ORGAN TRANSPLANT IMAGING Pancreas

What is an allograft?

An allograft is any tissue transplanted from one human to another.

List the 3 organ transplant examples.

• Renal

• Liver

• Pancreas

What can duplex/color flow imaging evaluate before or after transplant?

Duplex/color flow imaging can evaluate transplant vessels and complications before and/or after surgery.

List the 3 things duplex/color flow imaging evaluates in transplants.

• Stenosis or occlusion of vessels

• Signs of transplant rejection

• Abnormal fluid collections

List the 4 limitations of organ transplant imaging.

1. Bowel gas overlying the vessels or transplant

2. Depth of penetration, especially in obese patients

3. Scar tissue

4. Shortness of breath or rapid respirations

Simple reminder:
Transplant imaging can be limited by gas, depth, scars, and breathing motion.

What type of diabetes is pancreas transplant indicated for?

Diabetes mellitus type 1 only.

List the 4 benefits/goals of pancreas transplantation in type 1 diabetes.

• Effective method for achieving glucose control

• Potentially stabilizes or reverses diabetes-related complications

• Improves quality of life

• Reduces the need for insulin

Who may receive a pancreas-only transplant?

Patients who have healthy kidney function or already have a functioning kidney transplant.

What risk may be lower after a pancreas-only transplant?

The risk for kidney disease and other diabetic complications may be lower after transplant.

What transplant combination may be used for type 1 diabetes with significant kidney disease?

Patients may receive both a kidney and pancreas transplant.

List the 2 organs received in this type of transplant.

• Kidney

• Pancreas

What does receiving both organs reduce the need for?

It reduces the likelihood of needing insulin injections or kidney dialysis.

List the 3 types of pancreas transplants.

• Simultaneous pancreas-kidney, or SPK

• Pancreas after kidney, or PAK

• Pancreas transplant alone, or PTA

Explain SPK transplant and when it is used

SPK uses the same donor and has the highest success rate. It is used for severe type 1 diabetes with end-stage renal disease.

Explain PAK transplant.

PAK means pancreas after kidney. The organs come from different donors: pancreas from a deceased donor and kidney from a living donor.

Explain PTA transplant.

Answer:
PTA means pancreas transplant alone. It is an alternative to long-term insulin therapy.

List the 2 surgical techniques for pancreas transplant.

• Systemic bladder drainage

• Portal-enteric drainage

List the 5 key features of systemic bladder drainage.

1. Native pancreas is not removed

2. Donor pancreas includes a portion of donor duodenum

3. Ends of the duodenum are closed with staples

4. Transplanted pancreas is placed in the recipient’s right iliac fossa

5. Exocrine secretions drain into the urinary bladder

Simple reminder:
Systemic bladder drainage = donor pancreas in right iliac fossa and pancreatic secretions drain into the bladder.

Explain the Y-graft technique used for graft arterial revascularization.

The donor splenic artery and superior mesenteric artery are joined to a segment of the donor iliac artery, creating a Y-graft.

Where is the iliac portion of the Y-graft attached?

It is attached to the recipient right common iliac artery or external iliac artery.

Where does the donor splenic vein drain?

The donor splenic vein drains into the recipient systemic circulation through the common or external iliac vein.

List the 2 advantages of systemic bladder drainage.

• Lower technical complication rate

• Ability to monitor rejection by following urinary amylase levels

List the 6 disadvantages/complications of systemic bladder drainage.

• Venous outflow is directed away from the liver to systemic circulation

• Accelerated development of insulin resistance and atherosclerosis

• Exocrine secretions enter the urinary bladder

• Recurrent UTI, cystitis, and urethritis

• Metabolic acidosis and dehydration

• Hematuria and bladder stones

Simple reminder:
Bladder drainage helps monitor rejection with urinary amylase, but it can cause urinary problems, dehydration/metabolic issues, and systemic venous drainage problems.

List the 5 key features of portal-enteric drainage.

1. More widespread technique

2. Head of the pancreas may be placed in a cephalic position

3. Donor duodenum is connected side-to-side to a jejunal loop in the recipient

4. Allows resorption of pancreatic enzymes into the intestines

5. Pancreatic venous outflow drains into the portal venous system through the recipient SMV

Simple reminder:
Portal-enteric drainage sends enzymes into the intestines and venous outflow into the portal venous system.

What arterial configuration is still used with portal-enteric drainage?

Arterial revascularization still uses the Y-configuration.

List the 5 causes of pancreas graft failure.

• Vascular thrombosis

• Infection

• Pancreatitis

• Bleeding

• Anastomotic leaks

What is the main cause of graft failure?

Vascular thrombosis.

Why can graft failure be difficult to recognize clinically?

Many patients do not present with classic symptoms.

List the 5 possible clinical symptoms of graft failure.

• Fever

• Graft tenderness

• Abdominal pain

• Ileus

• Dysuria

In SPK transplant, what does rejection typically involve?

Rejection typically involves both grafts.

What lab value is monitored in SPK rejection?

Serum creatinine levels.

What transducer is used for pancreas transplant evaluation?

A curvilinear 3.5 MHz transducer.

List the 3 ultrasound techniques used in pancreas transplant evaluation.

• Grayscale

• Color Doppler

• Spectral Doppler

Describe the normal sonographic appearance of a pancreatic transplant.

A normal pancreatic transplant appears as homogeneous soft tissue surrounded by more echogenic soft tissue, which represents omental and peritoneal fat.

What flow should be assessed in the pancreas allograft?

Both arterial and venous flow of the allograft should be assessed.

What Doppler flow should be assessed within the transplant?

Color and spectral flow within the transplant.

List the 3 complications evaluated on sonography.

• Fluid collections

• Pancreatitis

• Rejection

Are resistive indices used for pancreas transplant evaluation?

No. Resistive indices are not used; the goal is to establish the presence of color and spectral flow

What helps guide the course of action in pancreas transplant evaluation?

Sonography and biochemical analysis help guide the course of action.

Is there a specific vascular parameter used to determine rejection?

No. There is currently no specific vascular parameter used to determine rejection.

Why is grayscale imaging limited for rejection?

Grayscale imaging is non-specific.

How should the pancreas transplant appear on grayscale?

The transplant should appear homogeneous with low-level echoes.

Why can pancreatic transplant echogenicity be difficult to assess?

It is difficult because of overlying bowel gas and lack of a nearby organ for comparison.

How can a renal transplant help during pancreas transplant imaging?

The renal transplant can be used as a guide to help find the pancreas.

Why is color Doppler used in pancreas transplant imaging?

Color Doppler is used to establish flow within the transplant.

What arterial connection should be looked for during the survey?

Look for the “Y”, which is the arterial connection.

How should the transplant artery be evaluated?

The entire length of the vessel should be interrogated.

What should you look for when evaluating the transplant artery?

Look for aliasing or any type of flow changes.

Why should native vessel flow be considered when evaluating the transplant?

Elevated flow in native vessels can cause elevated flow in the transplant.

Simple reminder:
Do not assume elevated transplant flow is always from transplant pathology; check the native vessels too.

What venous flow pattern should be expected in the transplant vein?

Answer:
Expect pulsatile flow within the vein.

List the 15 protocol steps/images for pancreas transplant evaluation.

• Grayscale — long pancreas transplant body/tail

• Grayscale — long pancreas transplant with measurement of pancreas thickness

• Grayscale — short axis pancreas transplant head/tail

• Grayscale — Y-graft, arterial vasculature, and donor portal vein

• Color and spectral — Y-graft from anastomosis, both superior mesenteric artery and splenic artery anastomoses

• Color and spectral — recipient artery proximal and distal to Y-graft anastomosis

• Color and spectral — splenic artery and superior mesenteric arteries within transplanted pancreas

• Color and spectral — intraparenchymal pancreatic arteries at pancreatic head, body, and tail

• Color or power Doppler image of the entire pancreas transplant

• Color and spectral — graft splenic vein

• Color and spectral — superior mesenteric vein

• Color and spectral — portal vein to the recipient vein anastomosis

• Color and spectral — proximal to the venous Y-graft anastomosis

• Color and spectral — distal to the venous Y-graft anastomosis

• Color and spectral — within the Y-graft

What worksheet/documentation tools are included for pancreas transplant studies?

A pancreas transplant worksheet and a pancreas transplant diagram.

What should the worksheet help document?

It helps document transplant location, grayscale findings, arterial graft findings, venous graft findings, fluid collections, and related comments.