VMED107 Equine Medicine PDF

VMED107 - EQUNE MEDICINE DISEASES OF THE URINARY SYSTEM By: Lourde Web Linghon DVM 5 TABLE OF CONTENTS 01 04 UROLITHIASIS HAEMATURIA 02 05 UROPERITONIUM POLYURIA/POLYDIPSIA (PU/PD) 03 PATENT AND PERSISTENT...

VMED107 - EQUNE MEDICINE DISEASES OF THE URINARY SYSTEM By: Lourde Web Linghon DVM 5 TABLE OF CONTENTS 01 04 UROLITHIASIS HAEMATURIA 02 05 UROPERITONIUM POLYURIA/POLYDIPSIA (PU/PD) 03 PATENT AND PERSISTENT URACHUS 01 UROLOLITHIASIS UROLITHIASIS Uroliths or calculi can form in the kidney (nephrolithiasis), ureters (ureterolithiasis), bladder (cystic urolithiasis) or urethra. If small, may be voided on urination or cause urethral obstruction. Most uroliths are composed of calcium carbonate and are spiculated and fragment easily those that also contain phosphate are smooth and hard and uncommon. UROLITHIASIS Aetiology Mineralization of a nidus – renal disease may provide the nidus for nephro- and ureterolithiasis. NSAID-induced nephropathy has been speculated to be a cause of nidus formation in horses with nephro- and ureterolithiasis. Urolithiasis also may be the consequence of disease of the upper portion of the urinary tract such as pyelonephritis. Abnormally low concentrations of natural inhibitors of mineral complexes in urine. High content of mucus produced by glands in the renal pelvis may prevent crystal aggregation. UROLITHIASIS Clinical signs of nephrolithiasis and ureterolithiasis Clinical signs of chronic renal failure (cachexia, anorexia, depression, dental tartar, oral ulcers, etc.). Calculi may cause or be the result of renal disease. UROLITHIASIS Clinical signs of cystic and urethral calculi Urine dribbling, dysuria or pollakiuria. Prolonged periods of penile protrusion. Haematuria, especially after exercise. Stilted hind limb gait. UROLITHIASIS Clinicopathological examination Evidence of renal failure may be found in a high percentage of horses with nephrolithiasis or ureterolithiasis. Haematuria. Evidence of cystitis – increased numbers of WBCs and RBCs, large number of bacteria. UROLITHIASIS Diagnosis Examination per rectum – a cystic calculus is easily palpated. - A ureterolith or dilated ureter can be palpated in some cases. Ultrasonographic examination – percutaneous or per rectum. Cystoscopic examination. Inability to pass a urinary catheter may indicate the presence of a urethral calculus. UROLITHIASIS Treatment Surgical removal of a cystic calculus: celiotomy and cystotomy. pararectal cystotomy. urethral sphincterotomy (mares). ischial urethrotomy (males). Urethrotomy at any site (for removal of urethral calculi). Electrohydraulic or laser lithotripsy via ischial uretrotomy. Antimicrobial therapy for concurrent bacterial infection. Renal function of both kidneys should be assessed before nephro or ureterolithiasis is treated surgically (nephrectomy, nephrotomy) because bilateral renal failure is a common finding. UROLITHIASIS Treatment Insuring complete removal of all fragments is important in preventing recurrence. Because urolithiasis may be the consequence of disease of the upper portion of the urinary tract, horses presented for urolithiasis should be examined for disease of the upper urinary tract. Treatment for pyleonephritis, if present, may prevent recurrence. Other preventive measures include: 1. Low calcium diet to just meet calcium and phosphorus requirements. UROLITHIASIS Treatment 2. Urinary acidification (to pH below 6) with: Ammonium chloride – commonly used but unpalatable. Ascorbic acid – questionable efficacy. Ammonium sulphate – 75 mg/kg twice daily. 3. Providing 1% salt (or 60–120g) in the concentration has also been recommended. 02 UROPERITONIUM UROPERITONIUM Aetiology and pathogenesis 1. Adults – bladder rupture. during parturition or after parturition (due to bladder necrosis). urethral obstruction by calculi (males). 2. Foals – bladder rupture and urachal tears, ureteral defects. Prenatal distension of the bladder (perhaps caused by partial torsion of the umbilical cord) coupled with pressure on the full bladder during parturition leads to rupture of bladder or urachus. Affected foals are usually male. UROPERITONIUM Aetiology and pathogenesis Congenital bladder defects may be responsible for uroperitoneum of some foals. Bladder and urachal rupture may occur due to lesions caused by urinary tract infections. Tenesmus associated with g.i. disease may cause urachal tears. Leakage of urine through a thin bladder wall. UROPERITONIUM Clinical signs (foals) Usually occur within the first week postpartum. Abdominal distension; fluid can be balloted, Tachycardia and tachypnoea. Anorexia and depression. Pollakiuria, anuria, urine dribbling, straining to urinate, or normal urination may be noted. Outward bulging of vaginal mucosa may be seen in fillies with rupture of a ureter. UROPERITONIUM Clinicopathological findings Concentration of creatinine in peritoneal fluid containing urine is usually double that of serum creatinine (exception is foals evaluated early after bladder rupture). Hypochloraemia, hyponatraemia, and hyperkalaemia in foals. These electrolyte abnormalities may not be seen in the adult. Foals are usually, but not necessarily, azotaemic. Calcium carbonate crystals may be seen in peritoneal fluid. UROPERITONIUM Diagnosis Clinical signs and clinicopathological findings. Ultrasonography. Dye (methylene blue or fluorescein) placed into the bladder and subsequently recovered in peritoneal fluid. Positive contrast cystography (do not use barium). For diagnosis of suspected ureteral defects, exploratory laparotomy and cystotomy are performed. The ureters are infused with dye such as methylene blue, and examined for leakage. Intravenous pyelography is not very useful. UROPERITONIUM Treatment Cystorrhaphy and/or resection of urachus. Preoperative therapy might involve: 1. Measures to lower the potential for cardiac arrythmia caused by high serum concentration of potassium. isotonic or hypertonic saline solution, IV. 5% dextrose, IV and insulin. calcium, IV. enemas of sodium polystyrene sulfonate (a potassium removing resin). mask induction and anaesthesia with isoflurane or sevoflurane, which are less arrythmogenic than halothane. 2. Peritoneal drainage. 3. Antimicrobial drugs.. 03 PATENT AND PERSISTENT URACHUS PATENT AND PERSISTENT URACHUS The urachus, which connects the foal’s bladder with the allantoic cavity, normally closes at or shortly after birth. A urachus that reopens after being closed is a patent urachus, and a urachus that does not close after birth is termed a persistent urachus. Aetiology The urachus may fail to close because of: Dilation of the urachus before birth caused by umbilical torsion. Clamping the umbilicus rather than allowing it to break spontaneously. The urachus may reopen because of: Umbilical infection. Lifting the foal by the abdomen. PATENT AND PERSISTENT URACHUS Clinical signs Moist navel. Urination from the navel. Navel region may be enlarged from infection. Clinical signs of infection, such as septicaemia or joint ill. Diagnosis Clinical signs. Umbilical ultrasonography – umbilical remnants are scanned for evidence of infection. PATENT AND PERSISTENT URACHUS Treatment Regardless the suspected cause, the foal should be thoroughly examined for evidence of systemic disease. If uncomplicated, merely preventing urine scald by daily cleaning and application of petroleum jelly to the umbilical region; administration of prophylactic antimicrobial drugs. If uncomplicated, cauterizing agents (silver nitrate, phenol, Lugol’s iodine) can be applied to the opening of the urachus for several days. Resection of the urachus and antimicrobial therapy are indicated as treatment of patent urachus if there is: lack of response to conservative therapy. evidence of umbilical infection. evidence of sepsis of any distant site (such as septicaemia or joint-ill). 04 HAEMATURIA HAEMATURIA Haematuria in horses can originate from the kidney, bladder, urethra, or reproductive tract. It is obvious if the urine is heavily contaminated with blood, but when urine is only blood-tinged, distinguishing haematuria from haemoglobinuria or myoglobinuria may be difficult. To establish that a reddish discoloration of urine is caused by red blood cells, urine can be centrifuged to observe a layer of red cells covered by clear urine. Normal equine urine may contain plant pigments that can stain bedding red or cause urine to turn brown or red after exposure to air or after contact with snow. HAEMATURIA Aetiology Urethral rents – a tear in the urethra that communicates with the corpus spongiosum penis causes haematuria in geldings and haemospermia in stallions. Urethritis – urethritis as a cause of haematuria is most likely an erroneous interpretation of the endoscopic appearance of the normal male urethra. The vasculature and cavernosal spaces surrounding the urethra become more prominent when the urethra dilates with air during endoscopic examination creating the appearance of severe inflammation. HAEMATURIA Aetiology Bacterial cystitis – rarely primary; usually secondary to urine retention caused by paresis or paralysis of the bladder, or by cystic urolithiasis. Pyelonephritis (suppurative bacterial infection of the renal pelvis and parenchyma) – may be the cause of severe, lifethreatening renal haemorrhage (pyelonephritis as a cause of renal haemorrhage is disputed, however). Idiopathic renal haemorrhage – may be the cause of severe, life-threatening renal hemorrhage. Reported predominantly in Arabians. HAEMATURIA Aetiology Urolithiasis. Verminous nephritis – caused by Halicephalobus gingivalis (previously known as Micronema deletrix). Renal neoplasia – of the most common tumours affecting the kidney, adenocarcinoma is more likely than lymphosarcoma to cause haematuria. Vesicular neoplasia – squamous cell carcinoma and transitional cell carcinomas. Blister beetle toxicosis – a cause of haematuria for horses fed alfalfa hay contaminated with the dead beetle. HAEMATURIA Aetiology Exercise-induced haematuria – usually microscopic but occasionally macroscopic; caused by repeated concussion of the bladder against the pelvis sufficient to cause mucosal damage during exercise. Nephrotoxic drugs – most commonly phenylbutazone administered to dehydrated horses. Vascular anomalies – such as renal arteriovenous fistulas; rare. HAEMATURIA Aetiology Polycystic kidney disease – congenital deformity of the renal tubular system leads to formation of cystic structures filled with urine: cysts eventually expand to cause renal failure (usually before 2 years of age); some affected horses have haematuria. HAEMATURIA Diagnosis Urethral rents – haemorrhage is observed to occur at the very end of urination; during endoscopy a tear in the urethra is seen on its convex surface at the level of the ischial arch (Figure 8.3). Urethritis – usually not considered to be a cause of haematuria; could be suspected when there is history of excess washing of the penis with disinfectant soaps. Bacterial cystitis – clinicopathological findings confirm the presence of urinary tract infection, and physical examination (thickened bladder palpated per rectum) and/or cystoscopic examination (thickened, hyperaemic, or ulcerated mucosa) localize the infection to the bladder. HAEMATURIA Diagnosis Pyelonephritis – clinicopathological findings confirm the presence of urinary tract infection, and urine collected from a ureter localizes the infection to the kidney. Renal biopsy confirms the diagnosis. Idiopathic renal haemorrhage – this diagnosis is made when known causes of renal haemorrhage are ruled out. Urolithiasis – typical history of haematuria after exercise; palpation of the bladder per rectum; endoscopic examination of the urethra and bladder, and ultrasonographic examination of the urethra, bladder, or kidney. HAEMATURIA Diagnosis Verminous nephritis – clinical signs of disease of other systems; Halicephalobus often causes concurrent encephalitis, osteomyelitis, and orchitis; larvae can be found in urine; renal mass seen during ultrasonography; renal biopsy may be diagnostic. Renal neoplasia – renal mass seen during ultrasonography; renal biopsy. Vesicular neoplasia – cystoscopy and biopsy. Blister beetle toxicosis – history of feeding alfalfa hay; signs of abdominal pain are seen concurrently; affected horses are often hypocalcaemic. HAEMATURIA Diagnosis Exercise-induced haematuria – a history of haematuria seen post exercise; horses that urinate before exercise are more likely to be affected (urine in the bladder acts a cushion against trauma). Nephrotoxic drugs – history of administration of a non-steroidal anti-inflammatory drug (often in excess) to a dehydrated or hypovolaemic horse. Vascular anomalies – lesion found during colour-flow doppler ultrasonography. Polycystic kidney disease – signs of renal failure; during ultrasonography an enlarged kidney containing well defined cysts is seen. HAEMATURIA Treatment Urethral rents – some heal without treatment. An 8-cm, vertical, cutaneous incision is created on the perineal raphe and centred on the ischial arch. The incision is extended through the tunica albuginea that surrounds the corpus spongiosum penis. Blood is thus diverted out this incision rather than through the rent which allows the rent to heal. Urethritis – horses usually respond to systemic antimicrobial therapy in conjunction with lavage of the urethral lumen with nonirritating antimicrobial drugs and sexual rest. HAEMATURIA Treatment Bacterial cystitis – correction of a predisposing cause (cystolithiasis or bladder paralysis); antimicrobial therapy based on culture and sensitivity and ability of antimicrobial drug to concentrate in urine (such as aminoglycosides, trimethoprim/sulfadiazine, fluoroquinolones, penicillin, and cephalosporins). Pyelonephritis – antimicrobial therapy based on culture and sensitivity and ability of antimicrobial drug to concentrate in urine. Idiopathic renal haemorrhage – nephrectomy if only one kidney is involved (after nephrectomy, however, the other kidney may bleed). HAEMATURIA Treatment Urolithiasis – surgical removal of the cystoliths and urethroliths; consider nephrectomy or nephrotomy for a nephrolith. Verminous nephritis – administration of larvicidal anthelminitic; possible nephrectomy. Renal neoplasia – no reported survivors; nephrectomy can be considered but metastasis will have likely occurred by the time the diagnosis is made. Vesicular neoplasia – no reported survivors; consider instillation of antineoplastic drugs into the bladder or partial cystectomy. HAEMATURIA Treatment Blister beetle toxicosis – symptomatic treatment with IV fluids. Exercise–induced–haematuria – treatment is not neccessary. Nephrotoxic drugs – cease administration of non-steroidal anti-inflammatory drugs, and intravenously administer fluids. Vascular anomalies – spontaneous resolution is reported. Surgical removal of an affected kidney. Polycystic kidney disease – treatment is usually unwarranted. 04 POLYURIA/PO LYDYPSIA (PU/PD) POLYURIA/POLYDYPSIA (PU/PD) Introduction The horse normally drinks 4–6% of its body weight (40–60 mL/kg) and produces half this amount (15 to 30 mL/kg body weight) of urine each day. When water consumption is greater than 10% body weight and urine production is greater than 5% body weight per day, the horse has PU/PD. Water consumption is easily measured, but, because urine production is not, PU often is assumed when stall bedding is unduly wet POLYURIA/POLYDYPSIA (PU/PD) Aetiology Excessive water intake that leads to polyuria: Psychogenic polydipsia – the most common cause of PU/PD in stabled horses; a type of stereotypic behaviour. Excessive salt consumption – a very rare viceoften is assumed when stall bedding is unduly wet Excessive urine production that leads to polyuria: Cushing’s disease (pars pituitary intermedia dysfunction) (see Chapter 9) – can cause polyuria by several different mechanisms: 1. Type 2 diabetes – excessively produced cortisol antagonizes insulin to cause glucosuria (diabetes mellitus). POLYURIA/POLYDYPSIA (PU/PD) Aetiology 2. Cortisol antagonizes antidiuretic hormone at the collecting duct (peripheral diabetes insipidus) 3. Pressure of the tumour within the pituitary gland may inhibit secretion of antidiuretic hormone (i.e. central diabetes insipidus). Type 1 diabetes (failure of pancreas to secrete insulin) – very rare in the horse; glucosuria results. Chronic renal failure – renal tubules fail to reabsorb water and electrolytes (an uncommon cause of PU/PD). Nephrogenic diabetes insipidus – hereditary condition or secondary to bacterial infection of the kidney. POLYURIA/POLYDYPSIA (PU/PD) Diagnosis 2. Cortisol antagonizes antidiuretic hormone at the collecting duct (peripheral diabetes insipidus) 3. Pressure of the tumour within the pituitary gland may inhibit secretion of antidiuretic hormone (i.e. central diabetes insipidus). Type 1 diabetes (failure of pancreas to secrete insulin) – very rare in the horse; glucosuria results. Chronic renal failure – renal tubules fail to reabsorb water and electrolytes (an uncommon cause of PU/PD). Nephrogenic diabetes insipidus – hereditary condition or secondary to bacterial infection of the kidney. POLYURIA/POLYDYPSIA (PU/PD) Treatment Psychogenic polydipsia – restrict water availability to meet maintenance (50 mg/kg/day) and increased requirements considering ambient temperature and exercise. Reduce boredom by turnout, increase forage and exercise. Cushing’s syndrome – treatment with pergolide mesylate, trilostane or cyproheptadine. Central diabetes insipidus – ADH replacement therapy is likely cost prohibitive. Nephrogenic diabetes insipidus – restrict water and salt consumption. Chronic renal failure – dietary supplementation with carbohydrates and fat, restriction of dietary protein to less than RESOURCES Did you like the resources on this template? 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