Left infrarenal region: anatomic variants, pathologic conditions, and diagnostic pitfalls.

Computed tomography (CT) is the preferred method for evaluating the left periaortic infrarenal region. Structures larger than 11 mm in cross-sectional diameter in this region are considered abnormal and should be evaluated for lymphadenopathy, hydroureter, or a vascular abnormality such as venous thrombosis or varicoceles. Normal structures include inferior mesenteric vessels, left gonadal vein and artery, and ureter. The diagnostic process may be complicated by variations in anatomy, including double inferior vena cava, left inferior vena cava, retroaortic left renal vein, circumaortic left renal vein, horseshoe kidney, crossed-fused renal ectopia, renal agenesis, and ureteral duplication. Familiarity with the anatomy of this region and awareness of normal variants are necessary to avoid errors in diagnosis. Radiologists should also be aware of problems in CT technique (nonopacified bowel, dynamic and unenhanced scanning) that can confuse the diagnosis.

Computerized tomographic appearance of renal cysts after extracorporeal shock wave lithotripsy.

We identified cysts in five kidneys of four patients who had lithotripsy. Three of these kidneys were evaluated with CT scans the day before and the day after lithotripsy and showed no change. The other two kidneys were studied by CT only after extracorporeal shock wave lithotripsy; hemorrhage was shown in one and cyst wall thickening in the other.

Computed tomography as a diagnostic aid in diabetic and other problem feet.

Determining whether osteomyelitis is present in patients with foot infections represents a significant diagnostic challenge. As bone uptake with nuclide scans can be affected by soft tissue infection, we performed computed tomography (CT) on seven patients to see if marrow or bone abnormalities could be seen and used to predict the presence or absence of osteomyelitis. The CT scans correctly predicted the presence or absence of osteomyelitis in all seven patients. Four patients had osteomyelitis and three patients did not. Nuclide bone scans had one false-positive and one false-negative result. In this small series, CT proved helpful in evaluating foot problems.

Pericardial cyst. A rare mass abutting the aorta.

Pericardial cysts are infrequently found. They are generally located in the cardiophrenic angle, dominantly on the right side. We present an example of a pericardial cyst in the anterior mediastinum abutting the ascending aorta.

Computed tomography of low periesophageal focal fat collections.

Focal fat collections in the middle compartment of the lower mediastinum are reported in the literature. However, this explanation for a mass in that location is not widely recognized. We found four cases of focal fat collections on routine computed tomography. We then reviewed 100 consecutive computed tomography scans and found another four examples.

Preservation of the eye in paranasal sinus cancer surgery.

Forty-one patients undergoing surgery between 1977 and 1985 for malignant tumors of the paranasal sinuses abutting or eroding the orbital walls were studied for the need to remove the orbital contents. All patients had preliminary computed tomographic scans to delineate the extent of orbital invasion. All were treated with preoperative radiotherapy. If the tumor mass could be peeled from the periorbita, the eye was saved. Preservation of eyes in the patients without periosteal invasion did not alter survival. Frozen-section control may be used to determine periorbital involvement. If the periorbita was minimally involved, it was locally resected. If invasion of the periorbita was extensive, an orbital exenteration was done. Only five of 41 patients required exenteration. Local recurrence of disease in the orbit has not occurred in these patients.

"Idiopathic" cerebellar calcifications: association with hypothyroidism?

During a 3-year period, unexplained intracerebellar calcifications were seen at computed tomographic (CT) examination in six patients. A surprisingly high association with hypothyroidism was seen, with two-thirds of these patients showing the abnormality. Although an uncommon finding at CT, the presence of cerebellar calcification may indicate hypothyroidism.

Calcified uterine leiomyoma simulating metastatic disease on bone scan.

We have reported a case in which focal uptake in a uterine fibroid simulated a sacral metastasis on bone scanning. CT suggested the correct diagnosis. However, a repeat bone scan using single photon emission computerized tomography (SPECT) was definitive in correctly localizing the abnormality. This method should be used when more precise localization is required than can routinely be obtained.

Epipericardial fat pad: CT findings.

Epicardial and mediastinal fat around the apex of the heart may produce the classic appearance of a cardiac fat pad filling in the anterior cardiophrenic angle on a lateral chest radiograph. A review of 50 computed tomographic (CT) scans of the chest that were normal save for possible cardiomegaly, together with chest radiographs obtained within a 14-day interval, revealed a wide variation in the configuration of this fat pad in 16 patients (32%). Depending on geometric circumstances, the fat pad may produce a well-marginated region of increased density, a region of increased density with poor margination, or an area of reduced density lying anterior to the heart. In an additional four patients (8%), however, a simulation of a cardiac fat pad was produced by cardiomegaly alone or by relative levoposition of the heart. In these four patients, the left side of the heart contacted the chest wall on the left over a larger than normal area and thereby excluded lung from the vicinity, simulating the appearance of a fat pad where none existed.

Patent umbilical vein. Diagnosis by technetium-99m tagged red blood cell scintigraphy.

Abdominal scanning with Tc-99m labeled red blood cells serendipitously demonstrated collateral flow in a patent umbilical vein in a patient with unsuspected advanced cirrhotic liver disease and portal hypertension. Knowledge of this was crucial in planning the optimal surgical approach in this patient, referred for resection of a bladder carcinoma. Furthermore, the nuclide study was helpful in clarifying several questions posed by a prior abdominal pelvic CT scan.

Variation in the thickness of the diaphragmatic crura with respiration.

Misinterpretation of the diaphragmatic crura on axial computed tomography images is a recognized pitfall in diagnosis. The right diaphragmatic crus is generally longer and thicker than the left. The authors observed a case in which the left crus was thicker than the right, causing diagnostic difficulty. Obtaining scans at full expiration and full inspiration clarified the situation. Confirmation of respiratory variation in crural thickness was obtained in ten patients. The crura increased in thickness on inspiration, compared with the size on expiration.

Pseudoaneurysms complicating pancreatitis: detection by CT.

Complications of pancreatitis such as pseudocyst formation and abscess are well known to radiologists. Secondary formation of pseudoaneurysms has not been emphasized in the radiologic literature. The great morbidity and mortality associated with pseudoaneurysms emphasize the importance of early detection. Three patients are described whose angiographically proved pseudoaneurysms were demonstrated on contrast material-enhanced abdominal CT scans obtained for evaluation of pancreatitis. A homogeneously enhancing structure within or adjacent to a pancreatic pseudocyst or contiguous with a vascular structure should be considered highly suspicious for an associated pseudoaneurysm.

Computed tomography of traumatic lung cyst: case report.

Blunt trauma to the chest may result in the formation of a traumatic lung cyst. The lesion itself is innocuous and requires no special treatment. Though it is important that traumatic lung cyst not be mistaken for a more serious complication of trauma requiring aggressive management, this distinction may be difficult to make on plain chest radiographs. However, in the setting of blunt chest trauma, the computed tomography appearance of a thin-walled cystic cavity completely surrounded by lung parenchyma is diagnostic of traumatic lung cyst.

Epicardial lipoma: a CT diagnosis.

Primary cardiac tumors are rare and epicardial lipomas are rare within this group. We are reporting a case diagnosed by CT in an 89-yr-old female.

Residual tumor masses following treatment for advanced histiocytic lymphoma. Diagnostic and therapeutic implications.

Forty percent or more of patients with advanced diffuse histiocytic (large cell) lymphoma will achieve prolonged disease-free survival with the use of intensive combination chemotherapy. These results are obtained only if complete resolution of all viable tumor is documented prior to the cessation of chemotherapy. Residual tumor masses at the time of re-staging usually are excised or biopsied to confirm the presence or absence of viable tumor. Three patients are reported who had with advanced histiocytic (large cell) lymphoma, and who demonstrated residual intra-abdominal tumor masses on CT scan following four courses of COPP chemotherapy. After two additional courses of a non-cross-resistant regimen and/or supplemental radiotherapy failed to reduce the size of the masses, abdominal exploration with removal of the tumors including splenectomy in one patient was performed, and in each instance no viable tumor was found. The patients have remained disease-free for periods ranging from 24 to 48 months. The various options available to evaluate such patients are presented, and a systematic approach which should avoid the unnecessary prolongation of potentially harmful chemotherapy or radiotherapy is proposed.

The renal parenchymal stone: a benign calcified renal mass.

Five patients are described, each with a densely calcified solitary mass in a peripheral location in the kidney. There was exophytic projection of the calcification in 4 cases. Three lesions were so completely calcified as to be regarded as stones. The bulk of the lesion was calcified in the 2 other cases, in which the noncalcified portion was either avascular or hypovascular. In no case was there evidence of a soft-tissue mass extending beyond the confines of the calcification. Pathologic correlation in 1 case showed only calcification in association with some renal scarring, and in a second case demonstrated an old organized and calcified abscess. Long-term follow-up in the other 3 cases has demonstrated complete stability without evidence of tumor. All cases are believed to represent examples of calcified renal parenchymal scars, resulting from old granulomatous disease, renal abscess, or hematoma. We propose that these lesions be regarded as solitary renal parenchymal stones without malignant potential, rather than calcified masses. The significance of the findings for patient management are discussed.