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  Discussion on Peritonitis
Author Message
New Member:
laurelw

Posted on Sunday, Oct 19, 2008 - 9:49 pm:

Hello, I'm hoping to get some help with a 22 year old QH mare that I took over care for just over two months ago. The mare had a festering abscess on her left hip that had previously been treated by placing a drain. The drain had been removed and the owner apparently thought the abscess was healed but it festered and broke skin again. It was fairly deep and on ultrasound appeared to be attached to the spleen. A abscess that appeared to be walled off was felt on her body wall on palpation as well. We treated the wound and initially began treatment with PPG IM. The next day we did a belly tap and discovered that the mare had peritonitis - protein was 1.5 g/dl. CBC showed her white count to be ~24,000. We switched her to SMZ/trimethoprim and rifampin for 10 days. White count after two weeks came back at ~18,000. We switched her to oral doxycycline and have done blood work every two weeks - ~15,800, ~14,000, now ~ 12,500, still not normal. Meantime, the wound has healed well and the mare has picked up some weight and become brighter.

We did another belly tap on her last week and the protein this time was 0.8 g/dl, but the cytological diagnosis came back as peritonitis, supportive. We repalpated her and found no evidence of the abscess that was on the body wall. The ultrasound showed that what was the external abscess no longer connects to the spleen but there is still a void that can't be identified, though it is probably fluid.

This all seems as though things are going well but the white count seems to be coming down too slowly and she still tests positive for peritonitis after 8 weeks of antibiotic treatment. I'm very concerned that we're stomping at the bacteria with the antibiotics but are not getting at whatever the primary cause is. She's still gaining weight though very slowly despite a french fries and chocolate shakes diet and she is still somewhat frail. I'm fairly convinced that if we stop the doxy when we get the white count within normal range, she'll deteriorate quickly.

Exploratory laparoscopy is not really an option as the closest equipped vet clinic is 5 hours away and the mare is not hearty enough to make the trip and then sustain the surgery.

Should we consider changing antibiotics? Perhaps IV rather than oral? What else are we missing? I'd appreciate any thoughts.
Moderator:
DrO

Posted on Monday, Oct 20, 2008 - 8:56 am:

Welcome Laurel,
If I understand you right she has been on oral doxycycline for 6 weeks and during that time the horse continues to improve (judging by clinical response and lab values) but is not yet normal. 6 weeks may be too quick to judge the treatment of internal abscesses and doxycycline is a good choice as it may be able to penetrate the abscess wall. As long as things are improving consider continuing as this is relatively easy to dose and inexpensive. Change if your horse's symptoms or labs plateau or worsen. Serum fibrinogen levels are another good way to check for chronic infection but requires special handling to be accurate.
DrO
New Member:
laurelw

Posted on Monday, Oct 20, 2008 - 12:39 pm:

Dr. O, thank you so much for your feedback. If we continue with the doxycycline what would be our gage for when to stop - when the white count is within normal or following a belly tap that comes back normal? Would the results of a serum fibrinogen potentially change our course of action? Thanks much.
Moderator:
DrO

Posted on Tuesday, Oct 21, 2008 - 6:32 am:

Consider treating for 3 weeks to a month after things return to normal. Monitoring fibrinogen is considered the gold standard for internal abscesses but I could not tell you why. I do think white counts can return to normal before the abscess is cured, in fact some horses with internal abscesses have normal WBC counts before treatment. I do think with abdominal abscesses the peritoneal fluid may be a sensitive indicator of what is going on.
DrO
New Member:
laurelw

Posted on Wednesday, Oct 22, 2008 - 5:04 pm:

Thanks very much. We'll stay the course and I'll let you know how it goes.
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