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Computed tomographic scans were reviewed in 46 patients with documented omental pathology to analyze the radiographic characteristics of benign and malignant disease. The normal omentum is identified on CT of the abdomen as a homogeneous fat density anterior to the transverse colon. Four distinct patterns of omental pathology were identified: (a) omental caking, (b) finely infiltrated fat with a "smudged" appearance, (c) cystic masses, and (d) discrete nodules. The smudged pattern of omental pathology was identified most frequently; it was present in 20 to 39 patients with malignant disease and in five of seven patients with inflammatory disease. Omental caking was present in 17 of 46 patients but was only identified in malignant disease. Computed tomography provides the most reliable radiographic technique to routinely evaluate omental pathology. A thorough understanding of the variable appearance of omental disease is important in identifying omental pathology.

Thirteen patients with benign angiomatous lesions of the extremities were evaluated by CT. The relationship of the lesion to specific muscle groups and fascial planes was defined better by CT than on plain radiography or angiography. Computed tomography without contrast enhancement demonstrated well circumscribed masses of lower attenuation value than the surrounding muscle. Eight of the 11 patients who received intravenous injection of contrast material showed characteristic punctate or curvilinear structures within the mass, which had attenuation values similar to normal blood vessels. The characteristic CT features of benign angiomatous lesions of the extremities are presented.

The ability to distinguish between pleural and peritoneal fluid is important in the management of patients with peridiaphragmatic fluid collections. The differentiation of subphrenic fluid from pleural effusion by CT may be difficult and requires a detailed understanding of the normal appearance of the diaphragm on transaxial images. We report 12 patients in whom peridiaphragmatic fluid collections could potentially be misinterpreted as peritoneal rather than pleural fluid. In all cases the presence of subsegmental, basilar atelectasis with subpulmonic fluid created confusing CT images. Subsegmental atelectasis formed a curvilinear band at the lung base that simulated the hemidiaphragm. Fluid anterior to the atelectasis caused a false impression of subdiaphragmatic (peritoneal) fluid. Computed tomography through the upper abdomen excluded intraabdominal fluid in all cases. In four cases ultrasonography confirmed fluid in a supradiaphragmatic, subpulmonic location, excluded peritoneal fluid, and identified subsegmental atelectasis. The presence of subpulmonic fluid and subsegmental atelectasis requires meticulous interpretation of transaxial CT images to avoid the incorrect localization of peridiaphragmatic fluid collections.

Although the potential for splenic injury during left sided thoracentesis or percutaneous renal biopsy is well known, its occurrence has been rarely reported. In a 1 year period we used computed tomography to detect acute splenic, perisplenic, and intraperitoneal hemorrhage in three patients after percutaneous diagnostic and therapeutic procedures in the lower chest and upper abdomen. One patient was asymptomatic, the second developed left upper quadrant pain, and the third required emergency splenectomy.

A case of malignant teratoma of the thyroid gland is presented. Computed tomography identified an inhomogeneous mass with dense calcifications involving the thyroid gland and compressing the upper airway. Enlarged, peripherally enhancing lymph nodes in the neck and mediastinum suggested its malignant etiology.

Pancreatic pseudocysts are a well-known complication of pancreatitis and may occur in unusual locations. We report a case of a child with hereditary pancreatitis who developed a subcapsular pseudocyst of the left kidney. The constellation of findings of calcific pancreatitis and a left renal subcapsular fluid collection should raise the possibility of a subcapsular pseudocyst.

Retroperitoneal hemorrhage caused by a renal tumor is usually due to a renal cell carcinoma or angiomyolipoma. The authors report a case of computed tomographic (CT) demonstration of renal metastases from choriocarcinoma with an associated perinephric hemorrhage. The CT features indicated the acute nature of the hematoma and its confinement within the extracapsular compartment of the perirenal space.

Computed tomography is frequently used in the initial workup of patients with suspected aortic dissection to distinguish dissection involving the ascending aorta from dissection limited to the descending aorta. We reviewed CT of 19 patients who were proven by aortography to have normal ascending aortas. In eight patients the superior extension of the pericardium was visualized and thought to be a potential source of a false-positive diagnosis of type A aortic dissection.

We report the CT findings in a case of primary seminal vesicle carcinoma. These consisted of unilateral enlargement of a seminal vesicle with associated stranding extending into the surrounding fat. This soft tissue stranding corresponded pathologically to direct tumor invasion.

A case of typhlitis (neutropenic colitis) is reported in which the initial diagnosis was suggested by CT. Radiologists performing CT should be aware of this potentially lethal complication of leukemia, which may appear as a clinically unsuspected finding on CT.

Cystic hygromas of the neck can simulate other benign lesions and occasionally extend into the mediastinum. Using computed tomography, we were able to confirm the suspected diagnosis, exclude other diagnostic considerations, and clearly demonstrate absence of mediastinal extension.

The extent of pathologic processes involving the mesentery is frequently difficult to assess by clinical examination and standard radiography. Contrast studies of the gastrointestinal tract only identify the effect of these processes on adjacent opacified bowel loops and frequently underestimate the extent of mesenteric pathology. Computed tomography has previously been used to characterize various mesenteric abnormalities, most often secondary to malignant or inflammatory disease. We report the characteristic CT appearance of diffuse mesenteric edema in 14 patients. Eleven patients had documented hypoalbuminemia, two patients superior mesenteric vein thrombosis, and one patient cirrhosis. The CT findings that allowed confident diagnosis of this entity include increase in density of the mesenteric fat, poor definition of segmental mesenteric vessels, relative sparing of the retroperitoneal fat, and association with subcutaneous edema.

A case of papillary carcinoma arising in a thyroglossal duct cyst is presented. The cystic mass may have a variable anatomic location: intralingual, suprahyoid, thyrohyoid, and suprasternal, along the course of the embryologic descent of the thyroid gland. Computed tomography allows characterization and precise identification of the extent of the lesion prior to surgical resection.

Computed tomography (CT) of the neck has been primarily applied to the assessment of malignant disease with few reports describing its utility in benign conditions. The authors report 13 cases of cystic neck masses evaluated by CT. Pathological conditions included brachial cleft cyst, laryngocele, thyroglossal duct cyst, cavernous lymphangioma, necrotic lymphadenopathy, and asymmetric jugular veins. Computed tomography was helpful in correctly predicting the etiology by determining the exact location of these masses in relation to the normal anatomic structures in the neck.

Eleven patients are described whose computed tomography (CT) examinations showed homogeneous, high density (62–76 Hounsfield units) renal masses. In two patients a hemorrhagic benign cyst was found at surgery. In the remaining nine patients the constellation of CT and clinical findings supported the benign nature of this lesion. Index Terms: Kidney, cysts—Kidney, hemorrhage—Computed tomography.

The ability to distinguish between pleural and peritoneal fluid is important in the management of patients with peridiaphragmatic fluid collections. The differentiation of subphrenic fluid from pleural effusion by CT may be difficult and requires a detailed understanding of the normal appearance of the diaphragm on transaxial images. We report 12 patients in whom peridiaphragmatic fluid collections could potentially be misinterpreted as peritoneal rather than pleural fluid. In all cases the presence of subsegmental, basilar atelectasis with subpulmonic fluid created confusing CT images. Subsegmental atelectasis formed a curvilinear band at the lung base that simulated the hemidiaphragm. Fluid anterior to the atelectasis caused a false impression of subdiaphragmatic (peritoneal) fluid. Computed tomography through the upper abdomen excluded intraabdominal fluid in all cases. In four cases ultrasonography confirmed fluid in a supradiaphragmatic, subpulmonic location, excluded peritoneal fluid, and identified subsegmental atelectasis. The presence of subpulmonic fluid and subsegmental atelectasis requires meticulous interpretation of transaxial CT images to avoid the incorrect localization of peridiaphragmatic fluid collections.

Actinomycosis is an unusual bacterial infection that most often affects the head and neck region. Abscesses occasionally associated with a draining sinus may result secondary to extensive tissue destruction. We report the CT appearance in a case of actinomycosis of the neck. A thick walled enhancing mass with a low attenuation center was identified between the sternocleidomastoid muscle and the strap muscles of the neck. Enhancement of the adjacent muscles was present. Surgery confirmed an abscess with inflammation of the adjacent muscle. Histologic examination of the specimen showed the presence of multiple yellow (sulfur) granules containing Actinomyces. Computed tomography correctly determined the extent of the mass and lack of involvement of the deep structures of the neck.

Rhabdomyosarcoma represents the most common soft tissue sarcoma in children. The CT findings in five patients with pelvic rhabdomyosarcoma are reported. In the three male patients the primary tumor originated in the prostate gland whereas in the two female patients the bladder was the primary site. The CT findings in the prostatic tumors included an enlarged, inhomogeneous prostatic mass with invasion of the perirectal fat. In two of these patients there was thickening of the levator ani muscle and one showed tumor invasion through the ischiorectal fossa and sciatic and obturator foramina into the pelvic musculature and bone. In the two patients with bladder tumors, one showed a large mass adjacent to the lateral aspect of the bladder and ascites, suggesting an ovarian primary tumor. The other patient with sarcoma botryoides (a subtype of rhabdomyosarcoma) had a diffusely thickened bladder. Two patients have had a follow-up CT demonstrating tumor regression posttherapy. The characteristically large size of these masses and propensity for local invasion in a young patient are typical features of pelvic rhabdomyosarcoma.

The CT findings in 70 patients with masses in or adjacent to the porta hepatis/hepatoduodenal ligament were analyzed. Underlying disease processes included metastatic disease (44 cases), lymphoma/leukemia (10 cases), biliary carcinoma (seven cases), hepatoma (four cases), benign disease (three cases), and gallbladder carcinoma (two cases). Location of the mass was confirmed in 62 patients and showed six patterns: four along the hepatoduodenal ligament or within the porta hepatis: another within the liver impinging on the hepatoduodenal ligament/porta hepatis: the sixth, an intraductal mass. Of the masses along the hepatoduodenal ligament or within the porta hepatis the four patterns were (a) well defined nodular masses caused by discrete nodes: (b) matted masses due to confluent adenopathy: (c) mixed, well defined and confluent masses in various locations along the hepatoduodenal ligament: (d) infiltrating, enhancing soft tissue densities obscuring the portal vein margins. No disease specific pattern was seen; nonetheless, knowledge of these patterns is very helpful in detection of masses in this region.

Although the clinical and radiographic manifestations of Thorotrast and its complications have been described, the computed tomographic (CT) appearance of Thorotrast deposition in the abdomen is less well known. Thorotrast produces a characteristic opacification of the liver, spleen, and abdominal lymph nodes. Two cases of patients with Thorotrast-induced angiosarcoma of the liver detected by CT are reported. Computed tomography in both cases demonstrated space-occupying lesions in the liver, which were readily detectable because of distortion of the Thorotrast-produced opacification.

A substernal goiter is a common mediastinal mass that can usually be recognized as contiguous with the body of the thyroid. We report the rare occurrence of a mediastinal goiter that demonstrated no connection with the cervical thyroid on either CT or at thoracotomy. Pathologic examination confirmed this to be an intrathoracic goiter.

Four cases of pneumatosis intestinalis detected by computed tomography (CT) are described. Plain abdominal films obtained on the same day as CT failed to show pneumatosis in three of the four cases. The CT appearances characteristic of pneumatosis intestinalis are cystic, linear, or curvilinear gas collections in the periphery of distended, partly fluid-filled loops of bowel. Two of the four cases had underlying bowel infarction. Evidence of pneumatosis should be carefully looked for in patients with acute abdominal pain referred for CT examination. Computed tomography may be a useful modality for the early diagnosis of bowel ischemia when plain abdominal films are noncontributory.