Question 4 from the second paper of 2014 and the very similar Question 27 from the first paper of 2005 interrogate the candidates' understanding of the indications for a lung biopsy, and the possible complications of such a course of action. It is the investigation of last resort when you cannot arrive at a diagnosis of a diffuse interstitial infiltrate, or other stubborn CXR blemish.
The LITFL lung biopsy page is a definitive resource for the time-poor exam candidate.
- Only do it if the other modalities have failed.
- If you're going to do it, do it early.
- It may have no impact on mortality, even if you achieve the correct diagnosis.
Rationale for an open lung biopsy
Generally speaking, one resorts to an open lung biopsy when one cannot arrive at the diagnosis, and when the differentials include possibilities with radically different (and potentially mutually exclusive) courses of treatment, for instance steroids versus antibiotics.
- Diagnosis of lung disease cannot be established by less invasive means (eg. BAL, bronchoscopic biopsy, HRCT, serological testing and PCR analysis of secretions)
- The lung disease is not responding to the current management
- Management for the differentials is substantially different and a tissue diagnosis will alter the course of management
- The management suggested has significant side effects, and a biopsy may prevent such management
- Prognosis will be influenced by tissue diagnosis, and may be grounds for a palliative course of management
- "While you're there": at the same time as the biopsy, some sort of helpful treatment may be performed in theatre (eg. drainage of an empyema or talc pleurodesis)
Potential findings from a lung biopsy:
- Pointless and late: a small amount of non-diagnostic necrotic lung was biopsied.
- Infectious aetiology
- Other e.g. PJP
- Inflammatory aetiology
- COP (cryptogenic organising pneumonia aka BOOP)
- Other interstitial pneumonias
- Connective tissue disease
- Capillaritis etc.
- Untreatable aetiology (resulting in a change of the goals of care)
- Fibrosis (eg. interstitial pulmonary fibrosis) or another interstitial lung disease
- Veno-occlusive disease
Complications of lung biopsy
- bronchopleural fistula
- major vessel damage
- failure to establish a diagnosis due to poor sampling
- Failure of procedure (aborted procedure) due to poor tolerance of single-lung ventilation
The biopsy must be performed in several regions of the lung, and must yield specimens which offer a representative sample, without sampling any areas of irreversible fibrosis or uninformative necrosis. It cannot be performed in patients who cannot be ventilated on one lung for prolonged periods. Risks and contraindications of of thoracotomy apply.
Evidence in support of lung biopsy
In their answer to Question 4 from the second paper of 2014, the college mention some numbers from "multiple case series in the literature". It would be lovely if they gave a reference. Those multiple case series are quoted as follows:
- High rates of specific diagnostic yield (65-95%)
- Results leading to treatment alterations in the majority of cases (42 – 89%).
Even in 1976 (Hill et al) the mortality rate from this procedure was zero, and the morbidity rate was around 4%. In that ancient case series, 33% of the patients enjoyed some sort of positive change in their management because of the biopsy result.
Flabouris and Myburgh (1999) reported something similar. Their complication rate was higher (21%) but these were "proper" mechanically ventilated ICU patients. "Open lung biopsy-guided alteration of therapy directly benefited 39%, and withdrawal was possible in 8.4% of the patients". However, the change to management did not discriminate survivors from non-survivors (i.e. it didn't matter that you changed to an appropriate therapy, the patient died anyway).
A retrospective series by Lim et al (2007) also reported that a specific diagnosis was achieved in 86% of the biopsied patients, and that in 64% changes to management occurred. Those who were biopsied earlier (within 1 week of intubation) did better in terms of mortality (63% survival vs 11%), which contrasts with the earlier studies.