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sis has a zoonotic potential, thus humans can have a similar disease course as dogs.

Urban sprawl and flooding rains have contributed to the emergence of different serovars causing clinical infections in animals.  These may vary in different parts of the country.  "Classic" Leptospirosis infections are due to serovars canicola and icterohaemorrhagiae, Serovars implicated in newer leptospiral infections are: grippotyphosa, pomona, bratislava, ballum, bataviae, hardjo, australis, and  autumnalis.  Micro agglutination tests offered at Michigan Animal Health Diagnostic Laboratory check for only 6 of the 10 mentioned serovars. Previous infection and vaccinations will have variable titers that often make the specificity of a single titer value indeterminate.  Rising titers (fourfold change) are usually needed over a 2-4 week period for a definitive serologic diagnosis. In addition, leptospiral organisms are fastidious and difficult to culture and isolate.  Because organisms can be found in healthy animals, isolation alone is not always diagnostic for infection.

LEPTOSPIRAL SYNDROMES:

The initial phase of leptospiral infection is Leptospiremia. Organisms penetrate mucous membranes or injured skin.  Leptospiremia peaks in about 4-12 days.  The subsequent clinical course is dependent on the hosts' immune response. With no or low antibody response moderate to severe clinical disease may  result.  The appearance of circulating antibodies coincides with clearance of the leptospiremic phase and onset of the leptospiuric phase.  In this phase organisms can remain in the kidneys and be shed in the urine for weeks to months.

The clinical picture of canine Leptospirosis varies with the serovar and its virulence.  Both acute and chronic forms exist. Classically, three types of naturally occurring disease have been described:  acute hemorrhagic syndrome, acute icteric syndrome, and uremic syndrome.  These can occur alone or in combination with one another depending on the type of infecting serovar.  Circulating leptospires can create endothelial injury which promotes platelet adhesion and activation of the clotting cascade (vasculitis).  Additional organ injury may occur from antigenic components that incite an inflammatory reaction.  Thus, leukocytosis with a left shift and mild to moderate thrombocytopenia may be present.  Biochemical abnormalities and electrolyte abnormalities parallel organ involvement.  An increased body temperature is not a consistent finding.

Therefore, in the case of Leptospirosis, the clinician and sonographer must be alerted to the potential for a systemic illness with multiorgan involvement.  Due to its zoonotic potential, latex gloves should be worn when in contact with potentially contaminated urine.

IMAGING FINDINGS IN LEPTOSPIROSIS:

1. Radiographic Findings:  These vary in the severity and frequency seen.
a) Organomegaly: Approximately 70% will have one or more of 

the following -  hepatomegaly, splenomegaly, renomegaly
b) Peritoneal effusions usually mild if present (Seen in 10%)
c)  Coarse linear interstitial lung disease (Seen in 40%)

The organomegaly is from a combination of cellular swelling, inflammatory infiltrates, necrosis, vascular congestion and edema.  The effusions may be from vasculitis , organ failure and/or hemorrhage.  The lung disease is a combination of fibrinoid necrosis, hemorrhage (perivascular, intra-alveolar, and sub pleural) and thrombosis (perivascular mononuclear cells occlude smaller vessels).

2.  Sonographic Findings:  About 85% of dogs with Leptospirosis present with one of more of the following monographic abnormalities:
a)  Renomegaly (Seen in 50%)
b)   Pyelectasia (Seen in 45%)
c)   Increased Cortical Echogenicity (Seen in 75%)
d)   Perinephric Effusion (Seen in 25%)
e)  Medullary Band Sign - (Seen in 30%) This is a .5 to 1 cm broad bright band seen in the medulla and is not the same as the "renal rim" sign which is a narrow bright rim at the cortico-medullary junction.

Other non-renal findings in Leptospirosis include diffuse hypoechoic liver, gall bladder wall edema, splenic infarction , bowel wall edema or hemorrhage, mild effusion and mild lymphadenopathy.

The abnormal renal findings can occur at variable time periods following infection.  Taken individually the sonographic findings are non specific.  A number of acute renal diseases can cause renomegaly and increased cortical echogenicity.  Pyelectasia (enlarged pelvis) can be a physiologic phenomenon due to fluid or diuretic administration and thus be non specific.  The identification of perinephric effusion and a medullary band sign is highly suggestive of an inflammatory renal disease such as Leptospirosis.  Histologically, perinephric effusion is identified as sub capsular renal vascular engorgement with edema and fluid leakage.  The medullary band sign is an area of hemorrhage, congestion, edema and necrosis in the kidney, is thought to be a more specific sign, and often is found early stages of the disease.

LEPTOSPIROSIS TREATMENT:

I will leave the topic of treatment to our Internal Medicine/ICU staff.  Suffice to say early antibiotic treatment and supportive care is important for a positive outcome.  This is why I believe that ultrasound plays a role in the initial work-up of some of these cases.  Also, remember that treatment strategies should involve the leptospiremic phase as well as the leptospiuric (carrier) phase. This is important since this condition is a zoonotic disease.

In conclusion, I have attempted to combine some of the important aspects of the clinical side of this disease in order to underscore the practicality of imaging strategies, and look forward to seeing many of you in our upcoming CE conferences in January and February.