Dogs that have Lyme disease do not develop the characteristic raised, red circular rash at the site of penetration like people do, so when a dog with Lyme disease also has a perianal mass, it is most likely unrelated. Many factors can cause a mass to form in the area around the rectum, some serious and some not so serious; and treatment of both conditions at the same time can present a problem.
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Lyme Disease Basics
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Lyme disease is caused by the Borrelia burgdorferi bacteria, and is transmitted by ticks. The infection generally lays dormant for two to five months after the initial bite; then, affected dogs begin showing symptoms such as fever, lameness, joint swelling, loss of appetite and lethargy. In very severe cases, Lyme disease can cause progressive kidney disease that can prove fatal even after the infection is eliminated.
Perianal Mass Basics
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The most common cause of a perianal mass is an impacted anal gland. This occurs when the dog is unable to express his anal glands during bowel movements, and the fluid builds up inside and breeds bacteria, causing and infection. Other more serious causes include various cancers, most commonly adenocarcinoma. Adenocarcinoma is a rapidly-spreading tumor that requires immediate, aggressive therapy for a good prognosis
Diagnosis
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Lyme disease is diagnosed through a combination of evaluation of risk and exposure factors and the results of antibody titers. Risk factors are heavily relied upon because a dog can test positive for antibodies even if he is not infected with the disease. Impacted anal glands are diagnosed by examination and occasionally a culture of the anal gland fluid. Adenocarcinoma is diagnosed through a biopsy, wherein the vet will remove a portion of the tumor and examine it microscopically to determine what types of cells are present and how quickly they are growing. X-rays can help determine if the tumor has spread to lymph nodes or other organs.
Treatment
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Lyme disease is easily treated with tetracycline antibiotics, but adenocarcinoma requires surgery to remove the tumor and radiation therapy to slow re-growth. The problem lies in the fact that a dog must be at his healthiest to withstand cancer treatment, as surgery and radiation put a huge stress on the immune system, allowing any bacterial infection to flourish. Treating the Lyme disease first will wipe the system clean of infection and better prepare the dog for the rigors of cancer treatment. On the other hand, time is of the essence with adenocarcinoma. Waiting until the dog is free of Lyme disease could take weeks, allowing the cancer to progress and spread. The final determination is best made on a case-by-case basis, depending upon the severity of each condition. If an impacted anal gland is the issue, it is easily remedied with antibiotics, sometimes even the same kind that treats the Lyme disease.
Prognosis
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Dogs with Lyme disease generally recover well, as long as kidney function remains intact. Impacted anal glands may become a chronic issue requiring long-term maintenance, but will not seriously compromise the health of the dog. Adenocarcinoma is not so easily beaten - the prognosis for these dogs is poor, with a median survival rate of just under two years without treatment. Surgery and radiation can lengthen this period of time, and keep the dog’s quality of life at a higher level during this period.
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