When Pigmenturia Isn’t Cystitis: A Case of Canine Renal Carcinoma

Pigmenturia is a term that can immediately raise concern in canine medicine, particularly for owners, but it’s often misunderstood or oversimplified. In essence, pigmenturia refers to urine that appears abnormally dark, red, brown, or orange due to the presence of pigments such as blood, haemoglobin, myoglobin, or bilirubin. The type of pigment and its concentration within the urine can greatly affect the overall colour, and purely assessing with the naked eye is unreliable.

While infection or inflammation of the lower urinary tract (such as cystitis) is the most frequent explanation in general practice, these changes in urine colour can also herald systemic or upper urinary tract disease, making careful differentiation essential.

Haematuria is the most recognized cause, and occurs when intact red blood cells enter the urine from any point along the urinary tract. This can result from cystitis, urolithiasis, trauma, or neoplasia affecting the kidneys, ureters, or bladder.

Haemaglobinuria often reflects intravascular haemolysis, where haemoglobin itself leaks into the urine, often secondary to immune-mediated haemolytic anaemia, zinc toxicity, or certain infectious and drug-related processes.

Myoglobinuria arises when muscle cells degenerate and release myoglobin into circulation and ultimately into urine, typically associated with severe muscle injury, heat stroke, or prolonged seizures.

Biliirubinemia can produce a distinct amber or orange hue and often indicates hepatobiliary disease or cholestasis rather than a structural urinary problem.

From a clinician’s standpoint, pigmenturia serves as a valuable though nonspecific clue demanding careful investigation. Distinguishing among these causes relies on integrating clinical history, laboratory findings, and imaging. Ultimately, pigmenturia should prompt broader thinking than “just cystitis.” It’s a sign — not a diagnosis — and may, at times, be the subtle first indicator of serious disease within the kidneys, muscles, or hepatobiliary system.

“Winston” a nine-year-old, male castrated, Dalmatian, was presented with a 2 month history of intermittent pigmenturia. He was otherwise completely asymptomatic. A routine urinalysis revealed blood and pigment, but no signs of bacterial growth on culture. Initially, treatment for presumed sterile cystitis brought transient improvement, but within weeks pigmenturia recurred.

A detailed physical examination showed Winston was in excellent systemic health. Haematology showed a mild non-regenerative anaemia, and biochemistry was largely unremarkable aside from a mild increase in urea.

Regional ultrasound showed a heterogenous echogenicity with distortion of the corticomedullary junction, of the left kidney. A complex mass lesion was visible within the cranial pole, approximately 7.5 cm in diameter. The right kidney and remainder of the urogenital tract was considered unremarkable.

Positive contrast retrograde urethrocystogram was performed to rule out pathology within the urethra, prostate and urinary bladder.

The left renal lesion was considered malignant and the most likely cause of the hematuria. Given the findings, Winston was considered an excellent candidate for unilateral ureteronephrectomy which was performed via midline celiotomy. Dissection should commence dorsolateral, through the perinephric fat. Once the kidney is mobilised and brought ventral midline, the renal artery and vein(s) are double ligated. The ureter was ligated close to its insertion into the urinary bladder.

Postoperative recovery was smooth, with renal values remaining within acceptable limits and pigmenturia resolving completely within days. At recheck six months later, Winston remained clinically well with no evidence of recurrence or metastasis.

Histopathology of the kidney confirmed a renal cell carcinoma.

Image 1: An intraoperative picture of the left paralumbar ‘gutter’ showing the left kidney with the associated mass lesion.

Blue arrow = left kidney with associated tumour

Orange arrow = normal urinary bladder

Primary renal neoplasia in dogs is uncommon, accounting for less than 1% of all canine tumours. When it occurs, renal cell carcinoma predominates, typically affecting older dogs with no breed predilection. Clinical signs are often subtle until late in the disease: intermittent haematuria or pigmenturia, vague abdominal pain, or non-specific malaise.

Importantly, pigmenturia should not automatically be attributed to cystitis causing hematuria, and broader approach should be adopted. While infection and inflammation remain common causes, upper urinary tract should always be considered, especially when pigmenturia persists or recurs despite appropriate empirical therapy.

For dogs with unilateral disease and preserved contralateral renal function, ureteronephrectomy remains the mainstay of treatment. Prognosis varies depending on histologic subtype, vascular invasion, and metastatic spread. Dogs with localized renal cell carcinoma often enjoy very good long-term outcomes following complete resection, often >4 years survival.

Adjuvant therapies are still investigational in veterinary medicine, but surveillance with periodic imaging and renal function monitoring is highly recommended, as recurrence or contralateral involvement may occur months to years later.

Gross pigmenturia is easily attributed as sterile or infectious cystitis. Recurrence despite empirical treatment strongly indicates investigation into upper and lower urinary tract causes.

When the lower urinary tract fails to explain the findings, remember the kidneys can hide silent pathology with significant clinical consequences if left untreated.