Monday, April 20, 2015

How To Place A Percutaneous Gastrostomy Tube

Gastrostomy tubes and their variants can be placed endoscopically, surgically, or percutaneously. The interventional radiologist can help determine which approach is best for patients. In particular, patients with pharyngeal issues, such as head and neck cancers, are good candidates for percutaneous placement. Here is one approach, which utilizes a Wills-Oglesby pigtail gastrostomy tube.

  1. Verify an appropriate window for the gastrostomy tube on pre-procedure imaging. In particular, make sure that the transverse colon does not lie between the anterior abdominal wall and the stomach.
  2. Check if the patient has a nasogastric tube. If not, using anesthetic gel and a glidewire, a Kumpe catheter can be fluoroscopically guided into the stomach. Have an assistant use the tube to insufflate the stomach.
  3. Once the stomach is sufficiently inflated, anesthetize the skin. A good location is midway along the greater curve as the passes will aim towards the fundus.
  4. A fastener is used to enter the stomach and pull it up towards the anterior abdominal wall. The introducer needle is used to initially access the stomach. Attach contrast to the needle and advance the needle under fluoro. Watch it tent the gastric wall, and then enter the gastric lumen. Intraluminal position can be confirmed by seeing the needle tip move freely, aspiration of gas, and injection of contrast outlining gastric rugae.
  5. Once intraluminal position is confirmed, the fastener is advanced through the needle, the needle withdrawn, and the fastener pulled back to lift the stomach up. If additional fasteners are desired, repeat Step 4.
  6. After the stomach is fastened, make a dermatotomy and then pass another needle into the stomach. Confirm intraluminal position as in #4. Pass a 0.035 inch wire into the stomach and watch it coil around the greater curvature past the fasteners.
  7. Withdraw the needle and serially dilate over the wire up to the size of the catheter. Work quickly as the stomach will begin to lose gas and deflate.
  8. Insert the catheter, withdraw the wire, pull the string to pig the catheter, and inject contrast to confirm final position. Suture the catheter into place. 

One protocol to clear the gastrostomy tube is to wait one day, then check the patient. If the patient is afebrile, without leukocytosis, and without peritoneal signs, start trial feeds. If the patient tolerates the trial feeds well after another day, clear the tube for full feeds.



Monday, April 6, 2015

Measurements in Interventional Radiology

Wires, catheters, and devices often have many measurements associated with them. These can often be confusing as each type of device uses its own measurement with its own unit. This post goes over some of the basic measurements one may encounter in the interventional radiology suite.

Needle Measurements

Needles, specifically hypodermic needles, are measured in a unit termed "gauge" (abbreviated G).  Unlike other measurements, a higher gauge number indicates a smaller needle. The gauge refers to the outer diameter. Typical needles encountered in IR include a 21 G needle to do micro puncture access, a 19 G needle to do direct access or transjugular liver biopsies, and 18 G needles to draw up medications. As an example, a 21 G needle has an outer diameter of 0.03225 in (0.8192 mm) and an inner diameter of 0.02025 in (0.514 mm). For more detailed measurements, see this needle gauge chart


Wire Measurements

Guide wires are typically measured in inches of thickness. Using the example above for a 21 G needle, one can see that an 0.018 inch wire can pass through a 21 G needle, because 0.018 inches is less than the inner diameter of 0.02025 inches. Similarly, an 0.035 inch guide wire can pass through a 19 G needle. For more detailed comparisons of wires, use this comparison chart to compare up to 5 wires at a time. 


Catheter Measurements

Catheters are often measured using the French scale, often abbreviated "Fr". A catheter of 1 French has an external diameter of 1/3 millimeter (mm). Therefore, a 3 Fr catheter has an external diameter of 1 mm. 

Source: "French catheter scale" by Glitzy queen00. Licensed under CC BY-SA 3.0 via Wikimedia Commons

Sheath Measurements

A sheath is used to stabilize access within a vessel. While also using the French system for catheters described above, the designation here indicates the largest French catheter the sheath will accept. So, a 6 French sheath will accept up to a 6 French catheter.

Other devices such as coils or TIPS shunts have measurements specific to them, which should be carefully considered before use. 

Monday, March 30, 2015

How to Place a Chest Port

Oncology patients often need long term central venous access for administration of chemotherapeutic drugs. The procedure below utilizes the 8 Fr Bard PowerPort, but the steps are generally the same for any type of port. Before starting the procedure, review the patient's history and recent labs, in particular the type of cancer, and any relevant imaging. If the patient is likely to have radiation to the right chest (for example, with right breast cancer), consider left chest port placement.
  1. Under ultrasound, visualize the right internal jugular vein, which should be compressible (unless thrombosed). The pulsatile carotid should medial/posterior. 
  2. Anesthetize the skin with 1% lidocaine without epinephrine. 
  3. Advance the 21G micropuncture needle into the jugular vein. 
  4. If there is spontaneous venous return, advance the 0.018 inch microwire to the caba-atrial junction under fluoro.  
  5. If no return but likely in vessel, attach connection tubing and aspirate. Dark blood should flow back easily.
  6. If bright red / pulsatile return, the needle is likely within the carotid artery, so withdraw the needle and hold pressure for 2-5 minutes. 
  7. Once access is gained, make a skin incision along the needle and then blunt dissect using the curved Kelly. 
  8. Exchange the needle for the 5 Fr micropuncture sheath and hub it. 
  9. Remove the inner 3 Fr stylet and the micropuncture wire, holding your finger over the 5Fr lumen. 
  10. Insert 0.035 in J wire and advance into the inferior vena cava. If the wire does not go straight down, consider whether it is in the aorta or in the pleural space. Take care not to irriate the atrium (will cause premature ventricular contractions). If difficult, ask patient take deep breath and hold, then advance. Make sure the J is facing right/posterior (take-off of inferior vena cava from right atrium). 
  11. Once the J wire is in the inferior vena cava, ask for the port and catheter. Flush the peel away sheath, and the catheter itself. 
  12. Mark the port pocket on the patient's chest (rule of thumb: 2-3 fingertips below the clavicle). 
  13. Anesthetize the entry point, make an incision using a #15 blade, anesthetize the pocket and tunnel, then blunt dissect both. The incision should be just long enough to fit the port, usually about 3 mm extra on each side. Lidocaine with epinephrine can be utilized to minimize bleeding in the deeper tissues. The pocket should be deep enough so that the port sits on the pectoralis fascia.  
  14. Attach the tunneling device and tunnel to the venotomy site in the neck. Pull the catheter such that about 15 cm are out at the venotomy site. It is easier to pull back the catheter later than to advance it.  Cut the tunneling device and a small amount of attached tubing off, as it is sometimes difficult to manually remove the tunneler. 
  15. Insert the peel away sheath and hub it. 
  16. Pull out the inner obturator and wire. The valve should maintain hemostasis. 
  17. Insert the catheter as far as possible through the peel away, then remove the valve and break the peel away sheath. 
  18. Peel the sheath away while applying pressure to the catheter to keep it subcutaneous. 
  19. Check positioning - pull back slowly until the tip is at the cavo-atrial junction. 
  20. Cut the excess catheter tubing. Carefully attach the proximal catheter to the port and secure it with the fastener. Suture the port in place (optional). 
  21. Attach a Huber needle and check that the port aspirates and flushes appropriately. 
  22. Close the incision using 2-O absorbable suture for the deeper layer using inverted or reverse horizontal mattress knots, and then the skin with 3-O running suture. Use Dermabond at the venotomy site and over the port incision. 
  23. If the patient is going directly to an infusion, leave the Huber needle attached and covered with a dressing. 
Source: Bard


Sunday, March 22, 2015

How To Place A Tunneled Dialysis Catheter (Permcath)

A common request for an interventional radiologist is placement of catheters, in particular a tunneled dialysis catheter (also known as Perm-A-Cath or Permcath). Here is one approach to placing the catheter via the right internal jugular vein. The approach utilizes an AngioDynamics dual lumen central venous catheter that measures 23 cm tip to cuff (28 cm tip to ports).
  1. Check the patient's height. If between 5 ft (150 cm) and 6 ft (180 cm), in general use a 23 cm tip-to-cuff AngioDynamics tunneled hemodialysis catheter. 
  2. Under ultrasound, visualize the right internal jugular vein, which should be compressible (unless thrombosed). The pulsatile carotid should medial/posterior. 
  3. Anesthetize the skin with 1% lidocaine without epinephrine. 
  4. Advance the 21G micropuncture needle into the jugular vein. 
  5. If there is spontaneous venous return, advance the 0.018 inch microwire to the caba-atrial junction under fluoro.  
  6. If no return but likely in vessel, attach connection tubing and aspirate. Dark blood should flow back easily.
  7. If bright red / pulsatile return, the needle is likely within the carotid artery, so withdraw the needle and hold pressure for 2-5 minutes. 
  8. Once access is gained, make a skin incision along the needle and then blunt dissect using the curved Kelly. 
  9. Exchange the needle for the 5 Fr micropuncture sheath and hub it. 
  10. Remove the inner 3 Fr stylet and the micropuncture wire, holding your finger over the 5Fr lumen. 
  11. Insert 0.035 in J wire and advance into the inferior vena cava. If the wire does not go straight down, consider whether it is in the aorta or in the pleural space. Take care not to irriate the atrium (will cause premature ventricular contractions). If difficult, ask patient take deep breath and hold, then advance. Make sure the J is facing right/posterior (take-off of inferior vena cava from right atrium). 
  12. Once J wire in IVC, ask for catheter. Flush dilators, peel away sheath, and both hubs. 
  13. Lay catheter on patient to judge where to make tunnel. The tip should be near the cava-atrial junction. 
  14. Mark the tunnel entry point on the patient's chest (rule of thumb: 2-3 fingertips below the clavicle). 
  15. Anesthetize the entry point, make an incision, anesthetize the tunnel, then blunt dissect the tunnel. 
  16. Attach the tunneling device and tunnel to the venotomy site in the neck. Pull the catheter all the way through to the hub. It is easier to pull back the catheter later than to advance it.  
  17. Dilate the tract (12 Fr blue, then 14 Fr pink) under fluoro until the tip is at the level of the clavicle, then insert the peel away sheath and hub it. 
  18. Pull out the inner obturator and wire. The valve should maintain hemostasis. 
  19. Insert the catheter as far as possible through the peel away, then remove the valve and break the peel away sheath. 
  20. Peel the sheath away while applying pressure to the catheter to keep it subcutaneous. 
  21. Check positioning - if at caba-atrial junction, fix in place. If too distal, pull back slowly while making sure the cuff stays within the tunnel. 
  22. Flush both ports, give heparin (volume to give on hubs), Dermabond venotomy site, place biostatic pad on tunnel entry site, and then suture to skin with 2-0 silk.
  23. Fold a 4x4 and Tegaderm the port to skin.
Variations on this procedure include measuring using the 0.018 inch wire to get an exact length for the catheter to use and how long to make the tunnel. If the hubs do not flush easily, they may be clotted. Aspirate all the clot out first, then flush. The catheter is ready to use at the end of the procedure, but plans should be in place for the patient to receive an AV fistula by vascular surgery. 

Wednesday, January 29, 2014

What Role Does CT Play in Screening for Lung Cancer?

The short answer is: depends

In December 2013, the United States Preventive Services Task Force (USPSTF) released a conditional recommendation for lung cancer screening. The Grade B recommendation states:
The USPSTF recommends annual screening for lung cancer with low-dose computed tomography in adults ages 55 to 80 years who have a 30 pack-year smoking history and currently smoke or have quit within the past 15 years. Screening should be discontinued once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery.

For more information about what this means from a radiology perspective, here is an interview from ARRS InPractice:
Why did the USPSTF come to these conclusions?
Lung cancer is a serious public health problem, causing one in four cancer deaths. It is estimated that seven percent of people born today will develop lung cancer in their lifetimes. Eighty-five percent of lung cancer is caused by smoking; 85 percent of lung cancer is fatal. 
The randomized, multicenter, National Lung Screening Trial (NLST) trial [1], which compared three annual LDCT scans with three annual posterior-anterior chest radiographs at 33 sites in the United States, found that LDCT screening correlated with significant reductions in lung cancer (20%) and all-cause (6.7%) mortality.

Is CT the best method for lung cancer screening?
The NLST trial showed such a major advantage for LDCT over radiography for lung cancer screening —a 20% reduction in lung cancer mortality—that the trial was stopped early. Thus, CT is currently the only available examination for effective lung cancer screening.

How low can the patient radiation exposure be reduced for effective lung cancer screening?
In published trials [2], estimated radiation doses using LDCT have been between 0.60 and 1.75 mSv per exam. It is predictable that satisfactory LDCT results can be achieved with submSv doses, equivalent to less than 4 months of ambient radiation (assuming the natural occurrence of 3 mSv per year).

Check out InPractice for the rest of the interview with Dr. Patrick Colletti.  The USPSTF Statement wording is interesting - if screening is conditional on 'willingness to have curative lung surgery', should providers have a discussion with patients about treatment options if cancer is discovered prior to screening? Does this extend to other screening modalities such as mammograms? As the latter experience has shown, screening is not always benign. Hopefully future recommendations further clarify when and for whom screening should be undertaken. The real question now is: will insurance companies reimburse for lung cancer screening scans?