Friday, 6 June 2008

B's Clinical Images in Medicine- A Quick Case-- The Answers

Dear Bloggers

Here are the answers to the recent blog case.

Professor Alan Lefor, Professor of Surgery at Jichi Medical School, Japan has provided an excellent set of answers to the case below:

It appears that with a history of dyspnea, cough, fever, poor dental hygiene and the attached x-rays, as well as hx of smoking, that this is a lung abcess. It looks like the superior segment of the left lower lobe. It could be a tumor with overlying infection, but there is an air-fluid level in the lung mass which to me suggests at least infection. It could be from Tuberculosis, or oral flora. Aspiration of oral flora is most common, and they typically occur in the posterior segments of the upper lobe or the superior segments of the upper lobe.

I would suggest a bronchsocopy for further evaluation, with cytology etc. Also AFB studies to r/o TBc. The pt needs a transtracheal aspiration to get definitive dx.

The treatment of this, at the least, would be antibiotics, but it may require surgical drainage if the pt does not respond to antibiotics, which should be done using a minimally invasive approach (VATS).

Thank you Professor Lefor.

Professor Tierney, Professor of Medicine, USCF, commented on a similar case some time ago on lung abscesses and I would like to share his words of wisdom with you today.

A lung abscess without teeth is cancer of the lung until proven otherwise.
The notion here is that edentulous patients have a much smaller oral burden of anaerobic organisms, which ordinarily originate in the teeth, and thus a cavitary, abscess-like lesion virtually always implies bronchial obstruction. In a series of several hundred similar infections reported from the West Los Angeles Veterans Hospital this rule was never broken. In general, drainage is as important as antibiotics in such patients, performed by sequential rigid bronchoscopies.

Thank you Professor Tierney.

Gurpreet Dhaliwal, M.D., Associate Professor of Medicine, UCSF, has also kindly commented on this case.

1) What is the diagnosis from the history, physical examination and X-ray findings?

There is an irregular air-fluid level and cavity in the mid-left lung, perhaps in direct communication with the bronchus. Differential diagnosis is listed below. If forced to choose among them, the reported fever provides modest weight for an infection (lung abscess), as does the poor dentition and the diabetes mellitus. Putrid sputum and weight loss, which also characterize abscess, are not mentioned. There is no reason it can not be TB or malignancy, both of which bacterial lung abscess is known to mimic, and vice-versa. The ischemic ulcer on the right lower limb is quite common in a smoker with diabetes, but could be a portal of entry for a blood-borne infection.

2) List the likely cause(s)

Common offenders are lung abscess (aspiration or hematogenous), tuberculosis, lung cancer or metastases, and autoimmune syndromes like RA or Wegeners. Uncontrolled DM (and its associated nonspecific immunodeficiency) might expand the possible list of infections.

3) What other tests would you do?

A sputum study for cytologic, mycobateriologic, and bacterial examination. CT imaging, bronchoscopy, or both may be required if sputum is unrevealing.

4) What is the current evidence based treatment of such a condition?

I don’t know the latest with regards to lung abscess (if that’s the correct dx). Usually prolonged treatment with antibiotics will suffice, with some very old data favoring clindamycin over PCN. Lung abscesses are “drained” by their communication with the bronchial tree.

Thank you Dr Dhaliwal

What happened with the patient?

The patient deteriorated with an increasing size of the abscess despite standard antibiotic treatment for this condition. At presentation, the abscess diameter by chest xray measurement was 6.5 cm (a poor prognostic feature). The patient did not receive a bronchoscopy.

Several days into the hospital admission, the patient developed sudden chest and abdominal pain. Radiological investigations revealed breakdown of the abscess with a resulting pyopneumothorax which required intervention by chest drainage.

Usual cultures of the fluid remained negative.

However, the pleural examination revealed the following: LDH 5021, total protein 4.2 and Adenosine Deaminase (ADA) was 70 U/L.

The above results are mainly consistent with the presence of either an abscess, empyema, carcinoma, rheumatoid lung or tuberculosis. However, the ADA level was >60 U/L making tuberculosis a more likely candidate.

As can be seen by the above observation chart, following drainage with a chest tube, the fever and pulse began to settle (red- pulse, blue- temperature).

As a physician, in a case such as this, I would rely more heavily on the observation chart such as the pulse and fever rather than watching the C-reactive protein. Remember, CRP is not a vital sign and is expensive whereas, pulse and temperature ARE vital signs and can be measured for free and actually show how the patient is improving!

The Current Evidence

In a recent review of the literature from UpToDate version 16.1 the vast majority of abscesses are caused by anaerobic organism inhaled into the lungs when in a recumbent position i.e. when sleeping.

Various organisms are involved in the infective process including peptostreptococcus, Prevotella, Bacteroides species and Fusobacterium species. There are other bacteria that can also cause lung abscess e.g. streptococcus, Tb, but the anaerobic organisms are by far the most common.

Indeed, as Prof Lefor mentions, the infection tends to affect posterior lung segments or upper segments of lung lobes where there can be infection in the recumbent position.

The history is usually one of cough, sputum, chest pain, fever and sometimes a foul putrid smell to the breath or a bad taste in the mouth.

It is important to try and obtain sputum for gram stain and culture. Tracheal aspirates are performed in Japan via the nasal cavity but can be uncomfortable and cause localised trauma to the nasopharyngeal mucosa. Bronchoscopy to obtain a specimen is considered controversal and should be performed by an experienced operator because spillage of fluid from the abscess cavity can result in further lung infection.

However, in cases where the abscess is unresolved by antibiotic therapy, bronchoscopic placement of a pigtail catheter to drain the abscess may be of use or percutaneous drainage can also be performed. In unresolving cases, surgery is sometimes required.

Antibiotic therapy is aimed at the underlying cause. The common antibiotic therapy for anaerobes is Clindamyin 600 mg IV Q8h, followed by 150 to 300 mg PO four times daily. The duration of therapy is at least 3 weeks and/or until there is symptomatic and radiological resolution.

Of course, malignancy should always be ruled out especially in a smoker. Hence, sputum should also be sent for cytology. In uncertain cases, a bronchoscopy and obtaining brushings, aspirates and bronchoalveolar lavage may provide helpful clues to the underlying cause.

Moreover, ruling out tuberculosis must be considered in 'at risk' patient e.g. from high risk areas, immune suppression e.g. HIV, and should prompt the physician to check a ZN stain on 3 daily sputa, TB PCR, a Tuberculin Skin test and Adenosine Deaminase in the pleural fluid. Fluid should be sent for long term TB culture and if still undecided, a Quantiferon test may help.

For a more indepth discussion on this subject I would suggest reading the current evidence in UpToDate 16.1

Please Consider....

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