EQUINE VETERINARY EDUCATION Equine vet. Educ. (2019) 31 (5) 255-259 doi: 10.1111/eve.12846


Clinical Commentary


Bloody urine – the list of differential diagnoses lengthens, but diagnostics remain the same


John Schumacher†* and James Schumacher‡ †Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, Alabama; and ‡Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee,


Knoxville, Tennessee, USA. *Corresponding author email: schumjo@auburn.edu


Keywords: horse; haematuria; endoscopy; ultrasound; urinalysis


Summary The cause of haematuria often can be surmised based on a horse’s signalment, recent history, and clinical signs that may accompany haematuria. The site, if not the cause, of haemorrhage can sometimes be revealed by examining that portion of the urinary tract palpable per rectum, by endoscopically examining the urethra and bladder, or by ultrasonographically examining the kidneys. When cystolithiasis or urethrolithiasis is determined to be the cause of haematuria, further examination is indicated to identify disease of one or both kidneys that might have precipitated formation of the urolith. Contrast-enhanced, cross-sectional imaging of the abdomen of small equids might be of value when a vascular anomaly of a kidney is suspected. Neoplastic cells can sometimes be found in the urine of


horses suffering from neoplasia of the bladder or in peritoneal fluid of horses suffering from renal neoplasia. When a kidney is determined to be the source of haemorrhage, urine can be obtained for bacterial culture and cytological examination by passing tubing through the biopsy port of an endoscope into the ureter draining the kidney in question. Histological examination of tissue obtained by biopsy of the kidney or the mucosa of the bladder may be indicated when neoplasia of one of these organs is suspected. Immunohistochemical examination of endoscopically obtained tissue from a cystic carcinoma can identify whether the neoplastic cells express COX-2 receptors, thereby determining if treating the horse with a COX-2 selective NSAID might be effective.


There are not many reported causes of haematuria in horses, but with the report by Rosales et al. (2019) in this issue of Equine Veterinary Education describing a horse with haematuria caused by polyps in the bladder, the list becomes a bit longer. With a good history and physical, endoscopic and ultrasonographic examinations, the cause, or at least the site, of haematuria can usually be readily determined. History and signalment may provide clues indicating the site of haemorrhage. For example, horses that urinate immediately before strenuous exercise may develop haematuria because of mucosal erosions that develop in the bladder’smucosa asa result of abdominal viscera pounding the bladder against the pelvis (Schott et al. 1995). Haematuria of two horses was reportedly caused by damage inflicted during exercise to that portion of a full and heavy bladder directly overlying a pubic exostosis or osteochondroma (Rebsamen et al. 2012). Haematuria caused by a cystolith may be evident only after


the horse exercises and is often evident only near the end of urination. So, when haematuria is reported to occur after exercise, the clinician should consider a cystolith, osteochondroma of the os pubis or exercise-induced haematuria as a possible cause. When a gelding develops haematuria evident only at the


very end of urination (i.e. terminal haematuria), the cause is most likely a urethral rent (Fig 1) or cutaneous habronemiasis of the urethral process (Brinsko et al. 2011). Haematuria caused by a urethral rent occurs when contractions of the bulbospongiosis muscle, which normally force urine from the urethra at the end of urination, force blood from the corpus spongiosum penis (CSP), which surrounds the urethra, through the rent into the lumen of the urethra. In addition, the drop in pressure in urethral lumen at the end of urination also causes blood to flow from the CSP, through the rent (Taintor et al. 2004). Horses with cutaneous habronemiasis develop haematuria if a lesion erodes the mucosa of the urethral process, because the CSP extends into the urethral process. The authors and another (Schott 2003) have observed


that owners of horses with idiopathic renal haematuria, a syndrome occurring most often in Arabian horses, often report finding clotted blood on the stall floor. Passing clots of blood, however, is also reported to be a feature of horses with a tumour in the bladder (Cornelisse 2003). Knowing that a horse with haematuria has been administered a


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Fig 1: An endoscopic view of the bladder of a horse with haemorrhagic cystitis is shown. Picture courtesy of Dr. Gary Magdesian.


© 2017 EVJ Ltd

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