CT evaluation of Crohn's disease: effect on patient management

CT scans from 80 consecutive patients with clinically symptomatic Crohn's disease were reviewed retrospectively to determine the effect of CT diagnosis on patient management. The initial clinical impression and any subsequent change in patient management because of the CT findings were noted. In 22 (28%) of the 80 patients, significant previously unsuspected findings led to a change in medical or surgical management. These included 12 patients with fistulae, four with abscess, two with avascular necrosis of the femoral head, two with sacral osteomyelitis, and single cases of pelvic inflammatory disease and femoral vein thrombosis.     

Computed tomography findings in gastrointestinal involvement by opportunistic organisms in acquired immune deficiency syndrome

The computed tomography findings in two cases of gastrointestinal superinfection by opportunistic organisms in acquired immune deficiency syndrome are presented. Findings included thickening of the mucosal folds and the bowel wall in the small intestine and colon associated with cytomegalovirus and cryptosporidiosis. These cases indicate that it is important to look carefully at the gastrointestinal tract when performing computed tomography in this group of patients. Unsuspected bowel pathology may be demonstrated, or disease may be confirmed in clinically suspected cases.     

Cyclosporine A inhibition of microcystin toxins

Cyclosporine A (CyA) given i.v. at a dose of 1.25 mg/mouse blocks a subsequent i.v. lethal dose (1.7-1.8 x LD50) of microcystin-LR for 24 hr, and is about 50% protective at 48 hr. Conversely, the fraction of mice that can be rescued by CyA (0.2 mg/mouse) after a lethal dose of microcystin-LR decreases rapidly with a pharmacodynamic half-time of only about 100 sec. The prophylactic action of CyA was tested against lethal doses of four microcystins. The acute lethality of 1.7-1.8 x LD50 dose of microcystin-LR, -RR, -LY, or -LA given 1 hr after administration of 0.2 mg of CyA is 0%, 0%, 58%, or 100%, respectively. Even a 0.6 mg/mouse dose of CyA is ineffective prophylaxis against a lethal dose of microcystin-LA. The inhibitory potency of CyA on microcystin toxicity can be completely reversed by the single L-amino acid substitution of alanine for arginine in the microcystin.     

Mr imaging of hepatic nodular regenerative hyperplasia

Nodular regenerative hyperplasia (NRH), a rare condition that is commonly associated with noncirrhotic portal hypertension, is not well described in the MR literature. Three patients at two institutions were identified who had both abdominal MR imaging and pathologic evidence of NRH. All examinations were performed at 1.5 T and included axial T1- and T2-weighted spin-echo (SE) images. The MR studies were reviewed by two radiologists in consensus. Two patients had multiple liver lesions that had high signal components on T1-weighted images and were predominantly isointense with liver on the T2-weighted images. One patient had no focal lesions identified. NRH, when visualized on MR images, appears as multifocal masses with shortened Tl and T2 similar to liver. NRH should be considered in the differential diagnosis of hepatocellular tumors, especially in patients with a predisposing condition.     

Rapidly enhancing hepatic hemangiomas at MRI: Distinction from malignancies with T2-weighted images

The purpose of this study is to describe a subset of atypical hepatic hemangiomas that enhance rapidly and diffusely and to determine whether heavily T2-weighted images could distinguish between atypically enhancing liver hemangiomas and hypervascular malignancies. A retrospective search of MR records identified seven patients with liver hemangiomas that demonstrated diffuse early enhancement and 23 patients with biopsy-proven malignant liver lesions that were hypervascular on dynamic gadolinium-enhanced MR images. Quantitative analysis of signal intensity measurements was performed on the T2-weighted images, heavily T2-weighted (TE < 140), and dynamic gadolinium-enhanced images. Blinded reader comparison of the T2-weighted images and gadolinium-enhanced images was performed. Hypervascular hemangiomas enhanced to a greater degree than hypervascular malignant liver lesions on the early phase gadolinium-enhanced images. Perilesional parenchymal enhancement was demonstrated in five cases of rapidly enhancing hemangiomas. Signal intensity and contrast-to-noise ratios on the heavily T2-weighted images of the hemangiomas were significantly greater than that of the hypervascular malignant lesions (P < .05). Hemangiomas were differentiated from the hypervascular malignant liver lesions with high accuracy (97–100%) by three blinded readers based on the T2-weighted images. A subset of hemangiomas have atypical rapid diffuse enhancement on dynamic gadolinium-enhanced images. These atypical hemangiomas can be distinguished from hypervascular malignant liver lesions on T2-weighted MR images.     

Ampullary carcinoma: Demonstration by current MR techniques

The objective of this study was to demonstrate the appearance of ampullary carcinoma using current MR techniques, including fat suppression, gadolinium enhancement, and MR cholangiography. Nine patients with ampullary carcinoma were examined by MRI at 1.5 T. MR examinations included T1-weighted spoiled gradient echo, T1-weighted fat-suppressed, and immediate postgadolinium spoiled gradient echo images for all patients and MR cholangiography for three patients. The imaging features of ampullary carcinomas, including tumor size and morphology, signal intensity, and enhancement characteristics, were determined. Ampullary carcinomas shown on MR images ranged in size from 1.5 to 5.5 cm. Tumors were low in signal intensity on precontrast T1-weighted spoiled gradient echo and T1-weighted fat-suppressed images relative to normal pancreatic tissue and enhanced less than normal pancreas on immediate postgadolinium spoiled gradient echo images. Tumor conspicuity was greatest on immediate postgadolinium spoiled gradient echo images. MR cholangiography demonstrated high grade obstruction of the common bile duct and mild dilatation of the pancreatic duct at the level of the ampulla with abrupt termination of the ducts in two untreated patients and moderate dilatation of the common bile duct in one patient who had a biliary stent. Ampullary carcinomas can be demonstrated on MR images as small masses arising at the ampulla. Tumors are well defined on immediate postgadolinium spoiled gradient echo images.     

Computed tomography of hepatic cavernous hemangioma

Fifty hepatic hemangiomas in 38 patients were evaluated by CT using sequential scanning following bolus injection. Lesions were assessed for the following CT features: (a) low density lesion on unenhanced scan; (b) early peripheral contrast enhancement; (c) progressive opacification from the periphery to the center; (d) a delay of at least 3 min before total opacification; and (e) eventual isodense appearance with or without unopacified cleft. The criteria for diagnosis of hepatic hemangioma were (d) and (e) plus at least two of the remaining three features. Forty-eight lesions were identified by CT; 38 displayed all five features, five lesions were missing one feature, and five lesions did not meet the criteria for diagnosis. Larger lesions required a significantly longer period to opacify (p less than 0.05). The positive predictive value of CT in the diagnosis of hemangioma was 100%.