CONDITION
Lyme Nephritis
Lyme nephritis is a form of kidney inflammation that can develop in dogs who have been infected with Borrelia burgdorferi, the bacterium transmitted by certain ticks. The condition arises when the immune response to the infection appears to affect the kidneys' filtering units, sometimes progressing quickly. It is seen most often in Labrador Retrievers and Golden Retrievers, though other breeds can be affected. Owners often notice a sudden change in thirst and urination, reduced appetite, lethargy, or weight loss. Some dogs may have had known tick exposure or a previous Lyme disease diagnosis, while in others the kidney signs appear without an obvious prior history. The presentation can range from subtle changes in drinking habits to more pronounced illness over the course of days to weeks. This page explores the patterns that may prompt investigation, what is understood about the immune and kidney mechanisms involved, how the condition is identified through blood work and urine testing, and the range of approaches used to support kidney function and manage the underlying process.
Why this matters now
Lyme nephritis tends to appear in young to middle-aged dogs, typically between two and five years of age, though cases outside this range are recognised. Labrador Retrievers and Golden Retrievers are disproportionately affected, with some lines or families showing higher susceptibility. The condition is more commonly seen in regions where Borrelia burgdorferi is endemic and tick exposure occurs regularly, particularly in areas with wooded or grassland habitats that support tick populations.
The onset can be abrupt, with kidney-related signs appearing over the course of days to a few weeks. In some dogs, the progression is rapid, with kidney function declining noticeably within a short window; in others, the changes may be more gradual, allowing time for investigation before clinical signs become pronounced. The speed and severity of progression vary considerably between individuals, and the trajectory is not always predictable from the initial presentation.
Signals & patterns
Early signals
Increased thirst and urination
An owner may notice the water bowl being emptied more frequently, or requests to go outside becoming more frequent, particularly overnight. This pattern reflects the kidneys' reduced ability to concentrate urine, prompting the body to compensate by increasing fluid intake.
Reduced appetite
A dog may begin to show less interest in meals, eating smaller portions or leaving food untouched. This change can be subtle at first, sometimes dismissed as fussiness, and often coincides with a general sense of being less engaged or enthusiastic.
Lethargy or quieter behaviour
The dog may seem less interested in play, walks, or usual activities, preferring to rest or sleep more than normal. This shift in energy can be gradual and may be mistaken for ageing or temporary tiredness until other signs become apparent.
Weight loss
Over a period of days to weeks, an owner may notice the dog feeling thinner when touched, or ribs and spine becoming more prominent. This loss often accompanies reduced appetite and can progress steadily even if food intake seems reasonable.
Later signals
Vomiting or nausea
As kidney function declines further, waste products accumulate in the bloodstream, and the dog may begin to vomit intermittently or show signs of nausea such as lip-licking, drooling, or reluctance to eat. These signs tend to appear when kidney damage has become more advanced.
Swelling in the legs or abdomen
Fluid may begin to accumulate in the tissues or body cavities, causing visible swelling in the limbs, belly, or around the face. This oedema reflects a loss of protein through damaged kidney filters and altered fluid balance within the body.
Pale gums or weakness
The gums may appear paler than usual, and the dog may seem unsteady or reluctant to move much. These signs can indicate anaemia or electrolyte disturbances linked to worsening kidney function and the systemic effects of accumulated toxins.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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