Haematuria can result from blood loss within either the urinary or reproductive tracts. It must be differentiated from other causes of discoloured urine including haemoglobinuria, myoglobinuria, and occasionally from drugs or chemicals that artefactually result in positive test results for blood on urine dipsticks. Occult haematuria refers to the presence of erythrocytes in the urine that are only evident on microscopy; gross haematuria refers to the situation when the quantity of blood in the urine is sufficient to be visible to the naked eye.

History and Physical Examination

A thorough history should be collected from all patients presented for investigation of haematuria. It has been suggested that the site of bleeding can be inferred from the pattern of haematuria (i.e., whether it occurs early, late or throughout urination), but this is not very reliable. However, it is generally the case that passing a bloody discharge between urinations signifies that the origin of the bleeding lies distal to the urethral sphincter, most often involving the prostate but also potentially originating from the urethra or genital tracts.

It is important when taking the history from the owners of patients with haematuria to establish if there have been any other alterations in the pattern of urination. Signs of dysuria and/or pollakiuria (abnormally frequent urination) point to a lower urinary tract cause for the clinical signs. In cats, a behavioural history should also be taken because of the frequent occurrence of idiopathic feline lower urinary tract disease (iFLUTD).

Physical examination as well as a detailed examination of the urinary tract should include rectal examination of the prostate in males and digital palpation of the urethra and sublumbar lymph nodes in both sexes. In males, the prepuce should be retracted so that the penis can be closely examined. Patients presented for gross haematuria should be very carefully examined for petechiation, ecchymoses or haematomas.

Differential Diagnoses for Haematuria

 Coagulopathy

 Urinary tract infection

 Urolithiasis

 Trauma

 Bladder (and urethral) tumours

 Idiopathic feline lower urinary tract disease (iFLUTD)

 Sterile haemorrhagic cystitis (cyclophosphamide)

 Prostatic disease

 Prostatitis

 Benign prostatic hyperplasia

 Prostatic tumours

 Vaginal/uterine disease

 Subinvolution of placental sites

 Pyometra

 Neoplasia

 Oestrus

 Renal (and ureteric) tumours

 Renal disease (uncommon)

 Glomerulonephritis

 Acute renal failure

 Polycystic kidney disease

 Renal telangiectasia

 Idiopathic renal haematuria

Laboratory Testing

If there is any indication from the history or physical examination that a coagulation defect is a possibility then this should be tested for as soon as possible. If the blood loss appears to be significant, then haematology should also be performed to evaluate the degree of anaemia and regenerative response.

Otherwise the first part of the diagnostic workup will usually be urinalysis. Examination of the urine should establish where intact cells are present in the urine or whether the patient could in fact have hemoglobinuria. Hemoglobinuria may occur either because of an intravascular haemolytic process (for example with IMHA) or due to erythrocytes being lysed in the urine; this is more likely to occur if the urine is dilute or alkaline. In addition to quantifying the severity of haematuria, the urine sediment should be examined for evidence of pyuria or bacteruria indicating that the patient may have a urinary tract infection (UTI). Crystalluria may be seen in patients with urolithiasis, although it may also be an incidental finding.

In some instances it may be helpful to compare the results of urinalysis in samples that are voided and collected by cystocentesis. If blood is only present in voided samples, then bleeding from the genital tract should be suspected. Urine culture should ideally only be performed on samples collected by cystocentesis, although with samples collected in this manner iatrogenic microscopic haematuria is a relatively common finding. If cystocentesis is performed first, then ideally an interval of at least 24 hours should be allowed before collection of a voided sample.

Diagnostic Imaging

If haematuria is significant and there is no evidence for a generalised coagulopathy, then in most instances diagnostic imaging focused on the urinary and reproductive organs is indicated. If a UTI is suspected from urinalysis, it is important to recognise that this does not usually result in gross haematuria; if this is present, then further diagnostic investigation may still be necessary, as the UTI may be a secondary problem.

Plain radiographs may be useful for the documentation of radiopaque uroliths and relatively large renal tumours. In addition, contrast radiography may be useful for delineation of bladder masses, radiolucent stones, and investigation of urethral disease. In many practices, ultrasonography has largely replaced the need for lower urinary tract contrast studies providing internal architectural information of the kidneys, bladder, and uterus or prostate. If the ultrasonographer is inexperienced, then care must be taken to differentiate masses from organised blood clots, which can appear similar.

Further Diagnostic Testing

Sometimes cases are encountered where the cause of haematuria is not obvious following the standard investigation described above. The diagnostic approach then differs according to whether the haematuria is occult or gross. In a patient with microscopic haematuria and no other clinical signs, a negative urine culture, and normal abdominal ultrasound, further diagnostic investigation is unlikely to be rewarding, and the patient should simply be reassessed at a later date. If the haematuria is grossly evident, then clearly further workup is indicated. In these patients, uroendoscopy can be very helpful in localising the source of the bleeding. However, it can also be frustrating; if the haemorrhage is extreme, visualisation can be very poor, and conversely if the haemorrhage is intermittent, cystoscopy can be completely normal.

Bleeding from the prostate can be very significant, even with benign disease (prostatic hyperplasia). With the consent of the owner, a pragmatic approach in male entire dogs is to perform castration and to monitor them for a clinical response. This is usually evident within 4 weeks of surgery. Whether pharmacological treatment for benign prostatic hyperplasia with finasteride or osaterone will be as effective in reducing bleeding is uncertain, but this remains a valid option if the owners are reluctant for castration to be performed.

Idiopathic renal haematuria remains in most instances a diagnosis of exclusion. A renal source for the haemorrhage can be confirmed either by performing cystoscopy and visualising bloody urine originating from one or both ureters or from direct visualisation following a cystotomy. However, even if blood is observed to be originating from only one ureter, extreme caution is advised before performing a nephrectomy. It is relatively common for the problem to be bilateral, even if this is not evident initially, and so surgery should only be considered in patients with life-threatening, uncontrollable haemorrhage or where ureteral obstruction with a blood clot has resulted in hydronephrosis. In other patients, there are anecdotal reports of successful treatment with ACE inhibitors or Chinese herbal therapies (yunnan paiyao); however, spontaneous remission of bleeding may also occur.

References

1.  Forrester SD. Diagnostic approach to hematuria in dogs and cats. Vet Clin N Am. 2004;34(4):849–866.