History
A 9-month-old 286.3-kg (629.9-lb) Charolais steer was referred because of a 3-week history of unthriftiness. Over the previous 5 days, the steer's health appeared to deteriorate further with a substantial loss in body weight. On the day of hospital admission, the steer had been recumbent in its pen. On physical examination, the patient was lethargic with a high heart rate (90 beats/min) and pale mucous membranes. The steer's body temperature and respiratory rate were within reference limits. The patient was observed to be restless and was kicking at its abdomen after passing a small amount of red-tinged urine. On abdominal palpation per rectum, the left kidney was enlarged.
Serum biochemical analysis revealed high fibrinogen (1,000 mg/dL; reference range, 200 to 600 mg/dL) and creatinine (3.7 mg/dL; reference range, 0.6 to 1.0 mg/dL) concentrations. A free catch urine sample was obtained and had a specific gravity of 1.007 and pH of 9.0. Urinalysis revealed hematuria (4+ blood) and proteinuria. Microscopic examination of urine sediment revealed bacteria (both rods and cocci) and high numbers of RBCs and WBCs. Bacteriologic culture of the urine resulted in growth of Enterococcus faecalis, which was considered a contaminant. Transcutaneous abdominal ultrasonography of the kidneys was performed (Figure 1).
Sagittal ultrasonographic image of the right kidney and proximal portion of the ureter of a 9-month-old 286.3-kg (629.9-lb) Charolais steer that had a 3-week history of unthriftiness and weight loss. The image was obtained via a transcutaneous approach at the right paralumbar fossa with a 3- to 5-MHz macroconvex transducer. Cranial is to the left.
Citation: Journal of the American Veterinary Medical Association 250, 12; 10.2460/javma.250.12.1363
Sagittal ultrasonographic image of the right kidney and proximal portion of the ureter of a 9-month-old 286.3-kg (629.9-lb) Charolais steer that had a 3-week history of unthriftiness and weight loss. The image was obtained via a transcutaneous approach at the right paralumbar fossa with a 3- to 5-MHz macroconvex transducer. Cranial is to the left.
Citation: Journal of the American Veterinary Medical Association 250, 12; 10.2460/javma.250.12.1363
Sagittal ultrasonographic image of the right kidney and proximal portion of the ureter of a 9-month-old 286.3-kg (629.9-lb) Charolais steer that had a 3-week history of unthriftiness and weight loss. The image was obtained via a transcutaneous approach at the right paralumbar fossa with a 3- to 5-MHz macroconvex transducer. Cranial is to the left.
Citation: Journal of the American Veterinary Medical Association 250, 12; 10.2460/javma.250.12.1363
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
The left and right kidneys are enlarged, measuring up to 9.8 cm (reference range, ≤ 7 cm) in the dorsoventral dimension (Figure 2).1 There is moderate loss of corticomedullary distinction. The renal calyces and pelves are dilated containing a mixture of anechoic fluid and hyperechoic lobulated structures with variable acoustical shadowing. The proximal portions of the left and right ureters are moderately dilated and contain similar echogenic suspended material that is observed to move from the renal sinus into the lumen of the ureters.
Same ultrasonographic image as in Figure 1. Notice the moderate loss of corticomedullary distinction (*). Dilation of the renal calyces (†) is evident. There are formed, echogenic, lobulated structures with variable acoustic shadowing (‡) within the calyces, which were also identified in the renal pelvis and proximal portion of the ureter. Notice the dilated right ureter (§).
Citation: Journal of the American Veterinary Medical Association 250, 12; 10.2460/javma.250.12.1363
Same ultrasonographic image as in Figure 1. Notice the moderate loss of corticomedullary distinction (*). Dilation of the renal calyces (†) is evident. There are formed, echogenic, lobulated structures with variable acoustic shadowing (‡) within the calyces, which were also identified in the renal pelvis and proximal portion of the ureter. Notice the dilated right ureter (§).
Citation: Journal of the American Veterinary Medical Association 250, 12; 10.2460/javma.250.12.1363
Same ultrasonographic image as in Figure 1. Notice the moderate loss of corticomedullary distinction (*). Dilation of the renal calyces (†) is evident. There are formed, echogenic, lobulated structures with variable acoustic shadowing (‡) within the calyces, which were also identified in the renal pelvis and proximal portion of the ureter. Notice the dilated right ureter (§).
Citation: Journal of the American Veterinary Medical Association 250, 12; 10.2460/javma.250.12.1363
Color flow Doppler ultrasonography was used to differentiate the ureters from the artery and vein. Ultrasonographic findings for the steer of the present report were consistent with bilateral pyelonephritis, either caused by hematogenous spread of an infection (rare) or secondary to an ascending infection.
Treatment and Outcome
The patient received isotonic balanced electrolyte solution (6 mL/kg/h [2.7 mL/lb/h], IV) overnight. Treatment with penicillin potassium (22,000 U/kg [10,000 U/lb], IV, q 6 h), ceftiofur hydrochloride (2.2 mg/kg [1.0 mg/lb], SC, q 24 h), and flunixin meglumine (0.5 mg/kg [0.23 mg/lb], IV, q 12 h) was also initiated.
The following morning the patient was bright, alert, and responsive, although mild tachypnea (88 breaths/min) was evident. The mucous membranes had an improved pink color and all other vital parameters were within reference range. The poor body condition and severity of the ultrasonographic findings suggested a chronic condition with poor prognosis, resulting in the owner electing euthanasia of the steer.
Necropsy revealed severe bilateral enlargement of the kidneys (approx 2 times normal size) secondary to bilateral pyelonephritis. Severe perirenal edema was also present. Bilaterally, the ureters were severely enlarged (approx 6 to 10 times normal size), firm, and corded. The bladder was normal in size. Interestingly, no urinary calculi were found on gross examination, although large clumps of mucopurulent exudate admixed with a small amount of gritty material were present bilaterally in the renal pelves, ureters, and the bladder. Although there were no complete obstructions, it is likely that the mucoid exudate acted as a functional obstruction resulting in ureteral dilation.
Histopathologic diagnoses of severe suppurative tubulointerstitial nephritis with microabscesses, severe interstitial fibrosis, pyelectasia, and pyeloureter were made. Bacteriologic culture of kidney tissue specimens resulted in a heavy growth of Corynebacterium pseudotuberculosis.
Comments
Pyelonephritis in cattle usually develops secondarily to ascending urinary tract infection, almost exclusively in females because of their shorter urethra, which facilitates passage of bacteria to the bladder,2 although pyelonephritis has been reported secondary to urolithiasis in males.1 The nonspecific clinical signs of the steer in the present report including chronic weight loss and anorexia have been associated with obstructive and chronic pyelonephritis.1 Azotemia is often not found even in cattle with bilateral pyelonephritis but may be present in chronic cases.1,2 Azotemia in cattle is often the result of prerenal causes such as dehydration.3 It is often not possible to establish an accurate diagnosis and prognosis on the basis of findings on clinical examination and hematologic testing alone.2 In the case described in the present report, the combination of findings on physical examination and urinalysis confirmed urinary tract infection, but whether there was unilateral or bilateral involvement of the kidneys and ureters was not clear from these test results.
The ultrasonographic finding most suggestive of pyelonephritis in the steer of the present report as in previous reports, was detection of a large amount of echogenic to hyperechoic, sometimes flocculent, suspended debris in the renal calyces.1,2 Mineralized concretions (as seen in this steer) and nephroliths can be associated with pyelonephritis and both have been shown to cast variable acoustic shadows.1,2 Gross renal enlargement, with dilated calyces and loss of normal renal architecture, are common with pyelonephritis.1,4 Typically, unaffected bovine ureters cannot be visualized with transcutaneous ultrasonography.1 Ureteral dilation is commonly identified on necropsy examination, although palpably turgid ureteral walls such as those identified in the steer of the present report are less common.2,4 Embolic lesions supporting hematogenous infection are small in size and cannot be distinguished via transcutaneous ultrasonography.1
Pyelonephritis in cattle has been commonly associated with Corynebacterium renale and Escherichia coli infections.1–4 To our knowledge, pyelonephritis in cattle caused by C pseudotuberculosis has not been reported before. Corynebacterium pseudotuberculosis most commonly causes caseous lymphadenitis in sheep and goats and has been rarely reported to cause cutaneous abscesses and mastitis in cattle.5 Corynebacterium pseudotuberculosis can cause nephritis, generally renal abscesses in sheep and goats, through hematologic spread from a systemic infection. In horses infected with C pseudotuberculosis, internal organ involvement is seen in < 10% of cases, with single organ involvement more common than multiorgan involvement. The kidneys in horses are the second most common abdominal organ affected (second to liver).6 Horses have been reported to have similar signs of anorexia, lethargy, and weight loss over periods of days to weeks, similar to the steer of the present report. In horses with renal involvement, bacteriologic culture of urine may be positive or negative for C pseudotuberculosis.
The clinical signs in the steer of the present report were unusual, as C pseudotuberculosis infections are rarely reported for cattle and there were no other lesions found that would have been consistent with a systemic infection. The route of bacterial infection of the kidneys in the steer is unknown, making a hematogenous or ascending urinary tract infection both possible. Consistent with previous reports, ultrasonography proved to be a critical component in the diagnosis of chronic, bilateral pyelonephritis.
References
1 Floeck M. Ultrasonography of bovine urinary tract disorders. Vet Clin North Am Food Anim Pract 2009; 25: 651–667.
2 Floeck M. Sonographic application in the diagnosis of pyelonephritis in cattle. Vet Radiol Ultrasound 2007; 48: 74–77.
3 Radostits OM, Gay CC, Blood DC, et al. Diseases of the urinary system. In: Radostits OM, Gay CC, Blood DC, et al, eds. Veterinary medicine. A textbook of the diseases of cattle, sheep, pigs, goats and horses. Philadelphia: WB Saunders Co, 2000; 479–500.
4 Hayashi H, Biller DS, Rings DM, et al. Ultrasonographic diagnosis of pyelonephritis in a cow. J Am Vet Med Assoc 1994; 205: 736–738.
5 Jost BH, Billington SJ. Corynebacterium and Arcanobacterium. In: Gyles CL, Prescott JF, Songer JG, et al, eds. Pathogenesis of bacterial infection in animals. 3rd ed. Ames, Iowa: Blackwell Publishing, 2004; 77–86.
6 Pratt SM, Spier SJ, Carroll SP, et al. Evaluation of clinical characteristics, diagnostic test results, and outcome in horses with internal infection caused by Corynebacterium pseudotuberculosis: 30 cases (1995–2003). J Am Vet Med Assoc 2005; 227: 441–448.
