CONDITION
Lyme Nephritis
Lyme nephritis is a rare but serious kidney condition that can develop in some dogs exposed to the Lyme disease bacterium, *Borrelia burgdorferi*. Rather than a direct infection of the kidneys, it appears to arise when immune complexes—clumps of antibody and bacterial antigen—lodge in the delicate filtering structures of the kidney, triggering inflammation and progressive loss of the kidney's ability to retain protein. The result is a protein-losing nephropathy: protein leaks into the urine, blood protein levels fall, and fluid may begin to accumulate in the tissues or abdomen. Owners often arrive at this page because their dog has become unwell quite quickly—perhaps drinking and urinating more than usual, losing appetite and weight, appearing lethargic, or developing visible swelling. The condition tends to appear in young to middle-aged dogs, with a mean reported onset around five to six years of age, somewhat younger on average than other causes of protein-losing nephropathy, though cases in younger and older dogs are recognised. Certain breeds, including Labrador Retrievers and Golden Retrievers, appear more susceptible. This page explores the outward signals that may be observed, the immune and kidney changes happening beneath them, the investigations used to build a picture of what is occurring, and the range of supportive and disease-modifying approaches that exist. It does not tell you what your dog has; it offers a framework for understanding what Lyme nephritis is and how it is approached in veterinary medicine.
Why this matters now
Lyme nephritis tends to appear in young to middle-aged dogs, with a mean reported onset around five to six years of age, somewhat younger on average than other causes of protein-losing nephropathy, though cases in younger and older dogs are recognised. Labrador Retrievers and Golden Retrievers appear predisposed, along with a smaller number of cases reported in Bernese Mountain Dogs and Shetland Sheepdogs. The condition can develop in dogs living in or travelling through areas where Ixodes ticks transmit Borrelia burgdorferi, though not every infected dog develops kidney involvement.
The kidney changes can develop quite rapidly in some dogs, with signs appearing over days to a few weeks, while in others the progression may be slower and more subtle. The severity varies widely; some animals show only mild increases in urination and thirst, while others progress to marked protein loss, fluid accumulation, and advanced kidney dysfunction. Early changes may be detected on blood or urine tests before an owner notices outward signs, though this is not always the case.
Signals & patterns
Early signals
Increased thirst and urination
An owner may notice the water bowl emptying more quickly than usual, or the dog asking to go outside more frequently, particularly overnight. This reflects the kidneys' reduced ability to concentrate urine as the filtering units are affected.
Reduced appetite or pickiness
The dog may show less interest in meals, eat smaller portions, or turn away from food that was previously enjoyed. This can be one of the earlier, less specific signs that something is changing.
Quieter behaviour or lethargy
Energy levels may drop; the dog may be slower to greet people, less enthusiastic about walks, or sleep more than usual. These changes can be gradual and easy to attribute to other causes.
Weight loss
Loss of body condition may become apparent over one to several weeks, sometimes before other signs are obvious. Muscle loss along the back or over the skull can be subtle at first.
Later signals
Swelling of the limbs or abdomen
Fluid may accumulate under the skin, particularly in the legs, or within the abdomen, causing visible distension. This reflects severe protein loss and low blood albumin levels.
Vomiting or nausea
As kidney function declines and waste products build in the bloodstream, dogs may vomit, appear nauseous, or drool. These signs tend to appear when kidney damage is more advanced.
Marked weakness or collapse
In more severe cases, profound lethargy, difficulty standing, or episodes of collapse may occur, reflecting advanced uraemia and the body's inability to maintain normal fluid and electrolyte balance.
Click to read about the biological mechanisms
How this is usually investigated
Investigation typically begins with a history of tick exposure or previous Lyme disease diagnosis, alongside the pattern of signs observed at home. Blood and urine tests form the foundation of the assessment, revealing how well the kidneys are filtering and whether protein is being lost. Additional tests may be used to confirm Borrelia burgdorferi infection, assess the extent of kidney damage, and exclude other causes of similar signs.
Chemistry panel
Urinalysis with sediment
Urine protein:creatinine ratio (UPC)
Serology for Borrelia burgdorferi
Abdominal ultrasound
Options & trade-offs
Management is usually built around supporting kidney function, reducing protein loss, and addressing the immune response to Borrelia burgdorferi. The combination of approaches chosen depends on the degree of kidney impairment, the rate of progression, and what is practical within the household. Different animals and owners find different balances workable, and the picture often shifts over time.
Antibiotic therapy targeting Borrelia burgdorferi
Doxycycline is commonly used to address the underlying bacterial infection, with treatment courses typically extending over several weeks. The rationale is that reducing the antigenic stimulus may lessen the immune-mediated kidney inflammation, though the benefit in established nephritis is not always clear. Some clinicians use it in combination with other supportive measures.
Trade-offs: The response to antibiotics is variable; some dogs show stabilisation or improvement in kidney parameters, whilst others continue to decline despite treatment. The timing of therapy relative to the onset of kidney signs may influence outcomes, and prolonged courses can carry gastrointestinal or other side effects.
Immunosuppressive therapy
Drugs such as ciclosporin or mycophenolate mofetil may be used to dampen the immune-mediated inflammation within the glomeruli, with the aim of slowing protein loss and preserving remaining kidney function. Corticosteroids are used cautiously, as high doses can worsen protein loss, though lower doses are sometimes part of a multi-drug regimen. Monitoring for side effects and adjustments over time are typical.
Trade-offs: Immunosuppression carries risks of infection, gastrointestinal upset, and other organ effects, and not all dogs respond favourably. The benefit must be weighed against the degree of kidney impairment already present, as advanced cases may be less likely to stabilise. Regular blood work is needed to monitor response and detect complications.
Supportive care for kidney function
This includes modifications to diet, often involving reduced protein or phosphorus content, alongside management of blood pressure, hydration, and electrolyte balance. Fluid therapy, either subcutaneous at home or intravenous in hospital, may be used during periods of decompensation. The goal is to reduce the workload on the remaining functional kidney tissue and manage the consequences of declining filtration.
Trade-offs: Supportive care addresses the effects of kidney disease but does not alter the underlying immune process. Some dogs tolerate dietary changes and fluid therapy well, whilst others find them difficult or show limited improvement in quality of life. The approach is often combined with other therapies rather than used in isolation.
ACE inhibitors or ARBs to reduce proteinuria
Drugs such as benazepril or telmisartan work on the renin-angiotensin system to lower pressure within the glomeruli, which can reduce the amount of protein leaking into the urine. They are often introduced alongside other measures when significant proteinuria is documented. Serial UPC measurements help track the response.
Trade-offs: These drugs can improve protein loss in some dogs but do not reverse underlying kidney damage. Blood pressure and kidney parameters need monitoring, as excessive lowering of pressure or worsening azotaemia can occur. The benefit is most apparent when introduced before severe kidney impairment is established.
Common misconceptions
"A positive Lyme test means a dog will develop Lyme nephritis."
Most dogs exposed to Borrelia burgdorferi, whether through natural infection or vaccination, do not develop kidney disease. Lyme nephritis is an uncommon complication that appears to require a particular combination of immune response, genetic susceptibility, and possibly other factors not yet fully understood. Routine serology reflects exposure, not future kidney risk.
"If kidney values improve on treatment, the condition is cured."
Stabilisation or partial improvement in blood work can occur with treatment, but the underlying damage to the glomeruli often persists and may progress over time. Some dogs experience periods of stability followed by later decline, and ongoing monitoring is typical even when initial responses are favourable. The term 'cure' does not usually apply to immune-mediated kidney disease.
"Lyme nephritis only occurs in areas where ticks are common."
Whilst the condition is more frequently seen in regions where Borrelia burgdorferi is endemic, dogs can be exposed through travel, relocation, or contact with ticks carried from other areas. A history of tick exposure is helpful when present, but its absence does not rule out the condition, particularly in dogs who have moved or whose early history is unknown.
Related conditions
Glomerulonephritis
Lyme nephritis is a specific form of glomerulonephritis—inflammation of the kidney's filtering units—in which the immune response to Borrelia burgdorferi infection appears to damage the glomeruli. Both conditions share the pattern of protein loss into urine and can present with similar clinical signs, though Lyme nephritis tends to progress more rapidly and is seen more often in certain retriever breeds.
Leptospirosis
Leptospirosis is another bacterial infection that can cause acute kidney injury and protein loss, and may be considered alongside Lyme nephritis when a dog presents with sudden kidney signs and a history of tick or environmental exposure. Blood tests and urine culture can help distinguish between the two, as both involve immune-mediated kidney damage but arise from different organisms and may require different approaches to treatment.
Anaplasmosis
Anaplasmosis is a tick-borne infection caused by Anaplasma bacteria, transmitted by the same Ixodes ticks that carry Borrelia burgdorferi. Dogs can be co-infected with both organisms, and some signs—such as lethargy, reduced appetite, or fever—may overlap, though anaplasmosis more often affects white blood cells and joints rather than the kidneys.
Ehrlichiosis
Ehrlichiosis is another tick-transmitted infection that can affect multiple organ systems, including the kidneys in some cases. Both Lyme nephritis and ehrlichiosis may present with non-specific signs such as lethargy and weight loss, and screening for tick-borne diseases often includes tests for multiple organisms when kidney involvement or systemic illness is identified.
Acute Kidney Injury
Lyme nephritis can be understood as one specific cause of acute kidney injury, in which kidney function declines over days to weeks rather than months. The distinction lies in identifying the underlying trigger—in this case, immune-mediated glomerular damage linked to Borrelia infection—while the clinical presentation of sudden changes in thirst, urination, and bloodwork abnormalities may be shared across many forms of acute kidney injury.
Understanding how the kidneys are functioning over time, and what signs at home might signal a change, can help frame observations and conversations at follow-up appointments. The broader context of immune-mediated conditions in dogs, and how different organ systems may be affected by similar mechanisms, is explored elsewhere in the Immune & Inflammatory Health pillar. For dogs with ongoing protein loss or declining kidney function, discussions around quality of life, monitoring schedules, and the practical realities of longer-term management are often useful as the picture unfolds.