Pyelonephritis (Kidney Infection) Cathy E. Langston, DVM, DACVIM (Small Animal) BASIC INFORMATION urine collected from the bladder to be negative despite infection in the Description kidney. Abdominal x-rays and an ultrasound may be recommended. Bacterial infection of the kidney is termed pyelonephritis . Infection Although culture of a piece of kidney tissue obtained by biopsy may occur within kidney tissue or in the renal pelvis, the area of increases the chance of finding the infection, the invasiveness of the kidney where urine collects before being transported to the the procedure makes it too risky for general use (the biopsy would bladder. need to be taken from deeper within the kidney than the average Causes kidney biopsy). Contrast x-ray studies, such as an excretory uro- In most cases, a urinary tract infection starts in the bladder and gram (intravenous pyelogram), are sometimes helpful. An excre- the bacteria travel upstream to the kidney. Anything that decreases tory urogram involves taking a series of x-rays after a dye (that the free flow of urine, such as obstruction of the urethra (tube shows up white on x-rays) is given intravenously. Other tests may that carries urine from the bladder to the outside), bladder, ureter be recommended to rule out diseases that cause similar clinical (tube that carries urine from the kidney to the bladder), or kid- signs and other causes of kidney disease. ney, increases the risk that the infection will spread to the kid- ney. The presence of stones and growths in the bladder and kidney TREATMENT AND FOLLOW-UP also increases the risk. Other contributing factors include chronic kidney disease, diabetes mellitus, and conditions that impair the Treatment Options immune system or cause dilute (watery) urine. Antibiotics are the mainstay of treatment of bacterial pyelonephritis The most common bacterial infection in the kidney is with and are often chosen based on a urine culture. If the urine culture is Escherichia coli . Other bacteria may also be involved, and fungal negative, a good antibiotic choice is one that is effective against infections occur rarely. E. coli . Kidney infections take much longer to cure than simple blad- der infections, so antibiotics are usually continued for 4-6 weeks. If Clinical Signs infection is related to a complete or partial blockage, removal of the If only one kidney is infected, no clinical signs may be noted, obstruction may be necessary to achieve resolution of the infection. and blood and urine tests may also be normal. If both kidneys are infected, signs may be those of kidney failure, such as increased Follow-up Care volume of urine, increased thirst, poor appetite, vomiting, nausea, With acute infections that cause complete kidney shutdown, and lethargy. Signs of a bladder infection, such as frequent urina- improvement in kidney function may be seen within 4-7 days of tion of small volumes of urine, pain on urination, and straining, starting antibiotics. With chronic kidney infections, no improve- may also be present. Blood in the urine can arise with infection in ment in kidney function may occur, but decreasing the amount of the kidneys or the bladder. ongoing damage in the kidney is still beneficial. If the infection causes acute kidney failure, decreased or no Repeating a urine culture 5-7 days after starting antibiotics is urine production may occur, and the kidneys may become pain- sometimes recommended to make sure the infection is resolving. ful and swollen. Fever and a high white blood cell count may be Culture is often recommended about a week after completing the present, but the absence of either of these does not exclude kid- antibiotics, and again a month later. Blood tests for kidney function ney infection. With chronic kidney infections, clinical signs may are usually performed at the same time. The need for repeated abdom- be minimal or absent. Chronic infection causes damage to the inal ultrasounds to monitor the course of the disease is variable. kidney; however, that results in scar tissue and shrinkage of the Prognosis kidneys. Kidney infections can be serious, life-threatening conditions, but of all the causes of complete, acute kidney shutdown, they are one of the Diagnostic Tests most treatable. About 75% of affected animals recover from an acute Initial diagnostic tests typically include blood tests to evaluate kidney infection. The success rate for chronic infections is much lower. The function and urine tests to evaluate urine concentrating ability. rate of progression of kidney failure with chronic infections is vari- A urine culture is performed, but it is not uncommon for culture of able; however, many animals can live for years after an infection. Copyright © 2011 by Saunders, an imprint of Elsevier Inc. All rights reserved..