Acute kidney injury and liver disease in an American bulldog with suspected leptospirosis

Abstract

A 6-year-old spayed female American bulldog was brought to a veterinary clinic with a 3-day history of vomiting, lethargy, anorexia, icterus, hemorrhagic diarrhea, and oliguria. The dog’s clinical signs, complete blood (cell) count, serum biochemistry, urinalysis, and diagnostic imaging were indicative of acute kidney injury and acute hepatopathy consistent with leptospirosis. Treatment for leptospirosis was initiated but, due to the dog’s lack of response and progression of clinical signs, euthanasia was ultimately elected after 3 d of hospitalization. The dog tested negative for Leptospira spp. on ELISA; urine, blood, and tissue PCRs; and immunohistochemistry. This case demonstrates that confirmation of leptospirosis can be challenging, even in an animal with the expected clinical presentation. Therefore, limitations of the diagnostic tests available, as well as the possibility of other, less likely differential diagnoses such as toxicosis, must be considered.

Case description

In August 2023, a 6-year-old spayed female American bulldog was brought to a veterinary clinic in southern Ontario with a 3-day history of vomiting, lethargy, anorexia, hemorrhagic diarrhea, and oliguria. The animal was up to date on vaccinations for rabies, canine distemper virus, canine adenovirus Type 2, canine parvovirus, and canine parainfluenza virus, with no history of Leptospira vaccination. The dog had a history of conjunctivitis, otitis externa, and perivulvar dermatitis, all of which were successfully treated. There had been no health concerns in the past year. The dog had no known travel history outside Ontario.

On physical examination, the dog was quiet, alert, and responsive, with a capillary refill time < 2 s, heart rate of 90 beats per min, respiratory rate of 28 breaths per min, and rectal temperature of 37.7°C. The dog was 5% dehydrated, appeared to experience pain on abdominal palpation, and was severely icteric (Figure 1).

Figure 1.

Severe, diffuse icterus of the dog’s skin, with petechiae and ecchymoses in the caudal abdominal region and hind limbs.

Several diagnostic tests were ordered following physical examination. A complete blood (cell) count (CBC) revealed a mild leukocytosis with mild neutrophilia [12.77 × 10⁹/L; reference interval (RI): 2.95 to 11.64 × 10⁹/L] and mild monocytosis (1.38 × 10⁹/L; RI: 0.16 to 1.12 × 10⁹/L), consistent with a stress response. Serum biochemistry revealed azotemia (urea: > 46.4 mmol/L, RI: 2.5 to 9.5 mmol/L; creatinine: 1269 μmol/L, RI: 44 to 159 μmol/L), hyperphosphatemia (> 5.20 mmol/L; RI: 0.81 to 2.20 mmol/L), hyponatremia (135 mmol/L; RI: 144 to 160 mmol/L), hypochloremia (95 mmol/L; RI: 109 to 122 mmol/L), hyperglobulinemia (51 g/L; RI: 25 to 45 g/L), elevated alanine aminotransferase (ALT: 341 U/L; RI: 10 to 125 U/L), elevated alkaline phosphatase (ALP: 1072 U/L; RI: 23 to 212 U/L), elevated gamma-glutyl transferase (GGT: 12 U/L; RI: 0 to 11 U/L), hyperbilirubinemia (> 477 μmol/L; RI: 0 to 15 μmol/L), and elevated amylase (1573 U/L; RI: 500 to 1500 U/L). Results of a SNAP (IDEXX) canine pancreatic lipase test were abnormal. Urinalysis of a cystocentesis sample revealed a urine specific gravity of 1.018, proteinuria (500 mg/dL; RI: < 50 mg/dL), pyuria (8/HPF; RI: 0 to 3/HPF), glucosuria (50 mg/dL), elevated urobilinogen (8 mg/dL; RI: 0.2 to 1.0 mg/dL), bilirubinuria (6 mg/dL), hematuria (> 50/HPF), elevated nonsquamous epithelial cell count (3 to 5/HPF), and suspected presence of bacterial cocci and rods. Abdominal radiographs revealed mild bilateral renal enlargement and abdominal ultrasound revealed enlargement of all abdominal lymph nodes. The diagnostic test results were suspicious for acute kidney injury and acute hepatopathy. The top differential diagnosis was leptospirosis. Other initial differential diagnoses included pyelonephritis, cholangiohepatitis, neoplasia, sepsis, and toxicosis. The dog’s prognosis was guarded to grave.

The dog was hospitalized on the day of presentation and treatment was initiated with ampicillin (Sterile Ampicillin Sodium Injection 250 mg; Teva Canada, Scarborough, Ontario), 22 mg/kg, IV, q6 to 8h, due to suspected leptospirosis. Gastroprotectants, including famotidine (Famotidine Omega 20 mg/2 mL; Omega Laboratories, Montréal, Quebec), 1 mg/kg, SC, q12h and sucralfate (Sulcrate 1 g/5 mL; Aptalis Pharma Canada, Markham, Ontario), 38.5 mg/kg, PO, q12h, were given due to the dog’s vomiting and in case of uremic gastritis. Additional medications given included S-adenosylmethionine (Denosyl 425 mg tablets; Nutramax Laboratories, Lancaster, South Carolina, USA), 16 mg/kg, PO, q24h, for liver protection; maropitant (Cerenia 10 mg/mL; Zoetis Canada, Kirkland, Quebec), 1 mg/kg, IV, q24h, as an anti-emetic; as well as methadone (Comfortan 10 mg/mL; Dechra Veterinary Products, Pointe-Claire, Quebec), 0.2 mg/kg, IV, q6h and gabapentin (Apo-Gabapentin 300 mg capsules; Apotex, Toronto, Ontario), 11.5 mg/kg, PO, q12h, for analgesia. Intravenous crystalloid fluids (Plasma-Lyte A 1000 mL; Baxter Corporation, Mississauga, Ontario) were given, starting at 1.5× maintenance rate and adjusted as needed. The dog was transferred to an emergency clinic overnight and returned the next morning. A SNAP Leptospira test (WITNESS Lepto; Zoetis Canada) was done that night and the result was interpreted as faintly positive.

Hematology and serum chemistries were rechecked the day after initial presentation. Most values were consistent with those on the previous day, with the major exceptions of a mild, non-regenerative normocytic hyperchromic anemia (red blood cells: 4.34 × 10¹²/L, RI: 5.65 to 8.87 × 10¹²/L; hematocrit: 0.273, RI: 0.373 to 0.617; hemoglobin: 109 g/L, RI: 131 to 205 g/L; MCHC: 399 g/L, RI: 320 to 379 g/L; reticulocytes: 6.5 K/μL, RI: 10 to 110 K/μL) and mild thrombocytopenia (116 × 10⁹/L; RI: 148 to 484 × 10⁹/L). A coagulation profile was performed and revealed a prolonged partial thromboplastin time (PTT: 18.5 s; RI: 10.6 to 16.8 s). A fecal parasitology antigen profile was negative for Giardia, flea tapeworm, hookworm, whipworm, and roundworm. Urine and blood PCR tests were negative for Leptospira spp. and serum ELISA was negative for Leptospira spp. antibodies. Despite these results, leptospirosis was still the top differential diagnosis based on clinical presentation, clinical pathology results, and urine abnormalities.

There was no improvement by the second day of hospitalization. Because of concern for a possible non-Leptospira infection, enrofloxacin (Baytril 2.27%; Elanco Canada, Mississauga, Ontario), 10 mg/kg, IV, q24h, was added to the dog’s treatment plan. In addition, metronidazole (Metronidazole 5 mg/mL; Baxter), 10 mg/kg, IV, q12h, was given because of vomiting and diarrhea. By the second night of hospitalization, the animal’s oliguria had progressed to anuria. Consequently, a bolus of furosemide (Furosemide Injection USP 20 mg/2 mL; Teligent Canada, Mississauga, Ontario), 2 mg/kg, IV, was given, followed by an additional dose the next day, with the goal of increasing urine output.

A CBC on the third day of hospitalization revealed progression to a moderate neutrophilia (23.44 × 10⁹/L), resolution of the anemia, and an improved platelet count (204 × 10⁹/L). An additional abdominal ultrasound revealed thickening of the gastric wall, thought to be uremic gastritis secondary to kidney and liver disease, as well as the previously noted renomegaly and abdominal lymphadenopathy. On physical examination, petechiae and ecchymoses were identified in the axillary region, caudal abdominal region, and hind limbs (Figure 1). These, in combination with the dog’s low platelet count and prolonged PTT, were suggestive of disseminated intravascular coagulation. By this point, the dog was showing clinical signs of tachypnea and dyspnea.

Due to the progression of clinical signs over several days and the dog’s grave prognosis, the client elected for euthanasia on the third day of hospitalization. On postmortem examination, severe, diffuse icterus of the skin, mucous membranes, and most abdominal organs was noted, as well as mild bilateral renal enlargement (~10 cm × 6 cm × 5 cm) with mild loss of corticomedullary definition, and mild, diffuse thickening of the gastric wall (~0.75 cm).

Tissue samples were sent to the University of Guelph Animal Health Laboratory (Guelph, Ontario). The major histologic findings were subacute renal tubular degeneration (Figure 2) and hepatocellular necrosis (Figure 3), consistent with leptospirosis. Additional lesions included edema and vascular congestion in the submucosa of the stomach, suggestive of uremic gastritis, as well as pulmonary alveolar hemorrhage and collapse with large numbers of circulating neutrophils in the alveolar septa, which could also support a diagnosis of leptospirosis.

Figure 2.

Microscopic image showing severe, acute, renal tubular degeneration/necrosis, characterized by cortical tubule cell hypertrophy with vacuolated cytoplasm (black arrow) and nuclear pyknosis (blue arrow). Hematoxylin and eosin, 20× magnification.

Figure 3.

Microscopic image showing severe, acute, hepatocellular necrosis with abundant mitotic figures (blue circles), as well as bile plugs within canaliculi (green circle), indicating cholestasis. Hematoxylin and eosin, 40× magnification.

Additional postmortem diagnostic tests included immunohistochemistry and Leptospira spp. PCR on kidney and liver samples. The results were negative for both tests.

Discussion

Leptospirosis is a difficult disease to diagnose based on clinical signs alone due to its variety of presentations and lack of pathognomonic signs. Clinical signs may include lethargy, inappetence, vomiting, diarrhea, oliguria, polyuria, polydipsia, icterus, fever, and hypothermia (1). Dogs with leptospiral pulmonary hemorrhagic syndrome may also show signs of acute respiratory distress, such as dyspnea and tachypnea (2). Complete blood (cell) count results associated with leptospirosis may include thrombocytopenia, anemia, and leukocytosis with neutrophilia. Serum biochemistry findings indicative of acute kidney injury and acute hepatopathy, such as azotemia, hyperbilirubinemia, elevated ALT, elevated AST, elevated ALP, hyponatremia, and hyperphosphatemia, can all support the diagnosis of leptospirosis (1). Due to the rapid progression of clinical signs and potentially fatal outcome, the recommendation is to treat all dogs with clinical signs and to interpret diagnostic test abnormalities suggestive of acute kidney injury and hepatic disease as if they identify the dog has leptospirosis, until proven otherwise (2). Additional diagnostic findings associated with leptospirosis may include hematuria and glucosuria on urinalysis; and splenomegaly, hepatomegaly, and renomegaly on abdominal radiographic and ultrasound imaging (1).

In the case described here, all initial diagnostic test results were supportive of leptospirosis, with no other obvious major differential diagnoses, leading to immediate treatment with antimicrobials. For dogs with signs of acute leptospirosis, including gastrointestinal signs, the recommendation is to begin treatment with a beta lactam antibiotic, such as ampicillin 20 mg/kg, IV, q6h. When the gastrointestinal signs resolve, the antibiotic can be changed to doxycycline (2). In this case, the dog’s gastrointestinal signs did not resolve; therefore, the dog was maintained on ampicillin for the duration of hospitalization. Concurrent fluoroquinolone use is typically not advised due to the risk of contributing to resistance in other bacteria (2). However, for this dog, enrofloxacin treatment was started in case there was another underlying bacterial infection such as pyelonephritis or cholangiohepatitis. The diagnosis of leptospirosis was not confirmed in this case and no measurable improvement was seen in response to ampicillin alone.

There are several possible confirmatory tests for leptospirosis, each with its own benefits and limitations. In this case, the antemortem tests conducted were Leptospira spp. antibody ELISA and Leptospira spp. urine and blood PCRs. Although the negative results for all these tests did not support the suspected diagnosis, leptospirosis could not be definitively ruled out. False negative results for Leptospira spp. antibody ELISAs are more likely to occur in the early stages of disease because antibody development typically requires 5 to 7 d (3). This is why no additional serologic testing, such as a microscopic agglutination test (MAT), was undertaken in this case. However, a MAT may have been beneficial in this case, as MAT is considered the current diagnostic test of choice for dogs with suspected leptospirosis (2). The “gold standard” for leptospirosis diagnosis is paired MATs, with the first MAT done on initial presentation and the second done 7 to 14 d later, with seroconversion defined as a 4-fold or greater change in titer (2,3). An additional benefit to MATs is the ability to differentiate Leptospira serogroups, though this may be limited due to cross-reactivity (2). False positives may occur if dogs have been vaccinated for Leptospira spp. In this case, the dog had never received a Leptospira vaccination, so this would not have been a concern if an MAT had been attempted (4).

Blood and urine PCR tests are of diagnostic value to identify animals with active Leptospira infections, though false negatives can occur with low numbers of bacteria, the presence of PCR inhibitors, and in animals that have begun antimicrobial treatment before sample collection (2). To maximize the chances of successfully diagnosing leptospirosis with PCR, blood and urine samples should be collected and stored before commencing antimicrobial treatment (2). In this case, both blood and urine PCRs were used. When financial limitations are present, blood PCR testing is recommended over urine initially, because Leptospira spp. levels are higher in blood than in urine for the first 10 d of disease (2). In addition, urinary shedding of Leptospira spp. is intermittent, which can also cause false negative results for urine PCR tests (2). Some healthy dogs can have Leptospira spp. in their urine, so a positive urine PCR should be interpreted in conjunction with compatible clinical signs. Liver and kidney samples were evaluated by PCR in this case and, though the negative results suggested that the dog was not infected with Leptospira spp., postmortem PCRs have limitations similar to those for antemortem PCRs (2). Because the dog in this case had received several days of antimicrobial therapy before the postmortem PCRs were conducted, a false negative result was more likely than if the samples had been taken before treatment.

Immunohistochemistry for Leptospira spp. is also prone to false negative results in dogs, with 1 study finding 40% of acute leptospirosis cases tested negative on immunohistochemistry (5). False negative immunohistochemistry results may be associated with low numbers of bacteria in the kidneys and liver, especially in acute infections (5).

With several negative results for Leptospira spp. using multiple diagnostic tests, it must be considered that, despite the clinical signs and results from serum biochemistry, CBC, urinalysis, diagnostic imaging, and histopathology all being supportive of leptospirosis, there may have been another disease affecting the dog in this case. The histopathologic results were not supportive of pyelonephritis or cholangiohepatitis and did not demonstrate evidence of neoplasia, leaving toxicosis as the top non-leptospirosis differential diagnosis. If not for financial limitations, the next step would have been to perform a general toxin screen using fresh kidney and liver samples. Although there are a limited number of toxins that could cause this presentation, one possibility is cyanobacteria (blue-green algae) intoxication. Cyanobacteria, found in water sources such as lakes and ponds, contain hepatotoxins that can cause clinical signs such as vomiting, lethargy, icterus, and anuria, as well as elevated liver and kidney values on serum biochemistry and hepatocellular and renal tubular necrosis on histopathology (6). However, some findings in this case, such as thrombocytopenia, neutrophilia, and respiratory distress, were consistent with leptospirosis but not cyanobacteria intoxication (6) In addition, this dog had no known history of interacting with any bodies of water where cyanobacteria intoxication may have occurred.

Although leptospirosis presentation may vary among dogs, veterinarians around the world must be able to recognize the signs of acute renal and hepatic disease associated with Leptospira spp. infection. Due to the limitations of each type of diagnostic test, a combination of blood/urine PCR and serologic testing, preferably paired MATs, should be used to reduce the risk of inaccurate results. Even with multiple diagnostic tests, leptospirosis may never be confirmed, as seen in the case presented here. It is important to consider other diseases, such as toxicosis, in these cases. However, leptospirosis should remain the top differential diagnosis until it can be definitively ruled out, as prompt, appropriate treatment will provide the dog with the greatest chance of survival.