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Review of Current Portal Venous Reconstruction Techniques Performed with Pancreaticoduodenectomy and Correlation with Post-Operative CT Imaging Appearances

The Russell H. Morgan Department of Radiology and Radiological Science
The Johns Hopkins Medical Institutions
Baltimore, Maryland

Introduction

Pancreatic adenocarcinoma is the fourth leading cause of all cancer-related mortality in the US and continues to carry a poor prognosis, with a 5-year survival rate 7.2%. (1)
Complete surgical resection is currently the only curative option, despite advances in chemotherapy and radiation regimens.
Surgical techniques have been evolving in the past decade in order to offer patients with increasing degrees of vascular involvement a chance at a surgical cure.
Newer surgical techniques include several methods of resecting and reconstructing the PV and SMV in order to completely remove tumors with venous involvement.

Introduction

Reconstruction of the PV-SMV complex, performed in conjunction with a pancreaticoduodenectomy (PD) procedure, results in complicated post-operative CT appearances, which overlap with the appearances of residual and recurrent pancreatic cancer.
Distinguishing between post-surgical changes and disease recurrence on follow-up CTs is imperative because a variety of options exist for the treatment of recurrent disease.

The PV-SMV Complex

While TNM staging system is commonly used for staging, categorization by resectability is most important for treatment decisions for pancreatic cancer.
Resectability categories:
- Resectable
- Borderline resectable
- Unresectable
In the absence of metastatic disease, the relationship of the tumor to the adjacent major blood vessels defines resectability.
The term “PV-SMV complex” is used here to describe the PV and/or the SMV, with or without involvement of the splenic vein.
The degree and location of tumor involvement of the PV-SMV complex is one of the factors in determining the resectability of pancreatic cancer.

The PV-SMV Complex

Studies support the value of resecting pancreatic tumors with PV-SMV complex involvement:
- Venous involvement is not associated with decreased survival in pancreatic cancer patients. (6)
- There is no increase in perioperative mortality in patients undergoing vascular resection. (7)
In the past decade, surgeons have resected pancreatic tumors with an increasing extent of venous involvement.
Currently, any amount of tumor involvement of the PV-SMV complex may be considered resectable, as long as it is technically feasible to reconstruction the portal venous blood flow.

The PV-SMV Complex

Illustrations by Corinne Sandone © JHU. Used with permission.
Wolfgang CL, Herman JM, Laheru DA, Klein AP, Erdek MA, Fishman EK, Hruban RH. Recent Progress in Pancreatic Cancer. CA Cancer J Clin. 2013 Sep;63(5):318-48.

PV-SMV Reconstruction (PVR)

Several surgical techniques are used to reconstruction the PV-SMV complex to maintain blood flow, referred to as PV-SMV reconstruction (PVR).
Techniques vary based on the extent and location of invasion of the PV-SMV and the natural anatomy.
- For tumor adherent to a small segment of the PV-SMV, the involved portion of the vein can be removed by tangential resection and either a primary closure or a secondary closure with a vein patch can be performed.
- For tumor involving a long segment of the PV-SMV, or for circumferential venous tumor involvement, the involved portion of the vein can be removed by segmental resection and either a primary end-to-end anastomosis or a secondary closure with an interposition graft can be performed.
PVR may also be an unplanned component of a PD procedure, performed for repair of intra-operative tears.

PV-SMV Reconstruction (PVR)

Reconstruction of a tangential venous resection

Venorrhaphy may also be performed for reconstruction of intra-operative venous tears, without tumor involvement of the PV-SMV complex.

PV-SMV Reconstruction (PVR)

PV-SMV Reconstruction (PVR)

Reconstruction of segmental venous resection

PVR may be performed with or without splenic vein preservation, with preservation preferred if technically possible.

Interposition grafts are most commonly autogenous, including IJ and renal vein, but may also be prosthetic.

PV-SMV Reconstruction (PVR)

CT of PD with PV-SMV Reconstruction

All post-PD pancreatic cancer patients at our institution are followed with dual phase pancreatic protocol CT.

Dual-phase technique
- Nonionic IV contrast material is injected at 3-5 mL/s
- Arterial phase images acquired at 30 sec after contrast and portal venous phase images acquired at 1 minute.
- Water is used as a neutral oral contrast
Multiplanar reconstruction
- Coronal and sagittal planes automatically created at CT console
- Coronal plane often best for evaluating PV-SMV changes
3D postprocessing
- Maximum-intensity-projection (MIP)
  - Projection of the highest-attenuation voxels in a dataset into a 2D image
  - MIP images are most valuable for evaluation of mesenteric vasculature
- Volume rendered images
  - Computer algorithm assigns specific color and transparency to each voxel based on attenuation characteristics
  - Data presented in interactive 3D display

CT of PD with PV-SMV Reconstruction

All of the cases shown in this presentation are patients with post-operative changes from PD with PVR, without the concurrent presence of residual or recurrent pancreatic tumor
To insure the absence of concurrent residual or recurrent tumor, only images from patients with complete surgical resection (R0 or R1) and only CTs from the immediate post-operative period are included. Recurrent malignancy is highly unlikely in the immediate post-operative period in patients for whom a complete surgical resection has been achieved.

The cases presented here are from our institution’s pancreatectomy database. Approval for the review of patients from the database was obtained from our Institutional Review Board and a waiver of informed consent was provided for medical record and CT review.

CT of PD with PV-SMV Reconstruction

PV-SMV: Venous narrowing on CT after PVR

PV-SMV: Venous thrombosis on CT after PVR

PV-SMV: Venous configuration changes on CT after PVR

PV-SMV: Venous findings on CT after PVR

Venous findings involving the PV-SMV are best characterized on coronal images.
Narrowing of the PV-SMV complex, including focal and long segment narrowing, as well as circumferential narrowing and eccentric defects, is a common finding after PD with PVR, and mimics the appearances seen with recurrent pancreatic cancer.
Thrombosis of the PV-SMV can occur after PVR, and is also a finding that can be associated with recurrent pancreatic cancer.

Perivenous space: Perivenous ST thickening on CT after PVR

Perivenous space: Induration/inflammation/fluid on CT after PVR

Perivenous space: Findings on CT after PVR

The perivenous space is well characterized on both axial and coronal images.
Perivenous soft tissue density is commonly seen after PD with PVR and may appear mass-like, mimicking pancreatic adenocarcinoma.
Perivenous induration/inflammation/fluid includes a range of appearances that are of low density and unlikely to be mistaken for pancreatic cancer.

Post-PVR changes vs. Recurrent pancreatic cancer

Post-op PVR

PV-SMV findings
- Concentric narrowing
- Eccentric narrowing/defect
- Thrombosis
- Venous configuration changes
Perivenous findings
- Perivenous soft tissue thickening
- Perivenous induration/inflammation/fluid

Recurrent pancreatic cancer

PV-SMV findings
- Concentric narrowing
- Eccentric narrowing/defect
- Thrombosis
Perivenous findings
- Perivenous soft tissue thickening

Considerable overlap exists between the normal post-operative appearance of the PV-SMV and surrounding tissues after PVR, and between the appearance of recurrent/residual pancreatic cancer.

Pearls and Pitfalls

Changes commonly seen with pancreaticoduodenectomy with PV-SMV reconstruction can be mistaken for recurrent pancreatic cancer.
Venous resections and reconstructions are becoming increasingly more common components of pancreaticoduodenectomy procedures.
Accurate interpretation of post-op pancreatic cancer patients must include detailed knowledge of the surgical history.
Look beyond “Whipple Procedure” to determine if a planned or unplanned portal venous reconstruction procedure was concurrently performed

Pearls and Pitfalls

Be familiar with the commonly seen patterns of the PV-SMV complex and perivenous space after venous reconstruction procedures in order to avoid over-calling recurrent pancreatic cancer in this patient population.
Establish the baseline post-op appearance of the PV-SMV and the perivenous space.
Use coronal images to evaluate the configuration of the PV-SMV.
Correlate with other available information (tumor markers, PET/CT).
When in doubt, do short term follow-up to assess for changes to baseline post-op study over time.

Teaching Points - Review

Current venous vascular reconstruction techniques performed in conjunction with pancreaticoduodenectomy for pancreatic cancer

Any amount of PV-SMV tumor involvement will be considered for resection as long as it is technically feasible to reconstruct the PV-SMV to maintain blood flow.

Teaching Points - Review

Teaching Points - Review

Patterns of CT findings following pancreaticoduodenectomy with reconstruction of the PV-SMV complex

There are basic patterns of the PV-SMV complex and perivenous space after venous reconstruction, and several of the normal post-operative findings have an aggressive appearance.

Teaching Points - Review

Teaching Points - Review

Differentiating post-PVR CT findings from recurrent pancreatic cancer
Be familiar with normal spectrum of CT patterns post-PVR, including aggressive appearances
Avoid the pitfall of overcalling recurrent local pancreatic cancer
Determine surgical details, beyond “Whipple” Note that the surgery might include an unplanned PVR.
Establish baseline post-op pattern Use coronal images to define post-op PV-SMV configuration. Compare to post surgical baseline to assess for changes over time.

Teaching Points - Review

References

SEER Cancer Statistics Factsheets: Pancreas cancer. National Cancer Institute. Bethesda, MD. Available at: http://seer.cancer.gov/statfacts/html/pancreas.html.
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Wolfgang CL, Herman JM, Laheru DA, Klein AP, Erdek MA, Fishman EK, Hruban RH. Recent Progress in Pancreatic Cancer. CA Cancer J Clin. 2013 Sep;63(5):318-48. Illustrations by Corinne Sandone © JHU. Used with permission.
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Ponziani FR, Zocco MA, Campanale C, et al. Portal vein thrombosis: Insight into physiopathology, diagnosis, and treatment. World Journal of Gastroenterology : WJG. 2010;16(2):143-155. doi:10.3748/wjg.v16.i2.143.

Acknowledgements:

Karen B. Bleich, M.D.
Ammar A. Javed, M.D.
Fabio Bagante, M.D.
Christopher L. Wolfgang, M.D.
Elliot K. Fishman, M.D.