Urology
April 2013 (Vol 34, No 4)

Case Report: Pyelonephritis and Chronic Renal Insufficiency in a Cat

  • by
  • Tina M. DeVictoria , BS , CVT

Mimi—a 5-year-old, 9.3-lb (4.23 kg), spayed domestic shorthaired cat—presented with a 2-day history of lethargy, a 50% decrease in appetite, and an increased frequency of urination; in addition, she had vomited once. Mimi was an indoor/outdoor cat and tended to roam when outdoors.

On physical examination, the patient was depressed but had normal mentation, was febrile at 105.3°F (normal: 100°F to 102.5°F) and had tacky mucous membranes, a normal capillary refill time of <2 seconds (normal: 1 to 2 seconds), tachycardia (heart rate: 220 bpm; normal: 120 to 140 bpm), and a respiratory rate of 28 breaths/min (normal: 8 to 30 breaths/min). On abdominal palpation, the patient was painful, particularly in the kidneys, and the urinary bladder was small and soft. The patient showed signs of dehydration, including tacky mucous membranes and decreased skin turgor.

Diagnosis

The diagnostic differentials were pyelonephritis, renal abscess, trauma, fever of unknown origin, infectious disease (e.g., FIV, FeLV), neoplasm, and tick-borne disease (bartonellosis).

Mimi was admitted to the hospital for in-house blood work, including a blood chemistry profile, a complete blood cell count, and electrolyte level testing. A urinalysis including bacterial culture and sensitivity testing was performed by an outside laboratory. The blood work showed dramatic leukocytosis (leukocytes: 28.92 ×103/µL; normal: 5.50 ×103/µL to 19.50 ×103/µL), neutrophilia (neutrophils: 26.78 ×103/µL; normal: 2.50 ×103/µL to 12.50 ×103/µL), basophilia (basophils: 0.17 ×103/µL; normal: 0 to 0.10 ×103/µL), hyperglycemia (glucose level: 235 mg/dL; normal: 74 to 159 mg/dL), and azotemia (blood urea nitrogen [BUN] level: 61 mg/dL; normal: 16 to 36 mg/dL; creatinine level: 3.2 mg/dL; normal: 0.8 to 2.4 mg/dL). The next day, the urinalysis results showed proteinuria (1+; normal: 0), glucosuria (2+; normal: 0), pyuria (white blood cell count: 11 to 20 per high-power field; normal: 0 to 3), and rod bacteria (10 to 25 per high-power field; normal: 0). The urine specific gravity was normal (1.026; normal: 1.015 to 1.060). The urine culture results did not arrive until 3 days after the patient was hospitalized. Mimi’s clinical signs and laboratory results were consistent with pyelonephritis.

Treatment

A 20-gauge intravenous (IV) catheter was placed in the patient’s right cephalic vein to begin administering Plasma-Lyte (Baxter Healthcare Corporation, Deerfield, IL) at 5 mL/kg/h IV. Once a sterile urine sample was collected, the patient was given ampicillin (22 mg/kg IV q8h, slowly) and enrofloxacin (5 mg/kg IV q24h, slowly and diluted). To avoid interference with the sensitivity test results, antibiotics were not initiated until the sterile urine sample (for urinalysis and urine culture) was collected. The patient’s temperature was monitored every 2 to 4 hours and ranged between 102.8°F and 105.3°F for the first 24 hours.

On day 2, Mimi’s BUN and creatinine levels improved to 40 mg/dL and 2.9 mg/dL, respectively. Mimi’s appetite was moderate, hydration was improving, temperature had lowered to 103.1°F, and abdomen was slightly more comfortable on palpation. On the urinalysis, glucosuria raised a concern for diabetes mellitus; however, the blood glucose level was normal. IV administration of ampicillin and enrofloxacin was continued.

On day 3, the BUN and creatinine levels (48 mg/dL and 2.8 mg/dL, respectively) were similar to those of the previous day, the temperature was still fluctuating, and the appetite had decreased. Due to these findings, the doctor recommended FIV and FeLV testing, the results of which were negative. Renal lymphoma and chronic renal insufficiency (CRI; also known as chronic kidney disease [CKD]) were added to the differential diagnosis. Three months before presentation, Mimi had undergone blood work consistent with stage 2 CRI, with an elevated BUN level of 46 mg/dL and normal creatinine level of 2.0 mg/dL; at that time, the patient was not being treated for renal insufficiency.

Table 1. Staging of Chronic Kidney Disease in Catsa,b

Stage

Feline Plasma Creatinine Concentration (mg/dL)

Condition

1

<1.6

Absence of azotemia

Other renal abnormalities are present (e.g., inadequate urine concentration without an identifiable nonrenal cause; abnormal findings on renal palpation and/or imaging; persistent proteinuria of a renal origin; abnormal renal biopsy results; a progressively elevating creatinine level).

2

1.6–2.8

Mild renal azotemia

The low end of this range lies within the reference range for many laboratories, but because the creatinine level can be insensitive for screening, patients with creatinine values close to the upper limit of normal often have excretory failure. The clinical signs are usually mild or absent.

3

2.9–5.0

Moderate renal azotemia

Systemic signs may be present.

4

>5.0

Severe renal azotemia

Systemic signs are usually present.

 

aIRIS substaging can be performed by measuring urine protein and arterial blood pressure.

bInternational Renal Interest Society. 2009 Staging of CKD. iris-kidney.com/pdf/IRIS2009_Staging_CKD.pdf. Accessed May 2012.

describes renal disease staging in cats according to the International Renal Interest Society.

The doctor recommended abdominal ultrasonography. The patient’s IV catheter was replaced to ensure that it was not contributing to the fever. IV administration of ampicillin and enrofloxacin was continued, and administration of cyproheptadine (1 mg/kg q12h PO as needed) was initiated to stimulate appetite.

On days 4 and 5, the patient’s BUN and creatinine levels remained stable, but high, at 47 mg/dL and 2.8 mg/dL, respectively. The IV fluid rate was increased by 4 mL/h. The urine culture results arrived, revealing Escherichia coli sensitive to marbofloxacin, so the patient was transitioned to marbofloxacin (5 mg/kg q24h PO for 28 days). The patient’s appetite and fever both improved. The final diagnosis was pyelonephritis with stage 3 CRI.

Outcome

On her final day in the hospital, Mimi underwent abdominal ultrasonography, which showed both kidneys to be moderately irregular in shape and decreased in size. The right kidney was more severely affected and smaller than the left kidney. There was also mild distention of the right renal pelvis, which can be due to inflammation and pyelonephritis. These results confirmed the presence of pyelonephritis and CRI. The patient was discharged with 28 days of oral marbofloxacin, long-term famotidine (0.5 mg/kg PO q24h), oral cyproheptadine as needed, a low-protein diet, and at-home subcutaneous fluid therapy (every other day). Appointments were scheduled to take place (1) in 14 days to recheck the patient’s kidney values and (2) 7 days after completion of antibiotic therapy to perform a urinalysis, culture, and sensitivity testing. The patient’s attitude, fever, and dehydration all improved during hospitalization, and the patient’s abdomen was not painful at discharge. Although the patient’s renal parameters were not completely corrected, they were stabilized.

Discussion

Pyelonephritis is inflammation of the kidneys caused by bacterial invasion. This often occurs due to an ascending urinary tract infection originating in the bladder. Typical clinical signs include lethargy, depression, anorexia, and renal pain; diagnostic findings include fever and leukocytosis.1 All of these were present in this case. Therefore, uncomplicated urinary tract infection could be ruled out in this case because this combination of clinical and diagnostic findings rarely occurs in bacterial infection of the bladder alone. Other clinicopathologic findings consistent with pyelonephritis include azotemia, polyuria, hyposthenuria, urinalysis results that are positive for bacteria, blood, and/or white blood cells, and ultrasonographic abnormalities (e.g., dilation of the renal pelvis, asymmetric filling of diverticula, dilated ureters)1

Box 1. Clinicopathologic Findings That Can Be Associated With Bacterial Pyelonephritis in Dogs and Cats1

• Fever
• Leukocytosis
• Renal pain
• Cellular casts in urine sediment
• Renal failure (i.e., azotemia, inability to concentrate urine, polydipsia/polyuria)
• An excretory urogram and ultrasonographic abnormalities (i.e., renal pelvis dilation or asymmetric filling of diverticula; dilated ureters)
• Bacteria in inflammatory lesions identified by renal histologic studies
• A positive result from a bacterial culture of ureteral urine obtained at cystoscopy (a Stamey test)
• A positive result from a bacterial culture of urine obtained after rinsing the bladder with sterile saline solution (a Fairley test)
• A positive result from a bacterial culture of fluid aspirated from the renal pelvis (pyelocentesis) using ultrasound guidance

  

In this case, the diagnostic approach included blood work (i.e., chemistry profile, complete blood count, electrolyte levels) to screen for azotemia, leukocytosis, electrolyte derangement, or concurrent disease; urinalysis with urine culture and sensitivity to screen for bacterial infection and determine the urine specific gravity; and abdominal radiography and/or ultrasonography to detect urinary tract disease.

Pyelonephritis can result in CRI. While pyelonephritis can often be resolved, CRI is progressive and can be managed, but not reversed.2 CRI is the most common kidney disease affecting cats and dogs. The cause of CRI is often unknown but may derive from infectious/inflammatory conditions, nephrotoxins, or cancer. In this case, CRI was likely caused by pyelonephritis. The signs of CRI can be similar to those of pyelonephritis, but they can be more chronic. In addition, CRI can be associated with more dramatic polyuria and polydipsia. Cats with CRI often present for urinating inappropriately or more frequently.

Treatment of pyelonephritis and CRI involves symptomatic treatment (e.g., treating vomiting, anorexia, dehydration, and/or fever) and antibiotic therapy based on culture results. Vomiting and anorexia can be treated with H2-receptor antagonists such as famotidine. A neurokinin-receptor antagonist such as maropitant citrate can be used if famotidine is not effective. Urinalysis, culture, and sensitivity testing are important for determining the appropriate antibiotic therapy. In Mimi’s case, marbofloxacin, a fluoroquinolone, was effective against E. coli. The prognosis for patients with pyelonephritis is usually good if it is uncomplicated by concurrent conditions or diseases. The disease progression for patients with CRI often depends on owner compliance, but CRI is incurable.

Treatment of CRI can include long-term therapies such as diet modification and fluid therapy. Diets that are low in protein and phosphorus decrease the requirement for renal clearance of phosphorus, urea, and other nitrogenous metabolites.1 While IV fluid therapy is often required to initiate treatment of kidney diseases, subcutaneous fluid therapy can be administered, even at home, to further manage kidney disease. Periodic blood work (to measure disease progression), urinalysis, and blood pressure monitoring are important. Mimi’s blood pressure was not monitored during hospitalization. Blood work alone can detect azotemia but can also evaluate parameters such as the phosphorus and potassium levels. Hypertension can develop in patients with CRI. Hypertension can cause or be caused by kidney disease, resulting in or exacerbating renal function changes. Therefore, treating hypertension is important for slowing progression of CRI.

Mimi’s case highlights a somewhat rare condition in veterinary patients. Unfortunately, Mimi’s condition required several days of in-hospital treatment. When Mimi was not improving as expected for a patient with pyelonephritis alone, additional diagnostics (i.e., FIV and FeLV testing and abdominal ultrasonography) were performed to ensure that she was receiving appropriate treatment. Blood pressure could have been monitored routinely to detect hypertension (which can contribute to or cause kidney disease) or hypotension (which can be secondary to shock). Abdominal ultrasonography is preferred to radiography and was pursued initially in this case because the owner agreed to it. The follow-up plan for the patient and the owner’s compliance with at-home treatments were ideal, so it is hoped that these factors will help slow the progression of Mimi’s condition.

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REFERENCE:

1. Renal failure. In: Nelson RW, Couto CG, eds. Small Animal Internal Medicine. 3rd ed. St. Louis: Mosby; 2003:608-623.

2. Microutsicos TM. Chronic kidney disease in small animal practice. Natl Assoc Vet Tech Am J 2010:18-24.

AUTHOR DISCLOSURE:

When Ms. DeVictoria wrote this article, she was working at Princeton Animal Hospital, Princeton, New Jersey. She now works for The Animal Hospital at Kingston and Blawenburg in New Jersey.

Tags: Urology Veterinary Technician Journal Feline