Tag Archives: POCUS

Valvular vegetations

Though transesophageal echocardiography is required in most patients suspected to have infective endocarditis because of better sensitivity, valvular vegetations can be seen on a transthoracic echocardiogram, especially when large. It is important for nephrologists to be aware of the characteristic features of these lesions as we frequently take care of patients with dialysis access infection and bacteremia. Essentially, vegetation is an infected mass usually attached to cardiac valves or implanted intracardiac materials such as pacemaker wires. Vegetations tend to be irregular in shape, mobile but attached to the upstream (= low-pressure) side of the valve. Fresh vegetations are usually hypoechoic or isoechoic to the myocardium whereas old lesions tend to be hyperechoic, and may be calcified. Valvular regurgitation due to destructive valve lesions is a frequent accompaniment and hence Color Doppler evaluation should always be performed. Following are two classic examples (grey scale)

A case of bilateral hydronephrosis

A young woman presented with abdominal pain that did not get better with empiric antibiotic therapy for presumed urinary tract infection. Renal sonogram revealed bilateral mild to moderate hydronephrosis. There were no stones, but scan of the bladder area revealed a protruding mass with pressure effect on the urinary bladder, which was the likely cause for hydronephrosis. Biopsy of the mass revealed B-cell lymphoma. She was started on chemotherapy and required placement of bilateral nephrostomy tubes for urinary obstruction.

Take home points:

Do not forget to scan the bladder when you see hydronephrosis

In women, always consider pelvic malignancy in addition to urolithiasis when unilateral or bilateral hydronephrosis is detected

Ureterovesical junction stone

We have previously talked about ureteral jets and the twinkle artefact. Here is an excellent clip shared by Dr. Robert Jones demonstrating twinkle artefact in the right distal ureter region suggestive of an ureterovesical junction stone. Shadowing from the stone is not always prominent in this region and twinkle artefact on color Doppler helps to make the diagnosis. Note the strong ureteral jet on the left compared to the right corroborating with obstruction on the right.

Take home point: Always look for the cause of hydronephrosis and utilize color Doppler to identify twinkle artefact when you see something suspicious for a stone.

A case of cardiogenic pulmonary edema

Nephrology was consulted for acute kidney injury and hypervolemia in a chronically ill nursing home resident. You decide to perform lung POCUS to assess extravascular lung water.

Multiple B-lines per rib interspace are noted bilaterally consistent with pulmonary edema. Chest X-ray shown for comparison.

But would you stop there? No. Focused cardiac ultrasound (FoCUS) may give an idea if the pulmonary edema is caused by pump failure or a result of other structural abnormalities of the heart. Here are the apical 4 chamber and 2 chamber views.

The left ventricle seems dilated and there is a mobile echodensity (yellow arrow, merged clip) on the anterior mitral valve leaflet. LV systolic function appears fine, may be hyperdynamic actually. Color Doppler images revealed severe mitral regurgitation along with a separate regurgitant jet across the leaflet coaptation line suggestive of leaflet perforation (yellow arrow, still image).

So the cause for pulmonary edema is severe mitral regurgitation secondary to valve destruction caused by endocarditis. Cardiothoracic surgery was consulted but unfortunately, the patient was too sick to be a surgical candidate.

Learning point: Multi-system POCUS often provides management-changing information.

Is there a model curriculum for Nephrology POCUS training?

We have proposed a model curriculum based on our experience and also listed the suggested number of scans for unsupervised practice by various organizations.

However, there is no universally accepted model or guideline at this time. The major hurdle is there is no clear consensus on what sonographic applications nephrologists should be learning. Some nephrologists lay emphasis on comprehensive renal ultrasound (billing analogous to radiologists), comprehensive vascular access ultrasound and procedural guidance, while others favor more focused and diagnostic applications used as an ‘adjunct to physical examination’. On the other hand, there are nephrologists who believe ultrasound is not our territory at all.

Personally, I belong to the diagnostic POCUS camp. Here is the rationale:

1. We are nephrologists and expected to know how the kidney looks like on ultrasound and the commonly encountered abnormalities. Fortunately, the kidneys are relatively easy to image and there are limited number of pathologies. Therefore, both comprehensive and limited (= used to answer a focused question) arguments make sense to me.

2. Probably, the most important thing that helps us in our day-to-day clinical practice is volume status assessment. If we really want to take ownership of this area, we NEED to know about the pump and pipes as well as the effects of leaky pipes. In other words, we should have a good understanding of the basic cardiac (including inferior vena cava assessment, venous waveforms etc.) and lung sonography.

3. Dialysis vascular access: It’s good to know how to use spectral Doppler and assess vascular abnormalities. However, this requires higher skill level (= more training) and is less helpful for a non-interventional nephrologist. One use I see is evaluation of the newly placed access for maturation in the nephrology clinic so that the patient does not need to make a trip to ultrasound department.

4. Procedural guidance: Using ultrasound guidance to place a dialysis catheter is pretty much a standard practice in the United States – so no arguments there. Kidney biopsy however is a grey area in the sense that the current training is not uniform among the nephrology fellowship programs. Interventional radiology performs these procedures at most places. If nephrology fellows are being taught how to do kidney biopsies, they should be taught how to use POCUS for marking (or real-time guidance) as well.

Will talk about other pertinent issues in future posts.

Comet tail artefacts from metallic objects

Here are the chest ultrasound images from a cardiac surgery patient. They were obtained from the sternal area and represent comet tail artefacts from sternal wires. They look like B-lines but they are in the black background of sternal shadow rather than hazy background of the lung. Moreover, they are arranged in zig zag pattern unlike B-lines.

Note the chest X-ray from the same patient showing sternal wires.

In terms of mechanism, these are a form of reverberation artefacts where the echoes generated from the main beam are repeatedly reflected, in repeated trips before going back to the transducer. Remember, time = distance in ultrasound language and the machine places echoes making repeated trips one below the other (taking more time to reach the probe = placed below), finally creating a vertical line. On the other hand, lung B-lines are ring-down artefacts. Consider watching my video (20 min-27:30) if you need to review these and other important artefacts.

Retroperitoneal lymphoma

Here is a renal sonogram obtained from an elderly woman demonstrating bilateral hydronephrosis as well as a heterogeneous mass encasing the left kidney.

CT scan of the abdomen included for comparison: shows multilobulated retroperitoneal soft tissue mass (arrow) encasing the left kidney (LK) causing its displacement anteriorly and superiorly. Similar mass involving the right kidney (RK) can be noted, but to a lesser extent (arrow).

Unfortunately, biopsy of the mass revealed aggressive B cell lymphoma.

Learning point: Lymphoma can present as obstructive nephropathy; pay attention to the area surrounding the kidney. In fact, the diagnosis was missed on a prior point of care ultrasound in this patient.

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