An updated review: Laboratory investigation of equine renal disease

A variety of laboratory tests are available to assist the clinician in the assessment of kidney health and function. The majority of widely used tests are indicative of altered renal function, not becoming abnormal until function is significantly compromised. These include serum urea and creatinine concentrations, serum electrolyte concentrations, urine specific gravity (USG), fractional electrolyte excretion ratios and symmetric dimethylarginine (SDMA) concentrations. Some of these parameters may also be affected by nonrenal disease. The results of a further group of tests can indicate renal damage, but do not reflect renal function. These include urine tubular enzyme concentrations, urine protein concentrations, urine neutrophil gelatinase-associated lipocalin (NGAL) concentrations and cytological abnormalities.     

In-hospital development of an aorto-cardiac fistula in a Warmblood gelding with chronic renal disease

A 20-year-old Warmblood gelding presented for evaluation and treatment of ventral oedema and azotaemia of unknown aetiology. On presentation, a diastolic heart murmur was appreciated and echocardiography revealed moderate aortic insufficiency due to chronic degenerative valve disease. The horse was hospitalised and failed to respond to oral and i.v. fluids and diuretics. Following discontinuation of all fluid and diuretic therapy, the horse became acutely agitated and developed monomorphic ventricular tachycardia. The ventricular tachycardia spontaneously converted to normal sinus rhythm, however the heart murmur changed in timing to a right basilar continuous murmur and bounding jugular pulses were noted. Repeat echocardiogram revealed an aorto-cardiac fistula with dissection into the basilar interventricular septum and left-sided chamber volume overload that was not previously present. Attempts at stabilisation were unsuccessful and euthanasia was elected. Post-mortem examination confirmed chronic renal disease of unknown aetiology in addition to an aorto-cardiac fistula originating from the right sinus of Valsalva with subsequent dissection into the basilar interventricular septum.     

Multiple congenital urogenital abnormalities in a Tennessee Walking Horse colt

A 9-month-old, Tennessee Walking Horse colt was examined for urinary incontinence. Cystoscopy revealed a single identifiable ureter that appeared abnormal, and sabulous urolithiasis. Only the left kidney, which appeared lobulated and hydronephrotic, could be located using ultrasound. Results of serum chemistries were consistent with renal failure. Necropsy revealed unilateral agenesis of the right kidney and ureter with severe left ureterolithiasis, bilateral cryptorchidism and segmental aplasia of the ductus deferens. Histopathological examination revealed cystitis and diffuse interstitial fibrosis of the left kidney. Congenital malformations should be included as differential diagnoses for urinary incontinence and urogenital disease. Ultrasonography and cystoscopy can be useful to diagnose suspected agenesis of the urinary system in adult horses.     

Retrospective study of the perioperative management and complications of ureteral obstruction in 37 cats

ObjectivesTo describe perioperative management and complications, risk factors and mortality rates in cats anaesthetized for treatment of ureteral obstruction.Study designRetrospective, clinical, cohort study.AnimalsThirty-seven client-owned cats anaesthetized for ureteral surgery.MethodsRecords with sufficient data for cats treated between March 2010 and March 2013 were examined for breed, age, gender, history, concurrent diseases, pre- and post-anaesthetic biochemical and haematological parameters, American Society of Anesthesiologists classification, anaesthetic protocol, surgical technique, surgeon, perioperative complications and mortality within 48 hours after extubation. Associations between risk factors and outcome variables were evaluated using univariable analysis. Odds ratios and 95% confidence intervals were calculated for significant parameters. Sensitivity and specificity using receiving operator characteristic curve analysis were calculated for creatinine, potassium level and standard base excess (SBE) to denote survival or non-survival.ResultsPreoperatively, all cats were azotaemic: mean ± SD urea was 31.6 ± 26.9 mmol L⁻¹ and median (range) creatinine was 562 μmol L⁻¹ (95 μmol L⁻¹ to off scale). Thirteen cats were hyperkalaemic (K⁺ > 6.5 mmol L⁻¹). Anaesthesia-related complications included bradycardia (n = 8, 21.6%), hypotension (n = 15, 40.5%) and hypothermia (n = 32, 86.5%). Seven cats (18.9%) died postoperatively. Non-survivors were significantly (p = 0.011) older (9.8 ± 1.9 years) than survivors (6.4 ± 3.1 years) and had higher potassium concentrations (p = 0.040). Risk factors associated with mortality were ASA classes IV and V (p = 0.022), emergency procedures (p = 0.045) and bicarbonate administration (p = 0.002). Non-survivors had higher creatinine concentrations (p = 0.021) and lower SBE (p = 0.030).Conclusion and clinical relevanceIntraoperative anaesthetic complications were common; increased age, poor health status, preoperative bicarbonate administration, hyperkalaemia and increased creatinine were associated with increased risk for death and can be used to predict risk for complications.     

Acute suprarenal occlusion in an American Miniature Horse

A 7-month-old Miniature filly was examined because of a 4-day history of abnormal posture, lethargy and weakness. On initial evaluation, the filly presented with an abnormal stiff gait in her hindlimbs associated with hindlimb ataxia and lumbar kyphosis. She showed hindlimb discomfort by weight shifting from one hindlimb to the other. A complete blood count revealed an acute inflammatory leukogram associated with hyperfibrinogenaemia. The measurement of the serum amyloid A concentration indicated anactive inflammatory process. Biochemistry and urinalysis results revealed a severe azotaemia associated with diluted urine despite clinical dehydration, consistent with acute renal failure. Medical treatment was initiated with fluid therapy and antimicrobials. The pain was managed with morphine sulphate only, to avoid further kidney damage. The filly maintained an abnormal gait during this time, became progressively more ataxic and uncomfortable, and developed colic episodes. Because the horse was unresponsive to pain management, euthanasia was elected by the client. Post-mortem examination revealed an occlusive thrombus within the abdominal aorta, firmly attached to the intima, partially recanalised and extending from the aorta 1 cm along the right renal artery. In the left and right kidneys, severe subacute neutrophilic pyelonephritis, with lymphoplasmacytic interstitial nephritis was noted. In the hindlimb muscles, multifocal myocyte necrosis and evidence of regeneration was present. To the authors’ knowledge, this is the first case of acute suprarenal occlusion to be described in a horse.     

Symmetric dimethylarginine values in koalas (Phascolarctos cinereus) based on oxalate nephrosis status

Oxalate nephrosis is a prevalent renal disease in koalas (Phascolarctos cinereus) of the Mount Lofty Ranges population in South Australia. The symmetric dimethylarginine (SDMA) assay is widely used in companion animals to diagnose renal disease, particularly in the early stages. This study aimed to determine: (1) reference intervals for SDMA in koalas and (2) SDMA values of koalas with oxalate nephrosis. Blood samples were collected from 41 Mount Lofty Ranges koalas euthanased on welfare grounds. Koalas were necropsied and, based on renal histopathology, were classified as unaffected (n = 22) or affected (n = 19) by oxalate nephrosis. Serum or plasma samples were analysed for creatinine, urea and SDMA and urine samples for urine specific gravity (USG). The reference interval for SDMA in unaffected koalas was 2.4–22.9 μg/dL. In koalas with oxalate nephrosis, SDMA was elevated in 74% of cases above the upper limit of the confidence interval. SDMA was elevated in three affected koalas with normal creatinine values. A positive correlation was found between SDMA and creatinine (R = 0.775, P < 0.001) and SDMA and urea (R = 0.580, P < 0.001) and a negative correlation between SDMA and USG (R = −0.495, P = 0.027). In conclusion, SDMA correlates well with other commonly used tests of renal function in koalas and should be included as part of the standard diagnostic process to increase the accuracy of oxalate nephrosis diagnosis in koalas.