Postmortem computed tomography of gas gangrene with aortic gas in a dialysis patient.

Recently, postmortem imaging is sometimes used as an alternative to conventional autopsy. However, there are few case reports of postmortem imaging of dialysis patients. Here, we report a fatal case of gas gangrene involving a 76-year-old man who underwent dialysis. He died suddenly before a diagnosis could be established. Immediately after his death, postmortem computed tomography (PMCT) revealed gas accumulation in his right upper extremity and ascending aorta. Gas gangrene progresses rapidly and may sometimes result in sudden death before it is diagnosed. In this case, PMCT findings were useful to diagnose gas gangrene. Intravascular gas is a common finding on PMCT and is generally caused by cardiopulmonary resuscitation and decomposition. However, the detection of gas in the ascending aorta by PMCT was not described previously. Moreover, Gram stain and culture of the exudate showed anaerobic Gram-positive bacilli which suggested that the gas generation in the blood was caused by Clostridia species. To the best our knowledge, this is the first report of a dialysis patient whose cause of death was determined as gas gangrene using PMCT.

Computed tomography detected pyelovenous backflow associated with complete ureteral obstruction.

INTRODUCTION: Pyelovenous backflow is a rare condition resulting from an increase in pressure in the renal pelvis due to urinary obstruction. CASE PRESENTATION: A 49-year-old woman developed high-grade fever and right-sided hydronephrosis after undergoing hysterectomy. Although the hydronephrosis was mild, retrograde pyelography revealed complete obstruction of the right ureter. Excretory phase scans of contrast-enhanced computed tomography showed pyelovenous backflow, which presumably decompressed the hydronephrosis. The pyelovenous backflow immediately disappeared after ureteroneocystostomy. CONCLUSION: We were presented with a patient showing pyelovenous backflow detected by contrast-enhanced computed tomography, which completely disappeared after ureteral obstruction release.

The Usefulness of Diffusion MRI in Detection of Lymph Node Metastases of Colorectal Cancer.

The aim of this study was to assess the sensitivity and specificity of preoperative diagnosis by diffusion magnetic resonance imaging (D-MRI) for lymph node metastasis of colorectal cancer. The b-value represents the diffusion factor (measured in s/mm(2)) and the strength of the diffusion gradients. The b-value used in this study was 1,000 s/mm(2). A total of 119 patients underwent D-MRI before resection of primary colorectal cancer (52 of the rectum, 67 of the colon) at our hospital between February 2005 and April 2006. Lymph node metastases judged by D-MRI were compared with postoperative pathological results. The form of lymph node metastasis was classified either as abundant or scarce type. The predictive values for lymph-node metastasis (sensitivity and specificity) by D-MRI were calculated from the result of this classification and lymph-node size. The study was divided into two periods: before the consensus meeting in January 2006, (n=79) (P-I), and after the adjustment of the criteria to improve the sensitivity and specificity based on the results of P-I (n=40) (P-II). Detection of lymph node metastasis using D-MRI in P-I had sensitivity of 61%, specificity of 73%, positive predictive value (PPV) of 55%, and negative predictive value (NPV) of 77%, while in P-II, these values improved to 79%, 95%, 94%, and 83%, respectively. Specificity and PPV for P-II were significantly higher than those for P-I (p<0.05). The diameter of lymph nodes judged to be metastatic on D-MRI (P-I vs. P-II: n=32 vs. 16) was 10.3±5.4 (3-28) vs. 9.1±3.0 (4-14) mm; 11.5±6.2 (4-28) vs. 9.2±3.1 (4-14) mm for truly positive nodes (n=18 vs. 15), and 6±3.8 (3-14) vs. 8 mm for false-positive nodes (n=14 vs. 1). On the other hand, lymph nodes judged negative by D-MRI (n=47 vs. 24) was 5.9±2.4 (3-16) vs. 5.7±2.8 (2-15) mm; 5.9±2.1 (3-16) vs. 5.3±2.1 (2-8) mm for truly negative (n=36 vs. 20), and 5.7±2.7 (3-12) vs. 7.8±4.9 (4-15) mm for false negative (n=11 vs. 4). As to the form of metastasis, all truly positive nodes were of the abundant type, and 6/11 (55%) in P-I and 1/4 (25%) in P-II false-negatives were of the scarce type. In conclusion, D-MRI seems useful for preoperative detection of metastatic lymph nodes in colorectal cancer, especially if the node is hyperintense and more than 9 mm in diameter.

Gastric leiomyosarcoma manifesting peculiar findings: radiological-pathological correlation.

Reported herein is a gastric leiomyosarcoma, which, nowadays, is extremely rare. Attention was focused not only on pathological findings but also on the histological basis of magnetic resonance imaging (MRI) findings. The patient was a 29-year-old Japanese woman. Preoperative T2-weighted MRI showed a large high-intensity gastric tumor with isointense streaks. The tumor was a broad-based large polypoid lesion and histologically consisted of fascicles of spindled cells having eosinophilic cytoplasm and cigar-shaped nuclei. Immunoreactivity for several smooth muscle markers including desmin on tumor cells, low amplification of both c-kit and PDGFRA cDNA on polymerase chain reaction, and absence of c-kit gene mutation in exons 9 and 11 strongly suggested that the tumor was not a gastrointestinal stromal tumor but a true leiomyosarcoma. In vitro MRI of the fresh tumor was obtained to explain the radiological findings on a morphological basis. In vitro MRI clearly depicted the very high-intensity areas separated by radially extended isointense lines. This radiological finding corresponded best to the most characteristic histological feature, that is, linearly extended fascicles of the tumor cells often with myxedematous change separated by radially elongated thin fibrovascular stroma: in other words, spouting appearance.

Volumetric analysis of a rhabdoid meningioma during preoperative follow-up. A case report.

The authors describe a case of rhabdoid meningioma (RM) in a 17-year-old boy that was determined by measuring the tumor volume during preoperative follow-up. The volume of the tumor located in the left occipital lobe, was measured every 1-5 months, using an image analysis software. The tumor volume doubling time (Td) ranged from 1.0 to 4.9 years in the first 11 months, but became 0.3 years in the last two months. The tumor grew rapidly in the last two months at which time surgery was performed. Pathological examination of the surgical specimen showed that the tumor contained rhabdoid cells (RCs). RCs were heterogeneously distributed in the tumor admixed with spindle-shaped cells. The areas where RCs were predominant had malignant histological features, with necrosis and high proliferation indices, whereas the areas with few RCs lacked the malignant features. The tumor grew slowly in the initial phase, possibly because components with low proliferation rates occupied most of the tumor. The tumor began to grow rapidly when the malignant component containing abundant RCs became predominant. To the authors' knowledge, this is the first report monitoring the volumetric change of RM periodically. Our investigation indicated that volumetric analysis is useful to decide surgical intervention of the meningiomas with potential malignancy.

Nonenhanced magnetic resonance lymphoductography: visualization of lymphatic system of the trunk on 3-dimensional heavily T2-weighted image with 2-dimensional prospective acquisition and correction.

The objective of this study was to evaluate the usefulness of the nonenhanced 3-dimensional heavily T2-weighted images obtained with 2-dimensional prospective acquisition and correction in visualization of the lymphatic system of the trunk. The thoracic duct, cisterna chyli, and lumbar lymphatics were well shown in 9 healthy volunteers. This nonenhanced magnetic resonance lymphoductography is thought to be a suitable method in visualization of the lymphatic system of the trunk.

Intrahepatic cholangiocarcinoma mimicking hepatic inflammatory pseudotumor.

A 50-year-old male with hepatitis B was referred for a small intrahepatic nodule. Magnetic resonance images raised strong suspicion of a benign lesion, such as an inflammatory pseudotumor, while the other radiological studies were equivocal. Furthermore, the high-intensity image on diffusion magnified-weighted imaging with a low B value strongly suggested a benign tumor. In spite of the absence of typical clinical or radiological findings, needle biopsy revealed an intrahepatic cholangiocarcinoma (ICC). The diagnosis of peripheral ICC rich in fibrous tissue seems to require needle biopsy for pathological examination with immunohistochemical staining because it frequently mimics other diseases, including benign tumors.

Clinical usefulness of diffusion-weighted imaging using low and high b-values to detect rectal cancer.

PURPOSE: The purpose of this study was to assess the potential role of diffusion-weighted imaging (DWI) using low and high b-values to detect rectal cancer. METHODS: The subjects were 15 patients diagnosed endoscopically with rectal cancer (m in 1 patient, sm in 0, mp in 3, ss in 7, se in 1, a in 3) and 20 patients diagnosed endoscopically with colon cancer and no other lesions (control group). Magnetic resonance imaging was performed using a 1.5T system. DWI was performed in the axial plane using echo planar imaging sequence (repetition time/echo time 1200/66, field of view 306x350 mm, reconstruction matrix 156x256, pixel size 2.0x1.4x8.0 mm) and acquired with 2 b-values (50 and 800 s/mm2). Low and high b-value DW images were analyzed visually. A lesion was positive by detection of a focal area of high signal in the rectum in high b-value images. The apparent diffusion coefficient (ADC) values of areas of high signal in high b-value images were calculated from the low and high b-value images. RESULTS: High b-value images enabled visualization of all 15 rectal cancers. In the control group, 13 cases were classified as negative and 7 cases as positive for rectal cancer. Sensitivity for detection of rectal cancer was 100% (15/15), and specificity was 65% (13/20). The mean ADC values in 7 patients with false-positive lesions and in 15 patients with rectal cancer were 1.374x10(-3) mm2/s (standard deviation [SD]: 0.157) and 1.194x10(-3) mm2/s (SD: 0.152), respectively (P=0.026). CONCLUSION: DWI with low and high b-values may be used to screen for rectal cancer.

Dynamic magnetic resonance imaging of solitary pulmonary nodules: utility of kinetic patterns in differential diagnosis.

OBJECTIVE: The aim of this study was to evaluate the clinical feasibility of dynamic magnetic resonance (MR) imaging with a 3-dimensional (3D) gradient recalled echo (GRE) volumetric interpolated breath-hold examination (VIBE) sequence to differentiate between benign and malignant solitary pulmonary nodules (SPNs). METHODS: Dynamic 3D GRE VIBE was performed in 45 patients with SPNs. For each lesion, the morphologic parameters, including the edge configuration, presence of peripheral enhancement (PE), and an internal signal on T2-weighted images, and the kinetic enhancement parameters were evaluated. RESULTS: All 29 of the malignant SPNs had internal enhancement, whereas 13 (81%) of the benign SPNs did not exhibit internal enhancement. A washout pattern was only observed in the malignant SPNs. The presence of PE was found in 56% of the benign SPNs and in 50% of the malignant SPNs. The lesion size was significantly different between malignant SPNs with PE and those without PE (P <0.01). The positive predictive value for malignancy was 91% (29 of 32 malignant SPNs). The negative predictive value was 100% (13 of 13 benign SPNs). CONCLUSIONS: A combination of morphologic criteria and kinetic information is useful for differentiating between benign and malignant SPNs. In particular, internal enhancement with PE and positive visual washout is thought be a useful tool.