January 2002

A 10-month-old boy is admitted to the hospital for evaluation of a right lower abdominal mass with intermittent fever for 1 month, documented to 102º F. There has also been some intermittent abdominal pain with diarrhea and one episode of emesis during this time. About 2 weeks prior, the patient had a right proximal thigh/inguinal abscess drained of about 3 cc of pus, growing Staphylococcus aureus. This was treated with cephalexin and resolved (figure 1 showing a well-healed scar). The right lower abdominal mass appeared just prior to admission.

His past medical history and family history are unremarkable and his immunizations are up to date.

His examination revealed a fever of 101.2º F and a firm right lower abdominal mass measuring 4 X 2 cm (figures 2–3). The rest of his exam was normal. His pelvic CT scan is shown in figures 4–6.

Part 1

What is the most appropriate course of action?

1. Needle aspiration
2. CT-guided incision and drainage
3. Celiotomy
4. Laparoscopy

Part 2

How would you initially treat?

1. Clindamycin
2. Ampicillin and gentamicin
3. Ampicillin, and gentamicin and clindamycin
4. Meropenem

Part 1 - Answer

The best answer is #2, CT-guided incision and drainage. However, if interventional radiology were not available, surgery (celiotomy) would be the next step. As seen in the figures of the patient and the CT images, there was an intra-abdominal abscess that was eventually going to externalize through the abdominal wall. This is probably what happened when he presented for I&D of the right upper thigh/inguinal abscess. He was taken to the interventional radiology area where this abscess was drained under CT guidance and cultured (figures 7–11).

Again, methicillin-sensitive Staphylococcus aureus was the only organism recovered. His drain was removed at about 7 days and he received a total of about 2 weeks of nafcillin with an uneventful recovery (figure 12). The underlying cause appeared to be a ruptured appendix. He returned several months later to undergo an elective appendectomy, which revealed a fibrotic appendix, supporting the theory of previous rupture. At follow-up several months later, he continues to do well.

When one reviews the most common organisms associated with acute appendicitis, S. aureus does not jump out as a common cause. However, in this case, this organism was recovered twice with what appeared to be evidence of previous inflammation of the appendix. Maybe that’s why this case is so unusual. Place S. aureus in an unusual location and you may get an unusual infection.

We are seeing abscesses drained without surgery more and more where interventional radiology is available. The benefits are obvious. There’s less anesthesia required and recovery time is faster. It was obviously the best course of action with this case, especially since the abscess was so easily accessible.

Part 2 – Answer

My choice would be #3, ampicillin, and gentamicin and clindamycin, pending identification of the cause(s). However, some experts may recommend the use of meropenem (Merrem, AstraZeneca) as monotherapy. It is a perfectly acceptable antibiotic for intra-abdominal infections in children. I prefer to reserve it for situations where resistance dictates its use or to avoid toxicity in special circumstances. Some experts would recommend gentamicin + clindamycin without ampicillin. I think that is fine also. Ampicillin probably does not add much to the regimen anyway, except additional coverage of enterococcus. As usual, I would recommend consulting John Nelson’s Pocket Book of Pediatric Antimicrobial Therapy when in doubt.

For Your Information:

• James H. Brien, DO, Pediatric Infectious Disease, Scott and White's Children's Health Center and Texas A&M University, College of Medicine, Temple, Texas. E-mail: jhbriend@aol.com