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An intriguing tale of B-lines in a dialysis patient

Dr. X is rounding on an ESRD patient who initially presented with dyspnea after missing a dialysis (HD) session; underwent dialysis in the hospital. Pt asymptomatic at the time of exam and lung POCUS revealed this in the upper anterior zones bilaterally.

Based on these findings (> 3 B-lines per rib interspace), Dr. X orders for another session of HD. Notably, pt says he is at his ‘dry weight’ and HD nurse says they could only get 1.5L off during first session. Dr. X doesn’t change his/her mind. Strangely, the patient becomes hypotensive during HD and only ~500cc fluid could be removed.

Why can’t we get more fluid out of a hypervolemic patient? Dr. X is perplexed and decides to more POCUS. Here is the IVC ultrasound.

IVC is small and completely collapsing with respiration. Just to make sure its not misinterpreted, hepatic and portal venous Doppler are obtained: non-congestive pattern. That means the tank is empty and that’s why the patient is not tolerating ultrafiltration.

Now Dr. X scans the lungs and finds similar findings on 8-zones LUS consistent with interstitial syndrome.

Why are the lungs still congested? Is the cardiac pump function OK? is there bad mitral regurgitation or diastolic dysfunction? Dr. X decides to perform limited cardiac ultrasound. Difficult windows but managed to get subcostal and apical views.

There is no pericardial effusion, left ventricular systolic function grossly seems OK. Little bit of maneuvering shows some aortic valve calcification. Aortic stenosis? gradient not measured but seems to be opening, LV doesn’t look obviously big/thick. Pt is 60+, kidney disease – some calcification expected. There appears to be some mitral annular calcification on the apical view (bright area in the lateral aspect + shadow), which is also not unexpected in patients with kidney disease. Color flow is not optimal but there appears to be no significant mitral regurgitation. May be there is a little aortic regurgitation.

How about diastolic dysfunction? Mitral inflow Doppler reveals impaired relaxation pattern (A>E), which is also common in older people and should not give pulmonary edema by itself. Click here for a refresher on diastology.

Dr. X performs lung POCUS again. This time, he/she notices something unusual about the pleural line. Takes a closer look with linear probe (high resolution – lower depth).

So the B-lines were not related to extravascular lung water but likely indicate lung fibrosis. Take home points: B-lines can be seen in lung fibrosis, contusion, pneumonia (ARDS) etc. in addition to congestion/edema. In these cases, pleural line is typically irregular, shows subpleural consolidations, may be thickened and some areas are spared. Diffuse involvement as in this Patient can create confusion. Also, do not rely on single-organ POCUS and think carefully when the clinical history and POCUS findings correlate (for example, this patient was at his dry weight when Dr. X ordered a repeat dialysis session).

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