Published online before print November 21, 2002, 10.1148/radiol.2261011547
(Radiology 2003;226:86-94.)
© RSNA, 2002
Segmental Misty Mesentery: Analysis of CT Features and Primary Causes1
Bo Kyoung Seo, MD,
Hyun Kwon Ha, MD,
Ah Young Kim, MD,
Tae Kyung Kim, MD,
Min Jung Kim, MD,
Jae Ho Byun, MD,
Pyo Nyun Kim, MD,
Moon-Gyu Lee, MD,
Suk-Kyun Yang, MD,
Eun-Sil Yu, MD and
Jin Ho Kim, MD
1 From the Departments of Diagnostic Radiology (B.K.S., H.K.H., A.Y.K., T.K.K., M.J.K., J.H.B., P.N.K., M.G.L.), Internal Medicine (S.K.Y., J.H.K.), and Pathology (E.S.Y.), Asan Medical Center, University of Ulsan College of Medicine, 388-1 Poongnap-Dong, Songpa-Ku, Seoul 138-736, Korea. Received September 18, 2001; revision requested October 22; revision received March 25, 2002; accepted May 13. Address correspondence to H.K.H. (e-mail: hkha@amc.seoul.kr).
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ABSTRACT
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PURPOSE: To review the computed tomographic (CT) features of segmental misty mesentery (SMM) in 29 patients and assess the primary causes of this CT finding.
MATERIALS AND METHODS: The authors analyzed the medical records and CT features of SMM in 29 patients. CT images were evaluated for the site, thickness, and vascular changes of the involved mesentery; bowel wall changes; lymphadenopathy; and the fat ring sign. The primary cause of SMM in five patients was determined at histopathologic examination, that in three patients was determined at surgical observation of the mesentery, and that in nine patients was determined on the basis of follow-up CT and clinical data. The primary cause of SMM in 12 patients was unknown.
RESULTS: Twenty-five of the 29 patients had various underlying diseases. Fourteen (48%) patients had a malignancy: 11 had intraabdominal cancer and three had extraabdominal cancer. Jejunal mesentery was more commonly involved than was ileal mesentery (P < .05). The mean thickness of the SMM was 4.0 cm. Mesenteric vessels were dilated in 27 patients (93%): 19 with venous dilatation and eight with either arterial dilatation only or both arterial and venous dilatation. At CT, seven (24%) patients had a thickened bowel wall; nine (31%) patients, lymphadenopathy; and two (7%) patients, the fat ring sign. The primary cause of SMM was edema in eight, malignant neoplasm in four, inflammation and/or fibrosis in five, and idiopathic in 12 patients.
CONCLUSION: At CT, SMM appears as a result of malignant neoplasms, inflammation, or vascular disorders.
© RSNA, 2002
Index terms: Abdomen, CT, 792.12111, 792.12112, 792.12113, 792.12115 • Abdomen, diseases, 70.246, 70.26, 70.288, 70.32 • Mesentery, CT, 792.12111, 792.12112, 792.12113, 792.12115 • Mesentery, diseases, 792.246, 792.26, 792.288
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INTRODUCTION
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The mesentery is a reflection of the peritoneum on the bowel surface; it also supports loops of the small bowel and the colon. The mesentery consists of two fused layers, within which lie mesenteric vessels, lymphatic vessels, nerves, and variable amounts of fat. At computed tomography (CT), normal mesenteric fat appears homogeneous and has an attenuation similar to that of subcutaneous tissues and the retroperitoneum. The usefulness of CT for evaluating mesenteric changes has been described in many previously published studies (1-12), and an alteration in the attenuation of mesenteric fat is often an important clue in determining the underlying cause of an abdominal abnormality. The term misty mesentery, which has been used by Mindelzun et al (13), refers to mesentery with increased attenuation at CT.
The presence of misty mesentery is commonly regarded as one of the CT signs of mesenteric panniculitis. Mesenteric panniculitis is a rare disorder that manifests grossly as a diffuse, localized, or multinodular thickening of the mesentery and microscopically as an infiltration by inflammatory cells—namely, myofibroblasts and foamy macrophages. The vessels traversing the lesion are often inflamed and sometimes thrombosed (14). Synonyms for mesenteric panniculitis include sclerosing mesenteritis (15), mesenteric lipodystrophy (16), liposclerotic mesenteritis (17), and the mesenteric variety of Weber-Christian disease (18). However, misty mesentery may be caused by a variety of other conditions, such as lymphedema, hemorrhage, trauma, and neoplasm (13). Although nonsegmental misty mesentery is a common CT feature of many pathologic conditions, occasionally we have observed a segmental pattern of mesenteric involvement. Thus, the purpose of this study was to review the CT features of 29 patients with segmental misty mesentery and to assess the primary causes of this CT finding.
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MATERIALS AND METHODS
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This study was approved by the institutional review board for human investigation at our institution. Informed patient consent was waived. The CT features and medical records of 29 consecutive patients in whom segmental misty mesentery was depicted on abdominal CT scans were analyzed. The CT scans had been prospectively collected by a radiologist (H.K.H.) during a 2-year period. The age range of the 29 patients (19 men and 10 women) was 18–85 years (mean age, 57 years). The primary cause of the mesenteric changes was determined at histopathologic examination of surgical specimens from five patients, at surgical observation of the mesentery in three patients, and on the basis of follow-up CT and clinical data from nine patients. The cause of the mesenteric changes in 12 patients was unknown.
CT was performed with either a Somatom Plus-S (Siemens, Erlangen, Germany) or a 9800 Quick System (GE Medical Systems, Milwaukee, Wis) CT scanning unit. The patients routinely received both oral (barium sulfate, E-Z-Cat; E-Z-Em, Westbury, NY) and intravenous (iopamidol, Iopamiro 300; Bracco, Milan, Italy) contrast materials. Barium sulfate was administered 1 hour before (600 mL) and immediately before (300 mL) the CT examination. Iopamidol was administered intravenously as a 120-mL bolus infusion at a rate of 2.0 mL/sec. Both nonenhanced and contrast material–enhanced CT scans were obtained in all patients.
In 24 patients, CT scanning was initiated 60-80 seconds after the beginning of the infusion, and spiral scans were obtained in 10-mm-thick transverse sections at 10-mm intervals from the dome of the diaphragm to the pubic symphysis. The remaining five patients underwent dynamic CT scanning that involved the acquisition of nonenhanced, arterial phase, and portal phase spiral images prior to, 27 seconds after, and 70 seconds after the initiation of the infusion. In these patients, scans were obtained in 10-mm-thick sections at 10–13-mm intervals from the dome of the diaphragm to the level of the fourth lumbar vertebra. In 14 patients, follow-up CT scans were obtained after a mean interval of 13.2 months (range, 0.8-36.7 months).
The CT scans were evaluated by two radiologists (B.K.S., H.K.H.), and interpretations were made by consensus. Normal mesenteric fat appears as a homogeneous area of low attenuation (-100 to -160 HU), similar to the attenuation of fat in the subcutaneous tissues and retroperitoneum. Segmental misty mesentery was defined as adipose tissue around the mesenteric vessels in association with a visually perceptible area of increased attenuation relative to that of subcutaneous or retroperitoneal fat, as well as a segmental distribution of changes along the branches of the mesenteric vessels—namely, the jejunal, ileal, and ileocolic vessels. Transverse CT images were evaluated for site and maximum thickness of the involved mesentery, status of the mesenteric vessels, presence or absence of bowel wall changes, lymph node enlargement, and the fat ring sign (ie, preservation of the fat nearest the mesenteric vessels) (15), and for observation of other abdominal organs.
The mesenteric vessels were considered to be dilated or engorged when they were larger than 3 mm in diameter or were increased in number (11,19); in equivocal cases, we compared the diameter of the vessels in the misty mesentery with the diameter of the uninvolved mesentery at a similar mesenteric level. The bowel wall was considered to be thickened when its thickness exceeded 4 mm (19–22). The mesenteric lymph nodes were considered to be enlarged when they had a diameter greater than 3 mm (19). After analyzing these CT features, we compared them according to the presumed primary cause. We examined the 14 patients who underwent follow-up CT for the presence or absence of changes in the involved mesentery.
One radiologist (B.K.S.) reviewed the patients’ medical records for clinical histories and presentations, previous abdominal surgery, and laboratory data. We also evaluated the surgical and histopathologic reports on 12 patients who underwent abdominal surgery (three subtotal gastrectomies, two liver transplantations, two hemicolectomies, one Whipple operation, one small-bowel resection, one hepatic lobectomy, one appendectomy, and one cholecystectomy), 10 of whom underwent the surgery within 1 month after undergoing initial CT. Surgical specimens from the misty mesentery were obtained from five of the 12 patients who underwent abdominal surgery; another five patients underwent only surgical observation of the mesentery. In three of the five patients who underwent only surgical observation of the mesentery, the surgical observation led to a determination of the primary cause of the misty mesentery, but in the other two patients, it did not help in determining the cause. In the remaining two patients, we did not observe specifically the mesentery at surgery because the mesentery appeared to be normal on preoperative CT scans. Misty mesentery was depicted on follow-up CT scans obtained after gastrectomy; the intervals between the acquisition of pre- and postoperative follow-up CT scans ranged from 8 to 52 months.
Commercially available computer software (SAS/STAT, version 6.12; SAS Institute, Cary, NC) was used to perform statistical analysis. When we compared the CT findings associated with the different primary causes of segmental misty mesentery, we used analysis of variance to compare the mean thickness of the misty mesentery and the Fisher exact test to compare the remaining parameters. P < .05 was considered to indicate a significant difference.
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RESULTS
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Of the 29 study patients, 25 had various underlying diseases of the abdomen and other sites—for example, the lung, thyroid, and testicles—however, the other four patients did not have underlying diseases (Table 1). At the time of CT, 14 (48%) of the 29 patients had malignancies, which were intraabdominal in 11 patients and extraabdominal in three. Five patients had lymphoma; four patients, gastrointestinal adenocarcinoma; two patients, pancreatic cancer; one patient, paratesticular sarcoma; one patient, thyroid cancer; and one patient, lung cancer. There was no CT evidence of metastatic lesions in the abdomen in the three patients who had an extraabdominal malignancy. In all 11 of the patients with intraabdominal malignancies the abnormalities that suggested a malignant tumor were demonstrated on CT scans. The tumor sites closely abutted the misty mesentery in six patients (patients 1, 2, 4, 5, 9, and 11) and were distant to the misty mesentery in the remaining five.
The site of segmental misty mesentery was the jejunal mesentery in 22 (76%) patients and the ileal mesentery in seven (24%). The maximum thickness of the involved mesentery ranged from 2.0 to 7.4 cm (mean, 4.0 cm). The vessels within the misty mesentery were dilated in 27 (93%) patients: 19 with venous dilatation, four with arterial dilatation, and four with both arterial and venous dilatation. The mesenteric vessels were displaced by bulky lymphadenopathy in one patient (Fig 1). The bowel wall was thickened in the loop adjacent to the misty mesentery in seven (24%) patients (Fig 2). Lymphadenopathy within the misty mesentery was seen in nine (31%) patients at CT (Fig 1). The fat ring sign was depicted at CT in two (7%) patients (Fig 3).
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Figure 1. Patient 1. Transverse contrast-enhanced CT scan obtained in a 51-year-old man with non-Hodgkin lymphoma shows markedly thickened ileal mesentery (black arrows) with increased attenuation. The mesenteric fat is replaced by lymphomatous masses, and there is marked compression of the mesenteric vessels. Ascites (white arrow) along the right paracolic gutter is also seen.
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Figure 2a. Patient 21. Perforated tuberculous enteritis in a 40-year-old man. (a) Transverse contrast-enhanced CT scan shows segmental misty mesentery involving the ileal mesentery (white arrows) along with bowel wall thickening (black arrows) in the distal ileum. (b) Histopathologic specimen of the involved mesentery after surgical resection of the ileum shows inflammatory infiltration of the mesentery by neutrophils and histiocytes (arrows). (Hematoxylin-eosin stain; original magnification, x200.)
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Figure 2b. Patient 21. Perforated tuberculous enteritis in a 40-year-old man. (a) Transverse contrast-enhanced CT scan shows segmental misty mesentery involving the ileal mesentery (white arrows) along with bowel wall thickening (black arrows) in the distal ileum. (b) Histopathologic specimen of the involved mesentery after surgical resection of the ileum shows inflammatory infiltration of the mesentery by neutrophils and histiocytes (arrows). (Hematoxylin-eosin stain; original magnification, x200.)
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Figure 3a. Patient 14. Paratesticular sarcoma in a 69-year-old man. (a) Initial transverse contrast-enhanced CT scan shows increased attenuation of the thickened ileal mesentery (arrows). (b) Transverse follow-up CT scan obtained 3 years after the CT scan in a was obtained shows further progression of the mesenteric thickening (open arrows). There is also evidence of the fat ring sign (solid arrows) preserving the fat nearest the mesenteric vessels. Histopathologic confirmation was not obtained, so we regarded this as an idiopathic case.
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Figure 3b. Patient 14. Paratesticular sarcoma in a 69-year-old man. (a) Initial transverse contrast-enhanced CT scan shows increased attenuation of the thickened ileal mesentery (arrows). (b) Transverse follow-up CT scan obtained 3 years after the CT scan in a was obtained shows further progression of the mesenteric thickening (open arrows). There is also evidence of the fat ring sign (solid arrows) preserving the fat nearest the mesenteric vessels. Histopathologic confirmation was not obtained, so we regarded this as an idiopathic case.
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Surgical specimens of the involved mesentery were obtained from five of the 12 patients who underwent abdominal surgery. In two of these patients, who underwent surgery for treatment of perforated tuberculous enteritis (patient 21) and acute appendicitis (patient 23), histopathologic examination of the misty mesentery revealed inflammatory infiltration with fibrotic changes (Fig 2). One patient (patient 9), who had descending colon cancer, had severe adhesions in the perisplenic space and omentum in the surgical field, whereas at histopathologic examination, the involved mesentery in this patient had only fibrosis without tumor infiltration. In one patient (patient 7) with gastric cancer, the mesentery had edematous changes without tumor infiltration (Fig 4). In the remaining patient (patient 5), who had non-Hodgkin lymphoma, the mesentery had lymphomatous infiltration.
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Figure 4a. Patient 7. Gastric cancer in a 56-year-old man. (a) Initial transverse contrast-enhanced CT scan shows increased attenuation of the thickened jejunal mesentery (open arrows) along with dilatation of the jejunal arterial branch (solid arrows). A mildly enlarged mesenteric lymph node (arrowhead) in the involved mesentery also is seen. (b) Histopathologic specimen of the involved mesentery, which was resected at gastric surgery, shows edematous changes in the mesentery without tumor infiltration. (Hematoxylin-eosin stain; original magnification, x200.)
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Figure 4b. Patient 7. Gastric cancer in a 56-year-old man. (a) Initial transverse contrast-enhanced CT scan shows increased attenuation of the thickened jejunal mesentery (open arrows) along with dilatation of the jejunal arterial branch (solid arrows). A mildly enlarged mesenteric lymph node (arrowhead) in the involved mesentery also is seen. (b) Histopathologic specimen of the involved mesentery, which was resected at gastric surgery, shows edematous changes in the mesentery without tumor infiltration. (Hematoxylin-eosin stain; original magnification, x200.)
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In five other patients from the group of 12 who underwent abdominal surgery, the involved mesentery was observed in the surgical field only; there was no surgical resection. There were severe edematous changes in the mesentery in two patients (patients 16 and 18) (Fig 5), who underwent liver transplantation owing to end-stage liver cirrhosis. In one patient (patient 24), who had acute cholecystitis, there was evidence of inflammatory change. No evidence of a mass or inflammation (ie, idiopathic cause) was seen in either of the patients who underwent surgery for treatment of nonfunctioning islet cell tumor of the pancreas (patient 10) and choledocholithiasis with cholangitis (patient 25). In the remaining two of the 12 patients who underwent surgery (patients 6 and 8, for gastric cancer), the mesentery appeared to be normal on preoperative CT scans; however, misty mesentery was demonstrated on follow-up CT scans obtained after gastrectomy but had improved by the time of the second follow-up CT examination that was performed after the patient underwent chemotherapy (Fig 6).
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Figure 5a. Patient 18. End-stage liver cirrhosis in a 47-year-old man. (a) Initial transverse contrast-enhanced CT scan shows increased attenuation of the mesentery (solid arrows). Splenomegaly (open arrows) also is seen. (b) Transverse follow-up CT scan obtained after liver transplantation shows marked regression of the mesenteric changes (arrows). Although histopathologic confirmation of the diagnosis was not obtained, we assumed that the mesenteric changes resulted from congestion and edema caused by portal hypertension.
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Figure 5b. Patient 18. End-stage liver cirrhosis in a 47-year-old man. (a) Initial transverse contrast-enhanced CT scan shows increased attenuation of the mesentery (solid arrows). Splenomegaly (open arrows) also is seen. (b) Transverse follow-up CT scan obtained after liver transplantation shows marked regression of the mesenteric changes (arrows). Although histopathologic confirmation of the diagnosis was not obtained, we assumed that the mesenteric changes resulted from congestion and edema caused by portal hypertension.
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Figure 6a. Patient 6. Gastric cancer in a 56-year-old man. (a) First transverse postoperative CT scan shows increased attenuation of the jejunal mesentery (open arrows). (b) Second transverse postoperative follow-up CT scan, which was obtained after the patient underwent chemotherapy, shows marked improvement of the mesenteric changes seen on the first scan (solid arrows in a). We classified this case as idiopathic because the mesenteric changes might have been caused by either neoplastic infiltration or nonneoplastic conditions, such as lymphedema or congestive change.
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Figure 6b. Patient 6. Gastric cancer in a 56-year-old man. (a) First transverse postoperative CT scan shows increased attenuation of the jejunal mesentery (open arrows). (b) Second transverse postoperative follow-up CT scan, which was obtained after the patient underwent chemotherapy, shows marked improvement of the mesenteric changes seen on the first scan (solid arrows in a). We classified this case as idiopathic because the mesenteric changes might have been caused by either neoplastic infiltration or nonneoplastic conditions, such as lymphedema or congestive change.
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In nine of the 17 patients who did not undergo surgery, the cause of misty mesentery was presumed on the basis of the CT findings and/or clinical data: congestive and edematous changes in four patients (patients 15, 17, 19, and 20) with advanced liver cirrhosis and portal hypertension and in one patient (patient 11) with pancreatic cancer invading the superior mesenteric vein, neoplastic infiltration in three patients (patients 1, 2, and 4) with lymphoma, and inflammation in one patient (patient 22) with acute pancreatitis.
In the remaining eight patients who did not undergo surgery, the exact cause of the segmental misty mesentery was unknown. Four (patients 26–29) of these patients with an idiopathic cause of segmental misty mesentery presented with acute abdominal pain and indigestion; however, their laboratory findings were normal. There were no other positive CT findings, except for the misty mesentery, in these patients (Fig 7). With symptom-based conservative treatment, these patients’ clinical symptoms subsided 2-3 weeks following CT. The fifth patient (patient 12) had dyspnea due to thyroid cancer with tracheal invasion. There was no evidence of metastatic lesions in the abdomen of this patient, who died owing to respiratory problems several days after undergoing CT. In the sixth patient (patient 13), who had lung cancer, a mass was seen in the right lower lung, but there were no other abnormalities in the abdomen except misty mesentery. This patient had no abdominal symptoms or abnormal laboratory findings. The seventh patient (patient 14) had paratesticular sarcoma and findings of segmental misty mesentery on preoperative CT scans. This patient subsequently underwent orchiectomy, but misty mesentery was still evident on the follow-up CT scan obtained 36.7 months after surgery (Fig 3). This patient did not have abdominal symptoms such as pain, fever, weight loss, or nausea. In the eighth patient (patient 3), who had non-Hodgkin lymphoma, misty mesentery along with paraaortic lymphadenopathy was seen on the initial CT scan. This patient underwent chemotherapy, but the follow-up CT scans obtained 3.5 weeks after the initial CT scan was obtained did not show any interval changes.
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Figure 7. Patient 26. Transverse contrast-enhanced CT scan obtained in a 59-year-old woman who reported having abdominal pain for 1 week but did not have demonstrable underlying disease at CT shows diffusely increased attenuation of the thickened jejunal mesentery (open arrows) along with dilated mesenteric vessels (solid arrows). This patient did not have any specific disease and had normal laboratory findings. Her symptoms spontaneously subsided 2 weeks after she underwent the initial CT examination. We classified this case as idiopathic.
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Overall, we were able to determine the primary cause of segmental misty mesentery with histopathologic examination of the surgical specimens from five patients (patients 5, 7, 9, 21, and 23), with surgical correlation in three patients (patients 16, 18, and 24), and with follow-up CT findings and clinical data in nine patients (patients 1, 2, 4, 11, 15, 17, 19, 20, and 22). We concluded that edema was the cause of the misty mesentery in eight patients, malignant neoplasm was the cause in four patients, and inflammation and/or fibrosis was the cause in five patients. In the remaining 12 patients (patients 3, 6, 8, 10, 12–14, and 25–29), the primary cause of the misty mesentery was unknown (ie, idiopathic). Also, the segmental misty mesentery in the 14 patients with intraabdominal or extraabdominal malignancies resulted from neoplastic infiltration in four patients, edema in two patients, and inflammation and fibrosis in one patient. The segmental misty mesentery in seven of these 14 patients was idiopathic.
The CT features associated with the primary causes of segmental misty mesentery are compared in Table 2. The patients with malignant neoplasms or inflammation had more frequent involvement of the ileal mesentery than did those with idiopathic causes (P < .05). The prevalence of arterial and venous dilatation was higher in the patients with malignant neoplasms than in those with inflammation or edema (P < .05). Lymphadenopathy within the misty mesentery was more commonly seen in the patients with malignant neoplasms than in those with edema, inflammation, or idiopathic causes (P < .05). There was no significant difference in bowel wall thickening among the primary causes of segmental misty mesentery (P > .05).
By the time of follow-up CT in 14 patients, the segmental misty mesentery had completely returned to normal in six patients (patients 4, 6, 8, 15, 16, and 25), had partially improved in six patients (patients 9, 10, 11, 18, 22, and 24), had worsened in one patient (patient 14), and had not changed in one patient (patient 3).
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DISCUSSION
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The term misty mesentery refers to the CT appearance of increased attenuation of the mesenteric fat owing to infiltration by inflammatory cells, fluid (ie, edema, lymph, or blood), tumor, or fibrosis (13). Misty mesentery is also considered an important CT sign of mesenteric panniculitis, which is characterized by nonspecific chronic inflammation with fat necrosis. Fibrosis can be demonstrated at histopathologic examination but is not a predominant finding. According to the results of a study performed by Kipfer et al (23) involving 53 patients with mesenteric panniculitis, 22 (42%) had diffuse mesenteric thickening; 17 (32%), a single discrete mass; and 14 (26%), multiple discrete masses. The predisposing factors of mesenteric panniculitis in these patients included concurrent or remote infection, healing appendicitis, recent surgery, mesenteric thrombosis, and residual suture material (12,16–18,23). On CT scans, the mesenteric panniculitis appeared as a well-circumscribed inhomogeneous fatty mass at the root of the mesentery.
The fat ring sign and the tumoral pseudocapsule also have been described as important CT findings for the diagnosis of this disease (12,13,15,24,25). The fat ring sign indicates the preservation of the densitometric values of the fat nearest the mesenteric vessels, and the tumoral pseudocapsule represents a peripheral band with soft-tissue attenuation that causes the normal mesentery to have limited inflammatory activity. Although such CT findings appear to be diagnostic for mesenteric panniculitis, in the clinical setting it has been difficult to obtain tissue specimen confirmation of misty mesentery when surgery was not performed for other reasons. The results of a recent study performed by Daskalogiannaki et al (25) supported this assumption: In only four of 49 patients with mesenteric panniculitis was the diagnosis pathologically confirmed. Accordingly, we presume that many other conditions might be mistaken for mesenteric panniculitis in the related literature.
Our study results showed that aside from the inflammation and fibrosis seen with mesenteric panniculitis, the cause of segmental misty mesentery was not only edematous changes resulting from vascular disorders but also direct neoplastic infiltration into the mesenteric fat. In 12 of the 29 study patients, however, the primary cause of the misty mesentery was unclear (ie, idiopathic), even in two patients (patients 10 and 25) in whom the involved mesentery was observed in the surgical field. The unknown cause of the misty mesentery in two other patients, who had gastric cancer (patients 6 and 8), is also worth noting: Although misty mesentery was detected on the postoperative follow-up CT scans obtained in these patients after gastrectomy and improved after chemotherapy, we assigned these patients to the idiopathic cause group because their misty mesentery might have been caused by either neoplastic infiltration or benign causes, such as lymphedema or congestive changes. It should be noted that segmental misty mesentery is a reversible CT finding. With the exception of the segmental misty mesentery in these two patients, the mesentery in all 14 patients who underwent follow-up CT improved after the underlying primary causes were corrected or eliminated.
Misty mesentery can be segmental or nonsegmental. Nonsegmental mesenteric involvement occurs most commonly in patients with inflammatory bowel disease or in patients who have experienced trauma and have mesenteric bowel injury, major bowel injury, or both. In such cases, the primary lesions are often adjacent to the misty mesentery. In contrast, as our study results demonstrated, segmental misty mesentery commonly results from edematous changes secondary to vascular disorder or neoplastic infiltration. The primary pathologic process can also exist at sites distant from the involved mesentery.
In our study, the jejunal mesentery was more frequently involved than the ileal mesentery (76% versus 24%). Although there is no exact explanation for this difference, some differences in vascular anatomy between the jejunum and the ileum seem to be involved. Because there are relatively fewer mesenteric vascular branching arches in the jejunum than in the ileum, the jejunum may be more easily affected by hydrostatic pressure. Another reason for the differences in mesenteric involvement between these two sites may be that most of the underlying diseases in these patients were in the upper part of the abdomen—for example, the liver, stomach, pancreas, and proximal descending colon.
It is interesting that mesenteric vascular dilatation within misty mesentery was demonstrated at CT in 27 patients (93%) in our study: in 19 patients with venous dilatation and in eight with either arterial dilatation only or both arterial and venous dilatation. We believe that the venous dilatation resulted mainly from hydrostatic pressure caused by portal hypertension or from vascular compression of the vein draining the misty mesentery. We presumed the arterial dilatation to have been caused by inflammatory hyperemia in patients with an inflammatory condition, such as inflammatory bowel disease or pancreatitis, or possibly by the increased blood supply in patients with malignant neoplasms.
In our study, fourteen (48%) of the 29 patients with segmental misty mesentery had an intraabdominal or extraabdominal malignancy: lymphoma in five patients, gastrointestinal adenocarcinoma in four patients, pancreatic tumor in two patients, paratesticular sarcoma in one patient, thyroid cancer in one patient, and lung cancer in one patient. Such an association between malignancy and mesentery has been reported in the literature. In a report by Kipfer et al (23), malignancy coexisted with mesenteric panniculitis in 16 (30%) of 53 patients; eight of these 16 patients had lymphoma, and the remaining patients had gastrointestinal or genitourinary cancer. In a more recent series reported on by Daskalogiannaki et al (25), the rate of coexisting malignancy was higher than that in other reports: 34 (69%) of 49 patients. Fifteen (44%) of the 34 patients had intraabdominal malignancies, which were mostly urogenital cancers, gastrointestinal adenocarcinomas, or lymphomas (25).
According to our study results and those of other researchers, the frequency of coexisting malignancy is high in patients with segmental misty mesentery, and, thus, close follow-up with CT or other examinations to search for hidden malignancy, especially gastrointestinal or genitourinary cancer, may be required for patients in whom segmental misty mesentery is detected but no demonstrable underlying disease is seen at CT. Furthermore, it should be noted that the segmental misty mesentery in such patients does not always indicate neoplastic infiltration. In addition to neoplastic infiltration, nonspecific edema or inflammation can cause segmental misty mesentery. Although Kipfer et al (23) suggested that mesenteric panniculitis is a nonspecific response to an underlying abdominal malignancy, that assumption does not explain the cases of extraabdominal malignancy. When we compared the CT features according to primary cause of segmental misty mesentery, the prevalences of lymphadenopathy and arterial and venous dilatation within misty mesentery and of ileal mesenteric involvement appeared to be higher in the patients with underlying neoplasms than in those with inflammation or vascular disorders such as portal hypertension. However, owing to our limited patient population, further studies are necessary to support this observation.
In conclusion, the segmental involvement of misty mesentery at CT does not always indicate panniculitis. Segmental misty mesentery can be seen with other pathologic conditions, such as neoplastic or vascular disorders. In our study, half the patients with segmental misty mesentery had an underlying malignancy. Therefore, close follow-up with CT or other examinations to search for hidden malignancy is warranted for patients who have findings of segmental misty mesentery without a demonstrable underlying cause at CT.
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ACKNOWLEDGMENTS
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We thank Bonnie Hami, MA, of the Department of Radiology, University Hospitals Health System, Cleveland, Ohio, for her editorial assistance in preparing this manuscript and June Young Lee, PhD, of the Department of Preventive Medicine, Korea University College of Medicine, Seoul, Korea, for his advice on the statistical analysis of the data.
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FOOTNOTES
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Author contributions: Guarantor of integrity of entire study, H.K.H.; study concepts and design, H.K.H.; literature research, B.K.S.; clinical studies, B.K.S., M.J.K.; data acquisition, B.K.S., M.J.K.; data analysis/interpretation, B.K.S., H.K.H.; manuscript preparation, B.K.S., H.K.H.; manuscript definition of intellectual content, H.K.H.; manuscript editing, A.Y.K., T.K.K., J.H.B.; manuscript revision/review, P.N.K., M.G.L., S.K.Y., J.H.K., E.S.Y.; manuscript final version approval, H.K.H.
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ABSTRACT
INTRODUCTION
