Ep 157: A 44-Year-Old with Cirrhosis and Shortness of Breath

This episode reviews pleural effusions and how to distinguish between their different causes.

Read more on this topic in Harrison's.

Harrison's Principles of Internal Medicine, 22nd Edition

Transcript

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[Ms. Heidhausen] This is Katerina Heidhausen, executive editor of Harrison's Principles of Internal Medicine. Harrison's Podclass is brought to you by McGraw Hill's AccessMedicine, the online medical resource that delivers the latest content from the best minds in medicine. And now, on to the episode. 

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[Dr. Handy] Hi, everyone. Welcome back to Harrison's Podclass. We're your co-hosts. I'm Dr. Cathy Handy. 

[Dr. Wiener] And I'm Dr. Charlie Wiener, and we're joining you from the Johns Hopkins School of Medicine. 

[Dr. Handy] Welcome to today's episode: a 44-year-old with cirrhosis and shortness of breath. 

[Dr. Wiener] Cathy, today's patient is a 44-year-old woman with cirrhosis secondary to non-alcoholic steatohepatitis. She is admitted for increasing shortness of breath over the past few weeks. She was diagnosed with cirrhosis about a year ago and is awaiting a liver transplant. She is compliant with her medications, which include spironolactone, furosemide, and rifaximin. She denies any fevers or new GI symptoms, although her physicians have noticed that her liver function has been slowly worsening over the last six months. 

[Dr. Handy] What are her symptoms over the last week? You mentioned some shortness of breath, but can you tell me more about that? 

[Dr. Wiener] Yeah, about a week ago, she noticed dyspnea on exertion that has now progressed to shortness of breath at rest. 

[Dr. Handy] Any orthopnea? 

[Dr. Wiener] Not really, but she does notice the shortness of breath is worse when she lies on her right side down. 

[Dr. Handy] How about her physical exam? 

[Dr. Wiener] Well, her vital signs are normal. Her neck veins are not distended, but she has decreased breath sounds and dullness to percussion 2/3 of the way up the right side with clear breath sounds on the left. Her abdomen is not distended and her liver is not palpable. She has no pedal edema. 

[Dr. Handy] Highest on the differential now is that she has a pleural effusion which is likely contributing to her current presentation. Did we get any imaging? 

[Dr. Wiener] Yeah, because there was also concern for a pulmonary embolism, she had a contrast CT that showed no pulmonary embolism but a large right pleural effusion. Cuts of the abdomen showed only a small amount of ascites. 

[Dr. Handy] Okay, so we have a woman with worsening ascites and a right pleural effusion. What is the question? 

[Dr. Wiener] The question asks, which of the following statements regarding this patient's pleural effusion is true? Option A. is, pleural fluid glucose is likely less than 20 mg/dL; option B. is, pleural fluid serum protein is likely less than 2 g/dL; option C. is, the pleural fluid LDH is likely greater than 200 U/L; option D. is, the pleural fluid white cell count is likely greater than 1000/microliter; and option E. Is that the pleural fluid triglycerides are likely greater than 200. 

[Dr. Handy] And what's her serum protein and LDH? 

[Dr. Wiener] Sure. Her serum protein is 6.0 with a slightly reduced albumin, and her serum LDH is normal at 150. 

[Dr. Handy] Okay. Let's start as we typically do by distinguishing if this effusion is an exudate or a transudate, and we'd be using classic Light's criteria for that. 

[Dr. Wiener] Yeah, let's stop for a second. Let's review the Light criteria because it has been a while since we had an episode where we went through them. 

[Dr. Handy] Well, in 1972, Dr. Light and his colleagues at Johns Hopkins published the criteria which have remained useful for the last 50 years in distinguishing a transudate versus exudate effusion. 

[Dr. Wiener] What is the mechanism of the difference? 

[Dr. Handy] Exudates are caused by any form of inflammation, including malignancy, and that allows protein-rich or cellular fluid to cross from the circulation or the interstitium into the pleural space. Transudates are formed by hemodynamic forces such as a high capillary pressure or a low oncotic pressure. And in that scenario, you get protein-poor fluid that transits into the pleural space and overcomes the natural clearance mechanisms. Transudative effusions are non-inflammatory. 

[Dr. Wiener] Okay, so specifically, what are the Light's criteria? 

[Dr. Handy] Light's criteria say that a patient has an exudate if they meet any of these criteria: one, the pleural fluid protein to serum protein ratio is greater than 0.5; two, the pleural fluid LDH to serum LDH ratio is greater than 0.6; or three, the pleural fluid LDH is more than 2/3 the upper limit of normal for serum. 

[Dr. Wiener] You mentioned that these criteria have lasted for 50 years, they must be accurate. How accurate are they? 

[Dr. Handy] They are very accurate at classifying exudates but misidentify about 25% of transudates as exudates. If one or more of the exudative criteria are met and the patient is clinically thought to have a condition producing a transudative effusion, the difference between the protein levels in the serum and the pleural fluid should be measured. If this gradient is over 31 g/L, the exudative categorization by these criteria can be ignored because almost all such patients have a transudative pleural effusion. 

[Dr. Wiener] How about our patient? 

[Dr. Handy] Based on the lab values and the history, I think our patient has a hepatic hydrothorax. That is ascites are tracking into the right pleural space through vents in the diaphragm. The negative pleural pressure actually sucks the ascites into the thorax. These patients often have concomitant abdominal ascites, but may not. 

[Dr. Wiener] And to our question? 

[Dr. Handy] Non-infected ascites fluid is a transudate, so the answer is B. The pleural fluid protein will be less than half the patient's serum protein. 

[Dr. Wiener] How do you treat this kind of effusion? 

[Dr. Handy] You have to treat it like you treat the ascites with volume control or other therapies to lower portal pressure. Rarely, a patient may require pleurodesis. 

[Dr. Wiener] And how about the other causes of transudates? 

[Dr. Handy] The most common cause is left heart failure, but you also have to think about nephrotic syndrome or any other cause of a low serum oncotic pressure. 

[Dr. Wiener] Okay, why don't you run through the other options in this question quickly? 

[Dr. Handy] Well, all the other options are typical of an exudate. A low pleural fluid glucose suggests bacterial infection, malignancy, or rheumatoid pleuritis. A high pleural fluid white count is not specific, and the differential will be helpful to distinguish infection versus malignancy. But transudates typically have a low white cell count. 

[Dr. Wiener] And how about triglycerides? 

[Dr. Handy] An effusion with high triglycerides appears milky and is termed chylothorax. They are seen after trauma or surgery involving the thoracic duct, but may also be seen in cases of mediastinal tumors such as lymphoma. 

[Dr. Wiener] And before we finish, the clinicians caring for this patient were appropriately concerned about a pulmonary embolism causing her dyspnea. Can PE cause a pleural effusion? 

[Dr. Handy] Absolutely. And the effusion is typically a unilateral exudate. It may be bloody or blood-tinged. 

[Dr. Wiener] Great, so the teaching points of today's case are that Light's criteria can be used to distinguish exudates versus transudates. Patients with liver failure often have ascites, which may track into the pleural space and cause a hepatic hydrothorax. The characterization of this kind of effusion is that it is typically a transudate. 

[Dr. Handy] You can find this question and other questions like it in Harrison's Self-Review. And if you want to read more about this topic, you can check out the Harrison's chapter actually written by Dr. Light. Visit the show notes for links to helpful resources, including related chapters and review questions from Harrison's, available exclusively on AccessMedicine. If you enjoyed this episode, please leave us a review, so we can reach more listeners just like you. Thanks so much for listening. 

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