- Definition
- Pathophysiology
- Systems Affected
- Genetics
- Incidence/Prevalence
- Geographic Distribution
- Signalment
- Signs
- Causes
- Risk Factors
BASICS
Discoloration of urine, red to brown in color, from increased excretion of RBCs (hematuria), hemoglobin (hemoglobinuria), or myoglobin (myoglobinuria).
- Normal urine contains ≅5000 RBCs/mL or <5 RBCs/hpf on sediment examination
- Microscopic hematuria (10 000–2 500 000 RBCs/mL) can be detected as 10–20 RBCs/hpf on sediment examination or a trace to + + + reaction on a reagent strip
- Macroscopic or gross hematuria can be observed with >2 500 000–5 000 000 RBCs/mL (≅0.5 mL of blood per 1 L of urine)
- Hemorrhage from kidneys, ureters, or bladder leads to hematuria throughout urination. Hematuria at the beginning of urination indicates lesions of the distal urethra, and at the end of urination indicates lesions in the proximal urethra or bladder neck
Hemoglobinuria is a consequence of intravascular hemolysis and hemoglobinemia, and is observed when hemoglobinemia has reached a concentration of 1 g/L, which induces a pink discoloration of plasma.
- Myoglobinuria is secondary to myoglobinemia due to muscle damage. Myoglobin is excreted in urine when plasma concentration exceeds 0.2 g/L
- Both hemoglobin and myoglobin are toxic to renal tubules
- Renal/urologic—pigmenturia, especially hematuria
- Hemic/lymphatic/immune—hemolysis; hemoglobinuria
- Hepatobiliary—hemolysis; hemoglobinuria
- Musculoskeletal—rhabdomyolysis; myoglobinuria
PSSM, malignant hyperthermia, and glycogen branching enzyme deficiency are genetic diseases of Quarter Horse breeds. Recurrent ER may be a genetic disease of Thoroughbreds.
Incidence of PSSM and other myopathies is common, yet clinical rhabdomyolysis is less common.
- NI affects neonatal foals and mule foals
- Vascular malformations more common in foals
- Proximal urethral defects, habronemiasis, and neoplasia of the penis and distal urethra occur in geldings and stallions
- Recurrent ER is a more significant problem in young, female racehorses
- Horses with pigmenturia often have obvious historical evidence of a primary problem—“tying-up,” toxin ingestion, dysuria from cystolithiasis or lower UTI, or penile neoplasia
- Observation of pigmenturia may be the presenting complaint—vascular anomalies, cystolithiasis, proximal urethral defects, renal or bladder neoplasia, IRH, or exercise-associated hematuria
- Findings with hematuria are consistent with the underlying disease processes (e.g. AKI/ARF, urolithiasis, UTI, neoplasia, toxin ingestion) or may be normal (e.g. vascular malformations, proximal urethral defects, exercise-associated hematuria, IRH)
- Findings with hemoglobinuria or myoglobinuria reflect the underlying disease processes
- AKI/ARF—microscopic hematuria is common due to glomerular and tubular damage
- Urolithiasis—postexercise hematuria is common with cystoliths
- UTI—infection anywhere in the urinary tract, including habronemiasis of the prepuce and distal penis
- Neoplasia—nephroblastoma, renal adenocarcinoma, hemangiosarcoma, squamous cell carcinoma of the lower urinary tract, transitional cell carcinoma, and other bladder tumors (e.g. leiomyoma, lymphosarcoma)
- Renal vascular anomalies—arteriovenous and arterioureteral malformations
- Proximal urethral defects—consistently found at the dorsocaudal aspect of the urethra near the ischial arch; likely from a “blowout” of the corpus spongiosum penis into the urethral lumen during contraction of the bulbospongiosus and urethralis muscles. It can produce hemospermia or hematuria at the end of urination
- Exercise-associated hematuria—microscopic hematuria can be a normal physiologic consequence of exercise due to increased blood pressure and filtration of RBCs across glomerular capillaries; its magnitude increases with exercise intensity; gross hematuria after exercise may develop, when the bladder mucosa becomes “bruised” by trauma against the brim of the pelvis; urination prior to exercise increases risk, as urine in the bladder cushions against injury
- Blister beetle (cantharidin) toxicity can lead to inflammation and bleeding of the urinary tract
- IRH—syndrome of recurrent, potentially life-threatening hematuria of renal origin
- Primary immune-mediated hemolytic anemia—NI; incompatible blood transfusions; idiopathic
- Secondary immune-mediated hemolytic anemia—hemolysis with infectious diseases (e.g. equine infectious anemia, piroplasmosis, Clostridium perfringens), neoplasia, or drug administration (e.g. penicillins)
- Exposure to toxins—red maple leaves; onions; phenothiazines; ionophores
- Secondary to reabsorption of RBCs from previous hemorrhage into a body cavity
- Liver disease
- Rhabdomyolysis—associated with exercise or other genetic (e.g. PSSM-1) and infectious (e.g. Streptococcus equi myositis, clostridial myonecrosis) diseases
- Nutritional myodegeneration—selenium deficiency
- Postanesthetic myopathy—due to crush injury of muscle during anesthesia and other factors, especially hypotension
- Atypical myopathy (see chapter Seasonal pasture myopathy/atypical myopathy)
DIAGNOSIS
TREATMENT
MEDICATIONS
FOLLOW-UP
MISCELLANEOUS