Biomedical subjects
Publications and source records attributed to N R Dunnick.
This article discusses the accuracy and complications of percutaneous biopsy of adrenal masses and the rapidly evolving new methods for noninvasive differential diagnosis using CT scan, MR imaging, and radio-nuclide scintigraphy. We offer our current recommendations for the evaluation of benign versus malignant adrenal masses and speculate on the optimal approach for the near future.
Retroperitoneal fibrosis is an uncommon inflammatory disease that leads to extensive fibrosis throughout the retroperitoneum. The majority of cases are idiopathic. The characteristic perivascular distribution of the idiopathic form supports the theory that the disease is an immune-mediated response to severe atherosclerosis. Evidence suggests that idiopathic retroperitoneal fibrosis may be part of a systemic fibrosing disease. Other less common forms include methysergide-related and malignant retroperitoneal fibrosis. The signs and symptoms of the disease are vague and nonspecific, and therefore the diagnosis relies heavily on radiologic findings. Once the diagnosis is suggested, the distinction must be made between malignant and nonmalignant retroperitoneal fibrosis, because the prognosis is dismal for malignant retroperitoneal fibrosis, but very good for other forms of the disease. Surgical biopsy remains the only way to definitively establish this diagnosis. Treatment may be surgical or medical, with the best outcome observed in patients receiving both.
PURPOSE: To assess the decisions made by uroradiologists regarding choice of type of intravenous contrast material (low-osmolar contrast media [LOCM] vs conventional ionic agents) and frequency of use of corticosteroid prophylaxis. MATERIALS AND METHODS: A questionnaire was mailed to 158 members of the Society of Uroradiology. There were 108 responses received, yielding a response rate of 68%. Results from 76 represented institutions were tabulated. RESULTS: Most respondents practice at institutions in which LOCM are used selectively rather than universally. Corticosteroid prophylaxis in patients at risk is used with similar frequency at both types of institutions. There is considerable diversity in pretreatment regimens (ie, type and dose of corticosteroid used). Although antihistamines are used by many uroradiologists (almost always in conjunction with corticosteroids), H2 receptor antagonists are used at only a few institutions. CONCLUSION: At institutions in which LOCM are used selectively, the majority of respondents use LOCM quite liberally, with most choosing these agents in patients at risk. Corticosteroid prophylaxis is widely used by respondents. There is much variation in the type of pretreatment regimen and its use in specific clinical settings.
PURPOSE: To assess the potential role of chemical shift and dynamic gadolinium-enhanced magnetic resonance (MR) imaging in the characterization of adrenal masses. MATERIALS AND METHODS: Fifty-one adrenal masses (35 adenomas and 16 nonadenomas) in 43 patients were evaluated with chemical shift MR imaging, dynamic gadolinium-enhanced MR imaging, or both. The relative change in the signal intensity (SI) ratio of the adrenal mass to liver and paraspinal muscles was quantitatively and qualitatively assessed. Opposed-phase gradient-echo (GRE) images were compared with in-phase images. RESULTS: With qualitative visual inspection, only adenomas showed a decrease in relative SI ratio on opposed-phase chemical shift images (specificity, 100%; sensitivity, 81%). Quantitative ratios corresponding to 100% specificity were also observed, with similar sensitivities. Adenomas could not be differentiated from nonadenomas with visual assessment of maximum SI after contrast material administration or washout. CONCLUSION: Characterization of an adrenal mass as an adenoma can be made with high specificity and acceptable sensitivity by visually comparing opposed-phase with in-phase GRE images.
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OBJECTIVE: The purpose of this study was to determine whether a relationship exists between CT-detected calcifications in the main renal artery and renal artery stenosis. We also evaluated whether renal artery calcifications are more indicative of stenosis in particular patient subgroups based on age, sex, or hypertensive status. MATERIALS AND METHODS: We retrospectively reviewed the examinations of 70 patients (122 kidneys) undergoing both abdominal CT and angiography for various clinical conditions, most commonly evaluation of a tumor or aneurysm. CT studies were evaluated for degree of calcification at the orifice and in the proximal and distal segments of the main renal artery. The angiograms were evaluated for degree of narrowing. Renal artery stenosis was defined as a reduction in cross-sectional area of 75% or more. A separate analysis was performed on male and female patients above and below 65 years of age, with and without hypertension. RESULTS: Renal arteries with clumps of calcium (> 3 mm in diameter) had a higher percentage of stenosis (7/16, 44%) than did renal arteries with less calcium (16/53, 30%), and renal arteries with no calcium had the fewest stenoses (9/53, 17%; p = .02). Calcifications in the renal artery were not good predictors of stenosis as they were frequently seen in arteries with nonsignificant narrowing and were occasionally seen in arteries with no narrowing. The patient's sex was not a significant factor in this analysis (p = .34). Renal artery calcifications in hypertensive patients showed a stronger association with renal artery stenosis, but the overall ability to predict stenosis remained poor. However, calcification may be significant in persons less than 65 years old, in whom this finding was associated with stenosis all three cases (100%). Similar calcifications in patients 65 years old or more were associated with stenosis in only 4 (31%) of 13 cases (p < .01). CONCLUSION: CT-detected calcifications in renal arteries are associated with stenosis, but their predictive value in the general population or in hypertensive patients is poor. These calcifications in a patient less than 65 years of age are a better indicator of stenosis of the renal artery.
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Adrenal cortical carcinoma is an uncommon but highly malignant tumor. Functioning tumors are detected earlier than nonfunctioning neoplasms such that patients with functioning tumors are younger and the tumors smaller than in patients with nonfunctioning tumors. Most tumors are quite large by presentation and are easily detected by imaging studies. CT is the primary imaging modality and can be used to stage most patients accurately. MR may be employed to clarify equivocal findings, especially the delineation of venous extension. Surgery is the only effective treatment, so precise tumor delineation is essential. Chemotherapy with ortho para DDD provides some palliation, but the prognosis remains poor.
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OBJECTIVE: The most common cause of primary aldosteronism is a small aldosterone-secreting adrenal adenoma. With improvements in CT technology, smaller adrenal lesions can now be detected. We reviewed our experience with 29 patients with primary aldosteronism to assess the sensitivity of CT in detecting aldosterone-secreting adenomas. MATERIALS AND METHODS: The records of all patients with biochemically proved Conn's syndrome who were referred for adrenal CT between 1982 and 1991 were reviewed. The CT examinations of each of these 29 patients were reviewed for evidence of hyperplasia or an adenoma. The interpretations were correlated with subsequent adrenal venous sampling (20 patients) or surgery (17 patients). RESULTS: Fourteen of 17 aldosteronomas were detected on CT scans (sensitivity, 82%). Adrenal tumors were not seen on CT scans in any of the 12 patients with hyperplasia, although the glands appeared diffusely enlarged in only seven of these patients. In no case was an adrenal tumor seen on CT scans that was not found at surgery (positive predictive value, 100%). CONCLUSION: If CT scans of patients with Conn's syndrome show a focal mass, ipsilateral adrenalectomy can be performed with the expectation of cure. If no mass is found, adrenal venous sampling can be used to detect an adenoma not shown on CT.
OBJECTIVE: The purpose of this study was to determine if enhancement provided by a smaller volume of a more concentrated nonionic contrast agent is equivalent to that provided by a larger volume of a less concentrated nonionic agent on dynamic, incremental abdominal and pelvic CT. SUBJECTS AND METHODS: During a 4-month period, 168 patients undergoing dynamic incremental abdominal and pelvic CT received 150 ml iopamidol-300 (45 g iodine). During the following 4 months, 119 patients received 125 ml ioversol-320 (40 g iodine). The same automated injector and scanning parameters were used for both groups. Absolute enhancement of the liver at three levels and of abdominal and pelvic vessels was calculated and analyzed by using Student's t-test. RESULTS: Arterial and venous enhancement in the upper part of the abdomen, at the level of the iliac crest, or in the pelvis was not significantly different with the two contrast agents. Both ioversol and iopamidol provided the same mean enhancement of the hepatic parenchyma at the level of the hepatic veins (45 H) and at the level of the portal vein (49 H). At the level of the gallbladder fossa, enhancement of liver parenchyma with the two contrast agents was significantly different (p = .04): mean enhancement was 45 H for iopamidol and 42 H for ioversol. A retrospective analysis of the liver enhancement profiles from 50 randomly selected patients from each group showed no significant difference in parenchymal enhancement. CONCLUSION: For dynamic abdominal and pelvic CT, no statistically significant difference was found between the mean enhancement of the liver and abdominal vessels after administration of 125 ml of ioversol-320 and that after administration of 150 ml of iopamidol-300. Therefore, 125 ml of ioversol-320 can be used instead of 150 ml of iopamidol-300 without compromising image quality. At current prices, this will result in savings of approximately 18% per patient.
To determine whether the well-documented hyperactivity of the hypothalamic-pituitary-adrenal axis in depressed patients includes adrenal gland hypertrophy, adrenal gland size was evaluated by computed tomography. Assessments consisted of (1) global ratings by two radiologists ignorant of the diagnostic identity of the subjects and (2) calculation of adrenal volume. Of the 38 patients with major depression, 12 were rated as exhibiting adrenal hypertrophy. Adrenal volumes in the depressed patients were significantly increased when compared with those of normal controls. Adrenal gland size was not correlated with dexamethasone suppression test results, patient age, duration of the depressive episode, or depression severity. These results are concordant with the hypothesis that chronic corticotropin hypersecretion in depression results in adrenocortical hypertrophy. Adrenal gland enlargement may be a measure of cumulative lifetime depression.
Although the prevalence of renovascular hypertension is low, clinical criteria can select a population in which renovascular hypertension is significantly more common (prevalence of 15%). In these selected patients, it is appropriate to proceed to a screening modality to look for a significant renal artery stenosis. Choices of the noninvasive methods include captopril-enhanced renal scintigraphy, magnetic resonance (MR) angiography, and intravenous digital subtraction renal angiography (DSRA). Intraarterial DSRA or conventional arteriography may also be used to reliably detect renal artery stenosis, with the advantage that both the diagnostic and the interventional procedure can be performed at the same setting. A high percentage of a group of patients who are selected by means of clinical and arteriographic studies will benefit from revascularization. Thus, the renal artery angioplasty may be performed during the arteriogram in which the stenosis is confirmed.
Magnetic resonance (MR) imaging has been proposed as a noninvasive alternative to vena cavography and computed tomography for the detection of venous extension of renal adenocarcinoma. However, spin-echo MR images may be compromised by the presence of flow-related artifacts, extrinsic compression, and respiratory or cardiac motion artifacts. Use of gradient-recalled echo (GRE) sequences is advantageous for imaging of vascular structures. To investigate the detection of vascular extension of tumor with the GRE technique, findings in the preoperative GRE MR images of 26 patients with renal adenocarcinoma were compared with findings at surgery and pathologic examination. Vena cava thrombus was correctly identified in 13 of 13 patients (100%). Renal vein thrombus was correctly identified in 23 of 26 patients (88%), and right atrial thrombus was correctly identified in four of five patients (80%). Use of GRE sequences allows accurate assessment of vascular structures that is sufficient for surgical planning.