Premature bullous pulmonary damage in AIDS: CT diagnosis

The computed tomographic (CT) scans of 55 patients with the acquired immunodeficiency syndrome (AIDS) were reviewed for evidence of pulmonary bullous damage. Although the average age of patients in this series was only 37 years, 42% (23 of 55) had CT evidence of pulmonary bullous changes. In contrast, the frequency of bullous changes detected at CT in a comparable number of immuno-compromised patients with acute leukemia was 16% (eight of 50) (P less than .01). CT findings of bullous damage included bullae or cystic spaces, areas of low attenuation, and vascular disruption. A visual scoring system was used to grade CT scans according to the percentage of lung demonstrating bullous change. Of the 23 AIDS patients with CT evidence of pulmonary bullous damage, 16 (70%) had one or more documented pulmonary infections, while three (13%) had no prior history of lung infection (P less than .05). Spontaneous pneumothorax was a complication of pulmonary bullous damage in three patients. Destruction of pulmonary parenchyma in patients with AIDS may represent the response of the lung to repeated infection.     

Adult cerebellar medulloblastomas: the pathological, radiographic, and clinical disease spectrum

The records of 34 patients over 16 years of age with cerebellar medulloblastoma were retrospectively reviewed. All patients were treated by surgery, and all surviving patients were given radiation therapy. The imaging characteristics of this rare entity were evaluated with regard to the tumor location in the cerebellum, and the prognostic effects of histological characteristics such as neuronal or glial differentiation and the presence of desmoplasia were investigated. Neither histological parameters nor tumor location (median, paramedian, or lateral cerebellar) affected patient survival. The desmoplastic variant was encountered in 38% of these adult medulloblastomas and occurred in all three cerebellar locations. The degree of surgical resection did not have a major effect on long-term survival; long-term survival was possible even in patients who had received only a biopsy. The extent of initial radiation therapy was positively correlated with recurrence-free survival; full neuraxis irradiation was associated with a 13% incidence of delayed spinal metastases, whereas 75% of patients treated with irradiation of only the posterior fossa and/or the whole brain developed spinal deposits. A similar local recurrence rate (12.5%) was noted in both irradiation groups. Chemotherapy resulted in palliation in some patients with metastatic disease.     

Persistent CT nephrogram: significance in the diagnosis of contrast nephropathy

The prospective study involved 50 patients without known renal masses or previous renal surgery who received intravascular contrast medium for various radiologic procedures and subsequently underwent unenhanced computed tomography (CT) of the kidneys 22-26 hours later. In 42 patients, cortical readings did not exceed 50 HU and corticomedullary attenuation differences (CMADs) did not exceed 10 HU. In seven patients (intermediate group), there was persistent cortical enhancement (mean attenuation, 58.3-84.8 HU; CMAD, 10.3-40.3 HU), but there was no significant rise in levels of blood urea nitrogen or serum creatinine. A single patient had contrast nephropathy and exhibited a mean cortical attenuation of 141.6 HU and a mean CMAD of 85.8 HU on the 24-hour CT scan. The authors have seen two additional cases of contrast nephropathy presaged by mean cortical attenuations of 162 and 209 HU on the 24-hour CT scan. One of these patients had been in the intermediate group in the prospective study. A cortical attenuation of 55-110 HU on a 24-hour postcontrast scan may help identify a group of patients with subclinical renal impairment who are at high risk of nephropathy on subsequent exposure to contrast medium, while cortical attenuations in excess of 140 HU seem to be an early indicator of contrast nephropathy.     

α-Adrenergic regulation of human renal function

Summary— Pharmacological and molecular cloning techniques have identified six human subtypes of α-adrenoceptors which are designated α_1A, α_1B, α_1D, α_2A, α_2B and α_2C. At the protein level human kidney expresses predominantly α_2A-adrenoceptors while other α₂-adrenoceptor subtypes or α₁-adrenoceptors have not been detected consistently in radioligand binding studies. However, the presynaptic receptors, which inhibit noradrenaline release in the human kidney, appear to belong to the α_2C-subtype. Intrarenal infusion of the nonselective α₁-adrenoceptor antagonist, phentolamine, and of the selective α₂-adrenoceptor antagonist, yohimbine, but not of the selective α₁-adrenoceptor antagonist, doxazosin, increase renal blood flow and renin release in hypertensive patients undergoing diagnostic renal angiography. Thus, α₂- but not α₁-adrenoceptors appear to mediate a tonic renal vasoconstriction and inhibition of renin release. Effects of systemically given α-adrenoceptor agonists and antagonists are difficult to interpret on a mechanistic level since direct effects in the kidney and indirect effects due to baroreflex activation and peripheral presynaptic and central sympatholytic actions may at least partially offset each other. Moreover, some of these drugs may additionally act independent of α-adrenoceptors, for example, via imidazoline recognition sits. The net result in a given subject may depend on the endogenous sympatho-adrenal tone. Thus, for each target population of interest, effects have to be described empirically for each drug.