Cholecystitis: diagnosis by MR imaging

Morphologic features which allow the diagnosis of acute cholecystitis by ultrasound and CT have now been observed by MR. When present, thickening of the gallbladder wall, intramural abscess, pericholecystic fluid, and the presence of gallstones may be more specific than MR characterization of gallbladder bile.

Sonographic guidance in diagnostic and therapeutic interventions in the pleural space

One hundred eighty-seven diagnostic and therapeutic interventional procedures in the pleural space were performed by using sonographic guidance. These consisted of diagnostic aspiration (118), drainage of malignant and nonmalignant effusions (41), empyema drainage (17), pleural sclerotherapy with tetracycline or bleomycin (7), and pleural biopsy (4). Diagnostic aspiration was performed with 20-gauge needles, and therapeutic and empyema drainages were performed by trocar technique with either a 7-French Sacks catheter or a specially designed empyema drainage catheter. Pneumothoraces were seen in 3% of the patients, and most of these were treated by the radiologist with placement of a Heimlich valve. We conclude that the use of sonography allows rapid localization of pleural fluid collections and instant monitoring of drainage of noninfected fluid collections and empyemas.

Transcystic biopsy: a new approach to posterior pelvic lesions

Six patients with masses located posterior to the bladder were biopsied using an anterior transcystic approach. Conventional biopsy needles were introduced through the bladder with both sonographic (five) and CT guidance (one). Clinically important diagnoses of recurrent carcinoma (four) or cytology-negative fluid (two) were made in all patients. One patient had a transient episode of minimal hematuria immediately after the biopsy. Otherwise, there were no complications. Transcystic biopsy appears to be a safe and effective technique for biopsy or aspiration of posterior pelvic masses.

Chronic cholecystitis. An analysis of diagnostic strategies

To define the optimal diagnostic approach for suspected chronic cholecystitis comprehensive management strategies were developed. Using a computer model, the frequency of appropriate surgery, inappropriate surgery, complications, death, and medical costs were compared in populations of patients with various disease prevalences. The optimal strategy began with ultrasonography, followed by an oral cholecystogram when the ultrasonogram was inconclusive. Oral cholecystogram also was employed when additional diagnostic studies failed to provide another explanation for the patient's symptoms. Compared with strategies using only ultrasonography or oral cholecystography, the combination strategy lowered the frequency of inappropriate surgery from 7.1 to 4.4% and direct medical costs from $1,877 to $1,766 per patient in a population with a 20% prevalence of chronic cholecystitis. The differences persisted at higher prevalences of cholecystitis and when sensitivities and specificities of the tests were varied over ranges reported in the literature. Diagnostic accuracy and direct medical costs could be improved by a more frequent interpretation of subtle abnormal ultrasonographic findings as inconclusive and by a more liberal use of oral cholecystography. This analysis demonstrates that a strategy combining ultrasonography and oral cholecystography is superior to the use of either test alone and is cost-efficient.

Sonography in the follow-up of 100 patients with thyroid carcinoma

High-frequency, high-resolution sonography was used to detect recurrent thyroid carcinoma in 73 patients with papillary carcinoma, 16 with medullary carcinoma, 10 with follicular carcinoma, and one with small-cell carcinoma. Of the 36 patients with negative sonograms, 35 had no other evidence of recurrence, while one had surgical proof of recurrence. Of 25 patients with positive sonograms, confirmed with surgery or radioactive iodine (I131) scanning (sonographic sensitivity 96%, specificity 83%), palpation was negative in 17 (palpation sensitivity 32%, specificity 100%). Thirty-two patient with positive sonographic findings had no objective clinical proof of recurrence. There were seven false-positive studies. This study suggests that sonography may be the method of choice for earliest detection and localization of recurrent carcinoma of the thyroid.

Focal periportal sparing in hepatic fatty infiltration: a cause of hepatic pseudomass on US

An unusual pattern of hepatic fatty infiltration was detected sonographically in 31 patients over a 1.5-year period. At appropriate gain settings and time gain compensation, the liver parenchyma demonstrated diffuse increased echogenicity except for a solitary hypoechoic area with relatively distinct margins, usually located in the medial segment of the left hepatic lobe. This hypoechoic periportal focus varied in size between 1.5 and 5 cm and was typically ovoid, but was occasionally spherical or irregular in shape. Eight patients with such foci underwent percutaneous needle biopsy because of concern that there was a space-occupying mass. Microscopic examination of specimens from the hypoechoic periportal region revealed normal hepatic parenchymal cells, while tissue samples from the surrounding liver had high fat levels. In the remaining 23 patients, correlative radiologic studies supported the diagnosis of fatty liver and excluded a central-mass lesion. A localized area of normal hepatic tissue should be considered among the possible diagnoses when a circumscribed hypoechoic periportal area is demonstrated within a fatty liver.

Percutaneous drainage of subphrenic abscess: a review of 62 patients

Sixty-two patients who presented with subphrenic abscesses had the abscesses drained percutaneously. Diagnosis of a subphrenic collection was usually made with sonography. Initial percutaneous drainage was accomplished with a combination of sonography and fluoroscopic guidance. More recently (in the last 31 cases) most drainages were done with sonographic guidance alone. Successful catheter drainage was achieved in 85% with a complication rate of 4.8%. Failure of catheter drainage (defined as any patient who was not cured by percutaneous drainage alone) occurred in patients with multiple collections or in whom the primary cause of the abscess necessitated surgery, for example, perforated ulcer, acute cholecystitis. Considerations for successful drainage include understanding the anatomy of the subphrenic space, recognizing the importance of a correct access route (avoidance of the pleura and lung), and the long time necessary for adequate drainage (longer than 10 days in 60%). An angled subcostal approach to the subphrenic space was used in 56 (90%) of 62 cases. No complications occurred in this group. The one pneumothorax that occurred in the remaining six cases was a direct result of using an intercostal approach through the parietal pleura into a subphrenic collection. We conclude that percutaneous drainage is a safe and effective method of treatment of subphrenic abscesses.

MR-guided aspiration biopsy: needle design and clinical trials

Nonferrous needles of pure brass, titanium, or copper, and ferrous needles of different alloys of stainless steel were analyzed for the size, area, and distribution of the image artifact created when the needles were placed in a 0.6-T magnet. Results demonstrated that a stainless steel prototype needle (type 316) would be visible on magnetic resonance images and would provide an artifact similar to that seen in computed tomographic-guided biopsies. Further testing of this prototype included assessment of the effect on the artifact when changes were made in annealing properties, gauge, length, needle-tip geometry, pulse sequence, and orientation relative to the magnetic field. To date, three human liver biopsies have been successfully and safely performed using a stainless steel type 316 needle.

Microbubbles as a contrast agent for neurosonography and ultrasound-guided catheter manipulation: in vitro studies

Tissue-equivalent ultrasound phantoms, including models of the ventricular system and cyst phantoms, may be useful for developing expertise in both biopsy procedures and shunt catheter placement that use ultrasound guidance. These phantoms have been constructed (1) to assess the ability to position biopsy needles and manipulate shunt catheters with conventional angiographic guidewires and (2) to evaluate the usefulness of microbubbles as an ultrasound contrast agent. Optimal catheter and needle position and catheter patency are demonstrated with microbubbles generated by hand injection of small volumes of saline, a safe ultrasound contrast agent that, to our knowledge, has not been previously exploited in neurosonography. Microbubbles can define biopsy needle location without direct imaging of the biopsy needle; they can also define the extent of communication or separation of fluid-filled or loculated spaces.

Staging rectal cancer by MR and CT

Sixteen patients with known rectal cancer were evaluated and staged with CT and MR, and at surgery. Detailed evaluation of the pathologic specimens was performed and correlated with CT and MR to determine the accuracy of staging. Most of the cases were advanced stages, and both CT and MR were equally effective in staging. Prone positioning using an air-distension technique was equally important for CT and MR examinations. Because of a positive contrast material (iodine), adequate CT examinations could be performed without prior bowel preparation; however, bowel cleansing was necessary for MR examinations. Both techniques could identify the primary tumor and invasion into perirectal fat and local organs. Neither CT nor MR were able to assess the extent of bowel-wall infiltration or tumor spread to normal size perirectal lymph nodes.

Preoperative evaluation of abdominal aortic aneurysms by computed tomography

A prospective, preoperative study was conducted of 50 electively repaired abdominal aortic aneurysms comparing the CT and angiographic findings with those described at surgery. CT demonstrated all 50 aneurysms and correctly identified their proximal extent in relation to the takeoff of the renal arteries in 47 patients (94%), while angiography detected 48 aneurysms (96%) and their correct relation to the renal arteries in all (100%). CT correctly identified 40 (98%) of 41 patients with two renal arteries, but only two (29%) of seven with three and none of two patients with four arteries. Common iliac artery involvement or lack thereof was accurately predicted in 42 (84%) of the 50 patients and internal iliac artery aneurysms found in one (33%) of three patients. It was concluded that CT is not sufficiently accurate for documenting location and patency of the renal arteries to allow its routine substitution for angiography in patients undergoing preoperative assessment of abdominal aortic aneurysms.

Pancreatic necrosis: CT manifestations

Pancreatic necrosis is a potential sequela of acute pancreatitis, which pathologically represents a collection of devitalized tissue. Appropriate therapeutic planning requires definition of this irreversibly damaged gland, the presence of which is not consistently diagnosed on the basis of clinical and laboratory data. Over an 18-month period, 22 patients with pancreatic necrosis were studied by one or more computed tomographic (CT) examinations. Retrospective analysis showed the findings to vary with the developmental stage of the necrotizing process. During the acute phase, there was considerable morphologic overlap of necrosis and pancreatic phlegmon. Typical findings were seen in the subacute and chronic stages and included diffuse enlargement of the gland with largely decreased central density. A thick, smooth surrounding rim produced a characteristic saclike configuration. CT-guided aspiration for culture material was performed in four patients with suspected superinfection. Negative gram stain and culture results in two patients allowed surgery to be performed on a more elective basis.

Drainage of pelvic abscesses through the greater sciatic foramen

A computed tomographic (CT) guided transgluteal approach through the greater sciatic foramen was used to drain pelvic abscesses and fluid collections in 21 patients. Ideal catheter placement should traverse the lower portion of the greater sciatic foramen at the level of the sacrospinous ligament. This avoids the vascular and neural elements that are located slightly cephalad at the level of the piriformis muscle. Percutaneous drainage through this approach was successful in avoiding surgery in 17 patients (81%). Pain was the most common complication and was generally associated with a more cephalad approach, transgressing the piriformis and the sacral plexus. CT-guided percutaneous drainage of pelvic abscesses through the greater sciatic foramen should be used when the more standard transperitoneal approach is not possible.

Percutaneous drainage of postoperative abdominal and pelvic lymphoceles

Eleven patients with postoperative abdominal and pelvic lymphoceles underwent percutaneous diagnostic and therapeutic intervention with either needle aspiration or catheter drainage. Although initial sonographic or CT examinations accurately identified these collections, definitive diagnosis required fluid sampling and laboratory analysis for confirmation. Seven pelvic and two retroperitoneal lymphoceles demonstrated a gross appearance and composition different from two lymphatic collections in the upper peritoneum. Nine patients underwent catheter drainage; two were managed by needle aspiration alone. Duration of catheter drainage was 4-120 days, substantially longer than is customary for standard fluid collections. Nine of 11 patients were cured by percutaneous aspiration or drainage alone. Bacterial colonization developed in three persistently draining lymphoceles. However, no clinical sepsis or bacteremia occurred. In another patient with persistent high-volume lymphatic output, sclerotherapy with tetracycline instillation was successful in rapidly closing the lymphatic fistula. Percutaneous drainage is a safe, effective procedure for drainage of postoperative lymphoceles.

Surface coil MR imaging of abdominal viscera. Part III. The pancreas

Eight healthy volunteers and 11 patients with pancreatic abnormalities were studied using a conventional body coil and a prototype magnetic resonance (MR) surface coil. Final pathologic diagnoses included carcinoma of the head (six), body (one), and tail of the pancreas (two) and chronic pancreatitis (two). In surface coil images of the volunteers, the body and tail of the pancreas was visualized in all cases but one, and the pancreatic duct was seen in five of eight cases. In-plane spatial resolution of 0.9 X 0.9 mm and 5-mm section thickness was obtained. At the same time, pancreatic surface coil images had a twofold improvement in the signal-to-noise ratio (SNR) compared with body coil images. T1-weighted spin-echo images gave greater SNR, reduced motion artifacts, provided superior anatomic detail, and offered more diagnostic information than comparable T2-weighted images. Significant abnormalities detected only by surface coil imaging included a small tumor surrounded by reactive edema and periglandular tumor invasion. This study demonstrates that surface coil imaging of the pancreas not only is feasible but provides an improved method for examining the pancreas by MR.

Surface coil MR imaging of abdominal viscera. Part I. Theory, technique, and initial results

Prototype surface coil magnetic resonance (MR) images were obtained from phantoms and 42 subjects at 0.6 T to assess the feasibility of imaging relatively deep abdominal structures. Surface coil images demonstrated a two- to fourfold improvement in signal-to-noise ratio (SNR) when compared with whole-body coil images with the same resolution elements. This improvement in SNR allowed us to obtain images with thinner sections, higher in-plane resolution, or, alternatively, a decrease in image time. Compared with body images, surface coil images demonstrated greater anatomic detail and reduction in motion artifacts. Despite the limited field of view in very large patients, the use of surface coils improves the diagnostic capability of MR imaging of the abdomen.

Gallbladder bile in cholecystitis: in vitro MR evaluation

Fifty-three samples of gallbladder bile were obtained at the time of cholecystectomy from patients with the clinical diagnosis of acute or chronic cholecystitis. Five bile samples from patients with clinically normal gallbladders also were obtained. Proton magnetic resonance (MR) relaxation times, protein content, and water content were determined for the bile samples, and the data were grouped according to pathologic diagnosis, which disclosed 11 cases of acute cholecystitis, 41 cases of chronic cholecystitis, and six normal gallbladders. There was no significant difference in the mean T1 and T2 values between the groups with acute and chronic cholecystitis. Patients with chronic cholecystitis were found to have more concentrated bile than those with acute cholecystitis. Protein content varied widely within both groups of patients. We conclude that T1 and T2 relaxation times do not reliably differentiate acute from chronic cholecystitis.

Surface coil MR imaging of abdominal viscera. Part II. The adrenal glands

Magnetic resonance (MR) imaging of the adrenal glands with a prototype surface coil was compared with conventional body coil images in five healthy volunteers and 15 patients with adrenal disease. The spectrum of abnormalities included five nonfunctioning cortical adenomas, of which two were in hyperplastic glands, four adrenal metastases, three pheochromocytomas, a functioning adenoma, a myelolipoma, and a partially calcified, cystic adrenal mass. In both body and surface coil images, anatomic detail was superior on T1-weighted images compared with T2-weighted images obtained with identical imaging time because of decreased motion artifact and superior contrast. In the T1-weighted studies, high-resolution surface coil images showed a threefold improvement in signal-to-noise ratio (SNR) over body coil images, which was manifest by better intrinsic resolution of small adrenal lesions and clearer definition of the extrinsic relationships of large masses to nearby organs. In addition, inferior vena caval invasion by two right adrenal metastases was better demonstrated using the surface coil than body coil MR or computed tomography (CT). Limitations of surface coil imaging include restriction in the field of view to a single gland and additional time required for patient positioning. Since the sensitivity of surface coils diminishes with depth, gains in SNR were limited in large patients with deeper adrenal glands. Despite these limitations, dramatic improvements in SNR and anatomic resolution indicate that surface coil MR imaging will be competitive with CT for examining the adrenal glands.

Intrahepatic amebic abscesses: indications for and results of percutaneous catheter drainage

Medical therapy is standard for intrahepatic amebic abscess and generally is effective. However, we have encountered a group of patients in whom percutaneous aspiration and drainage was indicated due to uncertainty of diagnosis or clinical deterioration of the patient. Twenty such patients underwent percutaneous drainage with ultrasound or CT guidance, and each patient was cured (appropriate antibiotics were administered concomitantly). The specific indications for intervention were to differentiate pyogenic from amebic abscess, pain and imminent rupture, poor response to medical therapy, false-negative results of serologic tests, noncompliance with medical treatment, left lobe abscess, and pregnancy. Diagnosis of amebiasis from examination of the fluid was seldom possible, while findings from core biopsy of the wall of the abscess led to diagnosis in three cases. Recurrence necessitating redrainage occurred in three patients; in each, catheters were removed the same day drainage was performed. There were three minor complications. Differences from percutaneous management of pyogenic abscesses included more rapid removal of catheters (four days), more frequent use of US guidance, and more common use of the prone angled approach to avoid pleural contamination. Catheter drainage may be curative and may expedite care for problematic amebic liver abscesses in selected cases.

Inadvertent percutaneous catheter gastroenterostomy during abscess drainage: significance and management

Eleven cases of inadvertent catheter insertion into the small bowel or stomach during percutaneous abdominal abscess drainage are reviewed. Recognition of the intraluminal catheter position was made by contrast-enhanced fluoroscopy in all patients 1-6 days after catheter insertion. No evidence of leakage of intestinal contents into the peritoneal cavity was noted either clinically or radiologically. All cases occurred after drainage of a centrally located midabdominal collection, but the ultimate outcome was not compromised. In nine of 11 cases, catheter drainage alone was sufficient; two cases required additional surgical drainage. Considerations for management include a prolonged period of catheter drainage to allow evolution of a fibrous tract and gradual catheter withdrawal. These data confirm the growing experience with purposeful percutaneous gastrostomy that percutaneous catheterization of the gastrointestinal tract can occur without major sequelae.

Lesser sac abscesses and fluid collections: drainage by transhepatic approach

Twelve abscesses and fluid collections in the lesser peritoneal sac were drained percutaneously using an access route across the intervening liver. This rather unusual access was chosen when other approaches were contraindicated because of surrounding colon, stomach, or spleen. All collections were drained successfully, and no specific complications such as hemorrhage, bile leak, or liver abscess occurred. Placement of an abscess drainage catheter should be done through the peripheral portion of the liver if possible. The technique offers a new, safe approach to percutaneous drainage of hitherto inaccessible collections.

The bile ducts after a fatty meal: further sonographic observations

The sonographic appearance of the response of the common hepatic duct to physiologic stimulation by a fatty meal was assessed in 131 patients referred because of right upper quadrant symptoms or abnormal liver chemical studies. In the determination of the presence or absence of biliary obstruction, the sensitivity of the examination was 84%, the accuracy of a positive test was 84%, and the accuracy of a negative test was 93%. This test proved helpful in several circumstances: equivocal duct caliber (6-10 mm); abnormal caliber (6-14 mm) with normal laboratory values; normal caliber duct with abnormal laboratory values; persistent question of cholelithiasis or asymptomatic pancreatic duct dilatation. Measurements of bile duct caliber alone may be insufficient to ascertain the presence of bile duct obstruction and fatty meal stimulation significantly improves diagnostic accuracy.

Thyroid and parathyroid ultrasonography

The introduction of high-resolution real-time small-parts sonography has made imaging the superficial structures of the neck a practical procedure. This article reviews the normal anatomy of the neck as well as the benign and malignant diseases affecting the thyroid and parathyroid glands.

Percutaneous drainage of pyogenic liver abscesses

This report summarizes the results of percutaneous catheter drainage in 23 cases of primary or secondary pyogenic liver abscess. The overall success rate was 76%. Only three (60%) of five cases of secondary abscess (infected hematoma or infected tumor) were cured with catheter drainage, but 11 (91%) of the last 12 primary pyogenic abscesses were drained successfully. Six patients with abscesses of less than 4 cm in diameter required catheter drainage for less than 72 hr. Although six abscesses in the series appeared septated or multiloculated, only one required more than a single catheter for curative drainage. Diagnostic and technical considerations for successful drainage of hepatic abscesses are discussed. The differential diagnosis includes echinococcal disease and hepatic amebiasis. Therapeutically, specific measures should be taken to ensure proper catheter position to prevent contamination of the subphrenic, perihepatic, and pleural spaces. Percutaneous catheter drainage should be attempted as a first choice of treatment in all pyogenic hepatic abscesses.