Anaplastic large cell lymphoma of T-cell phenotype in acquired immunodeficiency syndrome

A variety of shortcomings are associated with most currently used gastrointestinal contrast agents for magnetic resonance imaging (MRI). Artifacts resulting from peristalsis and other motions in the abdominal region are produced by many positive contrast agents (which increase signal intensity). Although this is not a problem for negative contrast agents (which decrease signal intensity), some negative contrast agents produce magnetic susceptibility artifacts that are especially pronounced at high field strength and with gradient echo pulse sequences. These susceptibility artifacts are produced by both paramagnetic and diamagnetic agents. It has been demonstrated in phantoms, however, that susceptibility matching can be used to produce contrast agents with desirable relaxation and contrast properties but without deleterious susceptibility artifacts. We now report results of animal tests of such an oral contrast agent, consisting of a suspension of superparamagnetic iron oxide particles and diamagnetic barium sulfate particles, compared to individual suspensions of the iron oxide and of the barium sulfate. Iron oxide was the least effective and the matched susceptibility mixture was the most effective for the intestine, which has traditionally been the most difficult region of the GI tract to visualize clearly. Matched susceptibility mixtures, which are inherently able to yield images free of susceptibility artifacts without compromising contrast, show promise of being improved oral negative contrast agents for use in gastrointestinal MRI.     

Bowel complications in gynecologic laparoscopic surgery and their immediate repair without laparotomy. Four cases

The objective of this study was to develop a method for 3D subtraction CT angiography and to optimize the visualization after semi-automatic segmentation. Ten patients with aneurysms of the abdominal aorta were examined using spiral CT. To reconstruct the vessels, as well as adjacent organs such as the liver and kidneys, one image data volume was acquired before and after injection of the contrast agent. The CT scans were obtained with a Siemens Somatom Plus 4. To improve the results of automatic segmentation, as well as visualization by maximum intensity projection (i.e. removal of bony structures), subtraction of both image volumes is necessary. However, small translation shifts disturb the subtraction process and produce artificial contours. To calculate the disparities along the three coordinate axes of two corresponding image volumes, a cepstrum filter is applied to a pair of image volumes. After detection of the disparities, which manifest as bright spots, the real shift of the two subsignals can be calculated. Translation of the corresponding image volume pairs to their correct positions improves the subtraction process. In all cases the size of the aneurysm and the abdominal organs could be better segmented and visualized. Application of the cepstrum filter and subtraction of the image volumes before and after contrast medium injection completely removes the bony structures in the image data and results in superior visualization results.     

Multishot echoplanar MR imaging of the female pelvis: comparison with fast spin-echo MR imaging in an initial clinical trial

OBJECTIVE: The purpose of this study was to apply multishot echoplanar MR imaging (EPI) to the female pelvis and compare image quality with that of fast spin-echo MR imaging. SUBJECTS AND METHODS: Twenty-one patients with suspected pelvic disease and five healthy female volunteers were prospectively examined. MR imaging was obtained using an EPI-capable 1.0-T imager and a pelvic phased-array coil. Axial EPI and fast Spin-echo sequences were obtained at identical image locations in each patient and volunteer. Spin-echo EPI images were obtained using a multishot number of 16. Acquisition time for each EPI sequence was 2 min 10 sec. Fat-suppressed T2-weighted fast spin-echo images were obtained in 2 min 12 sec. Paired EPI and fast spin-echo MR images were independently evaluated by three reviewers. RESULTS: Delineation of the perivaginal and parametrial venous plexus on EPI was rated superior to the fast spin-echo images in 62 (77%) of 81 cases. On EPI, uterine zone anatomy and ovary visualization were judged to be inferior in 44 (56%) of 78 cases and in 18 (33%) of 54 cases, respectively. For delineation of uterine abnormalities, including leiomyoma and adenomyosis, both sequences performed almost equally well. However, ovarian cystic lesions were revealed more precisely by the fast spin-echo sequence. An overall fat-suppression effect was seen on EPI images in 62 (77%) of 81 cases. CONCLUSION: Multishot EPI cannot replace fast spin-echo sequences for imaging the female pelvis; however, because EPI has a potent fat-suppression effect and heavily T2-weighted contrast, EPI sequences can be a valuable adjunct to routine examination.     

Topical contrast-enhanced CT and MR dacryocystography: imaging the lacrimal drainage apparatus of healthy volunteers

OBJECTIVE: The purpose of this study was to evaluate the feasibility of administering topical contrast material during helical CT dacryocystography and topical saline solution during MR dacryocystography to reveal the lacrimal drainage apparatus. SUBJECTS AND METHODS: Fourteen healthy volunteers underwent helical CT dacryocystography, MR dacryocystography, or both. Eight of the 14 subjects underwent both techniques; three subjects underwent MR dacryocystography, and three subjects underwent CT dacryocystography. Images were evaluated by two radiologists for degree of visualization of components of the lacrimal drainage apparatus. Each volunteer was questioned about the relative discomfort of contrast material and saline solution administration. RESULTS: The lacrimal drainage system was seen on both CT dacryocystography and MR dacryocystography. CT dacryocystography allowed two-dimensional and three-dimensional reconstructions on which adjacent bone anatomy could be seen. The MR dacryocystography two-dimensional reconstructions and maximum intensity projections also showed the drainage apparatus. However, smaller drainage structures were more consistently seen on CT dacryocystography than on MR dacryocystography. Saline solution was more comfortable than contrast material. CONCLUSION: CT dacryocystography and MR dacryocystography reproducibly and non-invasively revealed the lacrimal drainage apparatus and allowed a better physiologic examination than cannulation dacryocystography. MR dacryocystography can be performed without administration of ionizing radiation or contrast material, but this technique cannot show adjacent bone anatomy and less consistently showed the smaller drainage structures than CT dacryocystography.     

Diagnostic imaging of chronic inflammatory diseases of the intestine in children

Chronic inflammatory bowel disease (CIBD) in children is represented mainly by ulcerative colitis (UC) and Crohn's disease (CD). Infectious forms, Beh?et's disease and eosinophilic gastroenteritis are not included in this study. UC and CD are difficult to diagnose and to treat, and require a multispecialistic approach including pediatric gastroenterologists, surgeons, radiologists, endoscopists and pathologists. Progress in diagnostic techniques--i.e., nuclear medicine procedures, conventional, duplex and color-Doppler US, and endoscopy--has increased our knowledge of these diseases and it has made their diagnosis easier, opening new therapeutic perspectives. In our paper, after mentioning the major clinical and radiologic features of CIBD, we report on the patients hospitalized in the Gaslini Institute from 1984 to 1994. Thirty-six patients (age range: 3,9 to 14 years) were examined with several imaging techniques--i.e., plain radiography, US, contrast studies and CT--according to the clinical presentation and behavior of the disease. X-ray studies played the leading role in imaging mucosal disease spread (double contrast studies) and monitoring "surgical" complications (plain radiography). These techniques, which were always combined with US and, in some cases, CT, are also a major tool to study extraluminal CIBD spread--i.e., fistulas, pseudotumors, lymph nodes, abscesses and mesenteric changes. Color-Doppler US may play a critical role in the differential diagnosis of these and other small and large bowel pathologic conditions. The most typical CD patterns in bowel disease are listed in the paper, to give a contribution to the differential diagnosis of the chronic abdominal pain syndrome which is a very common condition in children.     

Effect of gadolinium on phase-contrast MR angiography of the renal arteries

OBJECTIVE: Our aim was to evaluate the effect of gadolinium chelates on image quality in phase-contrast MR angiography of renal arteries in patients suspected of having renal artery stenosis. MATERIALS AND METHODS: In 24 patients, axial three-dimensional phase-contrast MR angiography of the renal arteries was obtained on a 1.5-T MR imaging system before and after administration of gadolinium contrast agent. The improvement in distal renal artery signal-to-noise ratio after enhancement was measured and correlated with patient age, serum creatinine level, clinical estimation of renal artery flow, and the imaging parameter flip angle. RESULTS: On average, the distal renal artery signal-to-noise ratio increased 2.2-fold after gadolinium administration (p < .001). The increase was greatest in patients more than 60 years old (3.1-fold; p < .001) and in patients with serum creatinine levels greater than 3.0 mg/dl (4.3-fold; p < .01). After enhancement, we found an apparent increase in renal artery diameter (3.5 +/- 1.1 mm before enhancement versus 4.8 +/- 1.4 mm after enhancement [mean +/- SD; p < .001]). We believe this increase reflects improved visualization of slow blood flow along the artery wall. Although the visualization of renal arteries was better in most patients after enhancement, two patients had poorer image quality after enhancement because of increased venous signal obscuring the arteries. CONCLUSION: Gadolinium administration significantly increases distal renal artery signal-to-noise ratio on three-dimensional phase-contrast MR angiography in most patients. The signal-to-noise ratio improvement is greatest in older patients and in patients with impaired renal function. However, in some cases, increased venous signal may obscure arteries.     

Controlled release using temperature-responsive poly(N-isopropylacrylamide) gel

This study describes the sequential use of ferumoxide (superparamagnetic iron oxide) particles and nonspecific extracellular gadolinium chelate (Gd) for evaluation of focal liver lesions on MRI to evaluate order of contrast administration and imaging effect of the first contrast agent on sequences acquired after the second contrast agent. Thirteen patients underwent MR examinations that included ferumoxide and Gd. The order and timing of administration were as follows: separate sessions (three patients; Gd study 4-19 days before ferumoxide study), same session, Gd first (seven patients; Gd study 1-2 hours before ferumoxide study), and same session, ferumoxide first (three patients; ferumoxide administered less than 1 hour before Gd study). Postcontrast sequences were reviewed in a randomized, blinded fashion by two separate investigators. Determination was made regarding whether (a) the presence of the first agent administered could be detected on sequences obtained after the second agent and (b) the presence of the first agent interfered with the image quality of those sequences. No evidence for the presence of Gd was appreciated by either observer on postferumoxide sequences acquired in separate session studies. In same session, Gd first studies, the presence of Gd was observed in six of seven patients on T1-weighted spoiled gradient-echo (SGE) images obtained after ferumoxide administration. The presence of Gd was not apparent in seven of seven patients on T2-weighted fat-suppressed images obtained after ferumoxide. In same session, ferumoxide first studies, the presence of ferumoxide was appreciated on post-Gd sequences in two of three patients. The presence of ferumoxide did not appreciably diminish image quality on those sequences. Exact agreement was achieved by the independent investigators. Our results suggest that Gd and ferumoxide can be administered sequentially within one study session without substantial loss of diagnostic information obtained on sequences performed after administration of the second contrast agent. Administrating Gd first resulted in less of an effect of the visualization of the first agent on sequences acquired after the second agent.     

Magnetic resonance imaging protocol optimization for evaluation of hyaline cartilage in the distal interphalangeal joint of fingers

RATIONALE AND OBJECTIVES: To identify a single magnetic resonance imaging (MRI) protocol that will provide optimal signal-to-noise ratio, resolution, and image contrast with minimal susceptibility artifacts and that will allow clear delineation and visualization of cartilage, fluid, bone, tendons, and ligaments within the distal interphalangeal (DIP) joint of the human hand. METHODS: A highly optimized 2.4 T MRI system was constructed from a 31-cm horizontal bore magnet, using a solenoid radiofrequency coil. This was used to study the DIP joints of 16 healthy, asymptomatic volunteers. RESULTS: A range of image contrast protocols were explored, including spin-echo T1 and T2, field echo, chemical shift suppression to give water only images, and magnetization transfer. Susceptibility variations were explored by changing the field strength from 0.6 to 2.4 T. A spin-echo protocol with TR = 1500 msec and TE = 30 msec can routinely produce images with resolution 0.075 x 0.150 for a slice thickness of 1 mm in 13 minutes. That protocol can visualize simultaneously compact and trabecular bone, two layers of cartilage, synovial fluid, and synovium within the joint, tendons and ligaments, and the volar plate. CONCLUSIONS: Although the contrast is not fully optimized for any one tissue, the spin echo protocol (TR = 1500, TE = 30) provides sagittal MR images, which clearly delineate the major structures of interest within the DIP joint, and which will be used in future studies to compare changes in the DIP joint because of aging or osteoarthritis. Experience gained by applying the above methods to a total of 16 healthy, asymptomatic volunteers has enabled a single sequence to be identified, which although not optimized for any one tissue, nevertheless visualized simultaneously and clearly delineated compact and trabecular bone, two layers of cartilage, synovial fluid, and synovium within the joint.     

Quantification of intravascular and extravascular contributions to BOLD effects induced by alteration in oxygenation or intravascular contrast agents

A simple model is presented that allows quantitative separation of the contributions of signals from water in blood and extravascular parenchyma due to changes in blood oxygenation, induced either by brain activation or by alteration of inspired oxygen. The separation is based on the progressive attenuation of the signals in the vasculature of different levels when bipolar field gradient pulses are applied. Diffusion-weighted spin-echo echo-planar imaging sequences were used to measure signal changes under various conditions in both animals and human volunteers. Normoxic-hyperoxic episodes were induced in rats before and after injection of a superparamagnetic iron oxide contrast agent. Signal changes produced by visual stimulation were measured in human volunteers, and in volunteers subject to alternating normoxic-hyperoxic episodes, and with administration of Gd-DTPA. Analysis of the results with our simple model suggests that the apparent diffusion coefficient increases and R2 (= 1/T2) decreases upon brain activation, with a large component from extravascular water related to the decrease in the blood deoxyhemoglobin concentration. Furthermore, this study suggests that apparent diffusion coefficient of the extravascular component alone may provide localization of neuronal activation.     

Differential effects of sunscreens on UVB-induced immunomodulation in humans

Ischemic bowel disease is a rare disorder whose incidence is increasing as the mean age of the population increases. Diagnosis by clinical, laboratory and radiologic means is often difficult, and delay in definitive therapy results in substantial morbidity and mortality. A series of 26 consecutive patients, with proved acute superior mesenteric ischemia, was retrospectively reviewed: the authors report the diagnostic methods performed preoperatively, the site and the cause of infarction and the time passed between the first radiograph ans surgery. Plain abdominal radiographs were performed in 25 of 26 patients, screening abdominal US in 23 cases and CT in 19 cases. All radiological examinations were retrospectively reviewed by three authors, independently, to recognize the different signs of infarction. On plain abdominal films, the findings warranting a presumptive diagnosis of bowel infarction were air-fluid levels (84% of cases), dilated bowel loops (48%), thickened and unchanging loops (20%), gastric distension and gasless abdomen (12%), small bowel pseudo-obstruction (8%). Screening abdominal US demonstrated intraperitoneal free fluid (26%) and dilated bowel loops (22%). Abdominal CT showed air-fluid levels (79%), dilated loops and free intraperitoneal fluid (47%), intramural gas and thickened bowel loops (36.8%), engorgement of the mesenteric vessels (31%), mesenteric-portal gas, mesenteric thrombus and marked reduction in the volume of gas in the small bowel (10.5%) and paper-thin bowel loops (5%). The authors conclude that air-fluid levels, dilated loops and intraperitoneal free fluid are the most frequent findings, even though they are not specific. While abdominal plain film and screening ultrasonography can be negative, CT detects at least one abnormal finding and at least three abnormal findings in 73% of cases.     

Optimizing three-dimensional gadolinium-enhanced magnetic resonance angiography. Original investigation

RATIONALE AND OBJECTIVES: This primarily theoretical work examines three-dimensional gadolinium-enhanced magnetic resonance angiography f8p4Gd-MRA) with the goal of understanding how to achieve the best possible images with respect to signal to noise ratio (SNR) and k-space induced artifacts. Patient variables, contrast injection schemes, and pulse sequence parameters are considered for this purpose. METHODS: A theoretical analysis, including computer simulation, describes how contrast material injection profiles influence 3D Gd-MRA images, both in terms of intravascular signal and resultant artifacts. Further theoretical analysis of the spoiled gradient refocused pulse sequence describes how to maximize SNR. Clinical imaging complements computer modeling. RESULTS: Equations were derived relating contrast injection parameters and pulse sequence variables to SNR and artifacts. For present imaging equipment, administering contrast material over a duration of 60% to 80% of the total imaging time and using fractional echo techniques gives the best SNR without significantly sacrificing image quality. CONCLUSIONS: Three-dimensional Gd-MRA can be tailored to a specific clinical situation and imaging system through the use of proper breath-holding, bolus timing, Gd administration, and pulse sequence design.     

On the effect of lung filtering and cardiac pressure on the standard properties of ultrasound contrast agent

The goal standard of contrast echocardiography is the absolute measure of myocardial perfusion using a contrast agent. Actually, several contrast agents are developed. All these agents show left ventricular opacification after intravenous injection. However, none of these agents shows an acceptable enhancement of the myocardium yet using conventional imaging techniques. The explanation of this phenomenon should be easy by measuring the acoustic characteristics of the contrast agent and then making a comparison of these characteristics with those of the myocardium. In this study we present definitions of standard acoustic parameters of ultrasound contrast agent, the backscatter coefficient Bs and the scattering-to-attenuation ratio STAR. Afterwards, considering an intravenous injection of the contrast agent, and taking into account the effects of lung filtering and cardiac pressure, the standard properties of contrast agents are determined in different sites: right ventricle (before lung passage), left ventricle (after lung passage and taking into account the pressure effect) and in the coronary system. Calculations showed that the acoustic properties are considerably influenced by these two effects: lung filtering and cardiac pressure. Comparison of these properties with the tissue properties (myocardium) is then performed. This determines the contribution of the contrast agent to the enhancement of the tissue visualization. The simulations are performed on Albunex microspheres. The results reveal that the difference between scattering of the myocardium and scattering of intravenously injected Albunex is too slight to be visible on an echographic image.     

Bowel dysfunction in postmenopausal women

BACKGROUND/AIMS: The perimenopausal and postmenopausal states are frequently accompanied by a variety of symptoms of hormonal imbalance. Although vasomotor, vaginal and genitourinary symptoms prevail, gastrointestinal complaints such as abdominal bloating may occur. In this study, we investigated the nature and prevalence of gastrointestinal and irritable bowel syndrome (IBS)-type complaints in women going through their climacteric and postmenopausal periods. PATIENTS/METHODS: 228 women (170 postmenopausal and 58 premenopausal) who presented for evaluation at a primary care practice limited to women's health were evaluated prospectively by a previously validated gastrointestinal symptoms questionnaire designed to evaluate symptoms suggestive of IBS. At the time of their participation in the study, none of these women was presenting for evaluation of abdominal or genitourinary symptoms. RESULTS: Thirty-eight percent of postmenopausal women reported altered bowel function, in contrast to 14% of premenopausal ones (p < 0.001). Despite this, the two groups did not differ in regards to the occurrence of abdominal pain, diarrhea or constipation, suggestive of IBS. The prevalence of IBS-type complaints peaked to 36% during the climacteric period (40-49 years). Laxative usage (9.4% prevalence), gaseousness/excessive flatulence (48% prevalence) and heart-burn/acid regurgitation (34% prevalence) were also more common among postmenopausal women. Estrogen use did not affect gastrointestinal symptoms in any of the two groups. CONCLUSIONS: Although the possible role of aging on symptom perception-regardless of hormonal status-cannot be ruled out, these results suggest that peri- and postmenopausal women have a high prevalence of altered bowel function and IBS-like gastrointestinal complaints that should be carefully assessed. If the diagnosis of IBS is confirmed, appropriate treatment may improve patients' symptoms, although this approach requires further study.     

Germ cell formation and gametophyte differentiation in higher plants

OBJECTIVES: Magnetic resonance urography (MRU) is a new technique that uses heavily weighted T2 coronal images with fat suppression pulse. Urine appears white on MRU, resembling an intravenous urogram (IVU). Contrast agents are not necessary. This study describes the use of MRU in the diagnosis and treatment of patients with hematuria. METHODS: One hundred six patients with microscopic or gross hematuria and 6 normal volunteers underwent MRU between 1992 and 1995. A modified, heavily weighted T2 technique with intravenous administration of furosemide and ureteral compression was used. Thirty-two patients had other imaging techniques as well for comparison. RESULTS: MRU provided high-resolution images in almost all cases; 73 (69%) had a normal MRU. Significant findings in the 33 patients with abnormalities included renal cysts in 17 (51%), renal cell carcinoma in 6 (18%), transitional cell carcinoma in 5 (15%), ureteropelvic junction obstruction in 3 (9%), and stones causing obstruction in 6 (18%). Five patients with renal failure also had good visualization of the entire urinary tract. MRU was comparable to other imaging modalities except in identifying nonobstructing calculi. CONCLUSIONS: MRU provides an alternative to conventional imaging of the urinary tract, especially in those patients who have contraindications to ionizing radiation and contrast agents. Improvements in resolution, technique, and cost have to be addressed before it can be used regularly in urologic practice.     

Cost-effectiveness in diagnosing infantile hypertrophic pyloric stenosis

PURPOSE: The purpose of this study was to determine which imaging study, upper gastrointestinal series (UGI) or abdominal ultrasonography (US), is more cost-effective in diagnosing infantile hypertrophic pyloric stenosis (IHPS) using a decision analysis model. METHODS: Probabilities were calculated from a review of the records of all infants less than 6 months of age referred for UGI or US to rule out IHPS over a 3-year period from January 1992 to December 1995. Cost-effectiveness was determined from hospital charges for each imaging study and its possible outcomes. RESULTS: The positive predictive value of UGI was 1.0 and US was 0.98 in the 246 infants evaluated for possible IHPS. In patients who had an initially normal study finding (UGI or US), 25% of patients undergoing US first required a second study for persistent symptoms, whereas only 6% of patients who had a negative initial UGI finding required a second study. CONCLUSIONS: Cost analysis found UGI to be more cost-effective than US because fewer secondary studies were required. UGI provides information regarding other pathological conditions as compared with US.     

A comparative study of velocity measurements in major blood vessels using magnetic resonance imaging and Doppler ultrasound

Velocity measurements in major blood vessels were obtained in studies of volunteers using magnetic resonance imaging (MRI) and compared with Doppler ultrasound (US). The vessels studied were the abdominal aorta, superior mesenteric artery, common carotid artery, superficial femoral artery and middle cerebral artery. Using a paired t-test, no significant difference was found between velocity values estimated by MRI and US (p > 0.08). The relative advantages of each technique in radiological practice are discussed.     

Diagnosis of gallstone ileus

Gallstone ileus is a rare disorder, which, because it is often misdiagnosed preoperatively, may become life-threatening. The classic triad of Rigler (aerobilia, small bowel ileus and a calcified, dystopic stone) is visualized on abdominal plain films in only 14-35% of cases. Further work-up includes ultrasound, upper gastrointestinal series with water soluble contrast medium and computed tomography (CT). CT is especially reliable in demonstrating all three criteria.     

Current guidelines for antibiotic prophylaxis of surgical wounds

Appropriately administered antibiotic prophylaxis reduces the incidence of surgical wound infection. Prophylaxis is uniformly recommended for all clean-contaminated, contaminated and dirty procedures. It is considered optional for most clean procedures, although it may be indicated for certain patients and clean procedures that fulfill specific risk criteria. Timing of antibiotic administration is critical to efficacy. The first dose should always be given before the procedure, preferably within 30 minutes before incision. Readministration at one to two half-lives of the antibiotic is recommended for the duration of the procedure. In general, postoperative administration is not recommended. Antibiotic selection is influenced by the organism most commonly causing wound infection in the specific procedure and by the relative costs of available agents. In certain gastrointestinal procedures, oral and intravenous administration of agents with activity against gram-negative and anaerobic bacteria is warranted, as well as mechanical preparation of the bowel. Cefazolin provides adequate coverage for most other types of procedures.     

Current uses of gadolinium chelates for clinical magnetic resonance imaging examination of the liver

The use of gadolinium chelates has become an integral part of magnetic resonance imaging (MRI) of the liver and extrahepatic abdomen. Although liver specific contrast agents are now available, gadolinium chelates continue to offer significant advantages for abdominal MRI. The gadolinium chelates uniquely provide important information about tumor perfusion that is key in our assessment of liver masses. These paramagnetic contrast agents assist with liver lesion detection, characterization, and in establishing the volume of viable perfused tumor. Gadolinium chelates are equally important for MRI of the extrahepatic abdomen. The interstitial accumulation of these agents within peritoneal, omental, and gastrointestinal tumor produces marked enhancement and is key in accurate tumor staging. Depiction of lesions within solid visceral organs such as the pancreas, kidneys, and spleen is also improved following gadolinium injection. The versatility of this workhorse contrast agent assures that gadolinium chelates will continue to occupy a central role in any busy abdominal MRI practice.     

Local and systemic effects of water-soluble contrast media and barium in rats with chronic small bowel obstruction

RATIONALE AND OBJECTIVES: The local effects on the small intestine and systemic changes produced by different contrast media in small bowel obstruction, with time courses of 4 days, were evaluated. MATERIALS AND METHODS: Four groups, each with 10 normal rats and another four groups (also each with 10 rats) that had ligation of the terminal ileum (obstructed rats) for 4 days were given 3 mL of barium, meglumine sodium diatrizoate, iohexol, or saline (control animals). Radiographs were taken immediately, 1 and 4 hours after administration of contrast media. Immediately before sacrifice, blood samples were taken to determine the hematocrit (Hct), hemoglobin (Hb), white blood cell count (WBC), red blood cell count (RBC), and serum sodium, and potassium and chloride concentrations. Specimens of small bowel were taken for histologic and morphometric analysis. RESULTS: In obstructed rats, the image quality with iohexol improved on final radiographs despite being diluted in the great intestinal contents. There was an improvement in the serum electrolyte concentrations in the obstructed animals that were given any one of the contrast media, the best improvement being in the iohexol groups. A shortening of the length of epithelial cells when any one of the contrast media was administered was observed, as was an increase in the lymphatic space area in the diatrizoate group in normal rats. In the bowel proximal to the obstruction, the lymphatic space area was increased in the diatrizoate group and the size of the epithelial cells was higher in the diatrizoate and iohexol groups compared to the barium and saline groups. CONCLUSION: Our results suggest that iohexol offers good radiologic efficacy and excellent systemic and local tolerance in small bowel obstruction.