CONDITION
Ureteroliths
Ureteroliths are stones that form within the ureters—the narrow tubes that carry urine from each kidney down to the bladder. These stones may remain silent for some time, or they may partially or completely obstruct the flow of urine from one kidney, leading to a range of signs that can vary widely in how suddenly they appear. Owners often arrive here because their dog or cat has been vomiting, seems uncomfortable, has been straining to urinate, or has had blood noticed in the urine. In some cases, the stone is discovered during imaging performed for another reason, before any signs have developed. The clinical picture depends on whether the stone is causing obstruction, how complete that obstruction is, and whether infection or kidney injury has developed alongside it. This page explores the signals that may suggest a ureteral stone, the factors that contribute to stone formation and obstruction, the ways these stones are identified and assessed, and the range of approaches used to address them—from monitoring in stable cases to interventions that relieve obstruction when the kidney's function is at risk.
Why this matters now
Ureteroliths can form at any age, but they tend to appear more often in middle-aged to older dogs and cats, particularly in certain breeds with known predispositions to calcium oxalate stone formation, such as miniature schnauzers, Yorkshire terriers, Burmese cats, and domestic shorthair cats. Dietary factors—including the balance of minerals, protein content, and water intake—can influence the concentration of stone-forming substances in the urine. In some animals, underlying conditions such as high blood calcium levels or abnormalities in how the kidneys handle certain minerals may contribute to stone development over months to years.
A stone may begin forming silently in the kidney and then migrate into the ureter, where it may move slowly, lodge in place, or cause partial or complete obstruction depending on its size and the anatomy of the tube. The speed at which signs appear varies widely: some animals develop sudden discomfort when a stone shifts or obstructs, while others show gradual changes in behaviour or appetite as pressure builds in the affected kidney. If obstruction persists, the kidney upstream from the stone may enlarge with trapped urine, and kidney function may decline over days to weeks, though the pace and severity depend on whether one or both ureters are affected and how completely the flow is blocked.
Signals & patterns
Early signals
Vomiting or reduced appetite
An owner may notice occasional vomiting, often without obvious food triggers, or a pet that seems less interested in meals. This can occur when early kidney injury or inflammation develops, or when discomfort from the stone itself influences how the animal feels.
Subtle changes in urination
Some animals pass urine more frequently in smaller amounts, or seem to posture for longer than usual. Blood may tinge the urine pink or red, visible in the litter tray, on paving, or against snow.
Quiet discomfort or restlessness
A pet may appear quieter than usual, shift position frequently, or avoid jumping or climbing. The discomfort may be intermittent, waxing and waning as the stone shifts or pressure in the ureter changes.
Increased drinking
An owner may refill the water bowl more often, or notice a cat visiting the tap repeatedly. This can reflect the kidney's early struggle to concentrate urine normally when partial obstruction or injury is present.
Later signals
Marked lethargy or withdrawal
As kidney function declines or toxins accumulate in the bloodstream, a pet may become noticeably less active, sleep more, or seek out quiet corners. This often develops over days if obstruction is prolonged.
Persistent vomiting or inappetence
Repeated vomiting or complete loss of interest in food can signal worsening kidney injury or the build-up of waste products that would normally be cleared by the kidneys. The animal may also lose weight over a short period.
Pain on handling or movement
Some animals become reluctant to be touched along the flanks or lower back, or may vocalise when picked up. The pain may reflect kidney distension or inflammation around the obstructed ureter.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
Last reviewed: Invalid Date ·