VOTW: Lung Point

Hi all, this week's VOTW is presented by Drs Forrest, Yang and Schiller!

A 71 year old male w/ hx of COPD presented to the ED for altered mental status. He was found to be obtunded due to hypercapnia and was intubated in the ED. Several hours after admission to the MICU the patient suddenly desaturated to 64%. 

A POCUS was rapidly performed which showed…

Clip 1 shows a POCUS of the R anterior chest. On the left side of the screen, the pleural line has absent lung sliding. From the right of the screen, normal pleura with lung sliding is seen coming into the image with every breath. This is a “lung point” which is the exact point at which the pneumothorax starts. A chest x-ray confirmed a large R sided pneumothorax with mediastinal shift. A chest tube was placed by the ED team for a tension pneumothorax with improvement in vitals.

Image 1 shows an M-mode image obtained expertly by the team at the lung point which shows both "seashore sign" indicative of normal lung as well as "barcode sign" indicative of pneumothorax in one clip. You'll see this only if you use M-mode at the lung point.

M-mode showing areas of “sandy beach” alternating with “barcode sign” at the lung point

Lung sliding

In normal lung, the pleural line will appear to shimmer due to the movement of the visceral and parietal pleura sliding against each other. With a pneumothorax the contact between the two pleura are lost and the pleural line will appear still. 

*The presence of lung sliding rules out a pneumothorax at the location of the chest you are scanning. 

*Image the least dependent site (where air is most likely accumalate) to maximize sensitivity of the test (anterior chest in a supine patient).

*Reduce your image depth all the way! This way you don't have to squint while looking for lung sliding

Lung point

This is the point at which normal lung sliding and absent lung sliding are seen next to eachother simultaneosuly and is the exact point where the viseral pleural is peeling away from the parietal pleura. If found, this finding is highly specific for pneumothorax. It won't be seen with a large pneumothorax that envelops the entire lung.

Does absence of lung sliding always indicate pneumothorax?

No. Absence of lung sliding can be seen with many conditions including a bleb from COPD, right mainstem intubation (no left-sided lung sliding), patients w/ previous thoracic surgery (such as pleurodesis or VATS), pleural adhesions, ARDS, pulmonary fibrosis, atelectasis, and phrenic nerve paralysis. If the patient is stable, confirm the diagnosis with a chest x-ray or CT prior to placing a chest tube.

Which lung ultrasound artifacts rule out pneumothorax?

A-lines are reverberation artifacts that can be generated by air in normal lung tissue or air in the pleura so cannot be used to rule out pneumothorax.

B-lines indicate the presence of interstitial edema which can only be seen if the lung tissue is abutting the pleura. Even seeing one B-line is enough to rule out pneumothorax.
Happy sliding,

Your Sono Team

VOTW: DVT

This week’s VOTW is brought to you by Drs Kim, Nguyen and Sanghvi!

A patient with a previous history of DVTs no longer on anticoagulation presented with 4 days of right lower extremity pain, shortness of breath and chest pain. A POCUS of the lower extremities showed…

Clip 1 shows a non-compressible R common femoral vein containing echogenic material concerning for a DVT. The clot is seen extending into the saphenous vein as it takes off from the common femoral vein. Clip 2 shows the L common femoral vein also with a DVT extending into the saphenous vein. You can see that there is enough force applied with the probe to compress the artery completely, yet the vein is not fully compressed.

Chronic DVT

The appearance of these DVTs suggest that they are chronic. In general, chronic DVTs are more echogenic and have a more ragged appearing edge. Over time, DVTs tend to recanalize centrally. In image 1 below, you can see there is some areas that are recanalizing outlined in green. Image 2 shows an illustration of acute vs chronic DVTs.

DVT with area of recannalization

Acute vs Chronic DVTs

Acute DVT

An acute DVT generally has smoother edges and is less echogenic than a chronic DVT. Some acute DVTs cannot be seen with ultrasound and their presence can only be identified by the inability to collapse the vessel completely. If you are placing enough pressure to collapse the artery but the vein is not yet collapsed, this is concerning for a DVT.

Tips and tricks for lower extremity DVT studies

1. Use a linear transducer and choose the DVT setting

2. Squirt gel on the entire thigh instead of the probe so you don’t have to repeatedly re-gel the probe

3. Start in the inguinal crease and identify the take-off of the saphenous vein. This is a common site for a DVT and is the proximal starting point for our ED performed limited compression studies. Compress and take a clip here.

4. While the saphenous vein is considered a superficial vein, clots close to the sapheno-femoral junction should be treated with anticoagulation.

5. The common femoral vein bifurcates into the deep femoral vein (DFV) and superficial femoral vein (SFV). The DFV courses deep and is difficult to evaluate. The SFV is a mis-nomer and is actually a deep vein. Follow the SFV as far as you can down the thigh compressing every 2cm

6. Move onto compression of the popliteal region where the popliteal vein is on top of the artery (“pop on top”)

7. Compressing obliquely is a common reason the vein does not compress completely resulting in a false positive interpretation. Use your non-probe hand to assist in compressing the vein perpendicularly to the femur.

Back to the patient
A CTA chest was negative for pulmonary embolism and patient was discharged on oral anticoagulation and outpatient follow up.

Happy Compressing and De-compressing,

Your Sono Team

VOTW: Emphysematous Pyelonephritis

This weeks’s VOTW is brought to you by Dr. Dozois!

A 60 yo female w/ hx of DM presented with 1 week of progressively worsening R flank pain, fever and vomiting. Symptoms and UA was consistent w/ pyelonephritis. A POCUS was performed which showed…

Clip 1 and 2 shows the right kidney with echogenic foci with “dirty shadowing” in the renal parenchyma concerning for air within the kidney. This is concerning for emphysematous pyelonephritis.  A hypoechoic region towards the inferior pole of the kidney is concerning for a perinephric abscess.

Emphysematous pyelonephritis is a rare, severe gas-forming infection of the renal parenchyma with mortality rates ranging from 40-90%. Most (95%) are associated with uncontrolled diabetes. Usual pathogen is E. Coli. Management options include IV antibiotics plus percutaneous nephrostomy, or ureteral stenting, or nephrectomy which is becoming less and less preferred.

POCUS for pyelonephritis?

• POCUS is insensitive for pyelonephritis alone and kidneys usually appear normal. Abnormalities are identified in only 25% of cases. The most common finding is focal/segmental hypoechoic regions (edema).

• POCUS is useful for assessing complications of pyelonephritis including hydronephrosis, perinephric abscess, and emphysematous pyelonephritis all of which would prompt CT imaging and urologic evaluation.

• Considering POCUSing a patient with pyelonephritis if they are worsening despite antibiotics, if there is a concern for associated downstream obstruction or if they are in septic shock.

Back to the patient

The patient was actually a transfer from an outside hospital for emphysematous pyelonephritis seen on CT. Urology was consulted who admitted the patient to the SICU for a planned nephrectomy in the morning 😊