Acute kidney injury in dogs – sudden kidney failure

Overview

Kidney injury can reduce blood filtration, allowing waste products normally removed in urine to accumulate. Fluid balance, blood electrolyte levels and acid–base balance may also be disturbed.

The term AKI covers both mild injury detected early and severe loss of kidney function. Acute injury can also affect a dog with pre-existing chronic kidney disease.

Chronic disease usually develops over months or years before visible symptoms appear. With acute injury, kidney function may partly recover if the dog survives the severe phase.

Injury may begin at home or develop during hospital treatment for another condition.

Causes

Poisoning and reduced circulation

Grapes and raisins are foods that can cause acute kidney injury in dogs. Ethylene glycol in antifreeze can damage the kidneys.

Non-steroidal anti-inflammatory medicines and certain other drugs can harm the kidneys. Shock or prolonged poor circulation can deprive kidney tissue of oxygen.

Reduced circulation may be associated with low circulating blood volume or sepsis, a severe systemic infection.

Infections and urinary obstruction

Leptospirosis can cause severe acute kidney injury in dogs. Bacterial infection of the kidney pelvis, called pyelonephritis, may also be responsible.

Persistent urinary tract obstruction can damage the kidney tissue itself. With a blocked ureter, urine cannot travel normally from the kidney to the bladder.

A urinary stone, tumour or blood clot may cause the blockage. Several factors impairing kidney function may be present in the same dog simultaneously.

Risk factors

Pre-existing kidney disease increases the risk of acute injury developing during hospital care. Heart disease can make maintaining kidney blood flow and hydration a particularly delicate balance.

Sepsis is among the underlying conditions that threaten kidney circulation and function. Anaesthesia and medicines that can harm the kidneys require these risks to be considered during treatment.

At least daily monitoring of kidney function is recommended for hospital patients in recognised risk groups. Contact with an environment contaminated by rodent urine increases the risk of leptospirosis.

The bacterium survives best in warm, standing surface water and moist soil.

A partial blockage, or one affecting only one side, may be less obvious but can permanently damage the kidney.

Typical symptoms

Mild injury may cause no outwardly noticeable signs.

• Your dog eats less than usual or stops eating altogether.

• Your dog becomes tired or seems weak.

• Your dog vomits or has diarrhoea.

• Urine output falls sharply or stops completely.

• Conversely, much more urine than usual is produced.

• There are mouth ulcers or an unusual smell to the breath.

• Your dog becomes dehydrated with vomiting or diarrhoea.

Palpating the kidney area may cause pain even when the kidneys are not clearly enlarged.

During recovery, a dog may change from producing little urine to producing large amounts, so the return of urination does not mean recovery is complete.

A urethral blockage may cause howling or other clearly painful vocalisation during attempts to urinate.

Complications and consequences

Electrolytes, blood pressure and fluid overload

Potassium can accumulate in the blood if less is removed in urine. Severe excess potassium can cause life-threatening abnormal heart rhythms.

During a high urine output phase, potassium may instead fall too low. Severe kidney injury can involve excessive blood acidity, called metabolic acidosis.

High blood pressure has been reported in up to 80% of dogs with acute kidney injury. A severe rise can cause seizures or retinal detachment.

Excess fluid accumulating in the body can cause pulmonary oedema and make breathing difficult. A weight gain of at least 10% from fluid accumulation indicates severe fluid overload.

Blood clotting may become abnormal in either direction, creating a risk of bleeding or blood clots. Bleeding in the digestive tract can cause anaemia.

Outlook and remaining kidney function

Overall survival in dogs and cats with severe AKI is estimated at about 50%. An individual dog's outlook depends on the cause, reversibility, other illnesses and available supportive care.

The creatinine level or AKI grade does not determine how well the injury can reverse. Chronic kidney disease may remain after acute injury.

Diagnosis at the vet

Blood tests and urine examination

The vet establishes when symptoms began and asks about possible poisoning, medication and previous conditions. Repeated creatinine measurements assess sudden deterioration in kidney function.

Even a creatinine increase of 0.3 milligrams per decilitre, equivalent to 26.5 micromoles per litre, within 48 hours may be significant. The increase may indicate injury even if the final result remains within the laboratory's reference range.

Urine is examined for concentration, chemical composition and sediment. Casts found in the sediment can indicate kidney tubule injury.

Glucose in urine may be associated with impaired reabsorption in the kidney tubules. Urine culture is needed if infection is suspected or the cause of injury remains unclear.

Blood samples also monitor potassium and other electrolytes. Acid–base balance is checked at least daily in hospital.

Suspected leptospirosis is investigated with appropriately timed blood and urine samples and antibody testing. A single positive leptospiral antibody result may also reflect previous infection or vaccination.

All AKI patients have a blood count that includes a reliable platelet count.

Imaging and severity grading

Ultrasound examines kidney structure and looks for ureteral obstruction or other abnormalities. A kidney sample or biopsy is not generally necessary to identify every acute injury.

The 2026 IRIS grading system is based on creatinine, urine production and the need for renal replacement therapy. The AKI grade can change in either direction during hospitalisation.

Grading acute injury differs from staging stable chronic kidney disease.

Treatment

Treating the cause and hospital monitoring

The vet prescribes medicines according to the cause and the dog's changing condition. Leptospirosis and bacterial pyelonephritis require antimicrobial treatment appropriate to the organism involved.

A urinary blockage must be relieved so that urine can drain again. Potentially kidney-damaging medicines are stopped or changed according to the vet's judgement.

Mild grade I AKI without accumulated waste products does not always require hospitalisation. However, monitoring is initially daily until the condition stabilises.

Hospital care is recommended for AKI grades II–V. Pain is assessed every 4–6 hours and treated with pain relief suitable for a kidney patient.

Fluid therapy and dialysis

Intravenous fluids aim to correct a fluid deficit and maintain adequate kidney blood flow. The amount is adjusted to urine output and other losses; arbitrary amounts are not given in an attempt to flush the kidneys.

Weight and fluid balance are monitored at least morning and evening in hospital. If no urine is produced and excess fluid accumulates, fluids may need to be stopped.

A diuretic may increase urine output, but has not been shown to improve overall AKI outcomes. Dialysis removes waste products and excess fluid from the blood when the kidneys cannot do so.

Dialysis can give damaged kidneys time to recover. It is considered for problems such as severe uraemia, fluid overload or uncontrolled excess potassium.

Dialysis is indicated if other treatment cannot keep potassium below 6.5 millimoles per litre.

Nutrition and recovery time

Nausea and vomiting are treated so that the dog can receive the nutrition they need. Nutritional support begins if poor intake has lasted, or is expected to last, more than 48 hours.

A feeding tube is used if necessary. Food is not forced into the mouth, because this may cause food aversion or allow food to enter the airways.

Protein restriction is not recommended during acute hospital care because tissue breakdown increases nutritional requirements. A special diet for chronic kidney disease is considered only after discharge and once any pancreatitis has settled.

Hospital care for severe injury often lasts about a week and sometimes several weeks. In grades I–II treated early, adequate kidney function may return within 2–5 days.

However, the full recovery phase can take days to months. A lack of improvement in blood results during the first treatment days does not yet mean that kidney function cannot recover.

Prevention

Keep grapes, raisins, antifreeze and medicines out of reach to prevent poisoning-related injury. Non-steroidal anti-inflammatory medicines must not be given to a dog with diagnosed acute kidney injury.

The suitability of other medicines is also checked, because kidney injury can slow their removal from the body. Rodent control around the home reduces the risk of leptospirosis.

A dog with leptospirosis is kept separate from other dogs to prevent infection. A return to normal creatinine does not remove the need for monitoring, because the kidneys may remain more susceptible to further injury.

Important for dog owners

Tell the practice what your dog has eaten, any possible toxic substances and all current medicines. Bring the suspected substance's packaging if it is safely available. Record when your dog last urinated and when vomiting or other symptoms began.

Discharge is considered when creatinine has stabilised and symptoms remain controlled without intravenous treatment.

The first follow-up appointment is usually scheduled within a few days of discharge.

Kidney function is initially monitored at least every three months for one year.

Even an apparently fully recovered dog needs monitoring similar to that for stage 1 chronic kidney disease.

Follow the home plan for drinking, feeding and medication. Monitor appetite, urine volume, vomiting, weight and energy levels. Contact the practice before the scheduled check if your dog deteriorates again. Ask for copies of the test results and the aim of the next appointment.

Leptospirosis can pass from animals to people, so hygiene is important when infection is suspected.

Frequently asked questions

Is acute kidney injury the same as chronic kidney failure?

No. Acute injury starts suddenly and may be caused by poisoning or infection, for example. Chronic kidney disease usually develops over months or years. However, acute injury can also affect a dog that already has chronic disease.

Can a dog with kidney injury still urinate?

Yes. In acute injury, urine output may increase, decrease or stop completely. Output in the same patient can also change as the disease progresses. The vet therefore assesses repeated blood tests and the dog's overall condition alongside urine production.

Can a dog recover completely from acute kidney injury?

Recovery may be complete or partial. It can take days to months, and a slow response during the first days does not determine the outcome. Kidney function is monitored afterwards even in an apparently fully recovered dog. During the first year, checks take place at least every three months.

Should a dog with acute kidney injury have a renal diet?

Nutrition during acute hospital care is planned separately, and protein restriction is not recommended initially. Food can be given through a tube if the dog does not eat enough. The need for a specific renal diet is assessed after discharge and once any pancreatitis has resolved. Water in tube feeds is also included in total fluid intake.

Does acute kidney injury always require dialysis?

Not always. Dialysis is used for problems such as severe uraemia, fluid overload or excess potassium. It removes waste products and excess fluid from the blood. Its purpose is to give the kidneys time to recover when other supportive care cannot adequately control the situation.