Pyelonephritis is infection and inflammation of the upper urinary tract system, including the kidneys and ureters.

Most often, an upper urinary tract infection can be suspected based on evidence of a lower urinary tract infection using common diagnostic tools including blood work, analysis of the urine and diagnostic imaging (ultrasound and x-rays using a special dye to enhance the kidneys).

What is pyelonephritis?

• Infection/inflammation of the upper urinary tract system, including the kidneys and ureters

Anatomy

• See illustration right

Clinical signs

• Most clinical signs are referable to the lower urinary tract. In other words, the pet will display signs that appear very similar to a lower urinary tract infection, including frequent urination, urinating in small amounts, straining to urinate, blood in the urine which makes it appear tinted pink or brown, urine with a very strong odor or crying/vocalizing while trying to urinate.
• Cats may also urinate inappropriately outside the box
  The pet may also display signs including decreased or absent appetite, lethargy or severely decreased activity level or unusual behavior such as hiding from the owner
  The pet may also have a fever

Diagnosis

• Most often, an upper urinary tract infection can be suspected based on evidence of a lower urinary tract infection using common diagnostic tools including blood work, analysis of the urine and diagnostic imaging (ultrasound and x-rays using a special dye to enhance the kidneys).
  It is important to remain suspicious of a kidney infection if the pet has a history of multiple lower urinary tract infections
• Common laboratory findings include an increase in the white blood cell count (leukocytosis) to fight infection
• The pet may also be extremely painful in the abdomen, which may be evident when the pet is picked up, held or petted by the owner; the veterinarian can specifically massage or palpate the kidneys to determine if they are painful
  
• A complete analysis of the urine is essential for diagnosis of this disease. This test will allow the veterinarian to determine the extent of kidney damage by examining cells or bacteria that may be present in the urine.
  
• Additionally, the urine can be cultured – meaning that a small amount of urine is placed on a special plate of growth material that can be monitored closely in a laboratory for bacterial growth. This growth can then be analyzed under a microscope and also used to determine which antibiotic would be most effective.
  
• It will be important for the veterinarian to determine if the pet is in acute renal failure, or in a situation where the kidneys are not filtering the blood normally and are not creating urine (this is an emergency)
  In other words, the pet could very quickly become much more sick and need to be hospitalized and placed on aggressive intravenous (directly into the blood stream) fluid therapy and certain lab values, that indicate kidney function, will have to be repeated frequently
  
• Pets can have an acute form of this disease or a chronic form, which can be more difficult to identify
  If pyelonephritis persists a tissue biopsy may be necessary, meaning that a specialist will obtain a small section of the kidney to examine under a microscope

Treatment

• Long – term antibiotics are usually the treatment of choice. In other words, the animal will have to take the correct antibiotic (based on urine culture and sensitivity) at the correct dose for several weeks (up to 4-8 weeks)
  
• If the pet is in acute renal failure, it will need to be hospitalized quickly
  
• Frequent monitoring of the kidney blood values and urine will be necessary
  
• It is recommended to repeat a partial urinalysis and a urine culture about 4-7 days after discontinuing the antibiotics to be sure the infection is gone

Potential complications

• One major potential complication is the risk of irreversible kidney damage and failure
  If a pets kidneys do not function properly it is life threatening and often becomes the reason why pets are humanely euthanized

Home Care

• Ensure that the pet receives the medications prescribed and as directed
  Supportive care, meaning that the pet is warm, dry, and encouraged to eat and drink

Prognosis

• Depends on other complicating factors, if present
  
• Some animals can do well for a long time; other may only live a short time after diagnosis

References

• Nelson RW, CG Couto eds. Small Animal Internal Medicine, Third Ed. St. Louis, Mosby. 2003: 1279-1281.
• Tilley LP. FWK Smith Jr. eds. The Five Minute Veterinary Consult, Canine and Feline, Second Ed. Baltimore, Lippincott Williams and Wilkens. 2000: 694-695.
• Shaw D, S Ihle eds. Small Animal Internal Medicine NVMS First Ed., Balitmore: Lippincott Williams and Wilkins 1997: 339-341.