Rizwan Aslam

Advances in CT colonography for colorectal cancer screening and diagnosis

CT colonography (CTC) is a validated colorectal cancer test that provides an additional minimally-invasive screening option which is likely to be preferred by some patients. Important examination prerequisites include adequate colonic cleansing and distention. Tagging of residual material aids in the differentiation of true polyps from stool. Low radiation dose technique should be employed routinely for screening studies. Readers must be skilled in the use of both 2D and 3D interpretation methods.

Contrast-Enhanced CT Quantification of the Hepatic Fractional Extracellular Space: Correlation With Diffuse Liver Disease Severity

OBJECTIVE The purpose of this study was to determine whether contrast-enhanced CT quantification of the hepatic fractional extracellular space (ECS) correlates with the severity of diffuse liver disease. MATERIALS AND METHODS The cases of 70 patients without (46 men, 24 women; mean age, 59.1 years) and 36 patients with (23 men, 13 women; mean age, 63.1 years) cirrhosis who had undergone unenhanced and 10-minute delayed phase contrast-enhanced CT were retrospectively identified. By consensus one experienced radiologist and one trainee measured the CT attenuation of the liver and aorta to estimate the fractional ECS, defined as the ratio of the difference between the attenuation of the liver on 10-minute and unenhanced images to the difference between the attenuation of the aorta on 10-minute and unenhanced images multiplied by 1 minus the hematocrit. Findings were correlated with each patients Model of End-Stage Liver Disease (MELD) score. RESULTS The mean MELD score was higher in patients with than in those without cirrhosis (14.3 ± 7.3 versus 7.20 ± 2.4, p < 0.0001). The mean fractional ECS was significantly greater in patients with cirrhosis than in those without cirrhosis (41.0% ± 9.0% versus 23.8% ± 6.3%, p < 0.0001). The fractional ECS correlated with the MELD score (r = 0.572, p < 0.0001) and was predictive of cirrhosis with an area under the receiver operating characteristic curve of 0.953 (p < 0.0001). The sensitivity and specificity of an expanded fractional ECS greater than 30% for the prediction of cirrhosis were 92% and 83%. Multivariate linear regression revealed that the fractional ECS is complementary to the MELD score as a predictor of cirrhosis (p < 0.0001). CONCLUSION Noninvasive contrast-enhanced CT quantification of the fractional ECS correlates with the MELD score, an indicator of the severity of liver disease, and merits further study.

Persistent renal enhancement after intra-arterial versus intravenous iodixanol administration.

PURPOSE To examine the clinical significance of persistent renal enhancement after iodixanol administration. METHODS We retrospectively studied 166 consecutive patients who underwent non-enhanced abdominopelvic CT within 7 days after receiving intra-arterial (n=99) or intravenous (n=67) iodixanol. Renal attenuation was measured for each non-enhanced CT scan. Persistent renal enhancement was defined as CT attenuation>55 Hounsfield units (HU). Contrast-induced nephropathy (CIN) was defined as a rise in serum creatinine>0.5 mg/dL within 5 days after contrast administration. RESULTS While the intensity and frequency of persistent renal enhancement was higher after intra-arterial (mean CT attenuation of 73.7 HU, seen in 54 of 99 patients, or 55%) than intravenous contrast material administration (51.8 HU, seen in 21 of 67, or 31%, p<0.005), a multivariate regression model showed that the independent predictors of persistent renal enhancement were a shorter time interval until the subsequent non-enhanced CT (p<0.001); higher contrast dose (p<0.001); higher baseline serum creatinine (p<0.01); and older age (p<0.05). The route of contrast administration was not a predictor of persistent renal enhancement in this model. Contrast-induced nephropathy was noted in 9 patients who received intra-arterial (9%) versus 3 who received intravenous iodixanol (4%), and was more common in patients with persistent renal enhancement (p<0.01). CONCLUSION Persistent renal enhancement at follow-up non-contrast CT suggests a greater risk for contrast-induced nephropathy, but the increased frequency of striking renal enhancement in patients who received intra-arterial rather than intravenous contrast material also reflects the larger doses of contrast and shorter time to subsequent follow-up CT scanning for such patients.

Reduced Cathartic Bowel Preparation for CT Colonography: Prospective Comparison of 2-L Polyethylene Glycol and Magnesium Citrate

PURPOSE To prospectively compare adequacy of colonic cleansing, adequacy of solid stool and fluid tagging, and patient acceptance by using reduced-volume, 2-L polyethylene glycol (PEG) versus magnesium citrate bowel preparations for CT colonography. MATERIALS AND METHODS This study was approved by the institutional Committee on Human Research and was compliant with HIPAA; all patients provided written consent. In this randomized, investigator-blinded study, 50 patients underwent oral preparation with either a 2-L PEG or a magnesium citrate solution, tagging with oral contrast agents, and subsequent CT colonography and segmentally unblinded colonoscopy. The residual stool (score 0 [best] to 3 [worst]) and fluid (score 0 [best] to 4 [worst]) burden and tagging adequacy were qualitatively assessed. Residual fluid attenuation was recorded as a quantitative measure of tagging adequacy. Patients completed a tolerance questionnaire within 2 weeks of scanning. Preparations were compared for residual stool and fluid by using generalized estimating equations; the Mann-Whitney test was used to compare the qualitative tagging score, mean residual fluid attenuation, and adverse effects assessed on the patient experience questionnaire. RESULTS The mean residual stool (0.90 of three) and fluid burden (1.05 of four) scores for PEG were similar to those for magnesium citrate (0.96 [P = .58] and 0.98 [P = .48], respectively). However, the mean fecal and fluid tagging scores were significantly better for PEG (0.48 and 0.28, respectively) than for magnesium citrate (1.52 [P < .01] and 1.28 [P < .01], respectively). Mean residual fluid attenuation was higher for PEG (765 HU) than for magnesium citrate (443 HU, P = .01), and mean interpretation time was shorter for PEG (14.8 minutes) than for magnesium citrate (18.0 minutes, P = .04). Tolerance ratings were not significantly different between preparations. CONCLUSION Reduced-volume PEG and magnesium citrate bowel preparations demonstrated adequate cleansing effectiveness for CT colonography, with better tagging and shorter interpretation time observed in the PEG group. Adequate polyp detection was maintained but requires further validation because of the small number of clinically important polyps.

Multidetector CT of the Postoperative Colon: Review of Normal Appearances and Common Complications

If not properly recognized, the normal postoperative appearance of the pelvis following colorectal surgery can be misinterpreted as disease, including infection or recurrent tumor. However, multidetector computed tomography (CT) with the supplemental use of multiplanar reformation clearly demonstrates the expected postoperative anatomic changes in this setting. The high-resolution images achievable with multidetector CT enable the radiologist to play an important role in the postoperative assessment of patients following colon surgery. Whenever possible, the radiologist should be aware of the specific indication for the study, the type of surgery that was performed (ranging from segmental bowel excision to more extensive radical resection), and what anastomoses were created. This knowledge, as well as familiarity with the normal multidetector CT appearances of various postoperative complications, is critical for prompt diagnosis and appropriate management of these complications and for better differentiation of complications from normal findings.

Extracolonic Findings at CT Colonography

Computed tomographic colonography (CTC) is a validated tool for the evaluation of the colon for polyps and cancer. The technique employed for CTC includes a low-dose CT scan of the abdomen and pelvis that is typically performed without the administration of intravenous contrast. Using this technique it is possible to discover findings outside of the colon. By far, most extracolonic findings are determined to be clinically inconsequential on CTC and most patients are not recommended for further testing. However, some findings may result in additional diagnostic evaluation or intervention, which can lead to patient anxiety and increased morbidity and health care costs. Alternatively, some findings can lead to the earlier diagnosis of a clinically significant lesion, which could result in decreased patient morbidity and mortality as well as overall savings in downstream health care costs. The controversies of detecting and evaluating these incidental extracolonic findings on CTC are discussed.

Diagnosis of cirrhosis by spiral computed tomography: a case-control study with feature analysis and assessment of interobserver agreement.

Purpose: To determine the accuracy and interobserver agreement of spiral computed tomography (CT) in the diagnosis of cirrhosis. Materials and Methods: We retrospectively identified 126 patients who underwent spiral CT at our institution and who had a contemporaneous histopathologic confirmation of cirrhosis (n = 67) or clinical and biochemical evidence of a normal liver (n = 59). Two experienced readers independently recorded the overall likelihood of cirrhosis and the presence or absence of hepatic and extrahepatic findings of cirrhosis and portal hypertension on a 5-point scale from 1 (definitely absent) to 5 (definitely present/severe). Results: Receiver operating characteristic curve and &kgr; statistic analyses showed that the overall likelihood of cirrhosis was the most accurate and objective observation, with an area under the curve (AUC) of 0.97 for reader 1 and 0.90 for reader 2 and a &kgr; value of 0.70. Individual findings that were accurate and objective were diaphragmatic surface nodularity (AUC = 0.95 and 0.88 for readers 1 and 2, respectively, &kgr; = 0.75), global or segmental volume loss (AUC = 0.95 and 0.87 for readers 1 and 2, respectively, &kgr; = 0.70), and superior diaphragmatic adenopathy (AUC = 0.85 for both readers, &kgr; = 0.78). Of note, portal vein diameter was not significantly different between normal and cirrhotic patients as measured by either reader (P = 0.54 and 0.65). Conclusion: Spiral CT demonstrates high accuracy and interobserver agreement in the diagnosis of cirrhosis, suggesting CT may be a supplementary diagnostic test in patients who have contraindications to biopsy or have equivocal biopsy findings.

Delayed Enhancement of Ascites After IV Contrast Material Administration at CT: Time Course and Clinical Correlation

OBJECTIVE The objective of our study was to determine the prevalence and clinical predictors of delayed contrast enhancement of ascites. MATERIALS AND METHODS In this retrospective study, 132 consecutive patients with ascites who underwent repeated abdominopelvic CT examinations performed within 7 days of each other were identified. These patients included 112 patients who received and 20 who did not receive i.v. contrast material at the initial CT examination. For each examination, we recorded the CT attenuation of the ascites. For the follow-up scan, the presence of delayed enhancement of ascites was defined as an increase in CT attenuation > 10 HU over baseline. The Fishers exact test, unpaired Students t test, and logistic regression were used to determine predictors of delayed enhancement of ascites. RESULTS A threshold increase in the attenuation of ascites by > 10 HU or more between the initial and follow-up CT examinations occurred only when i.v. contrast material was given with the initial examination. The increased attenuation was due to delayed contrast enhancement of ascites and occurred in 15 of the 112 patients (13%). Of the 16 patients scanned less than 1 day apart, 10 (63%) showed delayed enhancement of ascites. Delayed enhancement was not observed 3 or more days after i.v. contrast material administration. For each 1 mg/dL increase in serum creatinine level, the likelihood of delayed enhancement of ascites increased (odds ratio, 2.02; 95% CI, 1.11-3.69). Multivariate logistic regression showed that a short time interval between examinations (p < 0.001), increased serum creatinine level (p < 0.001), and presence of loculated ascites (p = < 0.01) were independent predictors of the magnitude of delayed enhancement of ascites. CONCLUSION Delayed contrast enhancement of ascites occurs commonly after recent prior i.v. contrast material administration and should not be mistaken for hemoperitoneum or proteinaceous fluid such as pus.

Value of Intraoperative Sonography in Pancreatic Surgery.

The utility of intraoperative sonography for pancreatic disease has been well described for detection and evaluation of neoplastic and inflammatory pancreatic disease. 1– 8 Intraoperative sonography can help substantially reduce surgical time as well as decrease potential injury to tissues and major structures. Imaging with sonography literally at the point of care—the surgeons scalpel—can precisely define the location of pancreatic lesions and their direct relationship with surrounding structures in real time during surgery. This article highlights our experience with intraoperative sonography at multiple institutional sites for both open and laparoscopic surgical procedures. We use intraoperative sonography for a wide range of pancreatic disease to provide accurate localization and staging of disease, provide guidance for enucleation of nonpalpable, nonvisible tumors, and in planning the most direct and least invasive surgical approach, avoiding injury to the pancreatic duct or other vital structures.

Periprocedural complications by Child-Pugh class in patients undergoing transcatheter arterial embolization or chemoembolization to treat unresectable hepatocellular carcinoma at a VA medical center

BACKGROUND For patients with compensated cirrhosis, transcatheter arterial embolization with and without additive chemotherapy has been shown to improve survival. The aim of this study was to compare periprocedural complications in a population with hepatitis C virus-related hepatocellular carcinoma to evaluate for differences in complications by severity of liver disease. METHODS Patients with unresectable hepatocellular carcinoma treated by transcatheter arterial embolization with or without additive chemotherapy procedures from 2003 to 2006 were retrospectively reviewed and compared by Child-Pugh (CP) class. A total of 141 embolizations were done in 76 patients. RESULTS Complication rates were seen in 27% of CP class A and 17% of CP class B patients. There was no significant difference in the grade of complications between the 2 groups or between procedure types. Survival rate was dependent on the degree of liver dysfunction (3-year CP class A, 49%; CP class B, 13%; P = .0048). CONCLUSION Embolization procedures to treat hepatitis C virus-related hepatocellular carcinoma can be performed safely with low morbidity and mortality rates, even in patients with a compromised hepatic reserve.