Tag Archives: POCUS

Lung contusion

While nephrologists are not the first line of contact for trauma patients, we are often asked to evaluate the need for renal replacement therapy in these patients. It is important that we are aware of the sonographic findings seen in lung contusion so that we don’t confuse them with interstitial syndrome. As mentioned before, B-pattern in two or more sonographic lung zones bilaterally is suggestive of interstitial syndrome and this term encompasses pulmonary edema of various causes. Usually the pleural line is regular in these cases unless there is underlying lung disease such as pulmonary fibrosis.

Lung contusion is typically associated with B-lines in conjunction with pleural line irregularities, subpleural hypoechoic areas and may be localized pleural effusion. Unless the trauma is diffuse, these findings are localized to certain lung zones. The B-lines are frequently confluent, which means, too numerous and difficult to identify each line separately. In addition, Z-lines can be seen: lines that arise from the pleural line and fade away vertically and do not reach the edge of the screen.

It is also important to note that the contusion can be associated with pneumothorax, particularly in cases of rib fracture. Presence of B-lines almost always rules out pneumothorax even when you are not sure about absent pleural sliding. It is because there is air in between pleural layers, which does not allow B-lines to form. If you notice absent pleural sliding and suspect pneumothorax, look for ‘lung point’, which is the junction between normally sliding pleura and the pneumothorax with absent sliding. It is virtually diagnostic of pneumothorax.

Renal angiomyolipoma

A classic angiomyolipoma (AML) has abundant fat and therefore appears hyperechoic on a sonogram, similar to the sinus fat. Acoustic shadowing may be seen in up to a 3rd of the lesions. Unlike stones, these lesions do not typically exhibit twinkle artefact on color Doppler. Definitive diagnosis of AML is possible only by CT or MRI because they ‘diagnose’ fat and ultrasound can only ‘suggest’ fat. On non-contrast CT scan, the presence of regions of interest containing attenuations less than -10 HU allows confident identification of fat. Following are some examples of classic AMLs.

In patients with tuberous sclerosis, multiple renal AMLs are seen and often difficult to characterize on ultrasound. Corticomedullary differentiation is typically lost. Management should be guided by CT or MRI in such cases. Following is an example.

Small, well circumscribed bright lesions can be followed by ultrasound alone while any suspicion for malignancy warrants CT or MRI. The following lesion looks hyperechoic and most likely is AML but I would get a CT if possible because it’s more hypoechoic compared to sinus fat.

Renal cell carcinomas are hypoechoic to heterogeneous. They can be isoechoic also, which can be easily missed on quick scans. Therefore, it is important to image kidneys from multiple scan planes. Hardly takes an additional minute of your time! In addition, if you see anechoic rim surrounding the lesion or intralesional cysts or calcifications, think renal cell carcinoma. Following are some examples of RCC.

“Fat-poor AMLs” can be of heterogeneous echotexture or just isoechoic to renal parenchyma. It is challenging to differentiate them from malignancy and therefore, almost always require further imaging.

This jellyfish is not atelectasis!

Previously, we talked about atelectasis and pneumonic consolidations. Here is a unique case shared by Dr. Kylie Baker @kyliebaker888, where misdiagnosis could have lead to deleterious consequences.

A 70-year-old man with a history of substance abuse presented with left sided chest pain and presyncope. Right lung POCUS was normal and so was the left anterior scan. However, left posterior zone demonstrated anechoic pleural effusion and a mobile echogenic structure (***) that appeared to be an atelectatic lung vs. pneumonia (causing pleurisy) at first glance. Cardiac windows were difficult to obtain.

CT scan of the chest demonstrated ruptured thoracic aorta and left hemothorax, which means the echogenic structure on ultrasound was a blood clot and not lung tissue.

How to differentiate?

A blood clot appears homogeneous and does not have air bronchograms (dynamic or static) unlike the lung tissue. Moreover, there will not be any demonstrable blood flow within the structure. As mentioned before, pneumonia > atelectasis tends to be hyperemic. So, pay attention to detail.

Stone-In-Neck phenomenon

Stone-In-Neck or the ‘SIN’ sign is when you see an immobile stone lodged in the gallbladder neck, without any anechoic space between the neck and the stone. It is suggestive of cholecystitis even in the absence of other sonographic signs such as thickened gall bladder wall, Pericholecystic fluid, sonographic Murphy’s sign etc. One small study found that the sensitivity of this sign is 56.5% and the specificity 97% for cholecystitis.

Renal milk of calcium cysts

Renal milk of calcium refers to the viscous colloidal suspension of calcium salts found either within a calyceal diverticulum or within a simple renal cyst. Unlike stones, milk of calcium is typically asymptomatic and does not require intervention. In fact, shock wave lithotripsy is ineffective for the treatment.

The etiology of milk of calcium is unclear; however, it may be related to urine stagnation (obstruction) and infection. As a colloid suspension, the calcium salts gravitate to the most dependent portion of the cavity. This layering (gravitational) effect leads to the radiological finding of crescent-shaped dense lesion with a fluid level at the upper border of the stone and may change positions with patients’ position. This finding is reported in KUB, ultrasound and more evident on CT scan. Acoustic shadowing is usually absent but may be seen with larger depositions. Reverberation artefact is seen sometimes.

Hypertrophic column of Bertin

The renal column of Bertin is a medullary extension of the renal cortex in between the renal pyramids. Hypertrophic column of Bertin (HCB) is a normal variant that appears as a mass that extends towards renal sinus.

How to differentiate it from a real renal mass?

HCBRenal tumor
1. Usually isoechoic with rest of the cortex Can be isoechoic or heterogeneous but usually demarcates itself from the renal parenchyma. May contain calcifications or necrotic areas.
2. Protrudes inwards into the sinus fat and the renal outline is preserved Grows outwards and usually distorts the renal outline
3. On Doppler, the vascular pattern is similar to that of the surrounding renal parenchyma. Use power Doppler for better identification of flow. The vasculature is prominent in the periphery of the mass
4. May wrap around the medullary pyramid without distorting its architecture Distinct from pyramid, may compress

Some HCBs may demonstrate atypical characteristics on greyscale ultrasound and may need contrast-enhanced CT/MRI/ultrasound to make sure it is similar to adjacent cortical tissue.


Post-biopsy bleeding

Compared with biopsy of other sites, native renal biopsy has the greatest risk of post-procedure hemorrhage (1.2%). However, the incidence of major bleeding and death due to bleeding is very low (0.3 and 0.02% respectively).

Post-biopsy bleeding can occur into the perinephric space or the collecting system or in the form of a subcapsular hematoma.

On a sonogram, fresh hematomas appear anechoic and organizing ones are of mixed echogenicity due to clotting. There will be little to no Doppler flow because the blood is not flowing.

Note that urinoma can appear the same (urine is anechoic as well) and should be included in the differentials depending on the context (e.g. recent kidney transplant).

Patent track sign: a color Doppler signal along the course of a biopsy, indicating that the needle track has not collapsed and that there is still active bleeding from the procedure. The track usually extends out of the biopsied organ into a surrounding hematoma. Case courtesy of Dr Matt A. Morgan, Radiopaedia.org, rID: 50201

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