Vascular conspicuity differs among injection protocols and scanner types for canine multiphasic abdominal computed tomographic angiography

Intrahepatic Congenital Portosystemic Shunts

Patients with a single congenital portosystemic shunt (PSS) often fail to thrive and routinely experience episodes of hepatic encephalopathy. Although medical therapy may mitigate clinical signs, shunt attenuation improves long-term outcomes and allows for improved liver function. Intrahepatic PSSs are less common than their extrahepatic counterparts and pose some unique challenges. Minimally invasive intravascular approaches are generally recommended to treat IHPSSs with some exeptions including some patients with patent ductus venosus. Outcomes with percutaneous transvenous coil embolization are generally good, with low perioperative mortality rates and clinical improvement reported in greater than 80% of cases.

Factors Influencing Contrast Enhancement in Abdominal Computed Tomography Angiography in the Dog: A Systematic Review

Multidetector-row computed tomographic angiography (angio-CT) aims to achieve optimal opacification of the vascular compartment of interest. The distribution and quality of vascular opacification are influenced by patient-related factors, contrast medium (CM)-related factors, and scanner-related factors. This systematic review evaluates these factors and their effects on contrast enhancement. A comprehensive literature search was made in February 2024 across four online bibliographic databases (Web of Science, PubMed, Scopus, and CAB Abstract) in adherence with the PRISMA 2020 guidelines. After screening the 5990 unique published articles initially identified, 20 full-text original studies met the inclusion criteria for the final review. The amount of abdominal adipose tissue was found to significantly affect enhancement, which suggests the possibility of reducing the CM dose to minimize adverse effects or toxicity. The injection rate of the CM, rather than the injection duration, was identified as the most critical factor, with important clinical implications. For scanners with slower acquisition speeds or longer scan durations, maintaining a fixed CM injection duration may optimize vascular phase acquisition. In contrast, faster scanners benefit from bolus tracking, which allows for improved differentiation between vascular phases. Additionally, administering a saline flush post-CM injection enhances arterial opacification while reducing the necessary CM dose. This systematic review highlights essential factors influencing contrast enhancement in angio-CT for dogs and provides a foundation for future research aimed at optimizing imaging protocols in veterinary medicine.

Intra- and interobserver agreement in computed tomography localization of primary nonhematopoietic hepatic masses and comparison with surgical and histopathological outcomes in 21 cats

Computed tomography (CT) is commonly used in the staging of hepatic masses and for liver lobectomy planning. Mass location is an important factor in determining the feasibility of resection, including surgical technique and the likelihood of surgical complications. The objectives of this retrospective descriptive cross-sectional, observer agreement, method comparison study were to assess the reliability of CT in correctly determining the hepatic division and lobar site of origin of feline primary nonhematopoietic hepatic masses, compared with surgically confirmed locations. Furthermore, it provides an overview of the types and locations of liver masses found in a cohort of cats. Pre- and postcontrast CT images of 21 cats were independently and simultaneously reviewed by two observers. Intra- and interobserver agreements and descriptive statistics on demographic and histological diagnoses were calculated. Based on surgical assessment, it was found that masses most frequently originated from the left hepatic division (13/24, 54%). The most frequent lobar origins were the left lateral (8/24, 33%), left medial (5/24, 21%), and right medial lobes (5/24, 21%). No masses were found originating from the right lateral lobe. CT correctly determined hepatic division and lobar origin in 76% of cases, with good-to-excellent intra- and interobserver agreement. The hepatic division had higher agreements overall for both observers. Most of the masses were benign (17/21, 81%), and the most prevalent histological diagnoses were biliary cystadenoma (11/21, 52%) and hepatocellular adenoma (6/21, 29%). Findings suggest that postcontrast CT is a reliable method for correctly determining hepatic mass division and lobar origin in cats.

Confirmed and presumed canine insulinomas and their presumed metastases are most conspicuous in the late arterial phase in a triple arterial phase CT protocol

Arterial enhancement is the commonly described characteristic of canine insulinomas in contrast-enhanced computed tomography (CECT). However, this finding is also reported as inconsistent. The main aim of this single-center retrospective observational study was to describe the contrast enhancement (CE) pattern of canine presumed and confirmed insulinomas and presumed metastases in three consecutive (early, mid, and late) arterial phases. Included dogs had a medical-record-based clinical or cytological/histopathological diagnosis of insulinoma and quadruple-phase CECT. The arterial phases were identified according to published literature. The arterial enhancement of confirmed and presumed lesions was assessed using a visual grading score. Twelve dogs with a total of 17 pancreatic nodules were analyzed. Three dogs had multiple pancreatic nodules and nine had solitary findings. Four insulinomas were histopathologically confirmed. Late arterial phase (LAP) images demonstrated the largest number of pancreatic nodules reaching the highest enhancement scores (n = 13, 76%). All analyzed dogs had CT evidence of arterially enhancing nodules in the liver (n = 12), seven in the hepatic, splenic, or colic lymph nodes, and three in the spleen. Three out of five sampled livers and three lymph nodes were metastatic. All sampled spleens were benign. Avid arterial enhancement was the most dominant feature of canine presumed and confirmed insulinomas and presumed metastases in quadruple-phase CECT. The highest enhancement scores were observed primarily in LAP, followed by MAP. Authors, therefore, recommend including LAP in the standard CT protocol for dogs with suspected pancreatic insulinomas.

Investigation of scan delays for CT evaluation of inner wall layering and peak enhancement of the canine stomach and small intestine using a 20 second fixed-injection-duration and bolus tracking technique

Many gastrointestinal diseases affect the mucosal layer, suggesting that on computed tomography (CT) examination, detection of consistent inner wall layering of the gastrointestinal tract may aid in detection of disease. Changes in wall enhancement can also characterise specific diseases and provide prognostic information. The objectives of this mixed retrospective and prospective analytical study were therefore to identify the scan delays for peak detection of canine stomach and small intestinal inner wall layering and enhancement when using a 20 s fixed-injection-duration and bolus tracking technique. For each patient, 700 mg I/kg iohexol was administered intravenously. Bolus tracking was used to determine aortic arrival. Diagnostic scans were performed after a post-aortic arrival scan delay. Postcontrast CT series were grouped according to post-aortic arrival scan delay: 5 s (n = 17), 10 s (n = 18), 15 s (n = 23), 20 s (n = 10), 25 s (n = 6), 30 s (n = 14), 35 s (n = 17), 40 s (n = 24), and 180 s (n = 60). The stomach and small intestine were assessed for the presence of a contrast-enhancing inner wall layer and wall enhancement. Statistical modeling showed that the scan delays for peak inner wall layering and enhancement were 10 and 15 s for the small intestine, respectively, and 40 s for the stomach. For the injection protocol used in this study, assessment of the canine gastrointestinal tract may use scan delays of 10-15 s and 40 s.

Optimal delay for triple-phase hepatic computed tomography using a bolus-tracking technique in cats

The objective of this study was to provide the characteristics of hepatic computed tomography images and optimize their transition delay with a bolus-tracking technique for triple-phase hepatic computed tomography in cats. Dynamic triple-phase computed tomography was performed in nine healthy cats. The upper third of the liver was dynamically scanned every 0.5 s for 40 s. The time density curves of the aorta and hepatic parenchyma mean enhancement were analyzed. Triple-phase hepatic computed tomography was performed three times with a bolus trigger of 200 Hounsfield units of aortic enhancement. The transition delays of the arterial, portal, and hepatic parenchymal phases were respectively 0, 5 and 60 s in the first scan; 2, 7 and 62 s in the second scan; and 4, 9 and 64 s in the third scan. All computed tomography images were evaluated by a certificated radiologist. The arterial vessels and their main branches were well enhanced at a 2 s transition delay. The contrast of the portal vein to the liver parenchyma was most obvious at a 7 s transition delay. The mean enhancement of the hepatic parenchyma peaked at a 62 s transition delay, whereas the degree of enhancement of the hepatic vasculature decreased. In this study, the recommended transition delays for the arterial, portal, and hepatic parenchymal phases were 2 s, 7 s and 62 s, respectively, after triggering at 200 Hounsfield units of aortic enhancement. This information may be helpful in diagnosing feline liver diseases and provides a key reference for the clinical implementation of CT.

Lean body weight-adjusted intravenous iodinated contrast dose for abdominal CT in dogs reduces interpatient enhancement variability while providing diagnostic quality organ enhancement

Contrast-enhanced computed tomography (CECT) is increasingly used to screen for abdominal pathology in dogs, and the contrast dose used is commonly calculated as a linear function of total body weight (TBW). Body fat is not metabolically active and contributes little to dispersing or diluting contrast medium (CM) in the blood. This prospective, analytic, cross-section design pilot study aimed to establish the feasibility of intravenous CM dosed according to lean body weight (LBW) for abdominal CECT in dogs compared to TBW. We hypothesized that when dosing intravenous CM according to LBW, studies will remain at diagnostic quality, there will be a reduced interindividual contrast enhancement (CE) variability, and there will be less change to heart rate and blood pressure in dogs compared to when administering CM calculated on TBW. Twelve dogs had two CECT studies with contrast doses according to TBW and LBW at least 8 weeks apart. Interindividual organ and vessel CE variability, diagnostic quality of the studies, and changes in physiological status were compared between protocols. The LBW-based protocol provided less variability in the CE of most organs and vessels (except the aorta). When dosed according to LBW, liver enhancement was positively associated with grams of iodine per kg TBW during the portal venous phase (P = 0.046). There was no significant difference in physiological parameters after CM administration between dosing protocols. Our conclusion is that a CM dose based on LBW for abdominal CECT lowers interindividual CE variability and is effective at maintaining studies of diagnostic quality.

Clinical and CT sialography findings in 22 dogs with surgically confirmed sialoceles

Sialoceles are an uncommon canine salivary gland disease, and complete surgical resection is important for a positive outcome. Radiographic sialography has been described as a diagnostic test for presurgical planning; however, superimposition artifacts may limit the diagnosis and detection of all affected glands. Computed tomographic (CT) sialography is a promising technique for delineating the salivary gland apparatus. The aims of this retrospective, observational study were to describe clinical and CT sialographic findings in a group of dogs with confirmed sialoceles, to determine the sensitivity of CT sialography for detecting affected salivary glands using surgery as the reference standard and to determine interobserver agreement for CT sialographic assessments. Dogs were included if they underwent a CT sialography study followed by surgical resection of the diseased gland(s) and histopathological analysis. Computed tomography sialography studies of dogs with surgically confirmed sialoceles (n = 22) were reviewed by a European College of Veterinary Diagnostic Imaging (ECVDI)-certified radiologist and an ECVDI resident. Interobserver agreement was calculated using Cohen's kappa statistics. CT sialography results were compared to surgical findings to determine sensitivity. Contrast leakage was detected in 12 of 22 dogs (54.5%), with intrasialocele leakage being most frequently observed (7/12, 58.3%). There was substantial agreement (κ = 0.70) between reviewers identifying diseased glands, substantial agreement (κ = 0.62) on the diagnostic quality, and no to slight agreement (к = 0.13) in the detection of contrast leakage. The overall sensitivity of CT sialography to detect surgically confirmed diseased glands was 66.7% (95% confidence interval: 48.8-80.8). In conclusion, these findings support the use of CT sialography as an adjunct diagnostic test for treatment planning in dogs with sialoceles.

Intrahepatic venous collaterals in dogs with congenital intrahepatic portosystemic shunts are associated with focal shunt or hepatic vein narrowing

Dogs with congenital intrahepatic portosystemic shunts (IHPSS) occasionally have multiple smaller intrahepatic, tortuous blood vessels surrounding the primary shunt. This study was a retrospective, observational design that was also descriptive and anatomic in nature. Objectives were to characterize vascular morphology in IHPSS dogs presenting with intrahepatic venous collaterals (IVCs) relative to IHPSS dogs without IVCs, and to propose reasons for IVC development. The authors hypothesized that (a) IVCs develop secondary to flow resistance around a focal area of a shunt or draining hepatic vein narrowing and (b) the presence of IVC is associated with portal vessel development before intervention. Anonymized CT angiograms (CTA) and fluoroscopic portovenograms (FPV) of dogs with IHPSS were evaluated for the presence of IVCs, focal narrowing within the IHPSS, and intrahepatic portal vessels >5 mm long. Eleven of 47 (23%) dogs had IVCs identified. IVCs were significantly associated with focal narrowing in the shunt or draining hepatic vein on CTA (P = 0.039) and FPV (P = 0.021). IVCs were not associated with the presence of intrahepatic portal branches >5 mm long on portovenography (P = 0.42) or CTA (P = 0.49). Focal narrowing in the shunt (circumferential soft tissue narrowing >20% of the shunt diameter) was significantly associated with intrahepatic portal branches >5 mm long on both modalities (P < 0.001). IVCs are associated with focal narrowing of the shunt or draining hepatic vein in dogs with IHPSS. IVC should be distinguished from other conditions when evaluating a CTA for canine IHPSS.

Four-dimensional CT excretory urography is an accurate technique for diagnosis of canine ureteral ectopia

Computed tomographic (CT) excretory urography is commonly used to investigate canine ureteral ectopia (UE). Modern technology allows time-resolved CT imaging (four-dimensional CT excretory urography [4D-CTEU]) over a distance exceeding the detector collimation. Objectives of this prospective, observational, diagnostic accuracy study were to evaluate the diagnostic accuracy of CT excretory urography (CTEU) and 4D-CTEU for UE in dogs with lower urinary tract signs, assess the influence of pelvis positioning, and to determine the significance of the ureterovesical junction (UVJ) angle for UE diagnosis. Thirty-six dogs, with a total of 42 normotopic ureters, 27 intramural ectopic ureters, and three extramural ectopic ureters, underwent CTEU and 4D-CTEU with randomized pelvis positioning. Randomized CTEU and 4D-CTEU studies were scored by two observers for ureteral papilla location and murality on a grading scheme. Interobserver agreement, sensitivity, and specificity for ureter topia status and diagnosis were calculated. Computed tomographic excretory urography showed moderate interobserver agreement for the left ureter and perfect for the right ureter, whereas 4D-CTEU showed bilateral nearly perfect agreement between both observers. When comparing CTEU versus confirmed diagnosis, there was a sensitivity and specificity of 73% and 90.2%, respectively, whereas 4D-CTEU showed a sensitivity and specificity of 97% and 94.6%, respectively. An obtuse UVJ angle is significantly more commonly observed in ectopic intramural than normotopic ureters and is significantly associated with increased diagnostic confidence of UE. The use of a wedge to angle the pelvis did not increase the diagnostic confidence in determining ureteral opening position. Four-dimensional CT excretory urography is an accurate and reliable diagnostic technique to investigate UE as cause of urinary incontinence in dogs that is slightly superior to CTEU.

Canine intrahepatic portosystemic shunt insertion into the systemic circulation is commonly through primary hepatic veins as assessed with CT angiography

Congenital intrahepatic portosystemic shunts (IHPSS) in dogs are traditionally classified as right, left, or central divisional. There are few descriptive studies regarding the variation of IHPSS within these categories. This multicenter, analytical, cross-sectional study aimed to describe a large series of dogs with CT angiography (CTA) of IHPSS, hypothesizing that there would be variation to the existing classification. Ninety CTA studies were assessed for IHPSS type, insertion, and the relationship of the insertion to the primary hepatic veins. Ninety-two percent of IHPSS inserted into a primary hepatic vein (HV) or phrenic vein, 8% inserted directly into the ventral aspect of the intrahepatic caudal vena cava. The most common IHPSS type was a single right divisional (44%), including those inserting via the right lateral HV or the caudate HV. Left divisional IHPSS (33%) inserted into the left HV or left phrenic vein. Central divisional IHPSS (13%) inserted into the quadrate HV, central HV, dorsal right medial HV, or directly into the ventral aspect of the intrahepatic caudal vena cava. Multiple sites of insertion were seen in 9% of dogs. Within left, central, and right divisional types, further subclassifications can therefore commonly be defined based on the hepatic veins with which the shunting vessel communicates. Relating IHPSS morphology to the receiving primary HV could make IHPSS categorization more consistent and may influence the type and method of IHPSS attenuation recommended.

Use of a cavitron ultrasonic surgical aspirator for parenchyma-sparing and complex liver resections in dogs

OBJECTIVE

To report the clinical use of a cavitron ultrasonic surgical aspirator (CUSA) for the resection of hepatic lesions in dogs.

STUDY DESIGN

Clinical prospective study.

ANIMALS

Eleven client-owned dogs.

METHODS

Dogs requiring a hepatic nodulectomy, segmentectomy, and/or a lobectomy (including complex lobectomies) were enrolled. The number and location of procedures, blood loss, duration of surgery, and short-term complications were recorded.

RESULTS

Dogs underwent a mean of 2.3 ± 1.1 procedures. All masses were amenable to surgical excision regardless of their location and their relationship with major hepatic vessels. Dogs lost a median of 77 mL of blood (9.9-161), which corresponded to 4.3% of blood volume (0.8%-23.2%). The dog with the highest blood loss survived without requiring transfusion. The median duration of all CUSA procedures was 33.5 minutes (15-82). Short-term outcomes were assessed for the first 15 days, during which two complications were diagnosed. Cholangiohepatitis was diagnosed in one dog and resolved after medical management, and another dog developed necrotic pancreatitis and died.

CONCLUSION

Liver parenchyma-sparing nodulectomies and segmentectomies and liver lobectomies including complex lobectomies were achieved with a CUSA in all dogs.

CLINICAL SIGNIFICANCE

Use of a CUSA can be considered as an alternative for the removal of hepatic lesions in dogs.