Pancreatic transplant rejection: assessment with duplex US

The value of duplex ultrasonography (US) in the assessment of pancreatic transplants was studied in 22 patients over a 1 1/2-year period. Ninety-eight duplex US examinations were performed, and the Doppler arterial resistive indexes (RIs) correlated with clinical events after transplantation. The RI was 0.70 or less in the parenchymal vessels in all instances of normal transplant function and greater than 0.70 in seven of eight clinical episodes of rejection (87.5%). In all studies performed during these eight cases of rejection, the positive predictive value of an RI exceeding 0.70 was 100%. The negative predictive value of an RI of less than 0.70 in excluding rejection was 90%. High RI values were not found in isolated episodes of cyclosporine toxicity, pancreatitis, peripancreatic hemorrhage, or infection. Duplex US may prove to be more accurate in the diagnosis of rejection of pancreatic transplants versus renal transplants because the former cases have fewer causes of increased vascular impedance and diminished perfusion.     

Pancreatic transplantation using portal venous and enteric drainage: the postoperative appearance of a new surgical procedure

PURPOSE: To review the normal radiologic appearance of pancreatic transplants that use portal venous and enteric drainage, and to review the appearance of a variety of postoperative complications. METHOD: We retrospectively reviewed the computed tomographic (CT) scans, magnetic resonance (MR) images, and ultrasounds of patients who had undergone pancreatic transplantation using portal venous and enteric drainage. RESULTS: At CT, the normal pancreatic transplant appears as a heterogeneous mass composed of pancreatic parenchyma, vessels, and omental wrap. On MR imaging, a normal transplant demonstrates intermediate signal intensity on T1- and T2-weighted sequences. Sonographic evaluation of a normal transplant reveals a hypoechoic gland that contains readily detectable low-resistance arterial and venous Doppler waveforms. Acute postoperative complications include acute rejection, which has a nonspecific radiologic appearance, and transplant pancreatitis, which is often manifested on CT by stranding of the peritransplant fat. Chronic postoperative complications include small bowel obstructions, graft pancreatitis secondary to obstruction of the Roux loop, and chronic rejection. CONCLUSION: Knowledge of the radiologic appearance of the normal pancreatic transplant is required before transplant-related complications can be detected.     

Pancreas transplants: evaluation using perfusion scintigraphy

To determine the value of scintigraphic perfusion studies in evaluating pancreas transplant patients, we reviewed 56 of these studies in 22 patients who had 27 transplants. Seventeen patients underwent two or more studies. The perfusion studies were performed with 20 mCi (740 MBq) of 99mTc-DTPA injected as a bolus followed by eight to 16 serial 2-sec images and a 500,000-count immediate static image. Images were evaluated for (1) the time and intensity of pancreatic peak radioactivity relative to the time and intensity of the iliac arterial peak; (2) relative pancreatic to iliac arterial intensity on the static image; and (3) size, homogeneity, and definition of the pancreas. Clinical diagnoses at the time of scintigraphy of normal function (n = 36), rejection (n = 13), pancreatitis (n = 6), or arterial thrombosis (n = 1) were based on insulin requirement, urine amylase, serum glucose, serum amylase, response to therapy, cultures, CT, MR, sonography, scintigraphy with 67Ga or 111In-WBCs, percutaneous drainage results, angiography, surgery, and pathologic examination of resected transplants. Three 99mTc-DTPA perfusion studies showed no pancreatic perfusion, four showed decreasing perfusion on serial studies, and five showed progressive loss of definition of the pancreas on serial studies. Of the three patients with no detectable perfusion, one had a normally functioning transplant, one had arterial thrombosis with transplant infarction, and one had severe rejection with minimal function. Decreasing perfusion was associated with rejection in three patients and pancreatitis in one. Decreasing definition was seen in four patients with rejection and one with pancreatitis. We conclude that perfusion scintigraphy is useful, primarily when performed serially, although nonspecific for evaluating pancreas transplants.     

Case report: Renal replacement lipomatosis associated with renal transplantation

We report a case of extensive renal replacement lipomatosis demonstrated by ultrasound (US) and computed tomography (CT) in a 57-year-old woman with a history of two cadaveric renal transplants. One transplant was non-functional due to chronic rejection. The second renal transplant is functioning normally and the renal replacement lipomatosis did not cause mass effect on either of the renal transplants.     

MRI of the pancreas transplant: lack of correlation between imaging and clinical status

Twenty-five MRI scans were performed on 14 patients with cadaveric pancreatic transplants to determine the role of this modality in the evaluation of transplant dysfunction. Our population included 12 normal transplants and 13 recipients with pancreatic graft dysfunction (either rejection or pancreatitis). Six of the latter patients had two or more scans permitting reassessment of the same transplant in various states of health. T1-and T2-weighted MR images were evaluated qualitatively and quantitatively to see if certain patterns were associated with clinical status. We found that although MRI was capable of producing excellent images of the in situ pancreatic transplant, this modality was unable to reliably distinguish the normal from the abnormal transplant. This conclusion differs from prior assessments; possible reasons for this are discussed.     

MR (1.5 T) in the evaluation of pancreas transplant rejection

Graft rejection is the major cause of graft loss following pancreatic transplantation. Early detection of the rejection process is of great importance towards planning effective treatment when transplant recipients present with aspecific clinical findings suggesting rejection. Up to date, the demonstration of pancreatic transplant rejection has been attempted with nuclear medicine and sonography (US). The authors studied high-field (1.5 T) MR potentials in pancreatic transplantation and rejection and correlated MR findings with clinical and laboratory data. Eleven MR scans were obtained from 4 patients with suspected pancreatic graft rejection, and 9 MR images from 4 patients with normal pancreatic allografts. Qualitative image evaluation showed the pancreatic tissue of the patients diagnosed with rejection to be hypointense on T1-weighted scans and highly hyperintense on T2-weighted scans, as compared to normal grafts. Quantitative data were obtained by comparing the signal intensity of pancreatic grafts to that of the nearby muscle. On both T1- and T2-weighted images, pancreatic tissue/muscle signal-intensity ratios were significantly different, in rejecting transplants, from those of normal allografts (p less than 0.001). Our qualitative and quantitative findings suggest the use of MR imaging as a reliable means of detecting pancreatic graft rejection.     

Pancreatic transplant imaging

Forty-four clinical episodes of suspected (pancreas) transplant rejection in 17 pancreatic transplantation patients were reviewed retrospectively. The clinical impression of acute graft rejection, chronic rejection, or nonrejection in each episode was correlated with the results of 19 nuclear medicine, 12 ultrasound (US), and 44 magnetic resonance (MR) imaging studies. US was found to be a moderately sensitive (82%) method of detecting graft rejection. US also was effective in identifying intra- and peripancreatic fluid accumulations. Nuclear medicine imaging was also a sensitive technique (86%) and the only modality that provided physiologic information regarding graft perfusion. MR imaging allowed correct prediction of the presence or absence of graft rejection in 39 of 44 cases (sensitivity, 100%; specificity, 76%) and was an effective means of detecting pathologic fluid collections. Nuclear medicine, US, and MR imaging are all believed to be sensitive methods of detecting graft rejection and are complementary adjuncts to the clinical evaluation of pancreatic transplants.     

Pancreatic cancer versus chronic pancreatitis: diagnosis with CA 19-9 assessment, US, CT, and CT-guided fine-needle biopsy

The authors prospectively performed serum CA 19-9 assessment, ultrasound (US), computed tomography (CT), and CT-guided fine-needle aspiration biopsy (FNAB) of the pancreas in 81 consecutive patients with suspected chronic pancreatitis or pancreatic neoplasm. The final diagnosis was pancreatic cancer in 54 patients and chronic pancreatitis in 27 patients. CA 19-9 assessment, US, CT, and FNAB were considered nondiagnostic, respectively, in 0%, 25%, 19%, and 6% of cases. When a definite diagnosis was rendered, the positive predictive value was 90% for CA 19-9 assessment, 95% for US, 98% for CT, and 100% for FNAB; the negative predictive value was, respectively, 69%, 95%, 86%, and 100%. The accuracy of all diagnostic and nondiagnostic studies was 81% for CA 19-9 assessment, 72% for US, 77% for CT, and 94% for FNAB. It is concluded that CT-guided pancreatic FNAB is the most reliable examination for enabling differential diagnosis of pancreatic cancer and chronic pancreatitis. When the pancreas is well visualized at US, the negative predictive value for pancreatic cancer is more accurate than that of CA 19-9 assessment and CT.     

Fluid collections developing after pancreatic transplantation: radiologic evaluation and intervention

The usefulness of real-time sonography, duplex sonography, computed tomography (CT), cystography, diagnostic aspiration, and percutaneous drainage in the diagnosis and treatment of peri-pancreatic-transplant fluid collections was retrospectively assessed in 46 recipients of extraperitoneal pancreatic transplants. Forty-four abnormalities were identified in the extraperitoneal space at sonography, including four pancreatic pseudocysts associated with malfunction of the pancreatic duct, seven abscesses, six hematomas, nine urinomas, six early postoperative fluid collections that spontaneously resolved, six cases of pancreatitis, and six cases of vascular occlusion. Sonography (including pulsed Doppler sonography) was the procedure of choice in detecting fluid collections and diagnosing pancreatitis, rejection, vascular thrombosis, and pancreatic duct malfunction. CT was diagnostic in four of six hematomas; cystography was diagnostic in seven of nine urinomas. Sonographically guided percutaneous intervention enabled three patients to avoid surgery and allowed optimal surgical planning for six patients.     

MR diagnosis of pancreatic transplant rejection

To determine the role of MR imaging in the assessment of pancreatic transplant rejection, we prospectively obtained 13 MR scans in nine transplant patients. The presence of rejection was verified pathologically by pancreatic transplant biopsies in five patients. In two additional patients, rejection was proved by concordant renal transplant biopsy as well as by compatible clinical and laboratory data. In the remaining two patients, in whom no biopsy was done, clinical and laboratory data showed no evidence of rejection. The mean T2 of the seven pancreata undergoing rejection was significantly elevated (86 msec) compared with the mean T2 of the two transplants not undergoing rejection (59 msec) (p less than .002). These preliminary results suggest that MR may be useful in the noninvasive diagnosis of pancreatic rejection.     

Correlation of imaging and function in chronic pancreatitis

Chronic pancreatitis is a slowly progressive disease. Initially, only focal changes occur, but diffuse structural abnormalities accompanied by various degrees of functional impairment are seen in the late stage. Morphological abnormalities in chronic pancreatitis can now be detected with high accuracy by several imaging methods. The most sensitive method is ERP, which is able to detect slight ductal changes at an early stage. High-resolution US has become a valid alternative to CT for the visualization of parenchymal abnormalities. However, CT is more accurate than US in detecting small cysts and calcifications. By comparing ductal abnormalities (ERP) and parenchymal lesions (CT, US) with pancreatic function impairment, it has become quite clear that the morphofunctional correlation is tight only in the "late" or severe stages of chronic pancreatitis. In "early" or "moderate" stages of chronic pancreatitis, correlation of the degree of morphological abnormalities and pancreatic dysfunction is frequently poor. Studies comparing the value of the different imaging methods with pancreatic function tests in the diagnosis of chronic pancreatitis have found ERP and the duodenal intubation SC test to have the highest diagnostic accuracies. Correlation between the degree of ductal abnormalities (ERP) and pancreatic dysfunction in the SC test, and between the degree of parenchymal abnormalities (CT and US) and the SC test both proved significant. However, prediction of exocrine function based on morphological alterations, or vice versa, is not possible. The value of combining function testing with imaging is enhancement of the diagnostic accuracy in the presence of only "mild" morphologic abnormalities detected with the imaging techniques. In advanced stages of chronic pancreatitis, function testing is a valid complementary tool to characterize the clinical stage of the disease and may have an impact on therapeutic decisions in patients with advanced stages of chronic pancreatitis. Invasive function testing (SC test) can be replaced by oral pancreatic function tests, which yield equivalent results or clinical decisions.     

Helical CT in renal transplantation: normal findings and early and late complications.

Over a 5-year period, 346 helical computed tomographic (CT) studies were performed in renal transplant recipients. Helical CT proved useful in this context by depicting parenchymal, perirenal, renal sinus, pyeloureteral, and vascular complications in great detail. CT often delineates fluid collections and their anatomic relationship to adjacent structures better than ultrasonography (US), particularly in obese patients. CT-guided puncture and drainage can be performed in cases in which US is deemed inadequate. CT angiography can depict arterial diseases such as stenosis, thrombosis, arteriovenous fistulas, aneurysms, and pseudoaneurysms in the graft artery and in the recipient iliac arterial system, thereby obviating conventional angiography in some cases. Helical CT with three-dimensional image reformatting allows accurate imaging of the entire course of ureteral and periureteral diseases (eg, hydronephrosis, ureteral leak and stricture, pyeloureteral obstruction). CT can be used in the confirmation and staging of malignancies of the renal parenchyma and urothelium. It is also helpful in evaluating associated disease in the native kidneys, acute and chronic rejection, graft embolization, and end-stage disease. Although US and nuclear medicine examination are the imaging modalities of choice in renal transplantation, helical CT is a valuable alternative when these techniques are inconclusive.     

Echography, computerized tomography and retrograde cholangiopancreatography for the diagnosis of focal pathology of the exocrine pancreas

In spite of the improved imaging techniques currently available, mortality for pancreatic cancer is still high, and pancreatitis is often diagnosed only in its advanced stages. The authors investigated the value of different imaging techniques--i.e., US, CT, and ERCP--for an early diagnosis, when a more effective (curative?) treatment can be suggested. Fifty-six cases of pancreatic cancer and 36 cases of chronic pancreatitis were evaluated. The results indicate that ERCP, with the help of statistical methods, is superior to US and CT not only in evaluating early neoplastic or inflammatory lesions, but also for their differential diagnosis. In the latter case, ERCP can sometimes be used as a valid alternative to fine-needle aspiration biopsy.     

New sonographic imaging observations in focal pancreatitis

The imaging findings that ultrasonographically differentiate focal acute pancreatitis (FAP) from a malignant lesion of the pancreas are described. Focal acute pancreatitis is ultrasonographically (US) characterized as a hypoechoic, homogeneous, localized, subsegmental, non-expansive and diffusely demarcated lesion located mostly in the head of the pancreas. It could not be visualized using CT. Endoscopic retrograde cholangiopancreatography (ERCP) performed in 13 of the 32 patients, showed chronic pancreatitis. Focal acute pancreatitis disappeared in 1–6 months at US follow-up. The clinical diagnoses were acute pancreatitis in 11 patients, chronic pancreatitis in 12 patients, biliary disease in 5 patients, hepatopathia in 1 patient while the diagnosis was unknown in 2 patients. No patient developed any pancreatic cancer during a median of 85 months of follow-up. In conclusion, the present data indicate that patients with FAP at US, without any focal lesion seen on either CT or ERCP, have a benign pancreatic lesion, which resolves in 1–6 months; thus, such patients probably do not need any further investigation or follow-up at all. Received: 9 February 1998; Revision received: 28 May 1998; Accepted: 7 August 1998     

The role of diagnostic radiology in pancreatitis

Acute pancreatitis is a frequent inflammatory and necrotic process of pancreas and peripancreatic field. To detect the presence of infected or sterile necrotic components and hemorrhage of the pancreatic paranchyma is important for therapeutic approach. Chronic pancreatitis is characterized by irreversible exocrine dysfunction, progressive loss of pancreatic tissue and morphological changes of the pancreatic canal. Imaging modalities play a primary role in the management of both acute and cronic pancreatitis. CT and MR imaging confirm the diagnosis and detect the severity of disease. In chronic pancreatitis, MRCP after Secretin administration, Spiral CT and endoscopic US seems to replace diagnostic ERCP. However differentiation of pseudotumor of chronic pancreatitis from the pancreatic carcinoma is difficult with either imaging modalities.     

Duplex Doppler study of the transplanted kidney

The authors examined 34 renal transplant recipients with Duplex US, i.e. real-time sonography associated with pulsed Doppler, thus obtaining morphological and structural data about transplanted kidneys as well as hemodynamic information. Special emphasis was put on intrarenal vascular impedance and the relative resistive index, first mentioned by Rifkin in 1987. US diagnosis was compared with the results obtained at both biopsy and clinical follow-up. Only long-term renal transplants were considered; the patients were examined for a rise in serum creatinine level or for the onset of other signs/symptoms related to renal allografts. Our results confirm the utility of pulsed Doppler US in the diagnosis of renal transplant rejection, and allow reference values to be established for the resistive index. In agreement with literature data and assuming 0.9 as a resistive index value, Duplex-Doppler US specificity in diagnosing acute rejection was 100%, and sensitivity was 50%. However, the authors believed it more useful to assume 0.8 as a reference value for the resistive index, for it allows more renal transplant rejection episodes to be diagnosed, both acute and chronic, with an acceptable combination of specificity, sensitivity and predictive value. While the differential diagnosis of acute and chronic rejection is hardly ever possible with Duplex US alone, the combined use of Duplex US and real-time US makes it nearly always possible. As far as intrarenal impedance is concerned, our results seem to disagree with the scattered literature data on the subject, and to point towards its possible significant (though not extreme) increase also in case of chronic rejection.     

US-guided percutaneous pancreatography: an essential tool for imaging pancreatitis.

The pancreatic duct can be opacified when contrast material is injected through a fine needle percutaneously placed under ultrasound (US) guidance. Percutaneous pancreatography was performed in 63 patients with chronic pancreatitis diagnosed at US or computed tomography (CT). In 52 of these patients, endoscopic retrograde pancreatography (ERP) was unsuccessful or did not enable complete visualization of the duct. The percutaneous pancreatograms and other relevant images of these patients were retrospectively reviewed. Percutaneous pancreatography was successful in 54 patients (86%), in whom it clearly mapped the full ductal anatomy, depicted the relationship between cavities seen at US or CT and the duct, and allowed assessment of duct drainage after antegrade injection of contrast material. This information was not provided by other modalities. Percutaneous pancreatography is a valuable complement to CT, US, and ERP for imaging chronic pancreatitis.     

胰肾联合移植术后多层螺旋CT表现

目的 应用多层螺旋CT（MSCT）及其后处理技术评价胰肾联合移植术后移植物的影像学表现及并发症的征象。资料与方法 14例行胰肾联合移植术的患者作16次MSCT检查。采用GE Lightspeed 16螺旋CT扫描仪,行平扫及增强扫描,然后将所有图像传入GE AW4．0工作站进行多平面重建（MPR）、最大密度投影（MIP）及容积再现技术（VR）进行后处理。结果 14例移植胰腺中,MSCT显示12例胰腺实质正常,CTA显示胰腺血管无狭窄及栓塞等异常;1例移植胰腺右侧髂外动脉近起始部至股动脉处血栓形成,胰腺体积小、密度低,未见明显强化,术后病检示胰腺内脾动脉血栓形成,胰腺缺血坏死及胰腺急性排斥反应;1例胰腺包膜下积液。14例移植肾显示11例肾实质正常,1例动脉期肾皮髓质分界欠清晰,提示为轻度急性排斥反应,后亦经肾穿刺所证实;1例MIP显示2处移植肾动脉狭窄;另1例显示移植肾静脉瘤形成。7例患者中MSCT均可见胰周、肾周少量积液。结论 MSCT以及后处理技术能对胰肾联合移植术后移植胰腺和肾脏形态及基本功能状态作出评估。     

Imaging in whole organ pancreatic transplants and a multimodality review of its complications

This pictorial review will describe the normal anatomy of whole organ pancreatic transplants and the common surgical variants with which the radiologist should be familiar. Complications may be divided into (1) vascular: arterial occlusion and stenosis, venous thrombosis, pseudoaneurysms and arteriovenous fistulae, (2) parenchymal complications such as pancreatitis and the variety of peripancreatic collections, and (3) enteric complications including leak and fistula formation. The radiologist plays a crucial role in the initial assessment of graft anatomy and perfusion, prompt diagnosis, and increasingly, in the management of complications.     

Thickening of the renal collecting system: a nonspecific finding at US

The records of 22 patients in whom wall thickening of the renal collecting system was seen at ultrasound (US) were retrospectively reviewed. Wall thickening was found in 15 patients with renal transplants and seven with native kidneys. Severe thickening occurred with transplant rejection, but thickening also occurred with urinary tract infection, reflux, or chronic obstruction in both transplanted and native kidneys. As such, thickening of the renal collecting system seen at US is a nonspecific finding that must be correlated with the clinical and laboratory findings.