the body cause acidosis and kidney tubular cell damage. Oxalate combines with calcium to form crystals in kidney tubules.

Grapes and raisins

Grapes, raisins and currants can cause kidney injury in dogs. Tartaric acid is considered one likely toxic compound. Tartaric acid content varies between fruits. Kidney failure has also been reported after eating tamarind.

Medicines and excess vitamin D

NSAID toxicity often affects the gastrointestinal tract and kidneys. Ibuprofen can cause stomach ulcers or intestinal bleeding as well as kidney injury in dogs. Naproxen is also highly toxic to dogs.

Vitamin D occurs in vitamin products and some rodenticides. Excess cholecalciferol, or vitamin D, disrupts calcium and phosphorus balance. Persistently high concentrations can cause mineralisation of soft tissue in the kidneys. This can cause kidney injury or failure.

Some medicines used therapeutically, such as aminoglycoside antibiotics, can also harm the kidneys. Your vet assesses medication risk in light of your dog's diseases.

Risk factors

Access to substances affects exposure risk. Incorrect coolant storage, use and disposal contribute to ethylene glycol poisoning. In cold climates, cases are particularly associated with coolant maintenance in autumn, winter and early spring.

Pre-existing kidney disease increases the risk of hospital-acquired acute kidney injury. Heart disease and sepsis, a severe systemic infection, are also risk factors. Medication harmful to the kidneys is another factor to consider. Acute injury can also develop on top of chronic kidney disease.

Ibuprofen has a narrow safety margin in dogs. Previous tolerance is not a reason to give human medicines yourself.

Typical symptoms

Signs depend on the substance and time since exposure. Poisoning harmful to the kidneys may cause findings such as:

• Vomiting or diarrhoea with grape and raisin poisoning.
• Loss of appetite.
• Unusual tiredness or weakness.
• Increased drinking and urination early in ethylene glycol poisoning.
• Staggering and drunken-like behaviour.
• Reduced urine output or no urine production.
• Thirst and dehydration with vitamin D poisoning.

Grape-related vomiting or diarrhoea usually begins within 6–12 hours. Early ethylene glycol signs can appear from 30 minutes to 12 hours after exposure. A brief apparent recovery can occur at around 12 hours. However, kidney signs in dogs can develop within 36–72 hours. Vitamin D poisoning signs and laboratory changes often begin within 12–48 hours.

Complications and consequences

The kidneys and other organs can be damaged

In grape and raisin poisoning, kidney failure with little or no urine output can develop within 24–72 hours. Loss of urine production makes the outlook serious, and survival may require dialysis. Ethylene glycol breakdown products can cause severe metabolic acidosis, making the body excessively acidic.

Vitamin D-induced mineralisation can damage the heart, lungs and gastrointestinal tract as well as the kidneys. It can leave chronic kidney disease. Recovery from acute kidney injury can be incomplete in other cases too.

Excess fluid accumulation can cause life-threatening fluid overload. Consequences include pulmonary oedema and high blood pressure. The size of the creatinine increase does not directly indicate how well kidney function may recover. The substance causing poisoning is one key prognostic factor.

During recovery with high urine output, blood potassium can also fall. Long-acting vitamin D metabolites may require laboratory monitoring over weeks.

The outlook for ethylene glycol poisoning worsens as the interval between exposure and starting treatment increases.

Diagnosis at the vet

Exposure details and repeated measurements

Your vet needs information about the possible substance and amount. Assessment also considers your dog's age, weight and previous health. Diagnosing acute kidney injury combines history, clinical examination and laboratory findings.

A creatinine rise of 26.5 micromoles per litre from baseline within 48 hours can indicate an acute decline in function. The change can matter even while the result remains within the laboratory reference range. Serial creatinine measurements are preferably performed on the same high-quality analyser. SDMA can also help detect an acute decline in function.

Urine is checked for findings including casts, glucose and protein. Urine output is monitored to assess kidney function. Blood salts are checked, as disturbances are common, particularly in patients producing little urine. Acid–base balance is monitored in severe acute kidney injury.

Substance-specific tests

A specific blood test can look for ethylene glycol. Investigations for suspected exposure also include urine sediment microscopy and blood gas analysis. Urinary oxalate crystals may be detectable in dogs as early as 6 hours after exposure. If a confirmatory test is unavailable, ethylene glycol treatment can begin on justified suspicion.

After vitamin D exposure, blood calcium and phosphorus are particularly important tests. Kidney values and electrolytes form part of the same assessment. Normal, stable calcium and phosphorus and no signs at 72–96 hours argue against developing toxic effects. This assessment requires follow-up tests, rather than observations at home alone.

Ultrasound assesses urinary tract and kidney structure. A kidney sample is not usually needed to investigate acute injury unless a condition such as an infiltrative tumour is suspected. Clotting status is checked before kidney sampling.

Renal glucose loss into urine suggests kidney tubular damage. If the injury's cause is unclear, urine culture is also indicated. Ultrasound can investigate ureteral obstruction, which causes similar signs.

Treatment

Reducing absorption and specific treatment

Your vet decides whether inducing vomiting could help, based on the substance and your dog's condition. It is avoided if neurological status is unstable or the substance is corrosive. Salt and other home remedies are not used to induce vomiting. Activated charcoal use depends on whether it binds the particular toxin. It is unlikely to reduce ethylene glycol absorption.

Specific ethylene glycol treatment prevents toxic breakdown products forming. There is no specific antidote to vitamin D poisoning. Bisphosphonates may be used to lower calcium in its treatment.

Fluids are matched to your dog's actual needs

Dehydration and circulatory deficits are corrected under veterinary supervision. Further fluids are matched to urine output and other fluid losses. Intravenous fluids may need to be stopped in a dog producing no urine. Forced diuresis using large fluid volumes does not improve acute kidney injury outcomes. Fluid balance is assessed at least twice daily. Monitoring weight and urine volume forms part of this assessment.

Dialysis may be needed if conventional treatment cannot reduce blood potassium below 6.5 millimoles per litre. With a large ibuprofen overdose, plasma exchange or other blood purification methods may also be considered. Medicines harmful to the kidneys are reviewed and removed from the plan where possible. NSAIDs are contraindicated during acute kidney injury.

Increasing urine output during recovery can raise fluid requirements even while kidney values improve. Fluid type is also adjusted according to changes in blood salts and acid–base balance.

Nutrition is part of supportive care

Nutritional support is needed if loss of appetite has lasted or is expected to last over 48 hours. Protein restriction has no demonstrated benefit during the acute hospital phase. Water given through a feeding tube is included in total fluid calculations. A specific renal diet is considered only after discharge, once any pancreatitis has resolved.

Recovery and follow-up

Severe acute kidney injury often requires around 1 week in hospital. Some patients need several weeks of hospital care. Kidney recovery can continue over days to months. Unchanged kidney values in the first few days therefore do not yet show that recovery is impossible.

Discharge is possible when creatinine is stable and signs are controlled without intravenous treatment. The first check is usually arranged within a few days of discharge. Kidney function is then initially checked at least every 3 months for 1 year. Subsequent monitoring depends on chronic kidney disease stage.

Prevention

Correct coolant storage and disposal reduce the possibility of ethylene glycol exposure. Keep containers and spilled fluids out of your dog's reach. Supervising outdoor activity also forms part of poisoning prevention.

Human ibuprofen is unsuitable for treating your dog yourself. All medicines in a dog with existing kidney injury are assessed for their kidney effects and elimination. Kidney function in hospital patients at risk is monitored at least daily.

Store vitamins and rodenticides separately from your dog's food. Vitamin D occurring in both product groups makes identifying the product essential.

Important for dog owners

Packaging details help guide treatment

Remove your dog from the exposure site and prevent further exposure. Bring the packaging or a photograph of its ingredients and an estimate of the amount remaining. Packaging and any remaining tablets help identify the substance and quantity. Record as precisely as possible when exposure occurred and signs began.

Do not give your dog anything to treat poisoning before professional advice. Report current medicines and supplements too. Reduced kidney function can prolong the effects of medicines eliminated through the kidneys.

After discharge, monitor appetite, drinking, urination and general condition. Even an apparently fully recovered dog needs further kidney monitoring. Creatinine returning to baseline does not always mean full recovery of the original filtration capacity. Keep follow-up results for future medication and treatment decisions.

Frequently asked questions

Can a dog that seems well need treatment after poisoning?

Yes. Many toxins have delayed effects, so do not wait for signs before contacting a vet about an apparently normal dog. Ethylene glycol can also cause a brief apparent recovery at around 12 hours. Kidney injury can still progress afterwards.

Does activated charcoal help with every kidney toxin?

No. Charcoal use is selected according to the toxin, as benefit must be expected for that particular substance. It is unlikely to reduce ethylene glycol absorption. Charcoal also carries a risk of increased blood sodium. Do not give it yourself.

Why not simply give a dog with kidney injury as much fluid as possible?

An injured kidney may be unable to remove excess water. Too much fluid can cause life-threatening fluid overload. Fluids are therefore matched to urine output and other losses. Repeated weight and fluid balance checks help your vet adjust treatment.

Does urinating mean the kidneys are healthy?

Not necessarily. Urine production can also increase during acute kidney injury. Kidney function is therefore assessed using repeated laboratory measurements as well as urine volume. A creatinine change from baseline can matter even while the result remains within the laboratory reference range.

Can kidney function recover further after discharge?

Yes. Recovery after acute injury can continue over days to months. Initially, kidney function checks at least every 3 months for 1 year are recommended. Monitoring continues even after apparently full recovery, as filtration capacity may remain lower than before.