Variation of Proteinuria in Dogs with Leishmaniasis Treated with Meglumine Antimoniate and Allopurinol: A Retrospective Study

Introduction

Canine leishmaniasis (CanL) is a zoonotic parasitic disease (enzootic in the Mediterranean basin) caused by the intracellular protozoan Leishmania infantum. The disease is characterized by a heterogeneous clinical presentation in which renal pathologic conditions are often the principal cause of death. CanL-associated nephropathy is mainly characterized by glomerular damage and is primarily attributed to intraglomerular deposition of circulating immune complexes formed by organism antigens and the antibodies produced against it.^1–3 Glomerular lesions have been histologically classified as membranous glomerulonephritis, membranoproliferative glomerulonephritis, mesangial glomerulonephritis, and focal segmental glomerulosclerosis.^4,5 Glomerulopathy that characterizes renal involvement in CanL causes proteinuria and renal failure. Results of previously published studies carried out on dogs in the USA with naturally occurring chronic renal failure suggest that persistent proteinuria is associated with greater frequency of renal morbidity and mortality due to both renal and extrarenal causes.^6,7 Moreover, the risk of developing adverse outcomes increases as the magnitude of proteinuria increases.⁷ Nevertheless, regardless of the role of proteinuria as a mediator of renal injury, it is an important marker both for increased risk of adverse outcomes and for response to renoprotective interventions.⁶ In a recent study, allopurinol appeared to decrease proteinuria and prevent progression of renal disease in dogs with leishmaniasis and glomerulonephritis.⁸

The aim of the current study was to investigate whether the degree of proteinuria evaluated by the urine protein/creatinine ratio (UP/C) in dogs with leishmaniasis classified as clinical stage C (sick) according to the Canine Leishmaniasis Working Group staging system changes during antiprotozoan treatment with meglumine antimoniate in combination with allopurinol.⁹ In addition, when available, the variations and correlations between serum levels of albumin, total globulin, total protein, and albumin/globulin ratio (A/G), and respectively between all these parameters and UP/C, both before and after treatment, were evaluated.

Materials and Methods

Results

The medical records of 280 dogs with leishmaniasis were reviewed, and 53 cases met inclusion criteria. The remaining 227 dogs were excluded because of concurrent treatment with antiproteinuric medications, such as renal diet and angiotensin-converting enzyme inhibitors, and/or angiotensin receptor blocker (n = 141), antibiotics (amoxicillin trihydrate/clavulanate potassium, cefalexin, enrofloxacin, metronidazole, or doxycycline (n = 9), cardiovascular drugs such as furosemide, spironolactone, angiotensin-converting enzyme inhibitors, pimobendan, or amlodipine (n = 11), anti-inflammatory drugs such as glucocorticoids or nonsteroidal anti-inflammatory drugs (n = 6), diagnosis of leishmaniasis not in clinical stage C (n = 28), positive serology for Ehrlichia canis (n = 9), insulinoma (n = 1), hyperadrenocorticism (n = 1), incomplete diagnostic data pre- and postantileishmaniasis treatment (n = 12), suspected splenic neoplasia (n = 1), suspected perianal adenoma (n = 1), suspected inherited nephropathies (n = 2), and lack of preventive measures to avoid reinfection (n = 5). Of the 53 cases enrolled, 34 dogs were purebreeds (belonging to 18 breeds) and 19 were mixed-breeds. Thirty-two dogs (60.4%) were males (3 castrated) and 21 dogs (39.6%) were females (7 spayed). Median age was 6 yr (mean, 6.05 yr; range, 2–17 yr). Forty-one dogs (77.4%) were treated for 4 wk, 4 dogs (7.5%) for 5 wk, 5 dogs (9.4%) for 6 wk, and 3 dogs (5.7%) for 8 wk. The median duration of therapy was 4 wk (mean, 4.49 wk; range, 4–8 wk).

Results regarding serum protein concentration and UP/C ratio have been summarized in Table 1. A significant reduction of the concentration of total protein, total globulin, and UP/C was seen after treatment compared with pretreatment levels, as well as a significant increase of the concentration of albumin and the A/G. In some cases, however, despite the trend to normalization, mean and median posttreatment values remained outside the reference ranges.

TABLE 1 Results Recorded Before and After Antileishmaniasis Treatment in 50 Paired Samples*

*

Data are reported as median (I–III interquartile interval).

†

The P value indicates the level of statistical significance between pre- and posttreatment results (Wilcoxon signed rank test).

§

UP/C values are based on 53 paired samples.

A/G, albumin/globulin ratio; UP/C, urine protein/creatinine ratio.

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Before treatment, a significant negative correlation was found between UP/C and both serum albumin concentration (ρ = −0.41; P = 0.029) and A/G (ρ = −0.39; P = 0.006), and a significant positive correlation was found between UP/C and total globulin (ρ = 0.31; P = 0.027). No significant correlation between UP/C and total protein was found (ρ = 0.27; P = 0.062). After treatment, no significant correlations were observed between UP/C and total protein (P = 0.102), albumin (P = 0.531), total globulin (P = 0.083), or A/G (P = 0.297).

Creatinine values were used only for the IRIS staging system before and after antileishmaniasis treatment. Before treatment, 40 of 53 dogs (75.5%) were IRIS stage 1 and proteinuric, 11 of 53 dogs (20.7%) were IRIS stage 1 and borderline proteinuric, and 2 of 53 dogs (3.8%) were IRIS stage 2 and proteinuric. After treatment, 27 of 3 dogs (51%) were IRIS stage 1 and proteinuric, 18 of 53 dogs (34%) were IRIS stage 1 and borderline proteinuric, 7 of 53 dogs (13.1%) were IRIS stage 1 and nonproteinuric, and 1 of 53 dogs (1.9%) was IRIS stage 3 and proteinuric (Table 2).

TABLE 2 Number of Dogs Classified According to the IRIS Staging System Pre- and Posttreatment for Leishmaniasis

IRIS, International Renal Interest Society.

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After treatment, 7 of 53 dogs (13.2%) went from either a proteinuric or borderline proteinuric stage to a nonproteinuric stage, and 12 of 53 proteinuric dogs (22.6%) changed their stage from proteinuric to borderline proteinuric (Table 3). Moreover, 24 of 53 dogs (45.3%) were proteinuric before and after treatment, albeit with a significant reduction in the degree of proteinuria. Only 4 of 53 dogs (7.5%) remained proteinuric with a slight increase in the degree of proteinuria. Six of 53 dogs (11.3%) were borderline proteinuric before and after treatment. After treatment, 13 dogs (24.5%) had modified their need for antiproteinuric therapy according to the IRIS treatment recommendations based on values of serum creatinine and UP/C (Table 4).

TABLE 3 UP/C Values of 19 Samples that Changed the IRIS Substage of Proteinuria Pre- and Postantileishmaniasis Treatment

IRIS, International Renal Interest Society; UP/C, urine protein/creatinine ratio.

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TABLE 4 Results of the 13 Dogs that Changed Their Need for Antiproteinuric Therapy According to the IRIS Treatment Recommendations Based on Values of Serum Creatinine and UP/C

IRIS, International Renal Interest Society; Tx, antiproteinuric therapy; UP/C, urine protein/creatinine ratio.

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Discussion

Proteinuric chronic kidney disease is frequently found in dogs with leishmaniasis. In CanL, glomerular deposition of circulating immune antigen/antibody complexes plays an essential role in the pathogenesis of renal injury, with subsequent development of proteinuria.^1–5 There is strong evidence that proteinuria is a risk factor for the development and progression of renal failure, and that antiproteinuric treatment with dietary modification and angiotensin-converting enzyme inhibitors reduces protein excretion and disease progression in dogs with glomerulonephritis.¹¹

The correct therapeutic management of dogs affected by naturally occurring proteinuric glomerulonephritis involves identify and treating any potential underlying disease processes, including reduction of proteinuria and management of uremia and other complications of generalized renal failure.¹²

In the current study, the authors included all patients treated with the most widely used and recommended treatment protocol for dogs with leishmaniasis: the combination of meglumine antimoniate, which selectively inhibits leishmanial glycolysis and fatty acid oxidation, and allopurinol, which inhibits protein translation by interfering with RNA synthesis.^13–15

In the current study, laboratory findings detected before treatment (i.e., hyperproteinemia, hypoalbuminemia, hyperglobulinemia, decreased A/G, proteinuria) were consistent with those previously reported by other authors.^16,17 The hyperproteinemia caused by hyperglobulinemia observed in this study is in agreement with the findings of other authors who reported that in some dogs with leishmaniasis there is an increase in total protein levels due to a greater production of antibodies.¹⁶ With regard to serum albumin, the renal loss, a decreased synthesis consistent with the role of albumin as a negative acute phase protein, and decrease protein intake may represent the most likely cause of hypoalbuminemia in CanL.¹⁸ In this study, the authors found a significant negative correlation between UP/C and serum albumin concentration before treatment, as previously reported.¹⁹ After treatment, an increase in albumin values associated with a reduction of the UP/C, although the correlation between those two parameters was not statistically significant. Considering that all dogs included in this study were fed a balanced diet without a reduction in daily caloric intake throughout the treatment period, it is likely that the hypoalbuminemia might have been due mainly to the renal loss.

Similar to a recent study, antileishmaniasis treatment reduced the magnitude of proteinuria.⁸ Nevertheless, in contrast to the aforementioned study, which showed a significant reduction (P = 0.0005) in proteinuria after 6 mo of administration of allopurinol (10 mg/kg q 12 hr), the results reported herein showed a statistically significant reduction of UP/C after 4–8 wk of treatment. One possible explanation may be related to the mechanism of action of the two drugs used. Although allopurinol acts only as a leishmaniostatic drug, meglumine antimoniate is considered leishmanicidal and also increases the phagocytic capacity of monocytes and neutrophils.^20–23 Thus, the combined use of meglumine antimoniate and allopurinol could lead to a more rapid reduction of parasitic load, and consequently, of the circulating immune complexes that affect the kidneys. That hypothesis is supported by the results of previous studies on the follow-up of dogs with leishmaniasis treated with meglumine antimoniate and allopurinol that showed a marked decrease of parasitic load.^24,25 Furthermore, several studies demonstrated that the rapid clinical efficacy of meglumine antimoniate with allopurinol mostly depends on meglumine antimoniate, rather than on allopurinol, as demonstrated by trials in which the efficacy of meglumine antimoniate and allopurinol was similar to those already described for meglumine antimoniate alone.²⁰

Such a rapid reduction of proteinuria was also observed in human visceral leishmaniasis (Leishmania donovani) when a 10 day treatment with N-methyl-glucamine was applied.²⁶

In the current study, the authors observed a statistically significant reduction in the grade of proteinuria posttreatment. In addition, 13 of 53 dogs (24.5%) modified their creatinine and UP/C values; thus, according to the IRIS treatment recommendations, they did not need antiproteinuric therapy (i.e., angiotensin-converting enzyme inhibitors and renal diet) (Table 4).¹⁰ The results of this study provides an important and clinically relevant finding that may be useful in the clinical management of proteinuric dogs with leishmaniasis in clinical stage C. In addition, this finding may have some clinical use when planning an antiproteinuric therapy concurrent to the antileishmaniasis treatment with the meglumine antimoniate/allopurinol combination and in evaluating its therapeutic efficacy.

There were several limitations to the current study, with the most important being its retrospective nature. Although the majority of dogs included were treated for 4 wk, the lack of a standardized treatment protocol for the length of therapy was another important limitation. Moreover, due to lack of data, it was not possible to evaluate blood pressure in relation to other laboratory parameters (i.e., UP/C, albumin, total globulin, total protein, A/G) for the purpose of IRIS staging.

Conclusion

To the best of the authors’ knowledge, this is the first study reporting a statistically significant reduction in the magnitude of proteinuria in dogs with leishmaniasis in clinical stage C submitted only to antileishmaniasis treatment with the combination meglumine antimoniate and allopurinol. This information may be useful to the veterinary practitioner in the management of proteinuria in dogs with leishmaniasis.