Ascending urinary tract infections can occur more commonly than recognized clinically

Ascending urinary tract infections can occur more commonly than recognized clinically

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Mar 01, 2004

Signalment: Canine, Labrador Retriever, 8 weeks old, male, 17.8 lbs.


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Clinical history: The puppy was vaccinated and was doing fine at that time. The puppy presented the next day for vomiting and diarrhea. The puppy was on Albon and Baytril treatment last week for coccidia (treated by the breeder).

Physical examination: The findings include rectal temperature 100.2° F, heart rate 185/min, respiratory rate 20/min, pink mucous membranes, normal capillary refill time, and normal heart and lung sounds. There is a painful mass in the mid-abdomen.


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Laboratory results: A complete blood count, serum chemistry profile and urinalysis were performed and are outlined in Table 1. The fecal examination and canine parvovirus tests are negative.

Radiographic review: Survey abdominal radiographs were done. The abdominal radiographs show evidence of possible ascites and gaseous distension of the gI tract. There is no obvious foreign body or any obstructive gas pattern seen.

Ultrasound examination: Thorough abdominal ultrasonography was performed with the puppy positioned in dorsal recumbency.


Table 1: Results of laboratory tests
My comments: There is a small amount of free fluid accumulated within the abdominal cavity – a normal finding in this age of puppy. The liver shows a homogeneous texture in its parenchyma. Hepatic vessels are prominent. Doppler study shows normal flow velocity values. No masses noted within the liver parenchyma. The gall bladder is mildly distended, and its walls are not thickened or hyperechoic. The gall bladder does contain some sludge material. The spleen shows an inhomogeneous texture in its parenchyma - no masses noted. The left and right kidneys are similar in size, shape and echotexture. Each kidney shows an increased echogenicity in the renal cortex and a mildly to moderately dilated renal pelvis. The renal vessels are dilated in the right kidney. No masses or calculi were noted in either kidney. The urinary bladder is distended with urine and contains some urine sediment material - no masses or calculi noted. The left and right adrenal glands are similar in size and shape. The stomach, small intestine and colon are normal. The pancreas shows a homogeneous texture in its parenchyma.

Case management: In this case, most likely active pyelonephritis is present. It is likely that the existing pyelonephritis is contributing to the current azotemia. A bacterial urine culture is warranted. Fluid therapy and daily antibiotics for at least four weeks are a management approach to this case. I would probably use Clavamox BID in this puppy as the preferred antibiotic. Otherwise, supportive care for the management of renal failure is indicated. After about one month of medical therapy, one will then know the degree of residual renal disease present.

Canine pyelonephritis & case management Natural host defenses against ascending urinary tract infection include mucosal defense barriers, ureteral peristalsis, ureterovesical flap valves and an extensive renal blood supply. Pyelonephritis usually occurs by ascension of bacteria causing lower urinary tract infection. Hematogenous seeding of the kidneys does not usually cause pyelonephritis. In addition, an upper urinary tract infection is frequently accompanied by a lower urinary tract infection.


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Ascending urinary tract infections probably occur much more commonly than is recognized clinically - because many dogs with pyelonephritis are asymptomatic or have signs limited to lower urinary tract infection. Signs of pyelonephritis may be none or include polyuria/polydipsia, abdominal or lumbar pain, and/or signs associated with lower urinary tract infection - dysuria, pollakiuria, stranguria, hematuria, and malodorous or discolored urine. The physical examination may show no abnormalities or pain on palpation of kidneys and a fever.

The ascending urinary tract infection may be caused by aerobic bacteria - most common bacterial isolates are Escherichia coli and Staphylococcus species and less common bacterial isolates may include Proteus, Streptococcus, Klebsiella, Enterobacter and Pseudomonas species, which frequently infect the lower urinary tract and may ascend into the upper urinary tract.

Ectopic ureters, vesicoureteral reflux, congenital renal dysplasia and lower urinary tract infection increases the risk of an ascending urinary tract infection. Medical conditions that often predispose the dog to a urinary tract infection are diabetes mellitus, hyperadrenocorticism, exogenous steroid administration, renal failure, urethral catheterization, urine retention, uroliths and urinary tract neoplasia.

Clinical diagnosis of pyelonephritis is often presumptive - based on results from CBC, serum chemistry profile, urinalysis, urine culture and imaging procedures.

A definitive diagnosis is not usually required for planning treatment. Because many dogs lack specific signs attributable to pyelonephritis, any dog with urinary tract infection could potentially have pyelonephritis. Always consider the possibility of pyelonephritis as a differential diagnosis for any dog with fever of unknown origin, polydipsia/polyuria, chronic renal failure and/or lumbar/abdominal pain.