Delayed enhancement of ascites after i.v. contrast material administration at CT: time course and clinical correlation

CT of acute abdominopelvic hemorrhage: protocols, pearls, and pitfalls

Abdominal and pelvic hemorrhage may be secondary to a number of causes and is often a medical emergency. Patient presentation ranges from obvious trauma with evidence of hemodynamic instability to vague symptoms. CT has become the imaging modality of choice for identifying abdominopelvic hemorrhage. Recognizing acute hemorrhage as well as identifying its location and severity are key to expediting management. In the Emergency Department, ultrasound often used in the initial evaluation of trauma patients, but is not sensitive for subtle bleeds or injuries. CT is the best first-line imaging tool to identify abdominal hemorrhage and, compared with angiography, has been shown to be superior in detecting intra-abdominal bleeding, especially when the bleeding rate is low. Depending on location and etiology, abdominopelvic hemorrhage may have a characteristic appearance, such as the "sentinel clot" sign associated with blunt trauma to the solid organs or the "triangle sign" of a mesenteric bleed. The following pictorial essay reviews CT technique, study interpretation, and interpretative pearls and pitfalls in the recognition of acute abdominopelvic hemorrhage.

CT of the Difficult Acute Aortic Syndrome

Acute aortic syndrome (AAS) is classically attributed to three underlying pathologic conditions-aortic dissection (AD), intramural hematoma (IMH), and penetrating atherosclerotic ulcer (PAU). In the majority of cases, the basics of image interpretation are not difficult and have been extensively reviewed in the literature. In this article, the authors extend existing imaging overviews of AAS by highlighting additional factors related to the diagnosis, classification, and characterization of difficult AAS cases. It has been well documented that AAS is caused not only by an AD but by a spectrum of lesions that often have overlap in imaging features and are not clearly distinguishable. Specifically, phase of contrast enhancement, flow artifacts, and flapless AD equivalents can complicate diagnosis and are discussed. While the A/B dichotomy of the Stanford system is still used, the authors subsequently emphasize the Society for Vascular Surgery's new guidelines for the description of acute aortic pathologic conditions given the expanded use of endovascular techniques used in aortic repair. In the final section, atypical aortic rupture and pitfalls are described. As examples of pericardial and shared sheath rupture become more prevalent in the literature, it is important to recognize contrast material third-spacing and mediastinal blood as potential mimics. By understanding these factors related to difficult cases of AAS, the diagnostic radiologist will be able to accurately refine CT interpretation and thus provide information that is best suited to directing management. Online supplemental material is available for this article. ^©RSNA, 2021.

Enhancement rate of venous phase to portal venous phase computed tomography and its correlation with ultrasound elastography determination of liver fibrosis

INTRODUCTION

This study aimed to compare the correlation between the computed tomography (CT) enhancement rate of the venous to portal venous phase (VP-ER) and the extracellular volume (ECV) fraction with shear-wave ultrasound elastography (USE) findings in patients with liver fibrosis.

METHODS

We included 450 patients with clinically suspected liver cirrhosis who underwent triphasic dynamic CT studies and USE. We compared the USE results with the unenhanced CT phase, with enhancement in the hepatic artery phase (HAP), portal venous phase (PVP), and venous phase (VP), and with the ECV fraction and the VP-ER. We also compared the area under the curve (AUC) of the receiver operating characteristic (ROC) curve of the ECV fraction and VP-ER with that of the values obtained with USE.

RESULTS

The VP-ER was the most highly correlated with the liver stiffness value determined with USE (Pearson's correlation coefficient: r = 0.37), followed by enhancement in the PVP (r = -0.25), CT number on unenhanced CT scans (r = -0.22), the ECV fraction (r = 0.19), enhancement in the VP (r = 0.059), and enhancement in the HAP (r = -0.023) (all p < 0.01). The VP-ER showed a significantly higher AUC than the ECV fraction (0.75 vs 0.62) when the liver stiffness was >15 kPa in USE studies (p = 0.04).

CONCLUSION

Compared to the ECV fraction, the VP-ER is more useful for predicting all degrees of liver fibrosis on routine triphasic dynamic CT images.

IMPLICATIONS FOR PRACTICE

Although improvement is needed, the VP-ER has a higher diagnostic ability for liver fibrosis than the ECV fraction in clinical practice.

Longitudinal comparison of ascites attenuation between antemortem and postmortem computed tomography

OBJECTIVE

To investigate the changes in ascites attenuation between antemortem (AMCT) and postmortem computed tomography (PMCT) analyses of the same subjects.

METHODS

Thirty-five subjects who underwent unenhanced or enhanced AMCT within 7 days before death, unenhanced PMCT, and autopsy were evaluated. In each subject, ascites attenuation was measured at similar sites on AMCT and PMCT. Attenuation changes were evaluated in 42 unenhanced AMCT/PMCT site pairs (23 subjects) and 20 enhanced AMCT/PMCT site pairs (12 subjects). Factors contributing to CT attenuation changes were also assessed, including the time interval between AMCT and PMCT, serum albumin level, estimated glomerular filtration rate, and ascites volume.

RESULTS

Significantly elevated CT attenuation was observed between enhanced AMCT and PMCT (12.2 ± 6.3 vs. 18.7 ± 10.4 Hounsfield units; paired t-test, p = 0.006), but not between unenhanced AMCT and PMCT (13.5 ± 8.9 vs. 13.4 ± 9.3; p = 0.554). A significant inverse association was observed between the degree of CT attenuation change and the time interval between enhanced AMCT and PMCT (Spearman's rank correlation coefficient, r = -0.56, p = 0.01).

CONCLUSIONS

We confirmed an elevated level of ascites attenuation on PMCT relative to AMCT in subjects who underwent enhanced AMCT shortly before death.

Non-traumatic hemoperitoneum in the ED setting: causes, characteristics, prevalence and sex differences

PURPOSE

Prevalence and sex differences of non-traumatic hemoperitoneum in the Emergency Department has not been studied in the literature.

METHODS

Following IRB approval, multiple keyword searches were used to identify all cases of hemoperitoneum over a 55-month period. Cases were reviewed to confirm and quantify the hemoperitoneum. Maximum attenuation was used to grade blood density. Medical records were reviewed to determine cause, interventions and outcomes in each patient.

RESULTS

Of the 171 verified cases of non-traumatic hemoperitoneum, 76% of cases were in women. CT exams in women were positive for hemoperitoneum 0.25% of the time, while 0.13% were positive in men. Regarding size, 25.7% were large, 24.5% were moderate and 49.7% were small. Contrast-enhanced studies had HU values of 103 ± 19 (range 47-146) which were significantly higher than for non-enhanced studies with values of 82 ± 19 (range 43-121, p < 0.001). The most common cause of non-traumatic hemoperitoneum was ruptured ovarian cyst which was found in 58% of women (76 cases). Of these, 69 patients received observation, 6 patients underwent surgery and 1 patient received Vitamin K. For the 95 non-ovarian cyst cases, 65% patients were admitted and then discharged, 22% were discharged from the ED, 12% expired and 1% were transferred to a different hospital. Post-procedure hemorrhage was the second to most common cause in women (24/130 = 18%) and the most common etiology in men (14/41 = 34%).

CONCLUSIONS

In women, ovarian cyst rupture was the most common etiology of hemoperitoneum. Post-procedure hemorrhage was second in women and the most common etiology in men. Although unusual causes of hemoperitoneum will be encountered, understanding the most common causes of hemoperitoneum can provide a reasonable starting point when attempting to determine the most likely etiology of hemoperitoneum in any individual patient.

Ascites relative enhancement during hepatobiliary phase after Gd-BOPTA administration: a new promising tool for characterising abdominal free fluid of unknown origin

OBJECTIVES

To correlate the degree of ascites enhancement during hepatobiliary phase after gadobenate dimeglumine (Gd-BOPTA) administration with ascites aetiology.

METHODS

IRB-approved retrospective study, need for informed consent was waived. We included 74 consecutive ascitic patients who underwent Gd-BOPTA-enhanced liver MRI including hepatobiliary phase (HBP) images between January 2014 and December 2017. Ascites appearance on unenhanced and HBP images was classified as hypo-, iso- or hyperintense in comparison to paraspinal muscles. Ascites signal intensity on unenhanced and HBP images was measured using round ROIs and was normalised to paraspinal muscles (NSI). Normalised relative enhancement (NRE) between native phase and HBP was calculated. The results were related to ascites aetiology using Wilcoxon and Mann-Whitney tests.

RESULTS

On native images, ascites appeared hypointense in 95.9% of the cases and isointense in 4.1%, whereas on HBP images, it appeared hyperintense in 59.4% of the cases, isointense in 36.5% and hypointense in 4.1%. Mean ascites NSI was 0.52 on unenhanced images and 1.50 on HBP ones (p < 0.0001). Mean ascites NRE was 201 ± 133%. Ascites of non-malignant aetiology showed mean NRE of 210 ± 134%, whereas malignant ascites showed mean NRE of 92 ± 20% (p = 0.001). ROC analysis showed that a NRE < 112.5% correlates with malignant aetiology with 100% sensitivity and 83.4% specificity (LR = 5.667). NRE did not show any significant correlation with ascites thickness, eGFR and time interval between contrast administration and HBP acquisition (p > 0.05).

CONCLUSIONS

Ascites NRE in HBP after Gd-BOPTA administration is significantly lower in patients with ascites secondary to peritoneal carcinomatosis than in patients with non-malignant ascites.

KEY POINTS

• Ascites enhancement in the hepatobiliary phase after Gd-BOPTA administration may determine false positive findings when looking for biliary leaks. • Ascites enhancement in the hepatobiliary phase after Gd-BOPTA administration is lower in patients with peritoneal carcinomatosis than in patients with portal hypertension or congestive heart failure. • None of the patients with peritoneal carcinomatosis showed an ascites enhancement of more than 112% as compared with unenhanced images.

Peritoneal and pleural fluids may appear hyperintense on hepatobiliary phase using hepatobiliary MR contrast agents

AIM

To describe the effect of hepatobiliary-specific MR imaging contrast agent (HBCA) administration on the signal intensity of peritoneal and pleural fluid effusions on T1-weighted MR images.

MATERIALS AND METHODS

From October 2015 to May 2016 139 patients (mean 60±10 years old, 69 % males) with peritoneal or pleural effusions without biliary leakage who underwent HBCA-MRI (Gd-BOPTA or Gd-EOB-DTPA) at 1.5T and 3T were included from two centres. The fluid signal intensity was classified as hypo/iso/hyperintense before/after HBCA administration. The relative signal enhancement (RE) was calculated.

RESULTS

On hepatobiliary phase (HBP), peritoneal fluids appeared hyper/isointense in 88-100 % and pleural effusions in 100 % of the patients following Gd-BOPTA administration. All fluids remained hypointense following Gd-EOB-DTPA. The signal intensity of fluids increased with both HBCA but RE was significantly higher following Gd-BOPTA (p=0.002 to <0.001). RE was correlated with HBP acquisition time-point (r=0.42, p<0.001 and r=0.50, p=0.033 for peritoneal and pleural fluids).

CONCLUSION

The signal intensity of pleural and peritoneal fluids progressively increases following HBCA administration in the absence of biliary leakage. Due to its later hepatobiliary phase, this is more pronounced after Gd-BOPTA injection, leading to fluid hyperintensity that is not observed after Gd-EOB-DTPA injection.

KEY POINTS

• Fluids appear hyper/isointense on HBP in most patients after Gd-BOPTA injection. • Fluids remain hypointense on HBP after Gd-EOB-DTPA injection. • RE of fluids increases with time after liver-specific Gd injection. • RE of fluids is higher in patients with chronic liver disease.

Non-traumatic bladder rupture showing less than 10 Hounsfield units of ascites

Aim

Bladder ruptures are commonly misdiagnosed as gastrointestinal perforations or intestinal ischemia. If a diagnosis is made preoperatively, conservative treatment is a safe and effective option. We evaluated the validity of using the attenuation value of ascites, measured by non‐contrast computed tomography (CT), to identify patients with bladder ruptures.

Methods

A retrospective search of our hospital database identified 7 patients with confirmed bladder ruptures between 2007 and 2013. We also enrolled 18 patients with gastrointestinal perforations and 10 patients with intestinal ischemia with detectable ascites on abdominal CT that had undergone emergency exploratory laparotomy between 2007 and 2013. Between‐group comparisons of attenuation values of ascites as obtained by non‐contrast CT were evaluated.

Results

All attenuation values were less than 10 Hounsfield units (HU) in bladder rupture patients. Moreover, the attenuation value of ascites in cases of bladder rupture (median, 5.7; range, 3.1–6.1) was significantly lower than in cases of gastrointestinal perforation (median, 14.7; range, 4.7–25.4) and intestinal ischemia (median, 13.3; range, 6.0–18.1) (P = 0.004 for both comparisons).

Conclusion

Bladder rupture mimics gastrointestinal perforation and intestinal ischemia with acute kidney injury. Therefore, the diagnosis of bladder rupture using the attenuation value of ascites on non‐contrast CT is both useful and highly significant. We suggest that bladder rupture be considered in the differential diagnosis of patients presenting with acute abdominal pain and attenuation values of ascites of less than 10 Hounsfield units.

High attenuation pericardial fluid on CT following cardiac catheterization

High-density pericardial fluid may be seen on noncontrast CT performed following cardiac catheterization (CC), raising the possibility of hemopericardium. Our goal was to determine the clinical course and associations of incidentally discovered high-attenuation pericardial fluid on noncontrast CT performed soon after CC. Hospital database search over a 7.5-year period identified 211 patients who underwent CT of the chest and/or abdomen within 60 h before or after CC, 150 having CC first. Pericardial fluid volume and attenuation as well as relevant laboratory and clinical parameters were recorded. Bivariate associations with average pericardial fluid attenuation (HUavg) were assessed. Using the 61 patients with CT before CC as controls, 44 of the patients with CC first had attenuation values greater than the mean + 2SD of 22.6 Hounsfield unit (HU) and 19 had attenuation values greater than the maximum control patient value of 39.8 HU. All patients with incidental finding of high-density pericardial fluid followed a benign course. Bivariate correlations showed time gap between CC and CT (rho = -0.50, p < 0.001), estimated glomerular filtration rate (eGFR) (rho = -0.24, p = 0.004), and female gender (median (IQR) 17.4 (13.6, 29.6) vs. 15.8 (9.9, 23.7), p = 0.02) to be associated with HUavg. In multiple linear regression analysis, only time gap and female gender were independently significantly associated with average attenuation (both p < 0.001). The finding that patients with incidentally discovered high-density pericardial fluid followed an uneventful course suggests a benign etiology such as vicarious excretion, and in patients who are otherwise stable, observation rather than immediate intervention should be considered.

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 patient's 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.

Application of an isocratic methanol-based HPLC method for the determination of iohexol concentrations and glomerular filtration rate in patients with cirrhosis

BACKGROUND

Glomerular filtration rate (GFR) and mortality is more accurately determined by gold standard measures than serum creatinine-based estimates in cirrhosis. No formal validation of any gold standard method has been reported.

METHODS

An isocratic methanol-based method incorporating the reference standard iohexol-related compound C was developed and validated in 12 patients with cirrhosis by simultaneously determining GFR using iohexol and chromium-51 labelled ethylenediamine tetraacetic acid ((51)Cr-EDTA) clearance. Iohexol pharmacokinetics was also studied with the collection of blood and ascitic fluid at intervals following an iohexol bolus.

RESULTS

Triplicate assays produced a linear calibration curve (R (2)=0.99, N=5) over an iohexol concentration range of 23.6-755 µg/L. Mean (range) extraction recovery of iohexol from serum was greater than 95% (94-97%), with an intra-day coefficient of variation less than 3%. Twelve patients with cirrhosis with mean Child-Pugh score of 9 displayed a mean difference (bias) -1.3 mL/min/1.73 m(2) (-18 to +16) comparing iohexol with (51)Cr-EDTA. Iohexol equilibrated between blood and ascitic compartments after 4 h.

CONCLUSION

A simple, cheap, and accurate isocratic, methanol-based method for the determination of iohexol concentrations is described, validated according to Food and Drug Administration guidance. Iohexol demonstrated comparable performance with (51)Cr-EDTA in determining GFR. Delayed equilibrium of iohexol between blood and ascitic compartments suggests sampling beyond 4 h would improve accuracy of GFR determinations in patients with cirrhosis.

Enhancement of ascites during abdominal oncological endovascular intervention without iatrogenic extravasation in patients with chronic liver disease

AIM

To evaluate ascites enhancement during abdominal oncological endovascular intervention (IVR) without iatrogenic extravasation and the factors associated with enhancement of ascites.

METHODS AND MATERIALS

CT images were obtained using an IVR-CT system for 73 patients with chronic liver disease and ascites. The CT images were obtained at least twice during each IVR. Radiodensity values of ascites at CT were measured for the first and last CT images in each procedure. The factors evaluated for their association with elevated ascitic fluid density were age, interval from the first to the last CT scan, Child-Pugh score, albumin level, total bilirubin level, prothrombin activity, the need for transcatheter arterial chemoembolization (TACE), estimated glomerular filtration rate, total amount of contrast material (CM) per square metre of body surface area (/m(2)), amount of ascitic fluid, and the amount of CM entering the superior mesenteric artery (SMA) or coeliac artery/m(2).

RESULTS

The average ascitic radiodensity values for the first and last CT images were 18 and 51 HU, respectively. The percentage of patients with "significantly elevated" ascitic fluid density (≥10 HU) was 92%. Multivariate analysis showed that the total amount of CM/m(2) and the amount of ascitic fluid were significantly correlated and inversely correlated, respectively, with elevated ascitic fluid density.

CONCLUSIONS

Ascites enhancement without extravasation frequently occurs during abdominal oncological endovascular intervention in patients with chronic liver disease.