Neutral vs positive oral contrast in diagnosing acute appendicitis with contrast-enhanced CT: sensitivity, specificity, reader confidence and interpretation time.

OBJECTIVE: The study compared the sensitivity, specificity, confidence and interpretation time of readers of differing experience in diagnosing acute appendicitis with contrast-enhanced CT using neutral vs positive oral contrast agents. METHODS: Contrast-enhanced CT for right lower quadrant or right flank pain was performed in 200 patients with neutral and 200 with positive oral contrast including 199 with proven acute appendicitis and 201 with other diagnoses. Test set disease prevalence was 50%. Two experienced gastrointestinal radiologists, one fellow and two first-year residents blindly assessed all studies for appendicitis (2000 readings) and assigned confidence scores (1=poor to 4=excellent). Receiver operating characteristic (ROC) curves were generated. Total interpretation time was recorded. Each reader's interpretation with the two agents was compared using standard statistical methods. RESULTS: Average reader sensitivity was found to be 96% (range 91-99%) with positive and 95% (89-98%) with neutral oral contrast; specificity was 96% (92-98%) and 94% (90-97%). For each reader, no statistically significant difference was found between the two agents (sensitivities p-values >0.6; specificities p-values>0.08), in the area under the ROC curve (range 0.95-0.99) or in average interpretation times. In cases without appendicitis, positive oral contrast demonstrated improved appendix identification (average 90% vs 78%) and higher confidence scores for three readers. Average interpretation times showed no statistically significant differences between the agents. CONCLUSION: Neutral vs positive oral contrast does not affect the accuracy of contrast-enhanced CT for diagnosing acute appendicitis. Although positive oral contrast might help to identify normal appendices, we continue to use neutral oral contrast given its other potential benefits.

Case report. Uterine lipoma: advantage of MRI over ultrasound.

Pure fatty tumours of the uterus are exceedingly rare. A case of uterine lipoma demonstrated on ultrasound and MRI with pathological correlation is described. Ultrasound suggested the presence of a uterine lipoma but MRI permitted an unequivocal diagnosis. The usefulness of the various imaging methods is discussed in correctly diagnosing this entity and avoiding unnecessary surgery in the asymptomatic patient.

Necrotizing pancreatitis: a surgical approach independent of documented infection.

BACKGROUND: Strategies for the management of patients with necrotizing pancreatitis remain controversial. While consensus opinion supports operative necrosectomy for the treatment of infected pancreatic necrosis, the timing for surgical intervention is not completely resolved. Further, the indication for the surgical management of sterile pancreatic necrosis is also subject to debate. METHODS: The objective of this study was to evaluate outcome measures for the surgical management of necrotizing pancreatitis, independent of documented infection. A retrospective review was undertaken between 1994 and 2002 at a single county hospital. RESULTS: Twenty-one patients with CT-documented necrotizing pancreatitis underwent operative pancreatic necrosectomy with laparostomy within 21 days of initial diagnosis and had an average of three reoperations. Average length of stay (LOS) in the ICU was 36 days and in the hospital 67 days. Ten patients had documented infected necrosis based on initial intra-operative cultures, while I I had sterile necrosis. Overall, 95% (20/21) of the patients had a complication, with an average of three complications per patient. Common complications included ARDS (71%), sepsis (33%), renal failure (24%), and pneumonia (24%). The overall mortality rate was 14% (3/21), with a mean follow-up of 469 days. DISCUSSION: The surgical management of acute necrotizing pancreatitis, independent of documented infection, can be undertaken within 3 weeks of diagnosis with an acceptable morbidity and a low mortality rate. Creation of a laparostomy to enable ready, atraumatic debridement of the retroperitoneum is a safe alternative to standard repeat laparotomies and thus represents a useful adjunct to the surgical management of necrotizing pancreatitis.

Focal fatty infiltration of the liver: analysis of prevalence and CT findings in children and young adults.

OBJECTIVE: Focal fatty infiltration of the liver, a benign entity that can be confused with a malignant lesion, is well characterized in adults but not in children. The goal of this study was to determine by CT the prevalence and characteristics of focal fatty infiltration in children and young adults. MATERIALS AND METHODS: We retrospectively analyzed 305 consecutive contrast-enhanced abdominal CT examinations of 218 children and young adults with no known liver disease, performed during 2 years at our institution, to identify focal fatty infiltration of the liver. The imaging criterion for focal fatty infiltration of the liver on helical CT was a geometric or ovoid low-attenuation area adjacent to the falciform ligament, gallbladder fossa, or porta hepatis. If a patient's findings met the CT criterion for focal fatty infiltration of the liver, all previous abdominal CT and MR imaging examinations performed for that patient were reviewed to assess the evolution of focal fatty infiltration of the liver. RESULTS: Of 218 children and young adults, 20 (9.2%) met the CT criterion for focal fatty infiltration of the liver. In our population, focal fatty infiltration of the liver was identified only adjacent to the falciform ligament. The prevalence of focal fatty infiltration of the liver increased significantly with advancing age: 0% for ages 1 month-4 years; 7.3% for 5-9 years; 10.2% for 10-14 years, and 25.6% for 15-19 years (p < 0.0001). CONCLUSION: Focal fatty infiltration of the liver was identified in 9.2% of patients in our population, and occurrence of this lesion in children increases significantly with advancing age. However, focal fatty infiltration of the liver is uncommon in infants and young children and should be a diagnosis of exclusion.

Detection of small, functional islet cell tumors in the pancreas: selection of MR imaging sequences for optimal sensitivity.

PURPOSE: To determine the sensitivity and specificity of magnetic resonance (MR) imaging for depicting pancreatic small, functional islet cell tumors and the minimum number of sequences for expedient diagnosis. MATERIALS AND METHODS: Twenty-eight patients clinically suspected to have functional islet cell tumors underwent T1- and T2-weighted spin-echo (SE) MR imaging with and without fat suppression, T2-weighted fast SE imaging, and spoiled gradient-echo (GRE) imaging before and after injection of gadopentetate dimeglumine. Sensitivity, specificity, and the best and minimum number of sequences for definitive diagnosis were determined. RESULTS: MR images depicted proved islet cell tumors in 17 of 20 patients (sensitivity, 85%). Images were true-negative in eight patients with negative follow-up examination results for more than 1 year. Specificity was 100%; positive predictive value, 100%; and negative predictive value, 73%. Among 20 patients with tumor, T1-weighted SE images with fat suppression and nonenhanced spoiled GRE images each showed lesions in 15 (75%); T2-weighted conventional SE with fat suppression, in 13 (65%); gadolinium-enhanced spoiled GRE, in 12 (60%); and T2-weighted fast SE, in seven of 10 patients (70%). CONCLUSION: MR imaging accurately depicts small islet cell tumors. T2-weighted fast SE and spoiled GRE sequences usually suffice. Gadolinium-enhanced sequences are needed only if MR imaging results are equivocal or negative.

A multisite phase III study of the safety and efficacy of a new manganese chloride-based gastrointestinal contrast agent for MRI of the abdomen and pelvis.

The purpose of this study was to evaluate the safety and efficacy of a manganese chloride-based oral magnetic resonance (MR) contrast agent during a Phase III multisite clinical trial. Two hundred seventeen patients were enrolled who were already scheduled for MRI of the abdomen and/or pelvis. In this group of patients, it was postulated that the use of an oral agent would better allow discrimination of pathology from bowel. Patients with known gastrointestinal pathology including peptic ulcer disease, inflammatory bowel disease, obstruction, or perforation were excluded to minimize confounding variables that could affect the safety assessment. Of these 217 patients, 18 received up to 900 mL of placebo, and 199 patients were given up to 900 mL of a manganese chloride-based oral contrast agent, LumenHance (Bracco Diagnostics, Inc.). Safety was determined by comparing pre- and post-dose physical examinations, vital signs, and laboratory examinations and by documenting adverse events. Efficacy was assessed by unblinded site investigators and two blinded reviewers who compared pre- and post-dose T1- and T2-weighted MRI scans of the abdomen and/or pelvis. In 111 (57%) of the 195 cases evaluated for efficacy by site investigators (unblinded readers), MRI after LumenHance provided additional diagnostic information. Increased information was found by two blinded readers in 52% and 51% of patients, respectively. In 44/195 cases (23%) unblinded readers felt the additional information would have changed patient diagnosis and in 50 patients (26%), it would have changed management and/or therapy. Potential changes in patient diagnosis or management/therapy were seen by the two blinded readers in 8-20% of patients. No clinically significant post-dose laboratory changes were seen. Forty-eight patients (24%) receiving LumenHance and four patients (22%) receiving placebo experienced one or more adverse events. Gastrointestinal tract side effects were most common, seen in 29 (15%) of LumenHance patients and in 3 (17%) of the placebo patients. LumenHance is a safe and efficacious oral gastrointestinal contrast agent for MRI of the abdomen and pelvis.

Breath-hold MR cholangiography with snapshot techniques: prospective comparison with endoscopic retrograde cholangiography.

PURPOSE: To compare findings with magnetic resonance (MR) cholangiography with rapid acquisition with relaxation enhancement (RARE) and half-Fourier acquisition with single-shot turbo spin-echo (hereafter, half Fourier RARE) snapshot imaging techniques to those with endoscopic retrograde cholangiography (ERC). MATERIALS AND METHODS: Heavily T2-weighted thick-section (RARE) and thin-section (half-Fourier RARE) MR cholangiography were performed prospectively, on a 1.5-T imager, in the biliary tree of 61 consecutive patients before ERC. Findings at ERC were considered the standard of reference. The radiologist and endoscopist were blinded to each other's report. On- and off-site MR cholangiographic readings were performed to detect stones (n = 24), biliary dilatation (n = 34), or stenosis (n = 36). RESULTS: The sensitivity and specificity of MR cholangiography, respectively, calculated on a lesion-by-lesion basis, were 92.3% and 95.8% for cholangiolithiasis, 94.1% and 92.6% for duct dilatation, and 88.8% and 84.0% for stenosis. With snapshot MR cholangiography, on a patient-by-patient basis, differentiation between normal (n = 15) and abnormal (n = 46) results yielded a sensitivity of 92.4%, a specificity of 83.4%, and a positive predictive value of 95.6%. Pitfalls were caused by flow artifacts, compression by vessels, and low contrast between calculi and surrounding parenchyma. CONCLUSION: Snapshot MR cholangiography allowed noninvasive, accurate detection of biliary stones, strictures, and dilatation similar to that with ERC. Discrepancies regarding low-grade dilatation and strictures had no clinical relevance at retrospective review.

Safe and easy power injection of contrast material through a central line.

Power-assisted injection of contrast material into an antecubital vein is commonly used in CT and has been proven superior to manual injection. Power-assisted injection through a central line bares the risk of rupturing the line because manual control over the pressure applied by the power injector is lacking. We present a simple safety device which allows manual control of the pressure by means of an interposed three-way stopcock combined with a small syringe for pressure equalization.

Colorectal cancer. Radiologic staging.

The role of conventional CT scan and conventional MR imaging in assessing patients with colorectal tumors is now well established. Because both techniques have an unacceptably low accuracy for identifying the early stages of primary colorectal cancers (T1, T2N0 or N1 and early T3N0 or N1, or Dukes stage A, B1 and 2, and C1), their routine use for preoperative staging is not recommended. This low staging accuracy is related to the fact that neither method can assess the depth of tumor infiltration within the bowel wall and both have difficulty in diagnosing malignant adenopathy. These distinctions are necessary in order to determine correctly patient prognosis and tumor resectability. If the various publications on CT scan and MR imaging staging of primary colon tumors are summarized, a mean overall accuracy of approximately 70% can be established. The sensitivity for lymph node detection of malignant lymphadenopathy is only about 45%. The sensitivity for detection of positive lymph nodes is better for rectal tumors because any adenopathy in the perirectal area can be considered malignant because benign adenopathy is not seen in this area. For the early stages of colon cancer or recurrent tumor at the anastomotic site, endoscopic ultrasound or TRUS is the method of choice. Both TRUS and MR imaging with endorectal coils can demonstrate the various layers of the rectal wall, but the ultrasonographic examination can be performed at lower cost and is less time-consuming. Despite these limitations CT scan and MR imaging are useful for assessing patients suspected of having extensive disease, including invasion of fat or neighboring organs or metastatic spread to distant sites including, liver, adrenals, lung, and so forth. CT scan and MR imaging are also helpful in the following ways: in determining whether a patient will benefit from preoperative radiation or whether a patient with rectal cancer can undergo a sphincter-saving procedure; for designing radiation ports; and for detecting complications related to the neoplasm, such as perforation with abscess formation or preobstructive ischemia in patients with complete obstruction by tumor. In these cases, management often is based on CT scan and MR imaging findings and cross-sectional follow-up studies can establish the success of treatment. CT scan and MR imaging have a premier role in the detection of recurrent colorectal cancer. CT scan and MR imaging are superior to colonoscopy for diagnosing extrinsic mass-like tumor recurrences and they are the only methods by which patients with total AP resection can be fully evaluated. The overall accuracy of CT scan and MR imaging for detecting recurrent colorectal tumors ranges from 90% to 95%. Following AP resection, CT scan cannot reliably determine whether a soft tissue density in the surgical bed represents recurrent tumor, and it is important to obtain CT scan baseline studies 4 months after surgery and to repeat this examination at 6-month intervals. Scar tissue, even if initially masslike, shrinks over time and after 1 year should be smaller and its margins more sharply defined. Any apparent increase in size of a mass or any demonstration of adenopathy must be considered an indication for biopsy. Recurrent tumors that do not extend to the pelvis or abdominal sidewalls or invade bone or nerves can be resected. Subtle tumor recurrence or tumor foci in small nodes can be detected by PET scan and immunoscintigraphy, but their future role in the diagnostic imaging of colorectal cancer patients depends on the results of ongoing studies. Helical CT scan has the advantages of fast volume scanning associated with optimal bolus delivery, absence of artifacts related to motion, absence of missed slices, and availability of reformations in multiple planes and three-dimensional reconstruction (virtual reality). The role of this technique in patients with colorectal neoplasms has not been defined. (ABSTRACT TRUNCATED)

Diagnosis of duodenal leaks from kidney-pancreas transplants in patients with duodenovesical anastomoses: value of CT cystography.

OBJECTIVE: This study was undertaken to assess the value of CT cystography, using scans made with full bladder distention by a combination of iodinated contrast material and air and scans made after active voiding, for detecting duodenal segment leaks in patients with kidney transplants and pancreas transplants associated with small duodenal segments and duodenovesical anastomoses. SUBJECTS AND METHODS: 18 patients with such kidney-pancreas transplants underwent CT cystography for clinically suspected leaks from the duodenal segment. Six patients had two examinations, resulting in 24 CT cystograms. The CT protocol consisted of an initial series of pelvic scans (plain CT) without oral, IV, or bladder contrast material; CT cystogram with the bladder fully distended by iodinated contrast material and air; and, if the findings were negative, CT after voiding. If no leak was demonstrated, the remainder of the abdomen to the liver dome was examined. Diagnoses were proved by surgery or cystoscopy (n = 11) and clinical follow-up examinations (n = 13). RESULTS: Overall, bladder-duodenal segment leaks were demonstrated in 11 of 12 studies: one by plain CT, seven by full CT cystography, and four by CT after voiding following negative findings on full CT cystography. One surgically proved leak was missed by CT cystography owing to a large amount of pelvic fluid. In 12 studies without a leak, CT cystography results correlated well with clinical follow-up studies. There were no false-positive results. Sensitivity was 92%, specificity was 100%, and accuracy was 96%. CONCLUSION: CT cystography with a dedicated protocol is an accurate way to diagnose leaks of the duodenal segment in patients with bladder-drained kidney-pancreas transplants if administration of air combined with contrast material into the bladder and CT after voiding are used.

The role of imaging in patients with ascites.

Imaging plays a significant role in patients with ascites for assessing the size and the causes of ascitic fluid, for assisting sampling or draining of ascitic fluid, for selecting candidates for TIPS placement, and for surveilling and detecting complications after TIPS placement. Sonography and CT are primary imaging tools, and MR imaging is used in selected cases such as demonstration of peritoneal or ascitic fluid enhancement, particularly in patients with compromised renal function. Interventional procedures combined with CT and sonography play a major role in the assessment of patients considered for TIPS placement because of refractory esophageal bleeding or ascites. Before the TIPS procedure, these procedures are used to exclude contraindications such as polycystic liver disease, hypervascular hepatic tumors, and portal vein thrombosis. After the TIPS procedure, sonography combined with interventional procedures is used to detect immediate complications such as hemorrhage or intractable shunt-induced encephalopathy due to excessive portosystemic diversion and to detect and treat mid- to long-term complications such as shunt stenosis and occlusion through a routine surveillance program.

CT for the evaluation of carcinomas in the colon and rectum.

The role of conventional CT in assessing patients with colorectal tumors is well established. The low accuracy of CT for identifying early stages of primary colorectal cancers prevents the routine use of CT for preoperative staging. Nevertheless, CT is useful in examining patients suspected of having extensive disease, in deciding whether a patient will benefit from preoperative radiation, in designing radiation ports, and in detecting complications related to the neoplasm. For recurrent colorectal neoplasm, CT has the premier role. CT surpasses colonoscopy in detecting early masslike tumor recurrence at the anastomotic site because of its extrinsic component, and CT and MRI are the only methods that can fully evaluate cases of total abdominoperineal resection. After total abdominoperineal resection, however, CT cannot determine with certainty that a soft tissue density in the surgical bed represents recurrent tumor. In patients with colorectal neoplasms, preliminary results with multiplanar and three-dimensional reconstructions of helical CT images are promising, but their role needs further investigation.

Current CT/MRI examination of the lower intestinal tract.

For evaluating primary colonic and rectal malignancies, CT and MRI are often complementary imaging methods which are useful in assessing patients suspected of having extensive disease and in deciding whether a patient will benefit from preoperative radiation. CT is also helpful in designing radiation ports and in detecting complications related to the neoplasm such as perforation with abscess formation. MRI offers excellent tissue resolution which aids in distinguishing between localized colorectal disease and disease which invades muscle. Also, MRI can add information with coronal views for determining whether a sphincter-saving procedure can be performed, and may be of benefit for assessing the subtle extent of tumour into muscle and bone. However, CT and MRI lack the ability to assess depth of neoplastic involvement within bowel wall. This limitation is the major factor which, combined with the inability to diagnose metastatic tumour foci in normal-sized nodes and microinvasion of perirectal fat, prevents optimal tumour staging. Because of the low accuracy for assessing early cancer stages, neither CT nor MRI are recommended for routine use in preoperative staging. CT and MRI have a premier role in the assessment of recurrent colorectal neoplasm, with CT providing a slightly better overall evaluation due to volume imaging, easy image reconstructions in different planes, and availability of excellent oral and intravenous contrast agents. Cross-sectional imaging is the only method to evaluate fully patients with total AP resection, particularly male patients. Neither CT nor MRI can determine with certainty that a soft tissue density in the surgical bed following total AP resection represents recurrent tumour unless a clear mass is present which has increased in size over time. However, both methods surpass colonoscopy for detecting early mass-like tumour recurrence at the anastomotic site due to its extrinsic component. Cross-sectional imaging plays a prominent role in assessing inflammatory disease of the colon. Clinical history, laboratory data and extent of involvement are used together with results from radiographic examinations to reach a specific diagnosis. CT is preferred over MRI in the assessment of extent of inflammatory disease in and beyond the bowel wall. An additional benefit of CT over MRI is the fact that patients with abscesses or large fluid collection can undergo drainage while still in the CT scanner. CT and MRI can aid in the distinction between ulcerative colitis with minimal wall-thickening and Crohn's disease with marked wall-thickening combined with skip lesions and fistula and/or abscess formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Focal liver lesions: characterization with nonenhanced and dynamic contrast material-enhanced MR imaging.

PURPOSE: To evaluate prospectively the diagnostic accuracy of non-enhanced and gadolinium-enhanced magnetic resonance (MR) imaging in characterization of hepatic lesions. MATERIALS AND METHODS: Fifty-five patients with benign and 52 patients with malignant focal liver lesions underwent examination at 1.5 T that comprised nonenhanced and dynamic contrast material-enhanced images. Four experienced radiologists independently read the different sets of images without and with knowledge of clinical history. RESULTS: Receiver operating characteristic analysis showed that dynamic contrast-enhanced MR imaging added information to nonenhanced MR studies and thereby improved distinction between benign and malignant lesions (P < .05). Knowledge of clinical data further improved lesion characterization with nonenhanced and combined nonenhanced and contrast-enhanced MR imaging (P < .05). CONCLUSION: Dynamic contrast-enhanced MR imaging is a useful adjunct for characterization of hepatic lesions. Knowledge of clinical history still has a decisive effect on interpretation of MR images of the liver.

Pancreatic imaging. Computed tomography and magnetic resonance imaging.

In the assessment of patients with acute pancreatitis, CT is the modality of choice and should be used in any patient in whom the diagnosis is in doubt, treatment has not been successful, or complications are suspected. Early diagnosis of patients at risk is facilitated by CT, and newly introduced staging criteria have proved to be accurate and helpful in managing these patients. For chronic pancreatitis, CT, ultrasound, and ERCP can be used. ERCP, however, remains the gold standard, owing to its ability to depict the pancreatic duct accurately. Often the morphologic data need to be correlated with exocrine or endocrine dysfunction of the pancreas to obtain an accurate means of staging the severity of chronic pancreatitis. Great advances in imaging of pancreatic neoplasms have been made, and differentiation between various types of tumors involving this gland often can be ascertained. Nevertheless, at this time, the early diagnosis of small, malignant lesions of the pancreas is impossible in many cases. CT and to a lesser degree ultrasound are currently the methods of choice for detecting and staging the pancreatic neoplasms pictorially, whereas ERCP has established itself as the best method for visualizing the pancreatic duct and its changes related to pancreatic neoplasia. MR imaging of the pancreas has come a long way, and further improvements are expected with the use of oral and intravenous contrast agents. At present, MR imaging appears to be mainly a problem-solving modality, but it can show improved results for small lesions (particularly islet cell tumors), which do not alter the contour of the pancreas. MR imaging appears to be capable of discerning between the serous and mucinous components of cystic neoplasms and may have a role in the assessment of patients suspected of pancreas transplant rejection.

Imaging of the liver.

The liver continues to be a focus for various imaging methods, but MR imaging received most of the attention with new sequences or modifications of older techniques. Primary and secondary focal liver lesions were studied using various techniques, and most researchers agreed that characterization of lesions is the domain of MR imaging. For actual detection of lesions, particularly for number and size of lesions, CT, especially CT during arterial portography, was still considered the methods of choice. Innovative approaches included three-dimensional image analysis of metastases for segmental localization and fusion of images from several cross-sectional studies for improved characterization of lesions. Assessment of fatty infiltration in the liver was investigated using both CT and MR imaging, but the definitive role of cross-sectional imaging for this purpose is not yet established. Evaluation of venous vascular systems was also investigated using both color Doppler ultrasound and MR imaging, but the role of these techniques vis-á-vis each other needs further definition. Spectroscopy continued to advance but current limitations in localization and processing techniques prevented an enthusiastic endorsement by clinicians. Its potential for assessment of tumor response to chemotherapy is substantial.

Imaging of the liver.

New developments in imaging of the liver have continued during the past year. Ultrasonography, particularly color Doppler applications, and invasive CT techniques are used with increasing frequency. New contrast agents are being tested for improved ultrasonographic detection of liver lesions, and faster imaging sequences and variations on older techniques are innovations in the field of MR imaging. Correlation studies addressed the issue of which are the best-suited imaging methods for the various pathologic changes in the liver.

Colorectal cancer: cross-sectional imaging for staging of primary tumor and detection of local recurrence.

This review describes the use of cross-sectional imaging in the staging of colorectal carcinoma and detection of local recurrence. The contributions of CT, MR imaging, and sonography are discussed and illustrated. Colorectal carcinoma is the second most common tumor in the United States and the most common cancer in the gastrointestinal tract. The prognosis for patients with this neoplasm is closely related to the extent of tumor at the time of diagnosis. Accurate noninvasive preoperative assessment of tumor stage by one or a combination of radiologic techniques would enable appropriate treatment to be planned in each case. Also, determination of possible tumor recurrence would permit effective monitoring of success of therapy and surgical intervention for recurrent disease before widespread metastasis occurs.