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Hematuria (blood in the urine) in dogs and cats: differential diagnosis

Hematuria is blood in the urine, visible as red or brown urine or found only as red cells in the sediment, and the bleeding can come from anywhere between the kidney and the urethra or from a systemic bleeding disorder.[1,2,3]

Reviewed by Brian Toncray, DVM · October 22, 2026

Confirming the sign

Red urine is not always blood. Red cells in the sediment confirm hematuria, while a red supernatant with few red cells raises pigmenturia, such as hemoglobinuria from intravascular hemolysis, which belongs to the hemolytic anemia work-up.[4] Collect a cystocentesis sample for culture so that the result reflects the bladder.[1] In cats, hematuria usually arrives with other lower urinary tract signs such as dysuria, pollakiuria, stranguria and periuria, and those signs look the same across very different causes.[5] Watch the patient urinate if you can: blood at the start of urination, at the end, or throughout helps place the source. Signalment matters too: in dogs, recognized risk factors for transitional cell carcinoma include female sex, obesity, a strong breed association and exposure to older flea control products and lawn chemicals, so an older female terrier with recurrent signs deserves imaging early.[6]

Bladder and urethral differentials

Bacterial cystitis[1]

Supports it:Pollakiuria, stranguria and hematuria with a positive urine culture.

Argues against it:A negative culture from a cystocentesis sample.

Next test:Urinalysis with sediment and urine culture and susceptibility.

Urolithiasis[7]

Supports it:Stones on radiographs or ultrasound, with lower urinary tract signs.

Argues against it:No uroliths on imaging that covers the whole urinary tract.

Next test:Abdominal radiographs and ultrasound; urolith analysis guides dissolution or removal.

Feline idiopathic cystitis (cats)[5]

Supports it:A cat with lower urinary tract signs, sterile urine and no uroliths or mass; FIC is the most common cause of lower urinary tract signs in cats.

Argues against it:A urolith, infection or mass found on work-up.

Next test:Urinalysis, urine culture and imaging to exclude other causes; always palpate for a large, firm bladder, because urethral obstruction is life threatening.

Transitional cell (urothelial) carcinoma (dogs)[6,8]

Supports it:An older dog, often female and of a predisposed breed, with hematuria or stranguria and a mass, most often at the trigone.

Argues against it:A mass at the cranioventral apex with a history of infection or stones, which fits polypoid cystitis better.

Next test:Ultrasound, then a tissue biopsy by cystoscopy, surgery or catheter. Avoid percutaneous aspirates and biopsies because of the risk of tumor seeding.

Polypoid cystitis (dogs)[8]

Supports it:Hematuria, stranguria or pollakiuria with polypoid lesions mostly at the cranioventral bladder apex, and a history of urinary tract infection or urolithiasis.

Argues against it:A trigonal mass, or a positive BRAF V595E mutation test.

Next test:Ultrasound, cystoscopy, urine culture and BRAF mutation testing where available.

Prostatic differentials (male dogs)

Prostatitis, benign prostatic hyperplasia or prostatic neoplasia[9]

Supports it:A male dog with tenesmus, prostatomegaly or pain on rectal examination. Hyperplasia and prostatitis are diseases of intact dogs, but prostatic carcinoma also occurs in castrated dogs, so an enlarged prostate in a neutered dog raises concern for neoplasia. Hematuria was more strongly associated with prostatitis than with benign hyperplasia, and weight loss was associated with neoplasia.

Argues against it:A normal prostate on rectal examination and imaging.

Next test:Rectal palpation, prostatic ultrasound, urinalysis and culture.

Upper urinary tract differentials

Pyelonephritis[1]

Supports it:Fever, renal pain or azotemia with a positive urine culture.

Argues against it:A negative cystocentesis culture.

Next test:Urine culture and renal ultrasound.

Idiopathic renal hematuria (dogs)[2]

Supports it:Persistent hematuria traced to a kidney with no other cause found. In a series of 41 dogs, the prognosis was good and anemia or azotemia occurred infrequently.

Argues against it:A urolith, infection, mass or coagulopathy found on work-up.

Next test:Imaging, then cystoscopy to see which ureter the blood comes from.

Systemic differentials

Coagulopathy, such as anticoagulant rodenticide toxicosis[3]

Supports it:Hematuria with bleeding elsewhere and a prolonged prothrombin time.

Argues against it:A normal prothrombin time.

Next test:Prothrombin time and a platelet count.

First diagnostics for this sign

Run a complete urinalysis with sediment and a urine culture from a cystocentesis sample.[1] Image the whole urinary tract for uroliths and masses with radiographs and ultrasound.[7,6] Examine the prostate in male dogs.[9] Check a prothrombin time when there is bleeding at other sites.[3] In a male cat, palpate the bladder first, because an obstructed urethra changes the order of everything.[5]

Example: working the sign

Example. An eleven-year-old spayed female terrier has had blood in the urine and straining for two months, with two courses of treatment for presumed cystitis that helped only briefly. The urine culture is now negative. Ultrasound shows an irregular mass at the bladder trigone. Transitional cell carcinoma moves to the top of the list, ahead of polypoid cystitis, which typically sits at the cranioventral apex.[6,8] The plan is a cystoscopic or catheter biopsy, not a percutaneous aspirate, because of the seeding risk.[6]

Frequently asked questions

Is red urine always hematuria?

No. Red cells in the sediment confirm hematuria; red urine with few red cells suggests pigmenturia, such as hemoglobinuria from hemolysis.[4]

What is the most common cause of hematuria and other lower urinary tract signs in cats?

Feline idiopathic cystitis, according to the 2025 iCatCare consensus guidelines, though uroliths, infection and urethral obstruction must be excluded.[5]

Should I aspirate a bladder mass in a dog?

No. Percutaneous aspirates and biopsies of suspected transitional cell carcinoma risk seeding the tumor; biopsy by cystoscopy, surgery or catheter instead.[6]

Where in the bladder do polypoid cystitis lesions usually sit?

Mostly at the cranioventral apex, in dogs with a history of urinary tract infection or urolithiasis.[8]

Sources

  1. Weese JS, Blondeau J, Boothe D, et al. International Society for Companion Animal Infectious Diseases (ISCAID) guidelines for the diagnosis and management of bacterial urinary tract infections in dogs and cats. Vet J. 2019;247:8-25. PMID 30971357 · doi:10.1016/j.tvjl.2019.02.008
  2. Kortum AJ, Bazelle J, Gomez Selgas A, et al. Clinical findings and outcome following medical treatment in dogs with idiopathic renal haematuria: 41 cases (2001-2018). J Small Anim Pract. 2021;62(10):850-860. PMID 34075582 · doi:10.1111/jsap.13352
  3. Mooney ET, Agostini G, Griebsch C, Hickey M. Intravenous vitamin K1 normalises prothrombin time in 1 hour in dogs with anticoagulant rodenticide toxicosis. Aust Vet J. 2020;98(6):225-231. PMID 32189335 · doi:10.1111/avj.12931
  4. Garden OA, Kidd L, Mexas AM, et al. ACVIM consensus statement on the diagnosis of immune-mediated hemolytic anemia in dogs and cats. J Vet Intern Med. 2019;33(2):313-334. PMID 30806491 · doi:10.1111/jvim.15441
  5. Taylor S, Boysen S, Buffington T, et al. 2025 iCatCare consensus guidelines on the diagnosis and management of lower urinary tract diseases in cats. J Feline Med Surg. 2025;27(2):1098612X241309176. PMID 39935081 · doi:10.1177/1098612X241309176
  6. Fulkerson CM, Knapp DW. Management of transitional cell carcinoma of the urinary bladder in dogs: a review. Vet J. 2015;205(2):217-225. PMID 25747698 · doi:10.1016/j.tvjl.2015.01.017
  7. Lulich JP, Berent AC, Adams LG, et al. ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats. J Vet Intern Med. 2016;30(5):1564-1574. PMID 27611724 · doi:10.1111/jvim.14559
  8. Price MP, Thomas R, Breen M, Kendall AR, Vaden SL. Polypoid Cystitis: A Retrospective Case-Series of 112 Dogs. J Vet Intern Med. 2025;39(3):e70049. PMID 40375558 · doi:10.1111/jvim.70049
  9. Cazzuli G, Suarez G, Busconi S, Damian JP, Pessina P. Clinical signs associated with prostatic disorders in canines: Retrospective study in Uruguay (2011-2019). Open Vet J. 2023;13(10):1308-1317. PMID 38027403 · doi:10.5455/OVJ.2023.v13.i10.10