You’re a critical care fellow and get paged in the middle of the night to check on a peritoneal dialysis (PD) patient who has worsening shortness of breath. The patient was admitted due to shortness of breath with exertion, pedal edema, and possible heart failure. The resident on the floor orders a chest X-ray, and it looks like this.

On chart review, you notice the patient had moderate right pleural effusion 2 days before (see below). How did it progress so fast? Here’s the twist: an echocardiogram done on the same day shows a normal left ventricular ejection fraction and normal diastolic function (E/e’ about 10), with no major valvular issues. Strange, right? This doesn’t seem to fit with heart failure.

The next step is to confirm if the white-out on the X-ray is indeed pleural effusion. The easiest way to do this? POCUS. Here are images of the right lung obtained using a handheld ultrasound device. Normally, you look for effusion in dependent areas. But in this case, check out the anterior zone – it’s all fluid, consistent with a very large pleural effusion.

Below are more images from the right lung. Notice the basal region showing pleural effusion, a flattened diaphragm (which should be dome-shaped), and a bit of PD fluid. Left lung predominantly showed A-lines except for a small basal effusion.

Below are images of pleural effusions from the deep parasternal long axis view. The image might not be super clear since it was captured quickly, but I’m including a labeled image from a different patient to help you get oriented with the anatomy, where you can see both left and right pleural effusions.

The patient didn’t have any fever or other signs of infection. When the critical care fellow asked the nurse about the PD, they found out that there was a loss of 650 cc of fluid over 3 exchanges that night. What that means is instead of getting out ultrafiltration, the PD fluid was being lost into the body. What’s the number one differential here? It’s ‘sweet pleural effusion’ or ‘sweet hydrothorax’, an entity not many are familiar with. This is essentially PD fluid (which contains dextrose, hence ‘sweet’) leaking into the pleural cavity due to tiny, usually congenital, otherwise asymptomatic diaphragmatic defects. It typically presents on the right side and in the first year of initiating PD (our patient started PD about 6 months ago).

How do you confirm this? Check the glucose level when you do a thoracentesis. A high glucose level (pleural fluid to serum gradient >50 mg/dL) has high specificity for a pleuroperitoneal leak. In this case, the pleural fluid glucose was 563 mg/dL (serum glucose was in the hundreds). The patient was switched to hemodialysis. Here’s a follow-up X-ray showing near resolution of the effusion after draining about 1.2 L of fluid and stopping PD. You can also see the hemodialysis catheter.

Here’s a similar case I encountered and published previously – Case.

Also, a white-out lung pushing the trachea to the opposite side isn’t always due to pleural effusion. You can sometimes find surprises like this: an image courtesy of Dr. Robert Jones showing complete lung consolidation with some effusion in a case of bronchogenic carcinoma with complete bronchial obstruction.

Finally, a quick note to my nephro friends: when your patient shows unexpected symptoms, don’t just tinker with the PD prescription. Do a physical exam (= POCUS) – it can potentially prevent unnecessary hospital admissions.