9/20 HUP Report: Cystic Lung Disease, Pneumothorax ex-vacuo

Today at report we were joined by radiology to review some cases with interesting imaging. Here are some clinical pearls we discussed related to a couple of the cases:


Cystic Lung Disease

True cystic lung disease is rare! Other pathologic processes that may resemble cystic lung disease on imaging include:

  • emphysema, particularly bullous disease
  • cavitary lesions
  • honeycombing
  • bronchiectasis
  • pneumatocele

Below are some key identifying characteristics of four relatively more common cystic lung diseases:

  • Lymphangioleiomyomatosis (LAM)
    • seen almost exclusively in females; there have been case reports in males with tuberous sclerosis complex (TSC)
    • symptom onset usually age 20s-30s
    • can be associated with TSC; signs/symptoms include cutaneous angiofibromas, intellectual disability, seizures, ash-leaf spots, and shagreen patches
    • angioleiomyomas are also commonly found in kidneys
    • may be associated with chylous effusions (pleural effusion with most cystic lung diseases is rare)
    • radiology findings include diffuse homogenous cysts
  • Pulmonary Langerhan’s Cell Histiocytosis (LCH)
    • slight female predominance, symptom onset usually age 20s-40s
    • seen almost exclusively in current or former smokers
    • extrapulmonary manifestations are present in approximately 20% and include DI and cystic bone lesions
    • radiology findings progress from nodules to uneven and bizarrely shaped cysts with sparing of the costophrenic angles
  • Birt-Hogg-Dube Syndrome
    • autosomal dominant inheritance, symptom onset usually age 30s-40s
    • cutaneous fibrofolliculomas, common in midface
    • associated with renal neoplasms
    • radiology findings include lentiform/elliptical cysts especially basilar and abutting the mediastinum and pleura
  • Lymphoid Interstitial Pneumonia (LIP)
    • associated with auto-immune diseases or immunodeficiency; most strongly associated with Sjogren’s disease (present in 25-50%)
    • radiology findings include few thin-walled cysts in areas of ground glass opacity, may have internal septae or nodules


Pneumothorax Ex-Vacuo

A pneumo ex-vacuo is a air between the parietal and visceral pleura that is present when a lung cannot expand to fill this space following thoracentesis. This may happen for one of two reasons:

  • Lung entrapment: the lung cannot expand due to active disease that restricts the intrinsic elastic recoil of the lung or visceral pleura. This can occur due to malignancy, infection, or inflammatory processes.
  • Trapped lung: the visceral pleura can develop collagenous or fibrous rind (scar) from a remote or chronic inflammatory process that “traps” the lung and prevents it from expanding. This can occur due to history of inflammatory insult to the pleural such as infection, hemothorax, thoracic surgery or can result from chronic pleural effusion.





7/27 (HUP): pulmonary nodules, IR pearls

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%).

Screen Shot 2017-07-27 at 3.13.17 PM.png

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?


Nodule size

  • Large nodules (>~1cm) are more likely to be malignant

Nodule character

  • 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

Untitled document

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:

  1. 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.
  2. 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)
  3. Screen Shot 2017-07-27 at 4.31.55 PM.png
  4. 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


  1. 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