NHÂN CA DỊ DẠNG MẠCH MÁU GAN @ MEDIC

Thảo luận

Tĩnh mạch trên gan P thường là mạch máu duy nhất dẫn lưu cho thùy phải của gan; Tuy nhiên, có thể có biến thể vào khoảng 18% tổng số dân. Như một quy luật chung,nhánh tīnh mạch gan P dưới [inferior right hepatic vein ] dẫn lưu phân thuỳ VI và nhu mô gan liền kề, và đổ trực tiếp vào ngay sau P  tĩnh mạch chủ dưới , 3-5 cm xa tĩnh mạch trên gan P (2). Nhánh dưới  tĩnh mạch gan P có thể lớn hơn tĩnh mạch trên gan P.

Trong trường hợp hiện có, chúng tôi bất ngờ tìm thấy một aneurysmal portosystemic thông nối giữa nhánh P  tĩnh mạch cửa và nhánh dưới tĩnh mạch trên gan P ,  đại diện cho portosystemic shunt type 3 theo phân loại của Park et al. (1). Tĩnh mạch gan P cũng thông nối với cấu tạo này.

Shunt tĩnh mạch cửa chủ trong gan [intrahepatic portosystemic] là tình trạng bẩm sinh hoặc mắc phải bao gồm một giao tiếp giữa hệ cửa và hệ tĩnh mạch hệ thống chủ, nằm ở trong gan ít nhất một phần(3). Shunts mắc phải do là tuần hoàn bên thứ cấp trong gan cho cao áp TM cửa  và xơ gan (4), hoặc do chấn thương, làm sinh thiết gan hoặc phẫu thuật.

Shunt tĩnh mạch cửa chủ trong gan bẩm sinh là một tình trạng ít phổ biến được  hiểu rõ trong bối cảnh phát triển phôi thai của các hệ thống tĩnh mạch cửa  và  hệ trên gan. Vào tuần thứ tư của cuộc sống thai nhi, các hệ thống vitelline và rốn bắt đầu tan rã thành xoang gan [intrahepatic sinusoids] làm  tăng tương ứng  lần lượt TM cửa trong gan và tĩnh mạch trên gan.

 

Shunts cửa chủ bẩm sinh  là đại diện cho thông nối tĩnh mạch tồn lưu (3, 5). Chẩn đoán sớm và đánh giá định kỳ các shunt là quan trọng bởi vì nguy cơ liên tục của bệnh não gan với tiếp xúc với phơi nhiễm amoniac, đặc biệt là nếu các shunt tiến triển (6, 7). Ngoài ra, giảm lưu lượng máu đến gan có thể dẫn đến thoái hóa mỡ, rối loạn chức năng gan, và teo gan (8).

Siêu âm Doppler màu là phương tiện tạo hình chính để chẩn đoán của shunts portosystemic tĩnh mạch. Ngoài việc chứng tỏ dòng chảy tín hiệu giữa các mạch tham gia, và đánh giá hướng dòng chảy, nó có thể xác định tỷ lệ shunt bởi ước tính thể tích dòng chảy (6, 7). Tăng cường độ tương phản CT với xử lý kỹ thuật hình ảnh ba chiều thường được thực hiện để bổ sung cho siêu âm, đặc biệt ở những bệnh nhân béo phì hoặc ở những bệnh nhân với teo gan nặng (6).

CT multiplanar hình ảnh tạo bởi ba chiều hình ảnh xử lý kỹ thuật có hiệu quả hơn so với các hình ảnh hai chiều trong việc chứng minh biến thể nhỏ và mạch cong. Với việc sử dụng rộng rãi các kỹ thuật mạch shunt  như những có thể lân khéo quan sát bằng phương thức hình ảnh khác có thể được công nhận phổ biến hơn.

Discussion

The right hepatic vein is usually a single vessel that drains the right lobe of the liver; however, there may be a variant inferior right hepatic vein in about 18% of the population. As a general rule, the inferior Right hepatic vein drains segment VI and adjacent hepatic parenchyma, and flows directly into the right posterior aspect of the inferior vena cava, 3 to 5 cm distal to   the right hepatic vein (2). The inferior right hepatic vein may be larger than the right hepatic vein. In the present case, we found incidentally an aneurysmal portosystemic communication  between the right portal vein and the inferior right hepatic vein, which may represent a type 3 portosystemic shunt according to the classification of Park et al. (1). The right hepatic vein was also connected to this formation.

Intrahepatic portosystemic venous shunt is a congenital or acquired condition consisting of a communication between the portal and systemic venous circulation, situated at least partially within the liver (3). Acquired shunts may develop as intrahepatic collateral pathways secondary to portal hypertension and cirrhosis (4), or may result from trauma, liver biopsy, or surgery.

Congenital intrahepatic portosystemic venous shunt is an uncommon condition that is best understood in the context of the embryological development of the portal and hepatic venous systems. By the fourth week of fetal life, the vitelline and umbilical systems begin to break into intrahepatic sinusoids that give rise to the intrahepatic portal and hepatic veins, respectively.

Congenital portal-systemic shunts are thought to represent persistent venous communications (3, 5). Early diagnosis and periodic evaluation of the shunt are important because of the ongoing risk of hepatic encephalopathy with exposure to high ammonia levels, especially if the shunt may be progressive (6, 7). Additionally, reduction in blood flow to the liver may result in fatty degeneration, hepatic dysfunction, and atrophy of the liver (8).

Color Doppler US is recommended as the primary imaging modality for diagnosis of portosystemic venous shunts. In addition to demonstrating flow signals between the involved vessels, and evaluating flow direction, it may also determine the shunt ratio by estimating flow volume (6, 7). Contrast-enhanced CT with three-dimensional image processing techniques is usually performed to supplement US, especially in obese patients or in patients with marked liver atrophy (6).

Multiplanar CT images created by three-dimensional image processing techniques are more effective than two-dimensional images in demonstrating variant small and curved vessels. With extensive use of these techniques shunt vessels such as these that may elude observation by other imaging modalities may be recognized more commonly.

ULTRASOUND FAST for BREAST IMPLANT STATUS

Ultrasound Fast Alternative to MRI for Breast Implant Status
Pam Harrison
April 01, 2014

LAS VEGAS — High-resolution ultrasound done in a physician's office is a fast, convenient, and friendly alternative to MRI for ascertaining the status of breast implants, a pilot study suggests.

Researchers found a "higher than expected" rotation rate in 2 types of shaped cohesive gel implants and detected 2 ruptures that were later confirmed on MRI.


Dr. William Adams Jr.
"Clinically, our rotation rate is only about 2%. It was surprising that we were definitely able to show with ultrasound that the rotation rate was much higher," said William Adams Jr., MD, clinical associate professor of plastic surgery at the University of Texas South Western Medical Center in Dallas.

"This means that a fair number of rotations are going unnoticed by patients. We haven't had this type of information about shaped implants before, so it's something we can add to our discussion with patients when they are considering these types of surgeries," he told Medscape Medical News.

The study results were presented here at the American Institute of Ultrasound in Medicine (AIUM) 2014 Annual Convention in Las Vegas, Nevada.

MRI Screening

Currently, the US Food and Drug Administration (FDA) recommends that breast implant recipients undergo MRI screening 3 years after implantation and every other year thereafter to determine whether an implant has ruptured. However, even in the best studies, there is at least a 15% false-positive rate, Dr. Adams noted.

This means that a woman might be rescheduled for breast implantation surgery only to have the surgeon discover the implant was intact.

In addition, "MRIs aren't much fun for the patient; they're loud, the patient has to lie still for a long time, and they are very expensive," said Dr. Adams.

Because of this, very few women ever go for an MRI, especially when their implants seem to be fine, he said.

In fact, rotation is not an issue with round breast implants; orientation is an issue only for implants that resemble the natural shape of the breast, where rotation could result in a misshapen breast. Rotational status cannot be determined with MRI.

The researchers evaluated 74 patients with bilateral shaped cohesive gel implants using ultrasound. Of the implants in this cohort, 48 were Allergan 410 and 100 were Mentor CPG.

Both types of implants have a textured outer shell and untextured fiducial markers on their surface at the lower pole, which allow the surgeon to feel and assess implant orientation during surgery, the researchers report. It was previously assumed that textured implants become anchored to the surrounding tissue and do not rotate.

The fiducial markers were imaged using a Terason 2000+ ultrasound system with a TouchView linear array probes.

The ultrasound examination itself is painless and nonthreatening, much like the fetal–maternal ultrasound screening many women are familiar with, Dr. Adams noted.

Marker orientation relative to the nipple was determined by using a clock-hand position, where 6 was directly downward and 3 directly to the right. Any orientation between 5 and 7 o'clock was considered to be "unrotated."

On ultrasound examination, which took place 6 months to 7 years after implantation, 25% of the Mentor CPG implants and 21% of the Allergan 410 implants had rotated from their original position.

"The vast majority of these rotations will 'self-reverse' and the implant will reorient itself over time, so it's somewhat of a dynamic process," said Dr. Adams.

"Still, my personal opinion is that ultrasound will eventually replace MRI. It just has to have FDA 'blessing' before surgeons can openly recommend it," he explained.

The percentage of women who follow the FDA recommendation and go for MRI screening is not known, said Brad Bengtson, MD, from the Bengtson Center for Aesthetics and Plastic Surgery in Grand Rapids, Michigan. However, he told Medscape Medical News that he would be "shocked" if it were over 3%.

Dr. Bengtson and his colleagues published the first landmark evaluation of high-resolution ultrasound for the detection of breast implant shell failure (Aesthet Surg J. 2012;32:157-174). They concluded that the ultrasound approach is equivalent to MRI in terms of visualization of implant rupture, but that its relative accessibility, affordability, and real-time visualization represent "significant potential advantages" over MRI for this indication.

"Since our original research began in 2012, we have imaged more than 500 patients and detected more than 80 patients with implant shell failure. And in every patient with a rupture who has gone to surgery, shell failure has been confirmed, with no false-positives to date," Dr. Bengtson reported. "Patients need a better solution than MRI to follow their breast implants over time; unquestionably, that technology is high-resolution ultrasound."