Clinical Presentation of cats with solidified-blood uroliths

Solidified blood stones are an uncommon cause of urolithiasis, but for some the outcome is devastating.  The Minnesota Urolith Center analyzed stones composed of solidified blood (SB) in 14 cats evaluated at the University of Minnesota.  Eleven cats presented with lower urinary tract signs, of which 8 had urethral obstruction (UO); all UO cats were greater than 8-years-old while cats with typical causes of UO are usually younger (between 3 and 5 years old).  In 4 cats, SB uroliths were located in the ureter causing complete or partial urinary obstruction.

In 8 cats, stones were composed of 100% SB.  In 6 cats, SB uroliths contained other minerals (calcium oxalate or struvite).  

Solidified blood uroliths were rarely visible on survey radiography unless they were mixed with other minerals.  Ultrasonography was able to detect SB uroliths in the kidneys, ureters and bladder, but not in the urethra. 

We presume that SB uroliths result from an episode of bleeding into the urinary space sufficient to form a clot that when retained undergoes progressive hardening with aging.  To prevent urolith recurrence, stop the bleeding and if possible, remove the underlying cause (e.g. nephroliths, cancer, external trauma).   The role of urine dilution with increased water consumption might seem appropriate to reduce the concentration of red blood cells, platelets and coagulation factors, but the effect can be questioned because this strategy may also reduce the concentration of natural urine anticoagulants like urokinase and thrombomodulin. 

Cystoscopy image inside the urinary bladder of a female-spayed DLH cat with transitional cell carcinoma.  Small black uroliths are composed of 100% solidified blood.

Information in this student run project was undertaken by Divya Wagle (UMN CVM 2026)

See our detailed Feline Solidified Blood Uroliths Recommendations.