Despite pyelonephritis being commonly suspected in hospitalized patients, its definitive diagnosis remains challenging and reports of this disease in cats are limited to a small number of case reports.
With the goal of characterizing the clinical signs as well as clinicopathologic and ultrasonographic changes in cats with pyelonephritis, necropsy reports from 4 veterinary teaching hospitals were searched for cats with histopathologically diagnosed pyelonephritis. For inclusion in the study, all cats had to have undergone a full physical examination prior to death in addition to a complete post-mortem.
Seventeen cats were identified for inclusion in the study. The median age was 12 years (range 3-17 years). Spayed females (n = 14) were more prevalent than castrated males (n = 3). Anorexia (7/17), lethargy (6/17) and vomiting (5/17) were the most common presenting complaints. Common physical exam abnormalities included muscle wasting (8/17), hypothermia (6/17), and cardiac murmurs (6/17). Clinical signs classically associated with pyelonephritis, such as renal pain and pyrexia were present in only 3 and 2 cats, respectively. Serum chemistries and complete blood counts were available for 11 and 10 cats, respectively. Common clinical pathologic abnormalities included azotemia, hyperphosphatemia, and non-regenerative anemia in 11, 8 and 7 cats, respectively. Of the 5 cats for which urinalysis data was available, all had bacteriuria and 4 had isosthenuric urine. Of the cats that had a urinalysis performed, four also had urine samples submitted for culture. An additional cat had urine submitted for culture without a concurrent urinalysis. Four of the 5 urine samples submitted for culture yielded bacterial growth, with E. coli isolated in 3/4 of cultures. Of the cats that had abdominal radiographs performed (n = 3) all had renal abnormalities including atypically sized kidneys (n = 2) or mineralization (n = 3). Ultrasonographic appearance of the kidneys was abnormal in all cats for which this information was available (n = 4). Common changes included mineralization (n = 4) and pyelectasia (n = 2). Histopathology of post-mortem samples revealed purely neutrophilic cellular infiltrates in 7/17 cats, with bacteria being present in 3 cases. Lymphocytic-plasmacytic pyelonephritis was diagnosed in 6/17, none of which had intralesional bacteria noted. Concurrent lymphocytic-plasmacytic and neutrophilic pyelonephritis was present in the remaining four cats, with intralesional bacteria present in 2 cases.
These findings suggest that cats with pyelonephritis are far less likely to exhibit classical physical exam findings such as renal pain and pyrexia than is commonly assumed. In addition, they are likely to have renal azotemia and may have evidence of an active infection on urine sediment.
Small Animal Rotating Intern
Iowa State University
Friday, June 15
2:30 PM – 2:45 PM
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