South African Equine Veterinary Association Congress 2015 Protea Hotel Stellenbosch
Examination of affected horses is often unremarkable. In contrast, horses with haematuria due to
urolithiasis or neoplasms involving the penis are usually presented with additional complaints
such as pollakiuria, a foul odour to the sheath, or presence of a mass on the penis. With urethral
tears, laboratory analysis of blood reveals normal renal function although mild anaemia (packed
cell volume 25-30%) can be an occasional finding. Urine samples collected mid-stream catch or
by bladder catheterization appear grossly no rmal. Urinalysis may have normal results or there may
be an increased number of red blood cells on sediment examination, a finding that would also
result in a positive reagent strip result for blood. Bacterial culture of urine yields negative results.
The diagnosis is made via endoscopic examination of the urethra during which a lesion is
typically seen along the dorsocaudal aspect of the urethra at the level of the ischial arch. With
haematuria of several weeks duration, the lesion may appear as a fistula communicating with the
vasculature of the corpus spongiosum penis (CSP, cavernous vascular tissue surrounding the
urethra). External palpation of the urethra in this area is usually unremarkable but can assist in
localizing the lesion because external digital palpation can be seen via the endoscope as
movements of the urethra.
Urethral tears likely develop as a "blowout" of the CSP into the urethral lumen. Contraction of the
bulbospongiosus muscle during ejaculation causes increased pressure in the CSP, which is
essentially a closed vascular space during ejaculation. The bulbospongiosus muscle also
undergoes a series of contractions to empty the urethra of urine at the end of urination. Thus, the
proposed explanation for the haematuria at the end of urination in horses with urethral rents is a
sudden decrease in intraluminal urethral pressure while pressure within the CSP remains high.
Once the lesion has been created, it is maintained by bleeding at the end of urination and the
surrounding mucosa heals by formation of a fistula into the overlying vascular tissue. An
anatomical predisposition in Quarter Horses has not been documented but could be speculated
based on an apparent increased risk in this breed. Further, many horses have either asymmetry or
a widened perineum.
Since haematuria may resolve spontaneously in some geldings, no treatment may be initially
required. If haematuria persists for more than a month or if significant anaemia develops, a
temporary subischial urethrotomy is performed. With sedation and epidural or local anaesthesia, a
vertical incision is made over a catheter which has been placed in the urethra. The incision is
extended through the fibrous sheath surrounding the corpus spongiosum penis but not into the
urethral lumen to form a “pressure relief valve” or path of lower resistance for blood to exit the
corpus spongiosum penis at the end of urination. The surgical wound requires several weeks to
heal and moderate haemorrhage from the corpus spongiosum penis is apparent for the first few
days after surgery. Additional treatment consists of local wound care and prophylactic antibiotic
treatment (typically a trimethoprim/sulfonamide combination) for 7 to 10 days. Haematuria
should resolve within a week following this procedure.
Idiopathic renal haematuria: Idiopathic renal haematuria (IRH) is syndrome characterized by
sudden onset of gross haematuria. Haemorrhage arises from one or both kidneys and is
manifested by passage of large blood clots in urine. Endoscopic examination of the urethra and
bladder usually reveals no abnormalities of these structures but blood clots may be seen exiting
one or both ureteral orifices. Although a definitive cause of renal haemorrhage may be established
in some horses (renal adenocarcinoma, arteriovenous or arterioureteral fistula, etc.), the disorder
is termed idiopathic when a primary disease process cannot be found. Both sexes and a wide age
range have been affected; however, the majority of equids with IRH have been Arabian or partArabian horses.
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