The patients evaluated by B-mode ultrasound did not have significant morphologic changes related to structural kidney injury. The kidneys presented normal size and architecture, with homogeneous hypoechoic aspect compared to splenic parenchyma. Most patients had a preserved corticomedullary ratio. These results are in agreement with Bragato et al. (2015), who mentioned that diffuse renal changes can be hard to diagnose via B-mode ultrasound. When present, common changes would be nephromegaly, increased or decreased echogenicity of the renal cortex, renal pelvis dilation, among others.
Oyuela-Carrasco et al. (2009) observed that elderly patients may show an increase and later decrease in renal mass, which may be compatible with glomerulosclerosis and tubulointerstitial fibrosis, which in turn may lead to kidney injury. These results could explain the development of CKD observed in the present study, where the majority of the dogs were old, thus increasing the possibility that they already had some type of degenerative renal injury due to age, but without a correlation with kidney size.
In the present study, the parameters and indices evaluated by Doppler and CEUS did not show significant differences between groups or moments, and urea and creatinine levels remained within normal limits for the species throughout the experiment. Dong et al. (2013) described that CEUS can show changes in renal flow six weeks before creatinine values are significantly increased for the species, allowing an early diagnosis of renal diseases and their treatment. Similarly, Melo et al. (2006) and Martín et al. (2017) described the importance and reliability of Doppler flowmetry in identifying early changes in renal flow, anticipating irreversible structural damage to the kidneys. As such, the authors consider that there was no change in renal perfusion resulting from the treatment, and that the development of proteinuria and CKD were due to factors inherent to the patients and not the treatment.
Da Silva et al. (2014) reported that hematologic changes are common in patients with mammary neoplasia, often with presence of anaemia. They observed that 11% of bitches with mammary neoplasia had erythrogram correlated with tumour staging, where tumours in stage III, IV, and V had greater haematological changes. This study explains the present erythrogram findings, where patients had decreased erythrocyte count and haemoglobin at M0, but after surgery, these parameters gradually increased. This increase was significant starting at M3, which correlates with the absence of paraneoplastic anaemia in most patients after tumour removal.
Dietl et al. (2007) stated that between 50% and 70% of people with advanced stage neoplasia had anaemia caused by the tumour. However, De Oliveira et al. (2013) reported that changes in oncologic patient are not exclusively due to the presence of tumour or its location. Paraneoplastic syndromes may also be involved in hematologic changes, especially due to sequestering of iron and decrease in erythropoiesis and erythrocyte half-life. Surgical removal of the neoplasia is indicated as definitive treatment. The improvement seen on erythrograms in the present study supports these statements.
Figueiredo (2019) stated that inflammation is an important factor for neoplastic development and progression, and results from the tumour microenvironment composed of neoplastic cells, macrophages, neutrophils, lymphocytes, and other inflammatory cells, as well as cells that make up blood vessels, thus forming a pro-tumoral environment. The same author mentions that the presence of neutrophils and B lymphocytes in the tumour microenvironment may aid tumour growth and be related to a worse prognosis. In the present study, the number of bands and lymphocytes were higher in most of the moments in control group, however, no relationship was observed with prognosis in these patients.
In this context, Forget et al. (2013) cited that an inflammatory state can be better evaluated based on the neutrophil/lymphocyte ratio (RNL) and this parameter was considered by various studies as an important prognostic factor in patients with different neoplasia, where mammary neoplasia was one of the most common. Jia et al. (2015) determined that pre-treatment RNL is a predictive indicator of disease-free survival and overall survival in patients with mammary neoplasia regardless of the tumour size or patients’ age, where higher RNL values (> 2.0) indicate a poor prognosis. Correlating these findings with those of the present study, RNL was lower in the treated group during second and third months, which may be related to the high mortality rate in control group in these moments. In spite of a high RNL in several moments in both groups, the absolute lymphocyte and band counts were lower in treated group. This response may be explained by the anti-inflammatory effect of carprofen, which would reduce local and systemic inflammatory process [19].
Cavalcante et al. (2008) mentioned that prolonged use of carprofen can affect liver enzymes, with an increase in ALT being more common, reporting 20 cases of liver toxicity due to carprofen administration, where 18 dogs showed signs of liver toxicity after receiving carprofen for 19 days and two dogs at 60 and 180 days. The main clinical signs observed in these patients were vomit, anorexia, and jaundice, and they all had an increase in ALT levels (above the normal range). In the present study, increased ALT was observed in patients treated with carprofen; however, ALT did not rise above the normal limits for the species. This was contrary to results obtained by Autefage & Gossellin (2007), who administered carprofen to 110 dogs during 120 days and observed no clinical signs of liver toxicity or changes in liver enzyme levels during treatment.
Lucas et al. (2019) reported that NSAIDs can lead to acute or chronic kidney injury when used for prolonged periods. In the present study, no acute renal injury (azotaemia) was observed over six months when carprofen was given for 90 days. As for development of borderline and true proteinuria as markers of CKD, it was similar between groups, which highlights that the use of carprofen during the aforementioned period does not predispose to development of renal impairment. Results are in agreement with those obtained by Luna et al. (2007), who did not report renal changes in patients treated with carprofen during 90 days, by Raekallio et al. (2006) in patients treated during 60 days, and by Autefage & Gosselin (2007) in patients treated during 120 days.
From a physiologic standpoint, when there is hypovolemia, the renin-angiotensin-aldosterone system is activated, causing vasoconstriction and an increase in sodium and water resorption. Prostaglandins (PGE2, PGD2) stimulate compensatory vasodilation of afferent arterioles and angiotensin II stimulates vasoconstriction of the efferent arterioles, thus improving renal blood flow and avoiding possible renal changes. Prostaglandins are products of the conversion of arachidonic acid from COXs, so in the context of kidney injuries due to administration of NSAIDS, it could be said that acute renal injury has a hemodynamic origin because of the limitation of this compensatory system [25, 26, 27, 28]. This is the mechanism used by several studies [26, 27] to explain that the prolonged use of NSAIDS may result in the development of CKD; however, in the present study, this was not observed in association with administration of carprofen during 90 days within 180 days of follow-up.
It can be concluded that under the specified conditions, the use of carprofen for 90 days causes minimal changes in renal perfusion, red blood cell parameters, and ALT activity, reducing the amount of inflammatory cells in the blood, and does not result in kidney injury or change the mortality rate. As such, it is considered that carprofen can be used safely in patients that require auxiliary cancer treatment and in which its benefits will outweigh the side effects.