Hepatic veno-occlusive disease

　　1. Etiology

　　Factors such as certain biological toxins, chemical drugs, etc., can lead to edema and thickening of the small hepatic veins, followed by stenosis and occlusion, accompanied by corresponding lesions in the intraportal veins within the liver. The most commonly reported cases are caused by the intake of herbal medicines containing toxic alkaloids such as swainsonine, such as swainsonine, swainsonine, swainsonine, and swainsonine, as well as chemical drugs such as urane, vinblastine, azathioprine, etc. It can also be caused by aflatoxins, dimethyl nitrosamine, radiation, treatment, etc.

　　Other factors that may cause HOVD include: ① arsenic, mercury, and other toxic substances; ② congenital or acquired immunodeficiency syndrome; ③ estrogens, etc.

　　2. Pathogenesis

　　In the acute phase, the liver volume increases and the surface is smooth, with signs of lymphatic dilation and 'liver crying'. Under the light microscope, the intima of the central vein and sublobular veins is significantly swollen, with luminal stenosis or occlusion, obstructing blood flow. The sinusoids are significantly dilated and congested, accompanied by varying degrees of cloudy swelling, degeneration, and necrosis of hepatocytes. In severe necrotic areas, hepatocytes disappear, the reticular fibrous framework remains, red blood cells infiltrate the sinusoids and Disse's space, presenting typical hemorrhagic necrotic changes.

　　In the subacute phase, the liver surface shows reticular regional contraction, with endothelial proliferation and thickening of the central vein and sublobular veins, leading to fibrosis, luminal stenosis, and occlusion. During this phase, there may still be sinus dilation, congestion, and hemorrhagic necrosis of hepatocytes, with fibrosis of the central vein and no formation of pseudo-lobules.

　　The liver in the chronic phase further hardens, with atrophy of hepatocytes in the central area of the hepatic lobules, collapse of the reticular framework, and proliferation of fibrous tissue. The formation of pseudo-lobules can be seen, eventually leading to nodular cirrhosis. In some cases, portal vein fibrosis and thrombosis may occur, but the main hepatic vein is rarely affected.

　　Solanine poisoning is often not limited to the liver, but can also cause similar lesions in the small pulmonary veins, which can manifest as pulmonary hypertension, pulmonary congestion, and hypertrophy of the right ventricle, which should attract clinical attention. Most patients may have gastrointestinal, respiratory, and systemic symptoms before onset. The onset is acute, with severe upper abdominal pain, distension, rapid enlargement of the liver, tenderness, ascites, and may be accompanied by symptoms such as decreased appetite, nausea, and vomiting. Jaundice and lower limb edema are rare, and there is often abnormal liver function. The characteristic of the subacute phase is persistent liver enlargement and recurrent ascites

　　The chronic phase is mainly manifested by portal hypertension, similar to other types of liver cirrhosis.

　　Most patients before onset may have gastrointestinal, respiratory, and systemic symptoms. The onset is acute, with severe upper abdominal pain, distension, rapid enlargement of the liver, tenderness, ascites, and may be accompanied by symptoms such as decreased appetite, nausea, and vomiting. Jaundice and lower limb edema are rare, and there is often abnormal liver function. The characteristic of the subacute phase is persistent liver enlargement and recurrent ascites. The chronic phase is mainly manifested by portal hypertension, similar to other types of liver cirrhosis.

　　There is currently no effective preventive measure for this disease. Early detection and early diagnosis are the key to the prevention and treatment of this disease. Attention should first be paid to and improvements should be made to those factors closely related to our lives, such as quitting smoking, reasonable diet, regular exercise, and weight loss. Appropriate exercise can strengthen the physique and improve the body's ability to resist diseases. Anyone who adheres to these simple and reasonable lifestyle common sense can reduce the chance of developing veno-occlusive disease of the liver.

　　Laboratory tests and imaging examinations are not characteristic, so for suspected cases, a careful history should be taken and analyzed, and necessary auxiliary examinations should be performed. The most decisive examination is laparoscopic direct liver tissue biopsy, which is not only reliable but also safe (it can observe the bleeding condition of the sampling site while applying effective hemostasis), but due to the insufficient understanding of this disease, it is rarely implemented, and the diagnostic value of hepatic and inferior vena cava angiography for this disease is limited, but it can be used to differentiate from Budd-Chiari syndrome.

　　Before and after each meal, attention should be paid to oral hygiene, and the mouth should be rinsed with saline. During meals, the patient should chew slowly. The diet should be varied. The nutritional principles are high calories, high protein, high vitamins, and low fat. Avoid foods that are刺激性 and have a lot of plant fiber and are hard, as this may cause massive bleeding due to esophageal variceal rupture. Abstain from smoking and drinking, and do not consume beverages containing alcohol to avoid increasing the burden on the liver and exacerbating the condition.

　　1. Treatment

　　For early suspected cases, it is necessary to stop contact, intake, and application of hepatotoxic substances in a timely manner. In the acute phase, the following comprehensive treatment plan should be adopted:

　　1. Supportive Therapy:Polarized fluid intravenous infusion can be adopted during the acute stage.

　　2. Anticoagulation and Anti-aggregation Therapy:Subcutaneous injection of low-dose heparin, that is, 6250U of heparin is injected subcutaneously every 12 hours, lasting for a week, while dextran 40 (low molecular weight dextran) is administered intravenously to improve the microcirculation of the liver, lung, and kidney.

　　3. When there is a large amount of ascites and it is relatively refractory, abdominal compartment syndrome may occur:Abdominal fluid ultrafiltration and purification should be performed under the cooperation of the hemodialysis center, and then returned to the vein to reduce protein loss, while reducing or avoiding the adverse effects of abdominal compartment syndrome on the heart, lungs, liver, and kidney function.

　　4. Prevention and Treatment of Infection:Broad-spectrum antibiotics should be used for patients with concurrent infections.

　　5. Intermittent Oxygen Therapy:Hyperbaric oxygen therapy can be given to those who have the conditions, which is more beneficial for severe patients. It can promote the elimination of hypoxemia in the circulatory system, reduce liver edema, improve the overall energy metabolism process, especially the regeneration process of the liver cell mitochondria.

　　There are many drugs to promote liver cell regeneration, such as hepatocyte growth factor, glucagon-insulin, phentolamine, etc., which can be applied according to circumstances.The former two have a promoting effect on the regeneration of liver cells, while the latter promotes the expansion of the blood vessels around the hepatic sinus, increases the application. The former two have a promoting effect on the regeneration of liver cells, while the latter promotes the expansion of the blood vessels around the hepatic sinus, increases the blood flow of the liver, and increases the oxygen uptake rate and utilization rate of the liver.

　　In the chronic stage, the liver hardens, and portal hypertension syndrome appears, and appropriate porto-systemic or porto-pulmonary shunt surgery can be selected. Partial splenectomy can be performed for patients with significantly enlarged spleen, while splenectomy is only performed for patients with mild or moderate splenomegaly. However, surgical retention of the spleen is only performed in cases where there is gastrointestinal bleeding and need for decompression and hemostasis, and combined shunt and truncation are performed. Liver transplantation can be performed according to circumstances for patients with liver failure.

　　II. Prognosis

　　Approximately half of acute HVOD patients recover within 2 to 6 weeks, 20% die of liver failure; chronic HVOD mainly dies of complications such as portal hypertension and liver cirrhosis, such as hepatic encephalopathy, secondary infection, etc. Improving the sensitivity to this disease and early detection, actively adopting comprehensive treatment can further improve the cure rate and reduce the mortality rate or disability rate.