Blood in dog urine – causes, tests and treatment

Overview

Tests establish where the sign originates

Red blood cells in urine can come from any part of the urinary and reproductive systems. In males, benign prostate enlargement can also underlie bleeding. Blood in urine is therefore a finding whose cause needs investigation.

Normal urine is yellow or amber. Significant disease can also occur with normally coloured urine. Conversely, an unusual colour can result from pigments other than blood cells. Appearance alone therefore cannot give a precise diagnosis.

The blood field on a urine dipstick reacts to haemoglobin and myoglobin as well as red blood cells. A positive blood field is interpreted alongside urine microscopy.

Causes

Infection, stones and the prostate

When assessing bacterial bladder infection, haematuria is one possible finding supporting inflammation. In pyelonephritis, the bacterial infection is in the kidneys. Bacteria have often ascended there from the bladder. Stones, meanwhile, can cause painful, bloody urination. A tumour is another possible cause of urinary tract bleeding.

Benign prostatic hyperplasia is a hormone-related change separate from cancer. Red blood cells may be found in urine with bacterial prostatitis. Bladder infection can also follow prostate infection.

Blood clotting and less common causes

Accidental urinary tract injury can cause bleeding. Low platelets and inherited or acquired clotting disorders are also among the causes to distinguish. High blood pressure is one systemic cause considered.

In idiopathic renal haematuria, no cause is found for recurrent bleeding from the kidneys. This diagnosis is reached only after excluding other urinary tract and systemic causes.

Risk factors

Predisposing factors depend on the disease causing the blood. Benign prostatic hyperplasia is associated with ageing in entire males. Glandular tissue overgrowth can begin as early as 2.5 years of age. Cystic hyperplasia also becomes more common as the change develops after 4 years of age.

Pyelonephritis is more common in middle-aged and older dogs. Risk factors include kidney stones, recurrent urinary tract infections and kidney disease. Diabetes and Cushing's disease are also predisposing conditions. Reduced immune defences and urinary tract structural abnormalities are other possible risk factors.

A male dog's urethra narrows at the penile bone, where a stone can lodge. Obstruction risk with bloody urine is therefore also assessed by whether your dog can urinate.

Idiopathic renal haematuria has been described particularly in large-breed dogs under 2 years old. It has also been found in older dogs, including an 8-year-old Whippet. Age therefore does not remove the need for investigation.

Typical symptoms

Observations at home depend on the bleeding source and possible obstruction. Signs may include:

• Visible blood in urine.
• Urinating more often than usual.
• Passing only a little urine at a time.
• Straining during urination.
• Licking the penis or vulva more than usual.
• Urinary accidents indoors.
• Stronger-smelling urine with bacterial infection.

Prostate enlargement can cause bloody preputial discharge as well as blood during urination itself. Pyelonephritis can involve fever and vomiting. Increased drinking and urination can also be signs. With complete urethral obstruction, your dog strains without passing urine.

Acute prostatitis can cause severe abdominal pain. Chronic prostatitis, by contrast, may present only as recurrent urinary tract infections.

Complications and consequences

Effects of bleeding and the underlying disease

Clots formed by kidney bleeding can obstruct the urinary tract. Continuing blood loss can also cause anaemia, or too few red blood cells. Urethral obstruction can impair kidney function temporarily or permanently. During obstruction, blood potassium can rise enough to impair heart function.

Pyelonephritis can cause acute kidney injury. Bacteria from the infection can also enter the bloodstream. Severe prostatitis can cause sepsis and shock.

The outlook depends on the underlying disease. Recovery from pyelonephritis is generally good when your dog has no predisposing diseases. Recurrent infections or infections caused by resistant bacteria can worsen the outlook.

Delayed or ineffective kidney infection treatment can leave permanent kidney damage. Benign prostatic hyperplasia can predispose to prostatitis.

Diagnosis at the vet

A fresh urine sample and microscopy

Urine can be collected by free catch, catheter or a needle into the bladder. The collection method is considered, as a needle or catheter can itself introduce blood into the sample. Urine is preferably examined within 30 minutes. If this is impossible, the sample can be refrigerated for up to 24 hours. However, cooling can cause crystals to precipitate.

Normal urine generally contains fewer than 5 red blood cells per field at 400-fold magnification. Increased red blood cells indicate urinary or reproductive tract bleeding. Increased white blood cells can relate to inflammation, injury or a tumour as well as infection. Casts containing red blood cells suggest bleeding from the kidneys.

Urine specific gravity, or concentration, is measured with a refractometer. Dipstick white blood cell and nitrite fields are unsuitable for reliable assessment of animal urine. Abundant visible blood can also increase the urine protein-to-creatinine ratio. Protein results are therefore assessed alongside the rest of the urinalysis.

The blood field can also test positive when red blood cells break down in the circulation. Strongly coloured urine can also cause a false-positive dipstick result. Microscopy and other investigations distinguish these possibilities.

If urine contains many abnormal-looking epithelial cells, cytology can be performed on a fresh sample. Confirming benign prostatic hyperplasia may require examination of a tissue or fine-needle sample. Investigation of chronic bacterial prostatitis can also include the prostatic fraction of semen.

Culture and imaging investigate the cause

Urine culture is recommended in suspected bacterial cystitis. The culture sample is generally collected by a needle into the bladder unless this method is contraindicated. Culture from a free-catch sample can give a false positive or negative. The laboratory is therefore told how urine was collected.

Ultrasound can investigate bladder tumours, clots and stones. It can also find stones that plain X-rays do not show. In males, the prostate can be assessed by palpation through the rectum. Ultrasound shows prostate size and structure in more detail.

With benign hyperplasia, the prostate generally feels symmetrically enlarged and painless. Ultrasound can show cysts, or fluid-filled cavities, within the gland.

Blood tests assess general condition and kidney function. Investigations for unexplained bleeding may also include blood pressure, clotting tests and platelet counts. Endoscopy can show whether bloody urine is coming from a kidney at the ureteral opening. Intermittent bleeding can make its source hard to find during the examination.

With persistent or recurrent cystitis signs, a biopsy of the lining may be taken during endoscopy. Histological examination can investigate the cause even when urine culture is negative.

Treatment

Treatment targets the identified cause

Your vet selects treatment using the investigation findings. Pyelonephritis is treated with an antibiotic. The medicine may be changed when culture and susceptibility results are available. Severe kidney infection can require hospital care and intravenous fluids. Any underlying disease predisposing to infection is treated too.

Urinary stone treatment depends on stone composition. Calcium oxalate stones cannot be dissolved with medicine or diet. Struvite stones, by contrast, can be dissolved with an appropriate diet. A blockage preventing urine outflow needs urgent relief. In some cases, a stone can be flushed into the bladder for later removal.

Castration can treat symptomatic benign prostatic hyperplasia if your dog is not used for breeding. Medication reducing hormonal effects may be considered for a breeding male. A large prostate abscess may need surgical drainage.

Stones removed during bladder surgery have their composition analysed in a laboratory.

Follow-up depends on the diagnosis

After pyelonephritis, blood and urine checks are recommended 1–2 weeks after antibiotic treatment ends. By contrast, routine repeat culture is not recommended after an isolated episode of cystitis whose signs have resolved. In unexplained kidney bleeding, haematocrit, the proportion of blood occupied by red blood cells, is monitored if needed. Severe kidney bleeding may need specialist procedures, such as electrical or chemical treatment of the bleeding site.

After castration, a benignly enlarged prostate usually starts shrinking within a few weeks. Full atrophy often occurs over several months.

Prevention

Urinary stone recurrence is reduced by addressing factors predisposing to formation. Adequate water intake helps prevent stones. Your dog also needs several opportunities to empty the bladder during the day. Diet and monitoring for a dog that has already formed stones are planned according to the stone type found.

Preventing recurrent bacterial infections involves finding and treating predisposing diseases. Repeated antibiotic prescribing alone, without investigating the cause, generally does not produce lasting recovery. It can also increase bacterial drug resistance. Prevention therefore addresses the confirmed cause rather than urine colour.

X-ray checks every 3–6 months are recommended for dogs forming frequently recurring calcium oxalate stones. Small recurrent stones can then be detected before removal requires another operation.

Important for dog owners

Whether your dog can urinate is a key observation

Record whether urine passes in a normal stream, in small amounts or not at all. Small amounts and prolonged straining can relate to partial obstruction. Also note changes in urination frequency and any bloody discharge between urinations. Continuous or intermittent bloody preputial discharge can be associated with prostate enlargement.

Bring previous urine culture results if signs have recurred. Recurrent bacterial cystitis is defined as at least 3 episodes in 12 months or at least 2 in 6 months. Finding a different bacterium from the previous infection suggests a new infection.

At discharge, establish what urine colour to expect after the procedure performed. Slightly bloody urine is common after bladder surgery. Active dripping of bright blood is not part of normal recovery and requires contacting the treating practice.

Frequently asked questions

Does bloody urine always need an antibiotic?

Antibiotics are not a shared treatment for every cause of bloody urine. Possible causes include stones and tumours as well as infection. In suspected bacterial cystitis, diagnosis uses urinary signs, urine findings and culture. Choosing treatment therefore requires investigating the bleeding's cause.

Can a positive blood dipstick mean something other than blood?

Yes. The test's blood field reacts to free haemoglobin and myoglobin as well as red blood cells. When red blood cells break down in the bloodstream, haemoglobin can enter urine. The result is therefore assessed alongside urine microscopy. Sample appearance and the dipstick are only parts of the investigation.

Is bloody urine in a male always a prostate problem?

No. Benign prostatic hyperplasia can cause continuous or intermittent blood in urine. Infection, stones and tumours are also possible bleeding causes. Prostate ultrasound in males helps assess gland size and structure. Sex alone does not establish the cause.

Can blood clots prevent urination?

Yes. In kidney bleeding, clots can obstruct the urinary tract. Complete urethral obstruction prevents urine passing despite straining. This needs veterinary help immediately. Untreated obstruction can cause bladder rupture and urine leakage into the abdominal cavity.

Does a urine sample without crystals exclude stones?

No. Stones can form even when urine microscopy shows no crystals. Investigating stones uses X-rays or ultrasound alongside urine testing. Ultrasound can also find stones invisible on X-rays. It also assesses bladder clots and possible tumours.