11 Feb 2020
Alex Gough reviews more of the veterinary research in his monthly Veterinary Times column.
Alex Gough
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Urine specific gravity (USG) is a measure of the concentrating power of the kidneys and is related to the concentration of solutes in the urine.
Behrend et al1 performed a study to assess whether glucose in the urine, as may be found in a diabetic patient, affects the USG.
Urine samples from 102 dogs and 59 cats were used in the test, and pooled to create a variety of USGs. Glucose was then added to a small portion of each urine sample of a predetermined USG at serial dilutions, and the difference in USG after adding the glucose calculated.
The addition of glucose was found to increase the USG of the urine samples; but the more concentrated the urine, the less the difference after the addition of glucose. However, the changes in USG were not big enough to be clinically important.
The authors concluded even a large amount of glucose in the urine had only a minimal effect on USG; therefore, USG can be used as a marker of renal concentration ability, even in the presence of glucosuria.
Monte Carlo simulations are computational algorithms based on repeat random sampling to obtain results. Herman et al2 applied this technique to the problem of haemangiosarcoma diagnosis in the spleen.
A question always exists over how much of a spleen – or splenic mass – should be submitted to pathologists to optimise diagnosis, and how many sections they should examine.
This study examined 413 histopathological sections from 50 cases of canine haemangiosarcoma, with the presence of haemangiosarcoma in each section determined.
The Monte Carlo simulations were then performed – these suggested examining 5 sections of a spleen with a haemangiosarcoma gave a 95% chance of correctly diagnosing the haemangiosarcoma, and 10 sections gave a 98.6% chance of correctly diagnosing haemangiosarcoma.
The authors recommend the entire spleen is submitted for analysis, but the study suggested examining five sections from the spleen should be sufficient to make a diagnosis in most cases.
Imatinib is a tyrosine kinase inhibitor that has been used in dogs to treat various neoplasms.
Chen et al3 performed an in vitro study to assess the potential of using imatinib together with doxorubicin in the treatment of lymphoma.
A doxorubicin-resistant canine B-cell lymphoma cell line was used in this study that over-expressed a P-glycoprotein, a protein thought to be involved in doxorubicin resistance.
Imatinib was found to significantly potentiate the sensitivity to doxorubicin in these P-glycoprotein over-expressed cells. The study also suggested combining the drugs may reduce the efflux of doxorubicin, thereby increasing its retention.
The authors concluded imatinib reversed doxorubicin resistance and suggested imatinib may be helpful to combat doxorubicin resistance in the clinical setting. However, further in vivo studies are required to validate these results.
Toceranib phosphate is another tyrosine kinase inhibitor, which is licensed in the UK for the treatment of non-resectable intermediate-grade or high-grade, recurrent, cutaneous mast cell tumours in dogs. However, it has been used in the treatment of other neoplasms.
Lew et al4 performed a retrospective study to assess the efficacy and tolerability of toceranib phosphate in the treatment of heart base tumours. These tumours are common in older, brachycephalic dogs.
A total of 28 dogs with a histological, cytological or presumptive diagnosis of heart base tumour were included in the study. Of those, 27 dogs received toceranib as a single agent, while 1 dog received it in conjunction with metronomic chemotherapy – this dog was excluded from the response and survival analysis.
For the dogs on single-agent toceranib, an overall response rate of 10% was found; but with dogs presenting with metastasis, a response rate of 29% was found.
The overall median survival time was 823 days – and in dogs with metastasis, the median survival time was 532 days.
In total, 90% of dogs with clinical signs at presentation had an improvement in their clinical signs, with 81% showing a complete resolution. However, 54% of dogs showed signs of toxicity, with gastrointestinal signs the most common. Dose reductions were not usually required though.
The authors concluded toceranib is generally well-tolerated and is effective in the treatment of dogs with heart base tumours, even if the disease is advanced or metastatic.
Verterbal osteosarcoma is a tumour of the vertebra that can be painful and lead to neurological defects because of spinal cord compression.
Dixon et al5 performed a study to assess the effect of decompressive surgery on survival time, alone or combined with radiotherapy and/or chemotherapy.
A total of 22 dogs with primary vertebral osteosarcoma were included in the study.
The median survival time in dogs treated with surgery alone was only 42 days, but the range was wide – from 3 days to 1,333 days.
Three dogs were treated with surgery and chemotherapy, with a median survival time of 82 days. One dog was treated with surgery and radiotherapy, and lived for 101 days.
Six dogs were treated with surgery, radiation therapy and chemotherapy, and had a median survival of 261 days, with a range of 223 days to 653 days.
In all cases, the cause of death was related to the regrowth of the tumour.
The authors concluded that for selected cases, palliative decompressive surgery – combined with radiation therapy, possibly with the addition of chemotherapy – is the treatment of choice in vertebral osteosarcoma.
Extracorporeal shock wave therapy (ESWT) involves the use of high-intensity, focused acoustic pulses to induce shock waves in the target tissue. It has been used in tissue healing and orthopaedic conditions, but its use is controversial.
Barnes et al6 performed a randomised, prospective trial to determine the effect of ESWT on recovery after tibial plateau-levelling osteotomy (TPLO).
A total of 16 dogs were included in the study – these were randomly assigned to receive TPLO or not. Various parameters were measured – including subjective pain, stifle goniometry, stifle circumference, peak vertical force and vertical impulse.
Measures were compared pre-surgery, before ESWT, and two weeks and eight weeks post-surgery.
The peak vertical force and vertical impulse of the limbs that had been operated on in dogs treated with ESWT were higher eight weeks post-surgery compared with the preoperative values. In the control arm, the peak vertical force and peak impulse were lower two weeks post-surgery, and the vertical impulse was lower eight weeks post-surgery compared to before surgery.
The authors concluded ESWT in dogs that had undergone TPLO led to faster weightbearing.
Sotalol is a drug commonly used in the treatment of tachyarrhythmias in dogs, particularly those of ventricular origin. However, its beta blocking effect may reduce myocardial contractility, which could be clinically important in dogs with both arrhythmia and systolic dysfunction.
Treseder et al7 performed a prospective study of 10 healthy large-breed dogs to assess the inotropic and chronotropic effects of sotalol.
The dogs had a number of tests performed, including blood pressure measurement, Holter monitoring and echocardiography. The tests were repeated after about two weeks of sotalol treatment.
Sotalol reduced systolic function compared to baseline, and the maximum heart rate was reduced on Holter monitoring by 17 beats per minute compared to baseline.
The authors concluded sotalol has a mild negative inotropic effect and a mild negative chronotropic effect on higher heart rates.
