Introduction

The immune-mediated glomerulonephritis constitutes the main glomerular pathology in dogs. This disease has as main clinical characteristic proteinuria in the absence of inflammatory urinary sediment, resulting in nephrotic syndrome (proteinuria, hypoalbuminemia, hypercholesterolemia and edema). The commitment glomerular ends in the incapacitation of the whole nephron, and the disease progression results in chronic renal insufficiency (Grauer & DiBartola 2004). In our clinical routine in the city of Belo Horizonte, one of the main causes of glomerular lesion and proteinuria in dogs is the canine visceral leishmaniasis. In Brazil, this disease is caused by protozoan Leishmania (Leishmania) chagasi. The calculation of index protein/creatinine (P/C) urinary in dogs reflects the loss of protein urinary in 24 hours, and its use facilitates greatly the diagnosis of glomerular disease. In addition, the magnitude of protein loss estimated apparently presents some correlation with severity of glomerular lesions (Lulich & Osborne 1990, Krawiec 2004). Although many studies in the literature describe glomerular lesions in dogs, the data on its correlation with clinical and laboratory parameters are scarce (Costa et al. 2003).The objective of this work was to compare histopathologic lesions found in dogs naturally infected by visceral leishmaniasis with laboratory parameters as the index of value protein/creatinine urinary ratio and urea, creatinine and albumin serum levels.

Materials and Methods

From the great region of Belo Horizonte were selected 17 dogs that presented the serological positive test for leishmaniasis in the methods of ELISA and indirect immunofluorescence or positivity in parasitological tests, such as research of the parasite, culture and PCR in bone marrow. Animals that presented concomitant diseases with potential to cause renal lesion, such as pyometra, ehrlichiosis, various bacterial infections, intoxication, among others, were discarded from this work. According to the rules of ethics committee of the institution and with the consent of the owner, urine samples were obtained by means of cystocentesis, in order to realize the urinalysis, the uroculture and the P/C urinary ratio. Animals with positive culture or urinary sediment above the normal rate were discarded from the research. Also it was collected a sample of blood and performed a dosage of urea, creatinine and albumin. The euthanasia was performed using the association of xylazine hydrochloride, thiopental sodium and potassium chloride. In necropsy, fragments of the left and right kidneys were obtained, which ones were preserved in 10% formalin and after were submitted to processing routine for the histological evaluation with hematoxylin and eosin. Histopathologic lesions were classified in accordance with the recommended by World Health Organization and graduated in mild, moderate or severe.

Results

The results obtained in 17 animals are described in the Table 1.

Discussion and Conclusions

Among the 17 evaluated dogs, all of them somehow demonstrated a form of glomerulonephritis, where the most common one was the diffuse mesangial proliferative glomerulonephritis (7 animals: 41%), followed by the focal proliferative glomerulonephritis (5 animals: 29%), diffuse membrano-proliferative glomerulonephritis (3 animals: 17%) and diffuse glomerulosclerosis (2 animals: 12%). In another study of the lesion glomerular in dogs with leishmaniasis (Costa et al. 2003), the mesangial proliferative glomerulonephritis was also the most common one, although the second one was membrano-proliferative glomerulonephritis, followed by the focal proliferative. This difference might be occur by the small number of the animals in our study. In such a way, all the animals presented a level of protein loss in the urine. Among the evaluated histological patterns, the glomerulosclerosis is considered the most severe one, once it represents the final stage of lesion glomerular. The two animals with this histological form (11 and 15) showed accentuated protein loss and azotemia, determining the diagnosis of chronic renal failure. The diffuse membrano-proliferative glomerulonephritis is considered more severe than the mesangial proliferative form, because, despite of the proliferation of the mesangial cells and inflammatory mononuclear, occurs the wall thickening capillary. The two patients with this form of lesion were the ones that presented the highest index of protein loss, and all of them have already demonstrated azotemia. The histological pattern of the focal proliferative glomerulonephritis is similar to the diffuse mesangial proliferative glomerulonephritis, although the first one presents patterns of distribution focal and thus, is considered as less severe. In the animals that demonstrated diffuse mesangial proliferative glomerulonephritis, the ones that were classified as severe, showed higher values in P/C urinary ratio (animals 13 and 14). Among the five patients with focal proliferative lesions, only one (animal 10) demonstrated a serious protein loss and azotemia, while the other four demonstrated protein loss less intense. Of 9 animals with a value in P/C urinary ratio above 5, eight (89%) have already presented laboratory indicative of chronic renal failure. Only one patient with a P/C urinary ratio bellow this pattern, already presented renal insufficiency. In 14 animals where serum albumin was obtained, 12 (85%), presented hypoalbuminemia, compatible with the protein loss in the urine. However, other factors may contribute to the hypoalbuminemia in dogs with leishmaniasis, such as intestinal loss, vasculitis, malnutrition and compensatory decrease in function of the excess of the production of the globulins. Although it is difficult to determine the real contribution of urinary loss separately for hypoalbuminemia, the fact that patients with higher values of P/C index, were those that demonstrated lower serum albumin values (animals 14, 15, 16 and 17), what suggests the importance of this way of protein loss. Thus, it was observed in this group of studied animals, that the index of the value P/C urinary, seems to demonstrate good correlation with severity of lesion histological renal. Besides of this, it is an early way to identify the renal lesion in these patients before the development of the organ failure, because the protein loss precedes the development of irreversible glomerular lesion. This fact is important in many aspects. In countries where the treatment in dogs is permitted (for example, Italy), the same is performed with drugs with nephrotoxic potential, such as the amphotericin B and aminosidine. The identification of renal lesion before the development of insufficiency it may be useful in outline a plan for a differentiated treatment in these patients. In addition to the treatment of primary factor (the leishmaniasis itself), the treatment of glomerular lesion with nephroprotectant drugs, such as ECA inhibitors, that may be useful in the reduction of the self-perpetuation of renal aggression. It is even possible that the loss of protein can serve as a marker of therapeutic success. Finally, the presence of proteinuria persistent in an animal with negative serology for leishmaniasis in an endemic area must draw the attention of clinical for the possibility of false negative result and the need to effect other diagnostic tests (PCR, immunohistochemistry, culture), although other causes of glomerular disease should be considered. Extensive studies, with a greater number of animals and other techniques for the assessment of renal lesion (electronic microscopy and immunofluorescence), are necessary for the establishment of statistical correlation between the level of protein loss and graduation of renal lesion.

Table 1. Result of the index of P/C urinary ratio and serum urea, creatinine and albumin and renal histopathology, in 17 dogs naturally infected by canine visceral leishmaniasis.

Reference values: P/C urinary ratio: up to 0.2; Urea: from 15 to 40 mg/dl; Creatinine: from 0.5 to 1.5 mg/dl; Albumin: from 2.3 to 3.8 g/dl

References

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