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Published online before print January 17, 2007, 10.1148/radiol.2423060003
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(Radiology 2007;242:791-801.)
© RSNA, 2007

Genitourinary Imaging

Renal Involvement in Patients with Autoimmune Pancreatitis: CT and MR Imaging Findings1

Naoki Takahashi, MD, Akira Kawashima, MD, PhD, Joel G. Fletcher, MD and Suresh T. Chari, MD

1 From the Department of Radiology (N.T., A.K., J.G.F.) and Division of Gastroenterology, Department of Internal Medicine (S.T.C.), Mayo Clinic, 200 First Street SW, Rochester, MN 55905. Received January 2, 2006; revision requested March 1; revision received March 23; accepted April 20; final version accepted July 6. Address correspondence to N.T. (e-mail: takahashi.naoki{at}mayo.edu).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Purpose: To retrospectively evaluate computed tomographic (CT) and magnetic resonance (MR) imaging renal findings at clinical presentation, during treatment, and at follow-up in patients with autoimmune pancreatitis (AIP).

Materials and Methods: This HIPAA-compliant study received institutional review board approval. All patients included had previously consented to the use of their medical records for the purpose of research. Forty-five patients (38 male and seven female patients; mean age, 64 years) with diagnosis of AIP were included. Forty patients underwent CT or MR imaging at clinical presentation; 33 patients (including five without imaging at presentation) underwent follow-up. CT and MR images were reviewed in consensus by two radiologists for the presence of renal involvement. Various features were evaluated. Clinical characteristics at presentation were compared between patients with and patients without renal involvement.

Results: Of the 40 patients who underwent imaging at presentation, 14 (35%) had renal involvement (12 with parenchymal involvement and five with extraparenchymal involvement). Renal parenchymal lesions showed decreased enhancement and appeared as small peripheral cortical nodules, round or wedge-shaped lesions, or diffuse patchy involvement. Thirteen patients with renal involvement at presentation underwent a follow-up study. Renal lesions in 10 patients regressed (in nine, after steroid treatment) but progressed in three patients without steroid treatment. Renal lesions were found in two other patients during follow-up. No significant difference in the clinical characteristics was found between patients with and patients without renal involvement.

Conclusion: Renal involvement in patients with AIP is relatively common and predominantly involves the cortex of the kidney. The lesions improve after steroid treatment but can progress without steroid treatment.

© RSNA, 2007


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Autoimmune pancreatitis (AIP) is a unique form of chronic pancreatitis in which autoimmune mechanisms are involved in the pathogenesis of the disease (1,2). Morphologically, AIP is characterized by diffuse enlargement of the pancreas with irregular narrowing of the main pancreatic duct (3–5). Pathologically, it is characterized by abundant lymphoplasmacytic infiltrations and fibrosis (6,7). AIP represents approximately 7% of cases of chronic pancreatitis (8) and 2%–6% of patients who undergo pancreatic resection because they are suspected of having pancreatic cancer (9,10). AIP is probably a systemic disease with predominant involvement of the pancreas. The most common extrapancreatic sites of involvement include the biliary ductal system (68%–88% of cases), in which AIP causes biliary strictures (5,6,11–15); the salivary gland (12%–16% of cases) (6,14,16–18); and the retroperitoneum (3%–8% of cases), in which AIP causes retroperitoneal fibrosis (5,14,18–20).

Renal involvement in AIP has been noted in four case reports (19,21–23) and in one patient in a series of 29 patients with AIP (5). The imaging appearance of the renal involvement has been described in four patients; in three patients, the renal parenchyma was involved (5,23), and in one, the renal sinus was involved (19). The purpose of our study was to retrospectively evaluate the computed tomographic (CT) and magnetic resonance (MR) imaging renal findings at clinical presentation, during treatment, and at follow-up in patients with AIP.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Patients
The study was approved by our institutional review board. All patients had previously consented to the use of their medical records for the purpose of research. This study was Health Insurance Portability and Accountability Act compliant. Through a maintained database, we retrospectively identified 71 patients who received a diagnosis of AIP between 1986 and 2005. Twenty-six patients were excluded from the study: In 25 patients, contrast material–enhanced CT or MR images were not available at presentation and during follow-up. In one patient, permission was not given to use the medical records for the purpose of research.

A total of 45 patients (38 male and seven female patients; mean age, 64 years; median age, 68 years; range, 14–85 years) were included in the study. The diagnosis of AIP was determined on the basis of histopathologic findings (n = 30) and a combination of characteristic imaging features, increased serum IgG4 level, and response to steroid treatment of pancreatic enlargement or mass (n = 15) (14). Contrast-enhanced CT or MR images were available in 40 patients at clinical presentation (33 male and seven female patients; mean age, 64 years; median age, 69 years; range 14–85 years). Follow-up imaging studies were available in 33 patients, and this number included five patients whose imaging studies at the time of presentation were not available. Thus, 28 patients had both clinical presentation and follow-up images. Imaging studies available at clinical presentation and follow-up are detailed in Table 1.


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  		Table 1. Imaging Modality at Clinical Presentation and Follow-up in 45 Patients

 
CT and MR Imaging
Of the 40 patients, 38 patients underwent contrast-enhanced CT of the abdomen at the time of presentation. The scanning protocols were variable, but a dual-phase protocol for the pancreas was used in 29 patients and a single-phase study was used in nine patients. Single–, four–, eight–, 10–, 16-, and 64–detector row CT scanners were used in eight, four, eight, one, 10, and three patients, respectively, and the type of scanner was unknown in four patients. Briefly, our dual-phase protocol for the pancreas with multi–detector row CT scanners included optional nonenhanced scanning, followed by dual-phase scanning performed through the abdomen at 45- and 70-second delays after starting the administration of 150 mL of intravenous contrast material (iohexol, Omnipaque 300; GE Healthcare, Chalfont St Giles, England) at an injection rate of 3 mL/sec with a power injector (Medrad, Indianola, Pa). Section thickness for contrast-enhanced images was 2–3 mm in 23 patients, 5 mm in 11 patients, and 7 mm in four patients. Nonenhanced images were obtained in 22 patients, and the section thickness for them was 2.5–10 mm.

Ten patients underwent MR imaging of the abdomen by using a 1.5-T imager at the time of presentation. In one patient, only T2-weighted MR images were obtained to evaluate the biliary system, and in nine patients, a protocol for obtaining images of the pancreas was followed. Briefly, at the time of the study our protocol for imaging the pancreas included T1-weighted spoiled gradient-recalled echo (repetition time msec/echo time msec, 150/2.2–4.2; flip angle, 70°) and respiratory-triggered T2-weighted fast spin-echo (echo time, 85 msec; echo train length, 16) MR imaging before administration of contrast agent and dynamic multiphase T1-weighted three-dimensional spoiled gradient-recalled echo MR imaging (3.6/1.5; flip angle, 12°) after administration of 0.1 mmol per kilogram of body weight of intravenous contrast material (gadodiamide, Omniscan; GE Healthcare). Section thickness for T1- and T2-weighted images was 5–10 mm, and that for dynamic T1-weighted images was 2.5–5 mm.

Image Analysis
The CT and MR images of these patients were retrospectively reviewed for the presence of renal involvement by two radiologists (N.T. and A.K., with 6 and 16 years of abdominal CT and MR imaging experience, respectively) in consensus. Images were reviewed at a workstation in all but three studies in which only hard-copy images were available. Number of lesions (one, two, or multiple), laterality, maximal diameter of the lesion in millimeters, location (renal cortex, renal medulla, perirenal region, renal sinus, or renal pelvis), shape (round or wedge shaped), border (well defined or ill defined), attenuation for CT or signal intensity for MR imaging, and mass effect (cortical bulge) of the lesions were analyzed. Follow-up CT or MR images in 33 patients were analyzed for any change in the renal involvement or development of new lesions or scars. When patients underwent imaging studies at clinical presentation and follow-up, images from both studies were reviewed simultaneously.

Statistical Analysis
Clinical characteristics at presentation—which included age, sex, presence of abdominal or flank pain and hematuria, serum creatinine and serum IgG4 levels, type of pancreatic involvement (with diffuse or focal enlargement or without enlargement), involvement of any other organ, and history of renal disease—were recorded. To determine whether these clinical characteristics were linked with renal involvement, these parameters were compared in patients with renal involvement and patients without renal involvement by using either a nonpaired Student t test (age, serum creatinine level, and serum IgG4 level) or a {chi}2 test (sex, frequency of abdominal or flank pain and hematuria, type of pancreatic involvement, and frequency of other organ involvement or history of renal disease) with spreadsheet software (Excel 2003; Microsoft, Redmond, Wash). Differences with a P value < .05 were considered statistically significant. A histologic specimen of the renal lesion was reviewed when available. Types of treatment, follow-up duration, and serum creatinine level at follow-up visit were also recorded. Presence of abdominal or flank pain and hematuria were recorded when patients had progression or had renal involvement at follow-up imaging.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 
Findings at Presentation
Of the 40 patients with AIP and images at presentation, 14 patients (35%) had renal involvement. Twelve (30%) had renal parenchymal involvement, and five (13%) had perirenal, renal sinus, or renal pelvis wall involvement (Table 2).


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  		Table 2. CT and MR Imaging Findings of Renal Lesions at Presentation

 
Renal parenchymal lesions were mostly bilateral and multiple, predominantly involved the renal cortex, and were categorized into four different patterns. These patterns were small (subcentimeter) peripheral cortical nodules (n = 5) (Fig 1a, 1b), well-defined or ill-defined round lesions (n = 4) (Figs 2a, 3), well-defined wedge-shaped lesions (n = 6) (Fig 4), and diffuse patchy involvement (n = 1) (Fig 5a). All small peripheral cortical nodules and well-defined wedge-shaped lesions abutted the renal capsule. At least one of the renal parenchymal lesions in eight patients showed a mass effect with an outward bulge of the renal contour. On CT scans, the renal parenchymal lesions were low-attenuation areas, compared with the normal renal cortex during the first phase of enhancement. The lesions became less distinct during the second phase of enhancement, with some lesions becoming isoattenuating to the surrounding renal parenchyma. None of the lesions were visible on nonenhanced CT scans. On T1-weighted MR images, the lesions were isointense, and on T2-weighted images, they were mostly hypointense; small lesions were difficult to visualize. On gadolinium-enhanced dynamic MR images, lesions were hypointense during the early phase and became less distinct during the subsequent phases of enhancement.


Figure 1A
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  		Figure 1a: AIP in 74-year-old man. (a) Transverse contrast-enhanced CT image obtained during corticomedullary phase shows multiple small low-attenuation nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isoattenuating to the renal parenchyma during the nephrographic phase (not shown). Delayed nephrographic progression of the left kidney resulted from ureteral obstruction (not shown) caused by retroperitoneal fibrosis. Diffuse enlargement of the pancreatic head (arrow), intrahepatic biliary dilatation, and gallbladder distention are present. (b) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.4/1.5; flip angle, 12°) obtained during corticomedullary phase shows multiple small low–signal intensity nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isointense to the renal parenchyma during the nephrographic phase (not shown). (c, d) MR images were obtained 6 months later without any treatment. (c) Transverse fat-saturated T2-weighted fast spin-echo MR image (7060/85) shows multiple bandlike or broad-based triangularly shaped low–signal intensity areas (arrowheads) in the peripheral cortex of both kidneys. (d) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.6/1.5; flip angle, 12°) obtained during corticomedullary phase shows diffusely irregular and decreased nephrogram (arrowheads) in both kidneys. The inner cortex is less involved than the outer cortex. Note interval improvement of the pancreatic head enlargement (arrow), intrahepatic biliary dilatation, and retroperitoneal fibrosis.

 

Figure 1B
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  		Figure 1b: AIP in 74-year-old man. (a) Transverse contrast-enhanced CT image obtained during corticomedullary phase shows multiple small low-attenuation nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isoattenuating to the renal parenchyma during the nephrographic phase (not shown). Delayed nephrographic progression of the left kidney resulted from ureteral obstruction (not shown) caused by retroperitoneal fibrosis. Diffuse enlargement of the pancreatic head (arrow), intrahepatic biliary dilatation, and gallbladder distention are present. (b) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.4/1.5; flip angle, 12°) obtained during corticomedullary phase shows multiple small low–signal intensity nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isointense to the renal parenchyma during the nephrographic phase (not shown). (c, d) MR images were obtained 6 months later without any treatment. (c) Transverse fat-saturated T2-weighted fast spin-echo MR image (7060/85) shows multiple bandlike or broad-based triangularly shaped low–signal intensity areas (arrowheads) in the peripheral cortex of both kidneys. (d) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.6/1.5; flip angle, 12°) obtained during corticomedullary phase shows diffusely irregular and decreased nephrogram (arrowheads) in both kidneys. The inner cortex is less involved than the outer cortex. Note interval improvement of the pancreatic head enlargement (arrow), intrahepatic biliary dilatation, and retroperitoneal fibrosis.

 

Figure 1C
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  		Figure 1c: AIP in 74-year-old man. (a) Transverse contrast-enhanced CT image obtained during corticomedullary phase shows multiple small low-attenuation nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isoattenuating to the renal parenchyma during the nephrographic phase (not shown). Delayed nephrographic progression of the left kidney resulted from ureteral obstruction (not shown) caused by retroperitoneal fibrosis. Diffuse enlargement of the pancreatic head (arrow), intrahepatic biliary dilatation, and gallbladder distention are present. (b) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.4/1.5; flip angle, 12°) obtained during corticomedullary phase shows multiple small low–signal intensity nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isointense to the renal parenchyma during the nephrographic phase (not shown). (c, d) MR images were obtained 6 months later without any treatment. (c) Transverse fat-saturated T2-weighted fast spin-echo MR image (7060/85) shows multiple bandlike or broad-based triangularly shaped low–signal intensity areas (arrowheads) in the peripheral cortex of both kidneys. (d) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.6/1.5; flip angle, 12°) obtained during corticomedullary phase shows diffusely irregular and decreased nephrogram (arrowheads) in both kidneys. The inner cortex is less involved than the outer cortex. Note interval improvement of the pancreatic head enlargement (arrow), intrahepatic biliary dilatation, and retroperitoneal fibrosis.

 

Figure 1D
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  		Figure 1d: AIP in 74-year-old man. (a) Transverse contrast-enhanced CT image obtained during corticomedullary phase shows multiple small low-attenuation nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isoattenuating to the renal parenchyma during the nephrographic phase (not shown). Delayed nephrographic progression of the left kidney resulted from ureteral obstruction (not shown) caused by retroperitoneal fibrosis. Diffuse enlargement of the pancreatic head (arrow), intrahepatic biliary dilatation, and gallbladder distention are present. (b) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.4/1.5; flip angle, 12°) obtained during corticomedullary phase shows multiple small low–signal intensity nodules (arrowheads) in the peripheral cortex of both kidneys. The lesions became isointense to the renal parenchyma during the nephrographic phase (not shown). (c, d) MR images were obtained 6 months later without any treatment. (c) Transverse fat-saturated T2-weighted fast spin-echo MR image (7060/85) shows multiple bandlike or broad-based triangularly shaped low–signal intensity areas (arrowheads) in the peripheral cortex of both kidneys. (d) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.6/1.5; flip angle, 12°) obtained during corticomedullary phase shows diffusely irregular and decreased nephrogram (arrowheads) in both kidneys. The inner cortex is less involved than the outer cortex. Note interval improvement of the pancreatic head enlargement (arrow), intrahepatic biliary dilatation, and retroperitoneal fibrosis.

 

Figure 2A
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  		Figure 2a: AIP in 59-year-old woman. (a) Transverse contrast-enhanced CT image obtained during corticomedullary phase shows multiple well-defined round and well-defined wedge-shaped low-attenuation lesions in both kidneys. Open renal biopsy revealed tubulointerstitial nephritis. (b, c) MR images were obtained 12 months later without any treatment. (b) Transverse fat-saturated T2-weighted fast spin-echo MR image (8570/85) shows multiple bandlike or broad-based triangularly shaped low–signal intensity areas (arrowheads) in the peripheral cortex of both kidneys. (c) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.6/1.5; flip angle, 12°) obtained during corticomedullary phase shows decreased enhancement with volume loss (arrowheads) in the corresponding cortex in both kidneys.

 

Figure 2B
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  		Figure 2b: AIP in 59-year-old woman. (a) Transverse contrast-enhanced CT image obtained during corticomedullary phase shows multiple well-defined round and well-defined wedge-shaped low-attenuation lesions in both kidneys. Open renal biopsy revealed tubulointerstitial nephritis. (b, c) MR images were obtained 12 months later without any treatment. (b) Transverse fat-saturated T2-weighted fast spin-echo MR image (8570/85) shows multiple bandlike or broad-based triangularly shaped low–signal intensity areas (arrowheads) in the peripheral cortex of both kidneys. (c) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.6/1.5; flip angle, 12°) obtained during corticomedullary phase shows decreased enhancement with volume loss (arrowheads) in the corresponding cortex in both kidneys.

 

Figure 2C
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  		Figure 2c: AIP in 59-year-old woman. (a) Transverse contrast-enhanced CT image obtained during corticomedullary phase shows multiple well-defined round and well-defined wedge-shaped low-attenuation lesions in both kidneys. Open renal biopsy revealed tubulointerstitial nephritis. (b, c) MR images were obtained 12 months later without any treatment. (b) Transverse fat-saturated T2-weighted fast spin-echo MR image (8570/85) shows multiple bandlike or broad-based triangularly shaped low–signal intensity areas (arrowheads) in the peripheral cortex of both kidneys. (c) Transverse gadolinium-enhanced T1-weighted spoiled gradient-recalled echo MR image (3.6/1.5; flip angle, 12°) obtained during corticomedullary phase shows decreased enhancement with volume loss (arrowheads) in the corresponding cortex in both kidneys.

 

Figure 3
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  		Figure 3: AIP in 77-year-old man. Transverse contrast-enhanced CT image obtained during corticomedullary phase shows ill-defined low-attenuation lesion in left kidney (arrow).

 

Figure 4
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  		Figure 4: AIP in 53-year-old man. Transverse contrast-enhanced CT image obtained during corticomedullary phase shows a large well-defined low-attenuation area in the left kidney. This lesion was categorized as a wedge-shaped lesion. An additional small wedge-shaped low-attenuation lesion (arrowhead) is in the right kidney. The lesions showed gradual enhancement during the nephrographic phase (not shown).

 

Figure 5A
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  		Figure 5a: AIP in 75-year-old man. (a) Transverse contrast-enhanced CT image shows bilateral diffuse patchy low-attenuation areas in both kidneys. (b) Transverse contrast-enhanced CT image obtained 9 months after pancreatic head resection shows normal nephrogram. The patient had not received steroid treatment in the interim.

 

Figure 5B
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  		Figure 5b: AIP in 75-year-old man. (a) Transverse contrast-enhanced CT image shows bilateral diffuse patchy low-attenuation areas in both kidneys. (b) Transverse contrast-enhanced CT image obtained 9 months after pancreatic head resection shows normal nephrogram. The patient had not received steroid treatment in the interim.

 
Patterns of renal involvement that did not involve the renal parenchyma also were observed. One patient had a diffuse rim of soft tissue around the kidney (Fig 6). Another patient had irregular nodules in the bilateral renal sinuses (Fig 7). Diffuse wall thickening of the renal pelvis was present in three patients (Fig 8).


Figure 6
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  		Figure 6: AIP in 67-year-old man. Transverse contrast-enhanced CT image obtained during corticomedullary phase shows diffuse perirenal soft-tissue rim (arrowheads) around the left kidney. Delayed nephrographic progression of the left kidney resulted from ureteral obstruction caused by retroperitoneal fibrosis (not shown). Focal enlargement of the body and tail of the pancreas (arrows) is present.

 

Figure 7
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  		Figure 7: AIP in 72-year-old man. Transverse contrast-enhanced CT image obtained during corticomedullary phase shows ill-defined soft-tissue nodule (arrow) in the left renal sinus. Soft-tissue nodule was also present in the right renal sinus (not shown). Pancreatic head is enlarged and shows decreased enhancement. A biliary stent is in place.

 

Figure 8
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  		Figure 8: AIP in 48-year-old man. Transverse contrast-enhanced CT image obtained during corticomedullary phase shows diffuse thickening of the bilateral renal pelvis wall (arrows). Pancreatic head (arrowheads) is enlarged and shows decreased enhancement.

 
Histologic confirmation of the renal lesions was obtained in one patient who had multiple well-defined round and wedge-shaped lesions. The specimen showed tubulointerstitial nephritis with marked expansion of the interstitium with fibrosis and an inflammatory cell infiltrate. The inflammatory cells consisted predominantly of lymphocytes and plasma cells. Numerous plasma cells and rare tubular basement membranes stained positive for IgG4.

Fifteen patients had abdominal pain, which was not localized to the flank (Table 3). None of the patients had hematuria. Serum IgG4 level was available in 28 patients, and 23 (82%) patients had an abnormally increased IgG4 level. Serum creatinine level was available in 37 patients, and it ranged from 0.7 to 2.0 mg/dL. Patients with renal involvement had a serum creatinine level that ranged from 0.9 to 1.6 mg/dL. One patient without renal involvement had a history of a renal stone, but no other patients had a history of renal disease. Comparison of the clinical characteristics in patients with renal involvement and patients without renal involvement revealed no significant difference in the age, sex, frequency of abdominal or flank pain and hematuria, serum creatinine or IgG4 levels, type of pancreatic involvement, frequency of other organ involvement, or history of renal disease.


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  		Table 3. Clinical and Extrarenal Imaging Findings at Presentation with Comparison between Groups with and without Renal Involvement

 
Findings during Treatment and Follow-up
Thirty-three patients underwent follow-up CT or MR imaging studies. The findings are summarized in Table 4. The follow-up duration ranged from 1 month to 14 years, with a median follow-up of 4 months.


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  		Table 4. Imaging Findings of Renal Involvement at Follow-up Study

 
Of the 13 patients with renal involvement at the time of presentation, nine underwent steroid treatment, and the renal lesions improved or resolved after the steroid treatment in these nine patients. A lesion in one of these patients decreased in size and left a cortical scar. Renal lesions in another patient regrew after cessation of the steroid treatment. Following pancreatic resection, the diffuse patchy renal parenchymal involvement in one of 13 patients resolved without steroid treatment (Fig 5b).

Lesions in three of 13 patients without steroid treatment or surgical resection progressed. In two of these three patients, the lesions progressed to diffuse involvement of the renal cortex (Figs 1c, 1d, 2b, 2c). The lesions appeared as bandlike peripheral cortical abnormalities or broad-based triangularly shaped cortical abnormalities with or without cortical volume loss. On T2-weighted MR images, the lesions were hypointense, and on dynamic gadolinium-enhanced MR images, the lesions were hypointense during the early phase and isointense to the surrounding renal parenchyma during the subsequent phases. Another patient had an increase in the number of wedge-shaped lesions. One of the three patients developed pancreatic insufficiency, and another patient had recurrent episodes of cholangitis during the follow-up.

Of the five patients in whom imaging was available only during follow-up but not at clinical presentation, two patients had renal involvement. One of these two patients had diffuse patchy involvement of both kidneys 1.5 years after pancreatic head resection along with enlargement of the pancreatic tail, mediastinal and abdominal adenopathy, lung infiltrates, and pleural thickening. In this case, polyclonal lymphoplasmacytic infiltration was demonstrated in the lung, mediastinal lymph nodes, and pleura at surgery. The other patient had renal parenchymal lesions at the time of presentation according to the CT report, although images were not available for review. Follow-up CT 9 years after pancreatic resection showed several areas of scarring. Subsequently, the patient developed new well-defined wedged-shaped renal lesions 11 and 14 years after pancreatic resection. Further follow-up imaging demonstrated the evolution of multiple cortical scars in the corresponding locations.

Serum creatinine levels during follow-up were available in 11 patients with renal involvement at presentation. Two patients with diffuse involvement of the renal cortex at follow-up imaging had worsening of renal function, and the serum creatinine level increased to 1.6 mg/dL and 2.6 mg/dL within 1 year. Nine other patients had stable serum creatinine levels (range, 1.0–1.3 mg/dL; follow-up duration, 1–24 months; mean, 6 months). Of the five patients who had progression of renal involvement or who had renal involvement at the follow-up imaging study, none had abdominal or flank pain or hematuria at the time of follow-up.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
ADVANCES IN KNOWLEDGE
 References
 
We found that, in 35% (14 of 40) of our study population with AIP, renal involvement was observed on contrast-enhanced CT or MR images at the time of presentation. Renal involvement in these patients was typically parenchymal (12 of 14) but also involved perirenal tissue, the renal sinus, or the renal pelvis wall. Renal parenchymal involvement had various patterns, but the lesions were often multiple and predominantly involved the renal cortex. Nine patients with renal involvement underwent steroid treatment, with subsequent regression of the renal lesions. Renal lesions in one of these patients, however, regrew after cessation of the steroid treatment. Three patients without any treatment demonstrated progressive renal involvement. Two other patients had renal involvement after pancreatic resection: One patient had involvement at 1.5 years and the other had involvement at 11 and 14 years.

Sahani et al (5) described a case of renal parenchymal involvement in a series of 29 patients with AIP. Low-attenuation lesions were present in the kidneys on contrast-enhanced CT scans. The frequency of the renal involvement in their series was much lower than it was in our study, although in their study, the focus was not on renal involvement. It is unclear why our patient population had a higher frequency of renal involvement. Brennan and Pedrosa (23) described multiple wedge-shaped and round, low-attenuation lesions on CT scans in two cases. The appearances of these lesions were similar to those of the lesions in our study.

One can speculate that the small peripheral cortical nodules seen in five patients may represent a very early stage of renal involvement and that the three other patterns (round lesions, well-defined wedge-shaped lesions, diffuse patchy involvement) may reflect the evolution of the renal parenchymal involvement. We observed small peripheral cortical nodules progressing to diffuse cortical involvement in one patient. The small peripheral cortical nodules may be unique and a specific finding of the renal involvement from AIP.

When multiple ill-defined round or well-defined wedge-shaped lesions are seen predominantly in the cortex of the kidneys, the main diagnostic considerations are pyelonephritis (24,25) and vascular insult (24,26,27). Lymphoma or metastases may be considered in an appropriate clinical setting (28,29). When a solitary round low-attenuation lesion with gradual enhancement is present in the kidney, differentiation of AIP from renal cell carcinoma, particularly the papillary subtype, is difficult (30). Among the autoimmune diseases, Wegener granulomatosis is known to manifest as low-attenuation renal masses (31,32). It is important to recognize that such renal parenchymal lesions may be secondary to AIP, particularly when there is evidence of pancreatic abnormality.

Two patients in our series who had progression of renal lesions showed diffuse cortical involvement with low signal intensity in the periphery of the renal cortex on T2-weighted MR images. A similar appearance may be seen in patients with paroxysmal nocturnal hemoglobinuria (33,34) or renal cortical necrosis (35–37).

In one patient with renal parenchymal involvement in our series, histologic confirmation was obtained. Biopsy revealed tubulointerstitial nephritis with fibrosis and infiltration of lymphocytes and plasma cells. There have been three case reports in which renal involvement in patients with AIP was histologically proved (21–23). Histologically, two patients had tubulointerstitial nephritis with infiltration of lymphocytes and plasma cells, and one patient had infiltration of monocytes. It is speculated that the underlying histologic process in other patients with renal parenchymal involvement in our series may be similar to these histologically proved cases. The resemblance of the renal parenchymal lesions to pyelonephritis or lymphoma on images may be concordant with this speculation. Areas of low signal intensity seen on T2-weighted MR images may be caused by dense cellular infiltration and fibrosis. In the later phase of disease, fibrosis may progress, as seen in the cortical volume loss that developed in three patients in our series.

Soft-tissue masses in the renal sinuses in a patient with AIP have been described in a case report (19). The authors speculated that the soft-tissue masses were caused by retroperitoneal fibrosis, though histologic proof was not obtained. Differential consideration of the soft-tissue nodule in the renal sinus on a CT or MR image includes urothelial tumor or lymphoma. A perirenal rim of soft tissue has been described in lymphoma (38,39), retroperitoneal fibrosis (40–42), Rosai-Dorfman disease (43), and Erdheim-Chester disease (44). Thickening of the renal pelvis wall is a nonspecific finding, but it may represent an inflammatory process related to AIP.

Steroid treatment appears to be effective in improving and preventing the progression of the renal involvement. All patients who had renal lesions at presentation and underwent steroid treatment had regression of the renal lesions (nine of nine patients). Renal lesions in one patient, however, regrew after cessation of the steroid treatment. We observed the development or progression of the renal lesions in five patients who were not treated with steroids, and renal lesions developed more than a decade after pancreatic resection in one patient. The renal involvement appears to have little effect on the renal function at an early stage. Two patients without steroid treatment who had diffuse cortical involvement at follow-up had worsening renal function. The long-term effect of the steroid treatment is unknown. The longest follow-up duration after the steroid treatment for patients with renal involvement was only 12 months.

The differentiation between AIP and pancreatic cancer can be difficult when a focal or asymmetric enlargement of the pancreas is present (5,45–47). An increased IgG4 level is helpful in the differentiation but not pathognomonic. An increase in IgG4 level was seen in 82% (23 of 28) of patients with AIP in our series, but it was also seen in 10% (13 of 135) of patients with pancreatic cancer in our experience (unpublished data, 2005–2006). The presence of the renal lesions, as seen in our series of patients, may be used to aid in the differentiation between AIP and pancreatic cancer in difficult cases.

A limitation of our study is its retrospective nature. Also, imaging protocols were variable and the imaging technique was not tailored for evaluation of the renal lesions. When one considers that the renal parenchymal lesions were typically better visualized during the early phase of the contrast enhancement, the single-phase CT protocol might have been insensitive in the detection of the renal parenchymal lesions. Furthermore, histologic analysis of renal lesions was performed in only one patient. Another limitation was that the follow-up was incomplete and short.

Thus, our study findings indicate that renal involvement is relatively common in patients with AIP. Renal parenchymal lesions show decreased enhancement; predominantly involve the renal cortex; and often appear as small peripheral cortical nodules, round lesions, well-defined wedge-shaped lesions, or diffuse patchy involvement. A diffuse perirenal rim of soft tissue, a renal sinus nodule, or renal pelvic wall thickening can be seen. The renal lesions improve after steroid treatment, but they can progress without steroid treatment. When renal lesions, as seen in our series of patients, are present in association with pancreatic enlargement or an unusual pancreatic mass, the differential diagnosis also includes AIP.


   ADVANCES IN KNOWLEDGE
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
References
 


   ACKNOWLEDGMENTS
 
The authors thank Andrew J. LeRoy, MD, and Bohyun Kim, MD, for their critical review of the manuscript.


   FOOTNOTES
 

Abbreviations: AIP = autoimmune pancreatitis

Authors stated no financial relationship to disclose.

Author contributions: Guarantor of integrity of entire study, N.T.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, all authors; clinical studies, all authors; statistical analysis, N.T.; and manuscript editing, all authors


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 ADVANCES IN KNOWLEDGE
 References
 

  1. Yoshida K, Toki F, Takeuchi T, Watanabe S, Shiratori K, Hayashi N. Chronic pancreatitis caused by an autoimmune abnormality: proposal of the concept of autoimmune pancreatitis. Dig Dis Sci 1995;40:1561–1568.[CrossRef][Medline]
  2. Okazaki K, Chiba T. Autoimmune related pancreatitis. Gut 2002;51:1–4.[Abstract/Free Full Text]
  3. Irie H, Honda H, Baba S, et al. Autoimmune pancreatitis: CT and MR characteristics. AJR Am J Roentgenol 1998;170:1323–1327.[Abstract/Free Full Text]
  4. Horiuchi A, Kawa S, Hamano H, Hayama M, Ota H, Kiyosawa K. ERCP features in 27 patients with autoimmune pancreatitis. Gastrointest Endosc 2002;55:494–499.[Medline]
  5. Sahani DV, Kalva SP, Farrell J, et al. Autoimmune pancreatitis: imaging features. Radiology 2004;233:345–352.[Abstract/Free Full Text]
  6. Kamisawa T, Funata N, Hayashi Y, et al. A new clinicopathological entity of IgG4-related autoimmune disease. J Gastroenterol 2003;38:982–984.[CrossRef][Medline]
  7. Kamisawa T, Funata N, Hayashi Y, et al. Close relationship between autoimmune pancreatitis and multifocal fibrosclerosis. Gut 2003;52:683–687.[Abstract/Free Full Text]
  8. Uchida K, Okazaki K, Konishi Y, et al. Clinical analysis of autoimmune-related pancreatitis. Am J Gastroenterol 2000;95:2788–2794.[CrossRef][Medline]
  9. Hardacre JM, Iacobuzio-Donahue CA, Sohn TA, et al. Results of pancreaticoduodenectomy for lymphoplasmacytic sclerosing pancreatitis. Ann Surg 2003;237:853–858.[CrossRef][Medline]
  10. Yadav D, Notahara K, Smyrk TC, et al. Idiopathic tumefactive chronic pancreatitis: clinical profile, histology, and natural history after resection. Clin Gastroenterol Hepatol 2003;1:129–135.[CrossRef][Medline]
  11. Eerens I, Vanbeckevoort D, Vansteenbergen W, Van Hoe L. Autoimmune pancreatitis associated with primary sclerosing cholangitis: MR imaging findings. Eur Radiol 2001;11:1401–1404.[CrossRef][Medline]
  12. Ichimura T, Kondo S, Ambo Y, et al. Primary sclerosing cholangitis associated with autoimmune pancreatitis. Hepatogastroenterology 2002;49:1221–1224.[Medline]
  13. Kamisawa T, Egawa N, Nakajima H, Tsuruta K, Okamoto A. Morphological changes after steroid therapy in autoimmune pancreatitis. Scand J Gastroenterol 2004;39:1154–1158.[CrossRef][Medline]
  14. Kamisawa T, Egawa N, Nakajima H, Tsuruta K, Okamoto A. Extrapancreatic lesions in autoimmune pancreatitis. J Clin Gastroenterol 2005;39:904–907.[CrossRef][Medline]
  15. Nishino T, Toki F, Oyama H, et al. Biliary tract involvement in autoimmune pancreatitis. Pancreas 2005;30:76–82.[Medline]
  16. Akahane C, Takei Y, Horiuchi A, Kawa S, Nishimori I, Ikeda S. A primary Sjogren's syndrome patient with marked swelling of multiple exocrine glands and sclerosing pancreatitis. Intern Med 2002;41:749–753.[Medline]
  17. Kamisawa T, Tu Y, Egawa N, Sakaki N, Inokuma S, Kamata N. Salivary gland involvement in chronic pancreatitis of various etiologies. Am J Gastroenterol 2003;98:323–326.[CrossRef][Medline]
  18. Ohara H, Nakazawa T, Sano H, et al. Systemic extrapancreatic lesions associated with autoimmune pancreatitis. Pancreas 2005;31:232–237.[CrossRef][Medline]
  19. Fukukura Y, Fujiyoshi F, Nakamura F, Hamada H, Nakajo M. Autoimmune pancreatitis associated with idiopathic retroperitoneal fibrosis. AJR Am J Roentgenol 2003;181:993–995.[Free Full Text]
  20. Kamisawa T, Matsukawa M, Ohkawa M. Autoimmune pancreatitis associated with retroperitoneal fibrosis. JOP 2005;6:260–263.[Medline]
  21. Uchiyama-Tanaka Y, Mori Y, Kimura T, et al. Acute tubulointerstitial nephritis associated with autoimmune-related pancreatitis. Am J Kidney Dis 2004;43:e18–e25. 10.1053/j.ajkd.2003.12.006. Published March 2004. Accessed December 8, 2006.[CrossRef][Medline]
  22. Takeda S, Haratake J, Kasai T, Takaeda C, Takazakura E. IgG4-associated idiopathic tubulointerstitial nephritis complicating autoimmune pancreatitis. Nephrol Dial Transplant 2004;19:474–476.[Free Full Text]
  23. Brennan D, Pedrosa I. Lymphoplasmacytic sclerosing pancreatitis. AJR Am J Roentgenol 2005;185:1367–1368.[Free Full Text]
  24. Saunders HS, Dyer RB, Shifrin RY, Scharling ES, Bechtold RE, Zagoria RJ. The CT nephrogram: implications for evaluation of urinary tract disease. RadioGraphics 1995;15:1069–1085.[Abstract]
  25. Kawashima A, Sandler CM, Goldman SM, Raval BK, Fishman EK. CT of renal inflammatory disease. RadioGraphics 1997;17:851–866.[Abstract]
  26. Wong WS, Moss AA, Federle MP, Cochran ST, London SS. Renal infarction: CT diagnosis and correlation between CT findings and etiologies. Radiology 1984;150:201–205.[Abstract/Free Full Text]
  27. Suzer O, Shirkhoda A, Jafri SZ, Madrazo BL, Bis KG, Mastromatteo JF. CT features of renal infarction. Eur J Radiol 2002;44:59–64.[CrossRef][Medline]
  28. Honda H, Coffman CE, Berbaum KS, Barloon TJ, Masuda K. CT analysis of metastatic neoplasms of the kidney: comparison with primary renal cell carcinoma. Acta Radiol 1992;33:39–44.[Medline]
  29. Reznek RH, Mootoosamy I, Webb JA, Richards MA. CT in renal and perirenal lymphoma: a further look. Clin Radiol 1990;42:233–238.[CrossRef][Medline]
  30. Jinzaki M, Tanimoto A, Mukai M, et al. Double-phase helical CT of small renal parenchymal neoplasms: correlation with pathologic findings and tumor angiogenesis. J Comput Assist Tomogr 2000;24:835–842.[CrossRef][Medline]
  31. Fairbanks KD, Hellmann DB, Fishman EK, Ali SZ, Stone JH. Wegener's granulomatosis presenting as a renal mass. AJR Am J Roentgenol 2000;174:1597–1598.[Free Full Text]
  32. Verswijvel G, Eerens I, Messiaen T, Oyen R. Granulomatous renal pseudotumor in Wegener's granulomatosis: imaging findings in one case. Eur Radiol 2000;10:1265–1267.[CrossRef][Medline]
  33. Tanaka YO, Anno I, Itai Y, Abe T. Paroxysmal nocturnal hemoglobinuria: MR findings. J Comput Assist Tomogr 1993;17:749–753.[Medline]
  34. Roubidoux MA. MR of the kidneys, liver, and spleen in paroxysmal nocturnal hemoglobinuria. Abdom Imaging 1994;19:168–173.[CrossRef][Medline]
  35. Kim SH, Han MC, Kim S, Lee JS. MR imaging of acute renal cortical necrosis: a case report. Acta Radiol 1992;33:431–433.[Medline]
  36. Francois M, Tostivint I, Mercadal L, Bellin MF, Izzedine H, Deray G. MR imaging features of acute bilateral renal cortical necrosis. Am J Kidney Dis 2000;35:745–748.[Medline]
  37. Jeong JY, Kim SH, Sim JS, et al. MR findings of renal cortical necrosis. J Comput Assist Tomogr 2002;26:232–236.[CrossRef][Medline]
  38. Sheeran SR, Sussman SK. Renal lymphoma: spectrum of CT findings and potential mimics. AJR Am J Roentgenol 1998;171:1067–1072.[Abstract/Free Full Text]
  39. Urban BA, Fishman EK. Renal lymphoma: CT patterns with emphasis on helical CT. RadioGraphics 2000;20:197–212.[Abstract/Free Full Text]
  40. Rominger MB, Kenney PJ. Perirenal involvement by retroperitoneal fibrosis: the usefulness of MRI to establish diagnosis. Urol Radiol 1992;13:173–176.[Medline]
  41. Triantopoulou C, Rizos S, Bourli A, Koulentianos E, Dervenis C. Localized unilateral perirenal fibrosis: CT and MRI appearances. Eur Radiol 2002;12:2743–2746.[Medline]
  42. Emch TM, Miller MA. Retroperitoneal fibrosis involving the left kidney in a patient with a remote history of Riedel's thyroiditis. AJR Am J Roentgenol 2005;184(suppl 3):S97–S98.[Free Full Text]
  43. Brown WE, Coakley FV, Heaney M. Renal involvement by Rosai-Dorfman disease: CT findings. Abdom Imaging 2002;27:214–216.[CrossRef][Medline]
  44. Dion E, Graef C, Haroche J, et al. Imaging of thoracoabdominal involvement in Erdheim-Chester disease. AJR Am J Roentgenol 2004;183:1253–1260.[Free Full Text]
  45. Servais A, Pestieau SR, Detry O, et al. Autoimmune pancreatitis mimicking cancer of the head of pancreas: report of two cases. Acta Gastroenterol Belg 2001;64:227–230.[Medline]
  46. Koga Y, Yamaguchi K, Sugitani A, Chijiiwa K, Tanaka M. Autoimmune pancreatitis starting as a localized form. J Gastroenterol 2002;37:133–137.[CrossRef][Medline]
  47. Wakabayashi T, Kawaura Y, Satomura Y, et al. Clinical and imaging features of autoimmune pancreatitis with focal pancreatic swelling or mass formation: comparison with so-called tumor-forming pancreatitis and pancreatic carcinoma. Am J Gastroenterol 2003;98:2679–2687.[CrossRef][Medline]



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