Many thanks to Will Levine for walking us through an interesting case of a 58 year old woman with several days of chest tightness who was incidentally found to have multiple pulmonary nodules.
Along the way, we talked about the PERC (pulmonary embolism ruleout criteria), which can help rule out PE in low risk populations (ie populations with a low prevalence of PE, felt to be <15%).
The rule is really only validated for the ED (where the incidence of PE is likely low), but not the inpatient settings in which we usually practice.
We then got into a discussion of pulmonary nodules, and how several key features of them can help figure out the cause.
- Metastases tend to favor the lower lobes (since they’re often hematogenously disseminated, and blood flow is greatest in gravity dependent areas)
- Diseases like TB and certain pneumoconioses may favor the upper lobes (due to inhalation of the agent)
- Perilymphatic or centrilobular distribution?
- Large nodules (>~1cm) are more likely to be malignant
- Most solid tumor metastases tend to be well demarcated, with the exception of those that tend to bleed (melanoma, thyroid, Kaposi’s and other vascular tumors, RCC, choriocarcinoma)
- Fungal nodules are more likely to bleed and may have fuzzy borders (‘halo sign’)
Here’s a differential for multiple pulmonary nodules
And for those of you that were wondering about what the deal is with necrobiotic lung nodules in IBD, this may shed some light (or at least a faint glow).
Also thanks to James Chen (IR fellow) for speaking to us at intern report about some IR basics. Quick pearls:
- Tunneled catheters (like a small bore central catheter, which is really just a PICC that’s tunneled) can be pulled at the bedside as long as they’re uncuffed. The cuff is a little band of material around the catheter which stimulates scar formation by the body and thus holds the catheter in place without needing sutures etc; if a catheter is cuffed, IR must be the one to pull it.
- If you run into bleeding around a tunneled catheter, hold pressure at both the skin entry site AND the venotomy site (where the catheter actually enters the vein; see below)
- Easy trick to figure out on CXR whether a catheter is tunneled or not: if it courses above the clavicle, it means it’s a tunneled line; if not, it’s non-tunneled
- Singh B et al. Pulmonary embolism rule-out criteria (PERC) in pulmonary embolism–revisited: a systematic review and meta-analysis. Emerg Med J 2012. PMID 23038695