SYMPTOM
Blood in urine
Urine that appears pink, red, or brown in colour, or the presence of blood spots or drops at the end of urination.
Urinary tract infection
Bacterial cystitis is one of the most common causes of haematuria in dogs. The inflammatory response to bacterial colonisation of the bladder mucosa increases vascular permeability and can erode the urothelial lining, allowing red blood cells to enter the urine. Blood is often most noticeable at the end of urination and may be accompanied by increased frequency, straining, and discomfort. Female dogs are more commonly affected due to their shorter urethra.
Urinary stones (urolithiasis)
Stones within the bladder or urethra can cause mechanical irritation and trauma to the urinary tract lining as they move or as the bladder wall contracts around them during urination. Struvite and calcium oxalate stones are the most common types in dogs. The haematuria may be intermittent, sometimes more pronounced after physical activity. Stones that lodge in the urethra can block the outflow of urine, the pattern described under urethral obstruction.
Bladder or urinary tract neoplasia
Tumours of the bladder wall, most commonly transitional cell carcinoma, can produce persistent or intermittent haematuria as the tumour erodes through the mucosal surface. This is more commonly seen in older dogs, with certain breeds (Scottish Terriers, Shetland Sheepdogs, West Highland White Terriers) being overrepresented. The bleeding may be accompanied by other lower urinary tract signs that can mimic chronic UTI.
Coagulopathy or platelet disorder
Disorders affecting the blood's ability to clot normally can produce haematuria as part of a broader bleeding tendency. Thrombocytopenia, inherited or acquired clotting factor deficiencies, and exposure to anticoagulant rodenticides can all cause bleeding into the urinary tract. After a toxic dose of anticoagulant rodenticide, bleeding is typically noted 3 to 7 days later, and it can include bleeding into the chest that shows only as laboured breathing. In these cases, other signs of abnormal bleeding (such as pinpoint red spots or bruises on the skin or gums, or prolonged bleeding from wounds) may also be present.
Prostatic disease
In male dogs, prostatic conditions including benign hyperplasia, prostatitis, prostatic cysts, and prostatic neoplasia can produce haematuria or blood dripping from the prepuce independent of urination. Benign prostatic hyperplasia occurs only in entire dogs, and prostatitis is uncommon in neutered dogs. Prostatic blood enters the urine via the prostatic urethra, so it may be seen at the start of urination or as drops unrelated to urination, although the timing varies.
Trauma or vigorous exercise
Physical trauma to the urinary tract or kidneys can produce haematuria. Haematuria after blunt abdominal injury can indicate damage to the kidneys, bladder, or urethra. Haematuria after vigorous exercise is reported but rare and is regarded as a form of trauma, with blood appearing within minutes to a few days of the exercise. Red or brown urine after exertion is not always blood: haemoglobin and the muscle pigment myoglobin give the same positive result on a urine dipstick, and they cannot be told apart from blood by eye.
Feline idiopathic cystitis
In cats, no specific underlying disease is identified in around 60 to 70% of cases of lower urinary tract disease, and these cats are classed as having feline idiopathic cystitis, an inflammation of the bladder without a known cause. Bladder stones account for around 10 to 15% of cases, and bacterial infection is relatively uncommon in cats. The signs are difficulty passing urine, passing small amounts frequently, and blood in the urine, which is not always visible and may only be found on testing. Urethral plugs and obstruction occur in male cats, so in a male cat these signs overlap with those of urethral obstruction.
Urethral obstruction
A stone, a plug of crystals and mucus, or a tumour can block the urethra so that urine cannot leave the bladder. In cats this occurs almost exclusively in males, and in dogs the usual cause is a stone lodged in the urethra. Blood in the urine, frequent attempts to urinate and straining are common, so the early picture resembles cystitis. The distinguishing sign is repeated straining that produces only drops or no urine at all, often with crying or licking around the genital area. With a complete blockage, the signs of waste products building up in the blood develop rapidly: vomiting, dehydration, a low body temperature and severe dullness, and a rising blood potassium can slow the heart or disturb its rhythm. In cats, International Cat Care states that an untreated blockage can cause kidney failure and can be fatal within 2 to 3 days. Whether the bladder is full or empty cannot be judged by watching the animal.
Why timing matters
Early observation
When blood in the urine is first noticed, it typically represents an active process affecting the urinary tract lining or kidney. The timing of blood relative to the urine stream can provide initial characterisation: blood throughout the stream is more suggestive of a kidney or ureteral origin, although a bladder origin cannot be ruled out, blood at the end of urination often indicates a bladder origin, and blood at the beginning, or dripping independently of urination, suggests a urethral or genital source, which in male dogs includes the prostate. These are general guides only, because the stage at which blood appears varies for any one source. Early haematuria from UTI is often accompanied by other lower urinary tract signs and typically responds to appropriate treatment. Isolated, painless haematuria without other urinary signs warrants particular attention as it may suggest a neoplastic or structural cause.
Later presentation
Persistent or recurrent haematuria over weeks suggests an ongoing process. If initial treatment for suspected UTI has not resolved the bleeding, other causes become more important to consider. Chronic haematuria can lead to iron deficiency over time if significant blood loss is occurring, though this is uncommon with most causes of urinary tract bleeding. Progressive worsening of haematuria, from occasional pink-tinged urine to consistently red urine or the passing of clots, indicates an advancing process.
The trajectory depends on the underlying cause. UTI-related haematuria typically resolves within days of appropriate antibiotic therapy. Stone-related bleeding may fluctuate with the stone's position and movement within the urinary tract. Neoplastic causes tend to produce progressive or persistent haematuria that worsens over time. Haematuria attributed to exercise is rare, so other causes remain possible when urine is discoloured after exertion. Monitoring the pattern of bleeding, its relationship to treatment, and whether associated signs are developing or resolving provides important context about the underlying process.
Conditions commonly associated
Urinary Tract Infection in Dogs
Urinary tract infection is one of the most common causes of blood in the urine in dogs, through inflammation of the bladder lining.
Urinary Stones (Urolithiasis)
Urinary stones irritate the bladder lining through mechanical abrasion, causing microhaemorrhage that produces visibly blood-tinged urine, often intermittently.
Prostate Disease
Prostatic disease in male dogs can cause haematuria, with blood seen at the start of urination or dripping from the prepuce between urinations.
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Transitional Cell Carcinoma
Transitional cell carcinoma causes bleeding from the tumour surface into the urine, often the first sign noticed by owners.
Anticoagulant Rodenticide Toxicity
Impaired clotting from anticoagulant rodenticide ingestion can allow blood to appear in the urine.
Hydronephrosis
Blood-tinged urine can appear when the stones or obstructions that cause kidney swelling also irritate the urinary tract lining.
Hyperparathyroidism in Dogs
Blood-tinged urine can appear when calcium-based stones, a recognised complication of raised blood calcium, irritate the bladder lining.
Prostatic Hyperplasia
Benign prostatic hyperplasia in entire male dogs can cause persistent or intermittent blood in the urine, or a bloody discharge from the prepuce independent of urination.
Ureteral Obstruction in Cats
Irritation from a stone lodged in the ureter can allow blood to appear in the urine.
Ureteroliths
The stone's passage along the ureter irritates the lining and can introduce blood into the urine.
Urethral Obstruction
Blood in the urine with straining is common when the urethra is blocked. Repeated straining that produces only drops or no urine at all is the distinguishing sign.
Feline Idiopathic Cystitis
Feline idiopathic cystitis is the most common cause of lower urinary tract signs in cats, including blood in the urine, frequent urination and straining.
When to explore further
When blood is visible in the urine, a source of bleeding is present, and the cause cannot be judged from the colour seen at home. Bleeding that recurs after apparent resolution suggests an ongoing process rather than a transient event.
When haematuria is accompanied by straining, increased frequency, or apparent discomfort during urination, these lower urinary tract signs suggest an active inflammatory or irritative process in the bladder or urethra. When the straining produces only drops or no urine at all, particularly in a male cat or male dog, the pattern is that of urethral obstruction rather than cystitis. A complete blockage is life-threatening in either species, and in cats an untreated blockage can be fatal within 2 to 3 days.
When blood is present in the urine without any other urinary signs (painless haematuria), this pattern is noteworthy because it may suggest processes such as neoplasia or coagulopathy rather than inflammatory conditions that typically produce concurrent discomfort.
When haematuria occurs alongside signs of bleeding elsewhere, such as bruising, nosebleeds, or prolonged bleeding from minor wounds, the combination suggests a systemic clotting problem rather than a localised urinary tract issue, and bleeding may also be taking place internally where it cannot be seen.
When blood in the urine develops in an older dog, particularly breeds known to be predisposed to transitional cell carcinoma, the age and breed context adds weight to the finding even if initial signs are mild.
Noting the characteristics of the haematuria can help characterise the source: whether blood appears at the beginning, middle, or end of urination, its colour (pink, red, or brown), whether clots are present, and whether it occurs with every urination or intermittently. Observing whether the animal shows other urinary signs such as increased frequency, straining, or discomfort, and whether urine is actually being passed, provides additional context. Urine analysis is often the first step in understanding the cause of urinary bleeding.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS