CLINICAL IMAGING 1989;13:119-121 119 MESENTERIC CYST WITH ATYPICAL COMPUTED TOMOGRAPHY APPEARANCE SUSAN K. STEVENS, MD, MATILDE NINO-MURCIA, MD, RICHARD BLOOM, MD, AND KAREN L.M. CHANG, MD A case of mesenteric chylous cyst containing an unusual fluid-fluid level demonstrated on com- puted tomography but not on ultrasonography is presented. KEY WORDS: Mesenteric cyst; Omental cyst; Chylous cyst; Abdominal mass Mesenteric and omental cysts are uncommon lesions found in all age groups (l-3). A histologic classi- fication of mesenteric and omental cysts and a cor- relation with sonograms, computed tomography (CT) scans, and magnetic resonance (MR) images has recently been published (4). We present a case of mesenteric cyst with unusual CT and ultrasound findings. The CT findings were crucial in suggesting the correct preoperative diagnosis. CASE REPORT A 40-year-old man was admitted to the hospital with lower abdominal pain, IO-lb weight loss, and an abdominal mass of 6 months duration. The patient’s prior medical and family history were unremarkable and he had no previous history of abdominal sur- gery. Physical exam performed with the patient From the departments of Radiology (SK.%, M.N.), Surgery (R.B.), and Pathology (K.L.M.C.) Veterans Administration and Stanford University Medical Centers, Palo Alto, California Address reprint requests to: Matilde Nino-Murcia, M.D. De- partment of Radiology, Veterans Administration Medical Center, 3801 Miranda Avenue, Palo Alto, CA 94304. Received March 6, 1989. 0 1989 by Elsevier Science Publishing CO., ~nc. 655 Avenue of the Americas, New York, NY 10010 089917071/89/$3.50 supine demonstrated a soft 10 x 15 cm slightly tender mobile mass in the left upper quadrant of the abdomen that shifted position to the lower mid- abdomen with erect posture. Abdominal ultrasound demonstrated a 12-cm ho- mogeneously echogenic mass with posterior sound attenuation in the mid-abdomen adjacent to the left lobe of the liver, displacing the bowel. The patient was rescanned after voiding, and the mass was then found in the pelvis (Figure 1). Noncontrast abdomi- nal CT performed the same day showed an ll-cm, well-demarcated pelvic mass with a thick capsule. Postcontrast CT scan showed that the mass had moved to the left upper quadrant, suggesting a mesenteric origin. On both studies, an inner low- density rim having an attenuation value of -53 Hu was observed. The cyst content was homogeneous (-31 Hu) and contained a fluid-fluid level (Figure 2A and B). At operation, a cystic mass was noted arising from the root of the small bowel mesentery adjacent to the superior mesenteric artery and vein but discrete from surrounding bowel and retroperi- toneum. The excised mass was nearly spherical, 11 cm in diameter, and filled with thick, homogeneous, yellow-green fluid. Fat droplets were readily demon- strable with Oil Red 0 stains of this fluid. The wall was 0.4-2-O cm thick and composed of dense fibrous tissue with occasional lymphocyte nodules and a more diffuse lymphocytic, plasma cell, and macro- phage infiltrate. The luminal lining was composed of fibrocytes and macrophages, without recognizable epithelial or endothelial elements. The precise na- ture and origin of the cyst was not determined. The lymphocyte nodules suggested lymphatic cyst; however, the wall thickness, unilocularity, thick content, and lack of endothelial lining did not. Enteric epithelial lining was lacking, as were the fat necrosis and old blood that would suggest pseudo-
Transcript
CLINICAL IMAGING 1989;13:119-121 119
MESENTERIC CYST WITH ATYPICAL COMPUTED TOMOGRAPHY APPEARANCE
SUSAN K. STEVENS, MD, MATILDE NINO-MURCIA, MD, RICHARD BLOOM, MD, AND KAREN L.M. CHANG, MD
A case of mesenteric chylous cyst containing an unusual fluid-fluid level demonstrated on com- puted tomography but not on ultrasonography is presented.
KEY WORDS:
Mesenteric cyst; Omental cyst; Chylous cyst; Abdominal mass
Mesenteric and omental cysts are uncommon lesions found in all age groups (l-3). A histologic classi- fication of mesenteric and omental cysts and a cor- relation with sonograms, computed tomography (CT) scans, and magnetic resonance (MR) images has recently been published (4). We present a case of mesenteric cyst with unusual CT and ultrasound findings. The CT findings were crucial in suggesting the correct preoperative diagnosis.
CASE REPORT
A 40-year-old man was admitted to the hospital with lower abdominal pain, IO-lb weight loss, and an abdominal mass of 6 months duration. The patient’s prior medical and family history were unremarkable and he had no previous history of abdominal sur- gery. Physical exam performed with the patient
From the departments of Radiology (SK.%, M.N.), Surgery (R.B.), and Pathology (K.L.M.C.) Veterans Administration and Stanford University Medical Centers, Palo Alto, California
Address reprint requests to: Matilde Nino-Murcia, M.D. De- partment of Radiology, Veterans Administration Medical Center, 3801 Miranda Avenue, Palo Alto, CA 94304.
Received March 6, 1989.
0 1989 by Elsevier Science Publishing CO., ~nc. 655 Avenue of the Americas, New York, NY 10010 089917071/89/$3.50
supine demonstrated a soft 10 x 15 cm slightly tender mobile mass in the left upper quadrant of the abdomen that shifted position to the lower mid- abdomen with erect posture.
Abdominal ultrasound demonstrated a 12-cm ho- mogeneously echogenic mass with posterior sound attenuation in the mid-abdomen adjacent to the left lobe of the liver, displacing the bowel. The patient was rescanned after voiding, and the mass was then found in the pelvis (Figure 1). Noncontrast abdomi- nal CT performed the same day showed an ll-cm, well-demarcated pelvic mass with a thick capsule. Postcontrast CT scan showed that the mass had moved to the left upper quadrant, suggesting a mesenteric origin. On both studies, an inner low- density rim having an attenuation value of -53 Hu was observed. The cyst content was homogeneous (-31 Hu) and contained a fluid-fluid level (Figure 2A and B). At operation, a cystic mass was noted arising from the root of the small bowel mesentery adjacent to the superior mesenteric artery and vein but discrete from surrounding bowel and retroperi- toneum. The excised mass was nearly spherical, 11 cm in diameter, and filled with thick, homogeneous, yellow-green fluid. Fat droplets were readily demon- strable with Oil Red 0 stains of this fluid. The wall was 0.4-2-O cm thick and composed of dense fibrous tissue with occasional lymphocyte nodules and a more diffuse lymphocytic, plasma cell, and macro- phage infiltrate. The luminal lining was composed of fibrocytes and macrophages, without recognizable epithelial or endothelial elements. The precise na- ture and origin of the cyst was not determined. The lymphocyte nodules suggested lymphatic cyst; however, the wall thickness, unilocularity, thick content, and lack of endothelial lining did not. Enteric epithelial lining was lacking, as were the fat necrosis and old blood that would suggest pseudo-
120 STEVENS ET AL. CLINICAL IMAGING VOL. 13, NO. 2
FIGURE 1. Pelvic sonogram demonstrates a large mass
graphic appearance of our cyst, which demonstrated marked echogenicity with posterior acoustic attenu- ation, suggested the presence of a fat-containing or gas-containing lesion related to bowel. These find- ings are in accordance with those published by Behan and Kazam (6), who demonstrated that mix- tures of fat and water are echogenic on ultrasound. The CT images suggested the correct diagnosis of fat-containing mesenteric cyst and demonstrated a fluid-fluid level. In addition, a low-density concen- tric circle (-53 Hu) was noted that has not been described heretofore on CT (Figure 2A and B). This unusual appearance, however, could not be ex- plained based on the macroscopic or histologic findings. One explanation could be a difference in the concentration of fat within the fluid content
(arrows) with homogeneous internal echoes. Echogenicity and sound attenuation suggest primarily a solid mass. However, in this case the mass was secondary to a fat-con- taining cystic mass.
being greater toward the periphery of the cyst. Although the mesenteric cyst described herein
does not fall easily into any of Ros’ pathologic subgroups, the exact histologic classification of the
cyst of pancreatic origin. The patient had an un- eventful postoperative course.
DISCUSSION Chylous mesenteric cysts are rare, having an es- timated incidence of 7.3% of all abdominal cysts (5). They can vary in size from a few centimeters to those so large they fill the entire abdominal cavity. Beahrs (1) categorized these lesions into four groups: 1) embryonic and developmental; 2) traumatic or ac- quired; 3) neoplastic; and 4) infective and degenera- tive. More recently, Ros et al. reported a series of 41 mesenteric and omental cysts and established a pathologic classification based on examination of the wall and inner surface of the cyst by routine histo- logic techniques. The five large cyst subgroups in- cluded lymphangiomas, enteric duplication cysts, enteric cysts, mesothelial cysts, and nonpancreatic pseudocysts. Cysts were assigned to one of these groups by the presence or absence of a wall contain- ing either endothelial, enteric (with or without a double muscle layer with neural elements), or meso- thelial lining. Those without a discernible lining, that is, fibrous wall only, were classified as nonpan- creatic pseudocysts. The study emphasized further the importance of sonography, CT, and MRI in demonstrating the cystic nature of these abdominal masses and suggesting a preoperative diagnosis.
The mesenteric cyst described in this report dif- fers from those mentioned in the series bv Ros in at
FIGURE 2. Noncontrast CT [A) demonstrates pelvic mass with homogeneously low density and fat-fluid level (ar- row). Postcontrast CT (B) shows that the mass has shifted in position to the left upper quadrant. Note inner low-den- sity rim (-53 Hu).
least two important ways. First of all, -the sono- B
JUNE 1989 MESENTERIC CYST 121
cyst is far less important to the radiologist and surgeon than knowledge of its cystic rather than solid content, critical information revealed only on the CT examination in contrast with an ultrasound that was misleading.
REFERENCES 1. Bearhs OH, Judd ES, Dockerty MB. Chylous cysts of the
abdomen. Surg Clin North Am 1950;30:1081-1096. 2. Walker AR, Putnam TC. Omental, mesenteric and retroperito-
neal cysts: a clinical study of 33 new cases. Ann Surg 1973;178:13-19.
3. Vanek VW, Philips AK. Retroperitoneal, mesenteric and omen- tal cysts. Arch Surg 1984;119:838-842.
