Search PubMed⌕ Search

Biomedical subjects

R H Cohan

Publications and source records attributed to R H Cohan.

At least 55 records · Page 3Linked to original sources
PubMed1994

Abdominal aortic aneurysm morphology: CT features in patients with ruptured and nonruptured aneurysms.

OBJECTIVE: We evaluated a variety of internal architectural features in ruptured and nonruptured abdominal aortic aneurysms to determine whether any features are associated more frequently with ruptured abdominal aortic aneurysms. These features may be useful in identifying subtle ruptures when no obvious retroperitoneal hematoma is present and may be helpful in predicting unstable aneurysms at risk for rupture. MATERIALS AND METHODS: The CT scans of 52 patients with ruptured abdominal aortic aneurysms were reviewed and compared with those of 56 patients with asymptomatic nonruptured aneurysms exceeding 4.5 cm in diameter. All aneurysms were evaluated for size, rim calcification, thrombus amount, thrombus calcification, and lumen irregularity. In addition, four different thrombus patterns were identified and evaluated, including homogeneous, diffusely heterogeneous, periluminal halo, and crescent patterns. Statistical comparisons were adjusted for differences in size between the two groups. RESULTS: Age, gender, and aneurysm length were not statistically different between the two groups. A larger diameter was found in the ruptured aneurysm group: 7.4 (anteroposterior) x 7.9 (transverse) cm versus 5.9 x 6.1 cm (p = .00001). More thrombus surrounded the nonruptured aneurysms (p = .014). Thrombus calcification was seen in 25% (14/56) of the control group and in 13% (7/52) of the rupture group (p = .01). Two thrombus patterns, homogeneous and periluminal halo, were encountered with similar frequencies in both groups. The diffusely heterogeneous pattern was seen more in the control group. A crescent of increased attenuation was encountered only in patients with ruptured aneurysms, at an incidence of 21% (11/52) (p = .0005). Thick and thin wall calcifications were seen in both groups, but a focal discontinuity in circumferential calcification was seen only in association with ruptured aneurysms, at an incidence of 8% (4/52) (p = .008). There was no significant difference in the number of patients whose patent lumen was irregular. CONCLUSION: In our series, detection of a high-attenuation crescent or focal gap of otherwise circumferential wall calcification is associated with aneurysm rupture. The homogeneous, diffusely heterogeneous, and periluminal halo patterns are not specifically associated with aortic rupture. There were no significant differences in the amount of wall calcification or frequency of lumenal irregularity between patients with ruptured and those with nonruptured aneurysms.

Aged↗
PubMed1991

Selective use of low-osmolar contrast media.

Two thousand thirty-four consecutive patients presented for excretory urography within a 22-month period. Of 57 observed adverse reactions (incidence 2.8%), 54 occurred in 1219 low-risk patients injected with conventional ionic contrast media (HOCM) (incidence 4.4%) while three reactions were noted in the 815 high-risk patients receiving low-osmolar contrast media (LOCM) (incidence 0.4%). Despite strict enforcement of an unchanging list of high-risk criteria by the same pool of radiologists, LOCM use was not constant, increasing in use over time from 26.5% to 55.3% of urograms. In addition, frequency of LOCM selection increased transiently (from 33% to 52%) following a single life-threatening reaction to HOCM. Our results suggest that strict guidelines for use of LOCM are subject to loose individual physician interpretation. Physicians' perceptions of safety made it increasingly difficult to withhold LOCM and progressively more patients were included in high-risk groups.

Adolescent↗
PubMed1991

Extravascular toxicity of two magnetic resonance contrast agents. Preliminary experience in the rat.

We compared the relative toxicities of standard concentrations of two magnetic resonance imaging (MRI) contrast agents, ionic gadolinium diethylenetriaminepentacetic acid (DTPA) and low-osmolar gadolinium-1, 4, 7 tris (carboxymethyl)-10-(2'-hydroxypropyl)-1, 4, 7, 10 tetra-azacyclododecane (HP-DO3A) with that of the conventional radiographic contrast medium meglumine diatrizoate, when extravasated into the deep dermal tissues of laboratory rats. Gadolinium-DTPA caused moderate necrosis, hemorrhage, and edema which was not statistically different than meglumine diatrizoate. In contrast, gadolinium HP-DO3A was significantly less toxic than meglumine diatrizoate. Additional experience will be needed in order to determine whether these laboratory results will be clinically relevant in humans.

Animals↗
PubMed1991

Renal vein renins: inability to predict response to revascularization in patients with hypertension.

To determine whether the captopril-stimulated renal vein renin ratio (CSRVRR) could enable identification of patients with hemodynamically significant renovascular lesions who would respond to revascularization, the authors measured CSRVRRs in 143 consecutive patients with hypertension who had been selected because of clinical features suggestive of renovascular hypertension. All patients underwent conventional renal arteriography. Renovascular hypertension was the final diagnosis if revascularization resulted in cure or improvement in blood pressure. Complete data were available for 133 patients. Twenty patients had renovascular hypertension; CSRVRR was greater than 1.5 in 13 of these 20 patients (sensitivity, 65%). However, it was also greater than 1.5 in 54 of the 113 patients without renovascular hypertension (false-positive rate, 47.8%). The positive predictive value of CSRVRR was 18.6%; the negative predictive value, 89.3%. It is concluded that CSRVRR is not sufficiently sensitive to enable prediction of which patients will respond to revascularization and is not specific enough to exclude patients who do not have renovascular hypertension.

Adult↗
PubMed1991

Iodinated radiographic contrast media: comparison of low-osmolar with conventional ionic agents [corrected].

A large number of reports on radiographic contrast media have appeared over the past year. The majority of these compared various properties of the new, nonionic low-osmolar agents with those of conventional ionic contrast media, including types and rates of adverse reactions, nephrotoxicity, anticoagulant effects, degree of subcutaneous injury resulting from extravasation, and gastrointestinal tolerance. In this review, recent developments in each of these areas are discussed. Although, in general, the newer agents are safer and better tolerated than ionic contrast media, their greatly increased cost prevents them from completely replacing these media. In this time of increasingly cost-conscious health care, even expert opinion concerning indications for nonionic low-osmolar contrast media use (also summarized here) is widely divided.

Contrast Media↗
PubMed1990

Extravascular extravasation of radiographic contrast media. Effects of conventional and low-osmolar agents in the rat thigh.

We compared the damage resulting from intradermal injection of four commonly used radiographic contrast media in laboratory rats. Sixty percent meglumine diatrizoate (Reno M 60) and ioxaglate (Hexabrix) produced significantly more ulceration and crusting on gross inspection and more necrosis, edema, and hemorrhage on histologic evaluation than iopamidol 300 (Isovue) or 0.9% (normal) saline. Thirty percent meglumine diatrizoate (Reno M Dip) had an intermediate toxicity, resulting in significantly more visible swelling and more microscopically detected hemorrhage than iopamidol or saline, but less ulceration/crusting and necrosis than Reno M 60 and ioxaglate. Since the three contrast agents of similar osmolality produced different degrees of tissue damage, our results suggest that factors other than high osmolality are partially responsible for determining the severity of injuries from extravasated contrast media.

Animals↗
PubMed1990

Extravasation of nonionic radiologic contrast media: efficacy of conservative treatment.

The authors report four large-volume (greater than 20-mL) extravasations in adults and one intermediate-volume (18-mL) extravasation in an infant of iopamidol, a nonionic contrast medium, that occurred during dynamic enhanced computed tomography. The largest volume that extravasated (in two patients) was 150 mL. Although all five patients initially had swelling, erythema, and/or pain after extravasation, all recovered uneventfully. The authors suggest that emergent surgical drainage of all large-volume extravasations, a procedure that was recently recommended, is unnecessary. Large extravascular collections of nonionic contrast media can be well tolerated and are often resorbed without adverse sequelae.

Aged↗
PubMed1990

Ovarian vein thrombosis in oncology patients: CT detection and clinical significance.

During a 13-month period, ovarian vein thrombosis (OVT) was detected with CT in six patients with malignant tumors, five of whom were receiving high-dose chemotherapy at the time of diagnosis. None of these patients belonged to previously recognized risk groups. Unlike most patients with postpartum or postoperative OVT, only one of our patients was symptomatic, and none had related CT findings, such as uterine enlargement or other enhancing pelvic masses. Patients with malignant tumors, particularly those undergoing chemotherapy, are at risk for developing OVT. As OVT is often asymptomatic in these patients, and thrombus may resolve without treatment, anticoagulation may not be routinely necessary.

Adult↗
PubMed1990

Obliteration of the fat surrounding the celiac axis and superior mesenteric artery is not a specific CT finding of carcinoma of the pancreas.

Partial or complete obliteration of the fat surrounding the celiac axis and superior mesenteric artery on CT is considered so characteristic of pancreatic carcinoma that many consider it diagnostic. However, this finding may be present on CT scans of some treatable tumors. During a 2-year period, we retrospectively collected 10 cases of nonpancreatic tumors that obliterated the fat surrounding the celiac axis and/or superior mesenteric artery. Four patients had metastatic disease, three had lymphoma, two had primary small-bowel adenocarcinoma, and one had a diffuse retroperitoneal endocrine tumor. The scans were analyzed for presence, location, and morphology of the mass and biliary and/or pancreatic ductal dilatation. Of the patients with metastatic disease, three had focal, retropancreatic, periceliac masses without ductal dilatation. One had an infiltrative retroperitoneal process enveloping the pancreas and causing biliary dilatation. Of the patients with lymphoma, two had focal masses in the mesenteric root without ductal dilatation, and one had an infiltrative retroperitoneal process. Of the two patients with primary carcinoma of the small bowel, one had a mesenteric mass without ductal dilatation and the other had an infiltrative retroperitoneal process enveloping the pancreatic head and obstructing the ducts. The patient with the neuroendocrine tumor had an infiltrative retroperitoneal process enveloping the pancreas without ductal dilatation. Obliteration of the fat surrounding the celiac axis and superior mesenteric artery is not a specific CT finding of carcinoma of the pancreas. One cannot rely solely on its presence for the diagnosis of pancreatic carcinoma but should use other important findings such as a focal pancreatic mass and ductal dilatation.

Adenocarcinoma↗
PubMed1989

Role of linear tomography in evaluation of patients with nephrolithiasis.

One hundred twenty-four consecutive patients with suspected or known nephrolithiasis were referred for evaluation by linear tomography. Renal calculi were detected in 98 patients (79%). Linear tomography revealed more renal calculi than did preliminary KUB films in 46 patients (37%), although in only 10 cases (8%) was the tomogram positive if the KUB was negative. Exact quantification of the numbers and locations of renal stones is important in patients to be managed metabolically, and in those being evaluated in advance of or following percutaneous or extracorporeal lithotripsy.

Humans↗
PubMed1989

Interventional uroradiology.

Major interventional uroradiologic techniques including percutaneous nephrostomy, vascular augmentation and reduction procedures, percutaneous cyst aspiration, chronic peritoneal dialysis catheter manipulation and urethroplasty are reviewed. A brief history of the development and techniques for performing these procedures are included. The results of clinical series are assessed and their role in patient management is addressed. The development of these procedures has had a significant impact on patient care by providing effective nonoperative therapy.

Angioplasty, Balloon↗
PubMed1989

Intravenous digital subtraction renal angiography: use in screening for renovascular hypertension.

Intravenous digital subtraction renal angiography (DSRA) has been compared with conventional angiography only in small, selected series of hypertensive patients. The authors prospectively examined with intravenous DSRA 94 patients at increased risk for renovascular hypertension and compared these studies with conventional angiography. A stenosis of at least one main renal artery was identified with intravenous DSRA in 22 patients and confirmed in 20 patients. No significant stenoses were seen with conventional angiography in any of the 64 patients in whom lesions were not seen with intravenous DSRA. Since inadequate DSRA studies were considered positive for renal artery stenosis, the sensitivity of intravenous DSRA was 100% (25 of 25); specificity, 93% (64 of 69); positive predictive value, 83% (25 of 30); and negative predictive value, 100% (64 of 64). The authors conclude that intravenous DSRA is a sensitive test for identifying stenosis of the main renal arteries and is appropriate to use as a screening test among patients at increased risk for renovascular hypertension.

Adult↗
PubMed1988

Povidone-iodine sclerosis of pelvic lymphoceles: a prospective study.

Twelve patients presented for percutaneous catheter drainage of 13 postoperative pelvic lymphoceles. Six patients with 7 lymphoceles were treated with povidone-iodine sclerosis prior to catheter removal. Only 1 lymphocele (which continued to drain large amounts of fluid during and after the sclerosis procedure) recurred. Six patients with 6 lymphoceles had their percutaneous catheters removed without sclerosis. Fluid collections recurred in 3 instances, necessitating repeat percutaneous drainage (2 patients) or surgery (1 patient). Percutaneous therapy is the treatment of choice for patients with postoperative lymphoceles. Povidone-iodine sclerosis is often effective in preventing reaccumulation of fluid once the lymphocele cavity is collapsed.

Adult↗
PubMed1988

Hemodialysis-associated subclavian vein stenosis.

This study was undertaken to evaluate hemodialysis-associated subclavian vein stenosis (SVS) and to clarify treatment of this condition. Forty-seven patients underwent upper arm venography to evaluate fistula dysfunction. Subclavian vein stenosis was documented in 12. Eleven of 12 had elevated venous dialysis pressure (196 +/- 8.9 mm Hg), and six had arm edema. All 12 had previously undergone subclavian cannulation on the side of the fistula. Thirty-five patients showed no evidence of subclavian vein stenosis. Twelve of these 35 patients (mean venous dialysis pressure 113 +/- 2.3 mm Hg) had undergone previous subclavian cannulation on the side of the fistula. The mean age of the fistula at the time of venogram in patients with subclavian vein stenosis was 17.0 months versus 5.8 months in patients with ipsilateral subclavian cannulation without subclavian vein stenosis. Percutaneous transluminal angioplasty (PTA) was performed on 11 of 12 patients with SVS lowering venous dialysis pressure and restoring patency to the fistula in 100%. Lesions recurred in two of 11 patients and were successfully retreated with PTA. We conclude that SVS is a common dialysis problem that is amenable to treatment with PTA. Elevated venous dialysis pressures are a sensitive indicator of this condition.

Angioplasty, Balloon↗
PubMed1988

Comparison of intravenous digital subtraction angiography and conventional arteriography in defining renal anatomy.

Intravenous digital subtraction renal angiography (IV-DSRA) is frequently used in the preoperative evaluation of living-related (LR) kidney donors. However, the true accuracy of IV-DSRA in the donor population is difficult to assess since abnormalities of the kidney and its circulation are uncommon in this group. Therefore, we evaluated IV-DSRA in a group of patients more likely to have anomalies and abnormalities that would affect LR donor selection, donor nephrectomy, and subsequent transplantation. Hypertensive adults being evaluated for renovascular hypertension had IV-DSRA and conventional renal arteriograms, which were interpreted independently. We determined the accuracy of IV-DSRA, compared with conventional arteriography, in detecting multiple renal arteries, renal artery stenosis, fibromuscular dysplasia, and abnormal renal parenchyma. Technically unsatisfactory studies were excluded from analysis. Of 59 patients evaluated, 37 had abnormalities or anomalies. IV-DSRA failed to detect 28 of 50 findings in these 37 patients. In 21 patients with multiple renal arteries, IV-DSRA underestimated the number of main renal arteries in 8. Significant renal artery stenosis, present in 16 patients, was undetected by IV-DSRA in 3 of these patients. Mild fibromuscular dysplasia was not detected by IV-DSRA in any of the 5 patients with this condition, and abnormalities of renal parenchyma were not detected in 6 of the 8 patients with scarred or cystic kidneys. When compared with conventional renal arteriography in a hypertensive population, the IV-DSRA does not accurately detect abnormalities of the kidney and its circulation. If these data are confirmed in nonhypertensive subjects, preoperative evaluation of LR kidney donors using IV-DSRA alone may fail to detect potentially important anatomic abnormalities.

Adult↗
PubMed1988

Gastric adenocarcinoma: CT versus surgical staging.

Seventy-five patients with gastric carcinoma underwent preoperative staging with computed tomography (CT). In 14 patients, CT failed to demonstrate lymphadenopathy despite the presence of malignant lymph nodes at surgery. In 13 patients, CT demonstrated enlarged nodes, but no malignant involvement was found at surgery. Although spread to the pancreas was correctly predicted in three patients with lack of fat plane between tumor and pancreas, five patients lacking a fat plane had no invasion, whereas eight patients with an intact fat plane had invasion. Thirty-five patients (47%) were incorrectly staged with CT:23 (31%) were understaged and 12 (16%) were overstaged. CT does not accurately display the true extent of disease in patients with gastric carcinoma and therefore should not be used routinely for staging.

Adenocarcinoma↗