Equine Urinary System Diseases Quiz

Equine Urinary System Diseases

• Urinary System Diseases are a significant concern in equine medicine.
• A table of contents outlines the diseases discussed: Urolithiasis, Uroperitoneum, Patent and Persistent Urachus, Haematuria, Polyuria/Polydipsia (PU/PD).
• This focus is on the key aspects and diagnosis of diseases of the equine urinary system.

Urolithiasis

• Uroliths (calculi) can form in the kidney (nephrolithiasis), ureters (ureterolithiasis), bladder (cystic urolithiasis), or urethra.
• If small, uroliths may be voided or cause urethral obstruction.
• Most uroliths are calcium carbonate and spiculated.
• Some fragment easily; others containing phosphate are smooth, hard, and uncommon.
• Aetiology: Mineralization of a nidus (renal disease), renal disease can initiate nephro- and ureterolithiasis.
• Aetiology: NSAID-induced nephropathy might cause nidus formation in horses.
• Aetiology: Diseases of the upper urinary tract (e.g., pyelonephritis) could also be a factor in urolithiasis in horses.
• Clinical Signs of nephrolithiasis and ureterolithiasis: Chronic renal failure signs (cachexia, anorexia, depression, dental tartar, oral ulcers). Can be the cause or result of renal disease itself.
• Clinical Signs of cystic or urethral calculi: Urine dribbling, pollakiuria (frequent urination), dysuria (painful urination), penile protrusion, haematuria (blood in urine), especially post-exercise, and a stilted hindlimb gait.
• Clinicopathological Examination: Renal failure occurs in many horses afflicted with nephrolithiasis.
• Clinicopathological Examination: Increased WBCs/RBCs, and high bacteria counts indicate cystitis.
• Diagnosis Examination per rectum easily reveals cystic calculi.
• Diagnosis Palpation reveals ureteroliths in some cases.
• Diagnosis Ultrasonography, cystoscopy, and inability to pass a urinary catheter can also aid the diagnosis..
• Treatment Surgical removal of calculi (celiotomy, cystotomy, parectal cystotomy, urethral sphincterotomy in mares, ischial urethrotomy in males).
• Treatment Urethrostomy for urethral calculi removal.
• Treatment: Electrohydraulic/laser lithotripsy via ischial urethrotomy.
• Treatment Antimicrobial therapy for concurrent bacterial infections. Renal function assessment before surgery (nephrectomy/nephrotomy) is crucial as bilateral renal failure can occur.
• Treatment for preventing recurrence: Low calcium/phosphorus diet.
• Treatment for preventing recurrence: Urinary acidification (using ammonium chloride, ascorbic acid, or ammonium sulfate) as applicable.
• Treatment: Providing 1% salt may also be recommended in some cases.

Uroperitoneum

• Aetiology (Adults): Bladder rupture during/after parturition (due to bladder necrosis), urethral obstruction by calculi (in males).
• Aetiology (Foals): Bladder rupture and urachal tears, ureteral defects, prenatal bladder distension (possibly due to umbilical cord torsion) leading to rupture during parturition.
• Aetiology (Other): Congenital bladder defects, urinary tract infections, tenesmus (straining to defecate or urinate), and thinning of the bladder wall potentially contribute to uroperitoneum cases.
• Clinical Signs (Foals): Typically occur within the first week postpartum. Includes abdominal distension (fluid that can be "balloted"), tachycardia/tachypnea.
• Clinical Signs (Foals): Anorexia, depression, polyuria, anuria (no urination), urine dribbling, straining to urinate, normal urination, or outward vaginal mucosa bulging in fillies with ureter rupture.
• Clinicopathological Findings: Increased creatinine concentration in peritoneal fluid (often double serum creatinine, with exceptions in foals early after rupture). Electrolyte abnormalities (hypochloremic, hyponatremic, hyperkalemic) are common in foals.
• Diagnosis: Clinical signs, ultrasonography, dye injection into the bladder (methylene blue/fluorescein).
• Diagnosis Positive contrast cystography without barium.
• Diagnosis Exploratory laparotomy/cystotomy to examine ureters for dye leakage.
• Treatment: Cystorrhaphy (repair of bladder)/resection of the urachus is frequent.
• Treatment Preoperative Therapy for maintaining potassium balance, might involve isotonic/hypertonic saline, 5% dextrose, IV insulin, and calcium IV, and sodium polystyrene sulfonate (a potassium-removing resin) enemas.
• Treatment: Using inhalants like isoflurane/sevoflurane (less arrhythmogenic than halothane) for anesthetic induction.
• Treatment Consider peritoneal drainage and administer antimicrobial drugs.

Patent and Persistent Urachus

• Urachus: The urachus typically connects the foal's bladder to the allantoic cavity and normally closes at or shortly after birth.
• Patent Urachus: A persistent urachus (i.e., a urachus that does not close after birth) or a patent urachus (i.e., a urachus that reopens after being closed) involves the failure of normal urachus closure.
• Aetiology: Causes often include umbilical torsion before birth, inappropriate clamping of the umbilicus, and umbilical infection.
• Clinical signs: Moist navel, urination from the navel, likely enlarged navel region due to infection, septicemia, or joint illnesses.
• Diagnosis Evaluate clinical signs and perform umbilical ultrasonography.
• Treatment: Evaluate the cause, administer prophylactic antimicrobial drugs, consider cauterization of the urachal opening (silver nitrate, phenol, Lugol’s iodine) in uncomplicated cases.
• Treatment: Surgical resection of the urachus if conservative therapy fails or if there's evidence of infection or systemic disease.

Haematuria

• Definition: Blood in the urine, which can originate from the kidney, bladder, urethra, or reproductive tract.
• Aetiology: Urethral rents, resulting from tears; Urethritis (especially misdiagnosed from endoscopic views); Bacteria Cystitis (secondary to bladder paresis or paralysis which causes urine retention, or from cystic urolithiasis); Pyelonephritis (severe, potentially life-threatening renal hemorrhage; often debated); Idiopathic renal hemorrhage.
• Aetiology (Other): Urolithiasis, verminous nephritis from Halicephalobus gingivalis; Renal neoplasia (adenocarcinomas and transitional/ squamous cells are most common); Blister beetle toxicosis from horses consuming contaminated vegetation; Exercise-induced hematuria (microscopic but sometimes macroscopic); Nephrotoxic drugs (especially phenylbutazone in dehydrated horses); Vascular anomalies (rare, e.g., renal arteriovenous fistulas).
• Aetiology: Polycystic kidney disease (congenital deformity often causing cysts which lead to renal failure and hence, haematuria in some cases).
• Diagnosis: Urethral rents (especially visualized at the end of urination).
• Diagnosis: Urethritis (likely misdiagnosed because of normal male urethra endoscopic view showing inflammation).
• Diagnosis: Bacteria cystitis (confirmed with clinicopathological, and possibly urine culture, and sensitivity findings to confirm infection.
• Diagnosis: Pyelonephritis (examination may identify urine infection originating from the kidney, renal biopsies are confirmatory).
• Diagnosis: Idiopathic renal hemorrhage (when excluded other causes to determine if it is the underlying cause).
• Diagnosis: Urolithiasis (history and examination to discover if uroliths are present and haematuria observed post-exercise).
• Diagnosis: Verminous nephritis (signs of other systems problems).
• Diagnosis: Renal neoplasia (findings of a renal mass).
• Diagnosis: Blister beetle toxicosis (history of feeding alfalfa, also related to other abdominal pain conditions).
• Diagnosis: Exercise-induced hematuria (history of frequent exercise and hematuria after).
• Diagnosis: Nephrotoxic drugs (often excessive and administered to dehydrated horses).
• Diagnosis: Vascular abnormalities (ultrasonography).
• Diagnosis: Polycystic kidney disease (enlarged kidney and cysts typically observed during ultrasonography).
• Treatment (Urthral Rents): Some cases heal without treatment. An incision centred on the ischial arch and extended through the tunica albuginea can allow blood to escape from the urethra externally for faster healing.
• Treatment (Urethritis): Antimicrobial therapy coupled with urethral lavage and sexual rest is common treatment.
• Treatment (Bacterial Cystitis) Often involves correcting predisposing factors; antibacterial therapy guided by urine culture and sensitivity tests.
• Treatment (Pyelonephritis): Antimicrobial therapy targeted at the kidney and based on urine culture results and sensitivity results are important.
• Treatment (Idiopathic Renal Hemorrhage): Nephrectomy in cases involving one kidney is often the treatment of choice.

Polyuria/Polydipsia (PU/PD)

• Normal Equine Hydration: Horses consume 4-6% of their body weight in water and produce 15-30 mL/kg of urine daily.
• Polyuria/Polydipsia (PU/PD): Diagnosed when water consumption exceeds 10% body weight, and urine production surpasses 5% body weight daily.
• Aetiology (Excessive water intake): Psychogenic polydipsia (common in stabled horses), stereotypic behavior (rare).
• Aetiology (Excessive urine production): Cushing's disease (pars intermedia dysfunction), Type 2 diabetes mellitus (hypercortisalism), Type 1 diabetes, chronic renal failure, and nephrogenic diabetes insipidus (either inherited or secondary to kidney infections).
• Cortisol, Diabetes Mellitus: Cortisol in the collecting duct antagonizes ADH, resulting in peripheral diabetes insipidus.
• Pituitary/Diabetes Insipidus: Pressure within the pituitary gland can also reduce the secretion of ADH (central diabetes insipidus).
• Diagnosis: Evaluate water consumption, urine output; clinical findings and diagnostics of possible causes must be performed based on examination and clinical conditions.
• Treatment (Psychogenic polydipsia): Limit water access as appropriate.
• Treatment (Cushing's syndrome): Pergolide, trilostane, or cyproheptadine.
• Treatment (Central diabetes insipidus): ADH replacement (often cost prohibitive).
• Treatment (Other): Considerations for restricting water and salts, dietary supplements (with carbohydrates and fats, with reduced dietary proteins), and possible need for kidney examination will be considered on a case-by-case basis.

Test your knowledge on equine urinary system diseases, including conditions like Urolithiasis and Uroperitoneum. This quiz covers the key aspects, symptoms, and diagnosis related to the diseases affecting horses. Explore various urinary conditions and their implications in equine health.