Background: Pancreas transplantation is a major surgery with a relatively high complication rate. Due to its similar clinics, it is often very difficult to differentiate between pancreatitis and rejection. However, pancreas biopsy is a gold standard it requires an evaluation through an experienced pathology institute. This and often fear of complications after the biopsy make the procedure less frequent than necessary. Looking for an imaging method helping to diagnose complications after pancreas transplantation some research with CEUS was performed. First reports about its usefulness in diagnosing rejection were published. Our aim was to check whether the changes in CEUS parameter could help to distinguish it from pancreatitis.
Methods: A total of 107 B-mode, duplex and CEUS exams were performed using 1 mL SonoVue (Bracco) on a Siemens Acuson S2000 and Logiq S7 ultrasound machine. These were evaluated in 39 pancreas transplant recipients with normal pancreas transplants, organs with pancreatitis and grafts undergoing or after successful treatment of the rejection. This approach has been compared with other methods (MR, CT, Biopsy). The results were evaluated with the software package Vuebox (Bracco). Maximum intensity gain (Imax), time to peak (tpeak) and rise time were determined. We computed the difference between the results in pathologic conditions and the median of all test days without any pathology.
Results: According to our computation, each organ has its own baseline of the maximum intensity gain (Imax). Organs during rejection showed significant changes of the perfusion which was reflected in a lower Imax during CEUS. During pancreatitis Imax appeared to be higher or didn't change. In case of simultaneous presence of pancreatitis and rejection, no significant change of Imax was seen.
There was no significant change in rise time or time to peak during the rejection or pancreatitis.
Discussion: CEUS allows displaying the capillary perfusion of tissues. The changes seen in organs undergoing rejection are to be explained by the histologic findings (septal and acinar inflammation with an edema of the graft and occlusion of the microvessels, arteritis).  To the best of our knowledge, this is the first try using CEUS  for the evaluation of the perfusion in graft pancreatitis. Our observations correspond with the findings in native human and animal pancreatitis. The results can be explained by microvascular changes seen in pancreatitis (reduction of the number of capillaries and dilation of remaining vessels with hyperemia as a consequence). Higher Imax may be a result of the accumulation of Sonovue in obliterated vessels.
Conclusion: Pancreatitis and rejection cause different changes in the CEUS allowing to distinguish them from each other. Although pancreas biopsy remains the gold standard, CEUS could be a useful tool helping to indicate biopsies or in some centers even indicating an empiric therapy.