Monday, May 30, 2011

A Nasty Spider Bite

I was at work one day when I walked into the clinic exam room to find a new patient waiting for me. 
“Hello, my name is Sharon, I’m a physician assistant, how can I help you?”
The patient, whom I’ll call Roy, looked at me, then looked down at his bare knee.  My eyes followed his and I instantly knew why he had come.  The patient’s right knee was swollen and erythematous (red) on the outer aspect. 
“Okay, when did this happen, Roy?”
“A couple of days ago.  Initially I thought it was just a bad mosquito bite and it would go away the next day, but instead it got worse.”
“So this happened over the weekend, I presume?”
“Yes, I was doing some spring cleaning of my garage, getting rid of some trash, old things I didn’t want anymore.  I took some of the trash bags and a piece of broken down patio furniture out to the curb for the trash men to pick up.  And when I came back into the house to clean up for dinner that’s when I noticed something had bitten me.  I left it alone, thinking it was a mosquito bite, but like I said it only proceeded to get worse. Now it’s three days later and I can barely walk it hurts so bad.”
“I can see that.  Okay, well do you have any brown recluse spiders in your house or garage that you know of?”
“No, not that I know of.”
“Well, your knee reminds me of that kind of a bite.  Your history of doing spring cleaning in your garage, is a perfect scenario for such a spider bite.  Brown recluse spiders love living in a dark environment, where it’s quiet and they are unperturbed by anyone.  Your garage is such a place, until you started cleaning it out that is.”
“A spider did this to my knee?”
“Afraid so.”

Spring and summer tends to be the times that patients come in with spider bites they have encountered while cleaning their house, or garage.  Most spider bites are just bothersome, they go away within a few days, but then there is the brown recluse spider. 
This particular spider is a very small spider, no larger than a quarter in size.  But for its size it packs a powerful amount of venom in its bite.  Based on whether the patient has been bitten before or not will then judge the amount of response the patient has.  Patients can have a response from a bad spider bite which resolves over a week or so to full fledged immunological response where the whole area swells up, the patient has erythema, increased heat, fevers and the possibility of an infection. 
For us, medical providers we have to assess how widespread the spider bite/venom has gone, whether there is a surrounding infection, is the site draining infected fluid, what is the level of pain, is there the possibility of joint involvement, and whether the patient needs steroids to calm the immune system down. 

I proceeded to ask him the usual questions as to what medications he was one, what his past medical history was and what medication allergies he might have.  I then did my physical exam and measured the width of the erythema (redness) around the spider bite on his right knee, felt for warmth over the bite area, as well as over the medial aspect, palpated for any drainage of the center wound area, and had Roy bend his knee back and forth for me to make sure that his joint space was not affected, in other words he didn’t have any pain upon passive movement of his knee joint.  I also felt for any increased warmth or swelling over the upper aspect of his knee cap to make sure he didn’t have involvement of his bursa. 
Once I ascertained that the spider bite had not involved his knee joint, he just had cellulitis (inflammation and infection of his skin and skin structures) with swelling/pain due to the brown recluse venom I advised Roy of my findings. 
Roy, I’m going to give you an antibiotic to take at home twice a day for the infection as well as some steroids to take for the next 6 days.  The antibiotic will take care of the infection and the steroids will knock off your immune response as it’s trying to attack the venom.  This is going to take a while to resolve, you’re going to have pain for a while so I’ll also give you a narcotic prescription to take for the next 3-4 days.  If the antibiotic, Bactrim gives you any nausea, then take some yogurt with it every day.  The steroids can change your moods or make you hungry, so be aware of that and the Tylenol with codeine might make you a little ‘loopy’.  Any questions about your medicines?”
“No, I don’t think so.”
“Okay, well then let me explain to you how to keep the wound clean and keeping it bandaged.  I also need to see you back in two days, because of the location of your spider bite to make sure it hasn’t progressed into the knee joint and it’s responding to the medications.”
Once Roy agreed, he slowly hobbled out of the exam room and went to the front desk to acquire a return appointment to be seen on Friday.  I had already e-faxed in his prescriptions, so he could pick them up on his way home.  
Friday afternoon I looked at my schedule to see that Roy was scheduled to see me at 3 pm.  He was a no-show.  At 4 o’clock I had a phone message from his wife which said that he had been admitted to the hospital the previous evening with increasing pain, swelling and fevers.  The message stated that he had been seen by the orthopedic surgeons who had to drain his knee and the infectious disases doctors had come by and started him on IV antibiotics. 
I read the message again and thought to myself, “exactly what I didn’t want to have happened, happened to Roy. Crap!”

What happened to Roy can happen with any patient who has a severe response to the brown recluse spider venom.  One of the complications of a spider bite that is near a joint space is that the surrounding cellulitis (skin infection) will spread on into the joint space and it will become infected with the same organisms that the bite area/skin is infected with. 
At this time the joint has to be aspirated and drained for relief of pain as well as to do bacterial cultures on.  Patients then need to be treated for 6 weeks with antibiotics to make sure that the joint space does not remain infected.  Joint spaces are treated for this length of time due to the minimal amount of circulation it has. 

A week later, Roy was on my appointment schedule again.  I knocked on the exam door and went into to see him.  Roy was sitting down, crutches by his side, with his right knee totally bandaged up.
“Wow, Roy, I’m surprised to see you.  Bring me up to speed on what’s happened?”
“Well the infectious disease doctors told me that my knee joint became infected from the spider bite and that’s why I started running fevers the day after I saw you.  The bacteria that was involved was resistent, I think that’s the word they used, to the antibiotics you put me on.  So they had to put me on IV Vancomycin.  They also stopped the steroids because they told me that with the infection spreading like it was, the steroids were doing me more harm than good.  I was discharged from the hospital 4 days ago and the infectious disease doctors wanted you to check my wound to make sure it was healing up.  I’m supposed to go back and see them next week, until then I stay on my twice daily IV infusion of Vancomycin.”
“Wow, I’m sorry to hear what happened to you.  Let’s take a look under those bandages and see how your knee is.”
Roy removed the knee bandages and I could see that the wound was becoming smaller, it wasn’t quite as erythematous (red) or swollen, although the center of the wound was still draining out clear serous yellow fluid.  He was able to move his knee, fully extending it and then almost fully bending it without pain. 
“Roy, the message your wife left last week said that the orthopedic physicians had to drain your knee joint, so are the infectious disease doctors treating you for an infected knee joint or just for the skin infection?”
“The infectious docs said that my knee joint had become infected, so I have to stay on the IV Vancomycin for six weeks.”
“Alright, well you can bandage your knee back up.  You’re scheduled to see the infectious doctors again next week and I assume they will be following you until you finish your antibiotics.  If you have any questions or problems with it, you can call me otherwise just follow what the infectious disease doctors tell you to do.”
“Okay, well thanks for all your help.”

Being aware of the presence of brown recluse spiders is the best way to protect yourself from their venom.  Be aware of dark quiet spaces where they like to hide.  Be aware of where they live, they are typically in the Southern and Western U.S. not the Northern U.S.  And if you see one, kill it, you don’t want to end up being bitten by it!


  1. I just recently had a very similar sounding spider bite. They put me on two antibiotics (after testing my blood for infection, I'm assuming) but they never drained the swelling. It is on top of my left knee cap. The antibiotics have helped a lot, I can walk around now! But, the swelling (which feels like a big liquid bubble, yuck) is still there. Should I go back to see if they will drain it, or is it likely to go away on it's own over time?

  2. Isabella, I would go ahead and have your primary care provider drain the liquid abscess. You will heal faster this way. Thanks for the question.

  3. I hate to wake an old thread, but the lack of necrosis leads me to believe that a brown recluse was not involved. Anyone please remember the internet is full of misinformation.