Diagnosis of Congenital Cardiac Right-to-left Shunts with 99mTc-macroaggregated Albumin

Diagnosing right-to-left congenital cardiac shunts can be difficult. Cardiac catheterization and angiocardiography represent the traditional gold standard for diagnosis, but they are invasive. Nuclear scintigraphy using 99mTc-macroaggregated albumin (MAA) has been employed in humans as an alternate method of diagnosis. This study reviews eight dogs presented for evaluation of a suspect right-to-left cardiac shunt that were examined using 99mTc-MAA. In all, 2-4 mCi (74-148 MBq) of reduced particle 99mTc-MAA were injected IV in a cephalic vein and static images of the whole body, including right and left lateral, dorsal, and ventral views, were acquired for 60 s and stored into a 256 x 256 x 16 matrix. Shunt fractions were calculated. One dog with radiopharmaceutical distribution limited to the lungs did not have a shunt. Seven dogs had distribution of the radiopharmaceutical outside the pulmonary capillary bed, indicating bypassing of the pulmonary capillary circulation due to a right-to-left shunt. Four dogs had 99mTc-MAA within the brain. Three dogs that did not have brain uptake, but instead had a sharp cutoff of radioactivity at the level of the front limbs and neck, were diagnosed with reverse patent ductus arteriosus (PDA). The asymmetric distribution of the radiopharmaceutical is due to the location of the shunt, distal to the brachiocephalic trunk and left subclavian artery. Shunt fractions of dogs with extrapulmonary radioactivity ranged from 40% to 59%. Nuclear scintigraphy with 99mTc-MAA is a quick alternative method of diagnosing right-to-left cardiac shunts that permits quantification of shunt fraction. Distinguishing between reverse PDA and other right-to-left shunts may be possible based on the radiopharmaceutical distribution.     

Evaluation of a percutaneously controlled hydraulic occluder in a rat model of gradual venous occlusion

OBJECTIVE: To evaluate the efficacy of a percutaneously controlled hydraulic occluder (HO) in a rat model of gradual venous occlusion. STUDY DESIGN: Experimental study. ANIMALS: Ten male Sprague-Dawley rats. METHODS: HOs and perivascular transit time ultrasound flow probes were applied to the caudal vena cava (CVC). Occluders in group I rats (n=6) were gradually attenuated over 8 weeks, whereas occluders in group II rats (n=4) were not attenuated. Vena caval blood flow measurements were performed weekly in all rats for 8 weeks. After euthanasia, the CVC was evaluated grossly and by histopathology. RESULTS: Premature occlusion of the vena cava occurred during the 1st week in 3 rats (1 in group I, 2 in group II) because of kinking of the vena cava between the HO and the flow probe. For the remaining rats, mean blood flow in group I decreased significantly from 40.71 mL/min/kg at baseline to 4.68 mL/min/kg at 8 weeks (P=.0094, power=0.91). Group II rats maintained vena caval blood flow at all times during the study. Complete occlusion of the vena cava was confirmed at necropsy in all group I rats. CONCLUSIONS: Gradual occlusion of the CVC of rats was achieved with HOs over 8 weeks. This model is limited by the size of the experimental animals and comparatively large implants. CLINICAL RELEVANCE: HOs may provide a method for gradual occlusion of congenital portosystemic shunts.     

经三通管接分流管置肝脏膈面处理脑室-腹腔分流术腹腔端阻塞的效果观察

目的 观察经三通管接分流管置肝脏膈面处理脑室腹腔分流术后腹腔端阻塞的效果.方法 对脑室腹腔分流术后因大网膜包裹或扭折成角致分流管腹腔端阻塞者,不拔除其原分流管腹腔段,而是将其在腹腔入口处剪断后加接脑室导管三通管(埋于上腹部皮下),另接一新分流管(腹腔段)置于肝脏膈面;并将原腹腔段与三通管连接.结果 术后随访6～24个月,除1例出现脑室端分流管阻塞外,余11例患者症状消失,分流通畅.复查CT示脑室系统缩小至正常,脑组织间质水肿明显减轻.所有患者均无明显腹部不适症状.结论 经三通管再接新分流管置肝脏膈面处理脑室-腹腔分流术后腹腔端阻塞的效果好.     

城市街景改造设计的思考与实践——以重庆市华新分流道为例

街景改造是当前城市快速发展中有机更新的重要方式,设计思路对其有效实施有着重要作用。文章结合规划实践,以重庆市江北区华新分流道为例,研究街景改造的设计思路及应用。     

ACQUIRED PORTAL COLLATERAL CIRCULATION IN THE DOG AND CAT

We describe patterns of acquired portal collateral circulation in dogs and in a cat using multidetector row computed tomography angiography. Large portosystemic shunts included left splenogonadal shunts in patients with portal hypertension. Small portal collaterals were termed varices; these collaterals had several patterns and were related either to portal vein or cranial vena cava obstruction. Varices were systematized on the basis of the venous drainage pathways and their anatomic location, namely left gastric vein varix, esophageal and paraesophageal varices, gastroesophageal and gastrophrenic varices, gallbladder and choledocal varices, omental varices, duodenal varices, colic varices, and abdominal wall varices. As reported in humans and in experimental dog models, esophageal and paraesophageal varices may result from portal hypertension that generates reversal of flow, which diverts venous blood in a cranial direction through the left gastric vein to the venous plexus of the esophagus. Blood enters the central venous system through the cranial vena cava. Obstructions of the cranial vena cava can lead to esophageal and paraesophageal varices formation as well. In this instance, they drain into the azygos vein, the caudal vena cava, or into the portal system, depending on the site of the obstruction. Gallbladder and choledocal varices, omental varices, duodenal varices, phrenico-abdominal varices, colic varices, abdominal wall varices drain into the caudal vena cava and result from portal hypertension. Imaging plays a pivotal role in determining the origin, course, and termination of these vessels, and the underlying causes of these collaterals as well. Knowledge about these collateral vessels is important before interventional procedures, endosurgery or conventional surgery are performed, so as to avoid uncontrollable bleeding if they are inadvertently disrupted.     

TRANSSPLENIC PORTAL SCINTIGRAPHY USING 99MTC-MEBROFENIN IN NORMAL DOGS

Transsplenic portal scintigraphy using sodium pertechnetate is superior to per-rectal portal scintigraphy due to improved visualization of the portal vasculature with decreased patient and personnel exposure. The purpose of this study was to describe the use of 99mTc-mebrofenin, the radiopharmaceutical of choice for the evaluation of hepatic function, in place of pertechnetate for transsplenic portal scintigraphy in normal dogs. Sixteen juvenile dogs underwent transsplenic portal scintigraphy using 37-130 MBq 99mTc-mebrofenin in a 0.2-0.5 ml volume. After the initial dynamic acquisition obtained at 4 frames/s in right lateral recumbency, static right lateral, and ventral views were obtained at 5, 10, 15, 20, 25, 30, 40, 50, and 60 min. A nuclear angiogram of the splenic and portal veins was visible in all dogs, followed by rapid distribution of the radiopharmaceutical in the liver. Hepatic morphology was more easily defined than with pertechnetate. Transit time could not be calculated due to the high hepatic extraction of 99mTc-mebrofenin. Mean +/- SD shunt fraction was 0.8 +/- 0.8%. Time to peak liver activity was 3.1 +/- 1.1 min, and hepatic excretion T1/2 was 19.4 +/- 6.3 min. No visible blood pool and cardiac activity was seen after 5 min. The mean +/- SD time to visualization of defined biliary activity was 8.8 +/- 2.9 min. Absorption from the spleen was significantly higher than that reported for pertechnetate (87.9 +/- 8.2%, vs. 52.5 +/- 19.1%). 99mTc-mebrofenin can be used in place of pertechnetate for transsplenic portal scintigraphy, with the advantage of combining quantitative parameters of liver function with the already known advantage of transsplenic portal scintigraphy.     

Outcomes after extrahepatic portosystemic shunt ligation in 49 dogs

OBJECTIVE: To evaluate outcomes after attenuation of extrahepatic portosystemic shunts in dogs using surgical silk. DESIGN: Retrospective study. PROCEDURE: Case records were reviewed for degree of surgical attenuation, experience of the primary surgeon, perioperative mortality and problems related to persistent portosystemic shunting or shunt ligation. Presence of portosystemic shunting after surgery was evaluated by ammonia tolerance testing, measurement of postprandial serum bile acid, plasma urea and cholesterol concentrations and liver enzyme activity. The influence of age, postocclusion portal pressure, primary surgeon, degree of attenuation and postoperative biochemical findings on the occurrence of postoperative problems was assessed. RESULTS: The mortality rate was 2.1%. Shunt attenuation was complete in 34% and partial in 66% of dogs. Portal hypertension necessitating ligature removal was encountered in only one dog. Five dogs experienced neurological abnormalities (seizures or ataxia), possibly as a manifestation of 'postligation seizure syndrome'. Postoperative liver function was normal in 78% of dogs, including 70% with partial shunt attenuation. Experience of the surgeon was related positively to outcome after partial attenuation (P = 0.002). Postoperative biochemical evidence of abnormal liver function was the most sensitive predictor of recurrence of clinical signs referable to persistent portosystemic shunting. CONCLUSIONS: In the hands of an experienced surgeon, surgical attenuation of single extrahepatic shunts was safe and effective, even in animals with partial attenuation. Most dogs with biochemical evidence of persistent shunting suffer relapse of clinical signs within 18 months of surgery. Postligation neurological syndromes of variable intensity may be more common than previously thought.