C. Y. Kazakaov, C.D. Muratova, S.I. Akbarov, X.T. Yusufzoda CURRENT RADIOLOGY OPTIONS FOR VARIOUS LIVER DISEASES
The modern radiology diagnosis of diseases of the abdominal cavity is completely different from the roentgenology of the digestive tract of the 40-70s of the twentieth century. For decades, only review pictures, barium contrasting of the stomach and intestine, and cholecystography were used to study this anatomical zone. Possibilities to assess the liver, pancreas and bile ducts, and extraorganic tumors were limited and based mainly on indirect signs. With the development of endoscopy the frequency of using X-ray methods for esophagus, stomach and large intestine examinations began to decrease.
Key words: radiology, liver, ultrasound, CT and MRI.
Introduction. Radiation diagnosis of liver disease today is mainly based on the use of ultrasound, CT and MRI, and less frequently PET. The use of radiodiagnostic methods in major liver diseases depends on the characteristics of the disease itself and the capabilities of the method. In diffuse liver disease, radiological diagnostic methods play an auxiliary role. They are used for differential diagnosis (exclusion of tumor lesions), assessment of the size and structure of the organ, and dynamic monitoring. For example, in hepatitis (viral, toxic, and alcoholic), the findings of radiological diagnostic methods are nonspecific. The liver may be enlarged or reduced in size, and there may be signs of heterogeneous liver structure on ultrasound. Diffuse enlargement of the liver may be seen. The diagnosis of fatty liver infiltration by radiological methods is quite reliab. Typically, areas of fatty infiltration alternate with areas of normal liver parenchyma. Fatty infiltration does not result in disruption of hepatic vascular architectonics or mass effect. The pattern of fatty infiltration can undergo rapid dynamics, which has important differential diagnostic and prognostic value. On ultrasound, fatty liver dystrophy is clearly visible. It appears as diffuse changes in the liver with reduced echogenicity, interspersed with areas of unchanged tissue. The CT scan shows a significant decrease in the density of the liver parenchyma (up to 20-30 Hounsfield units). Due to decreased density, the affected segments become clearly visible against the background of unchanged sections of hepatic tissue and liver vessels. Normally the density of the liver is slightly higher than that of the spleen. Therefore, with fatty infiltration, a decrease in liver tissue density can be seen even without the aid of densitometry. MRI is rarely used to confirm the diagnosis, as ultrasound and CT scanning are sufficient for this purpose. However, if MRI is performed in these patients, special examination programmes (pulse sequences with signal suppression from fatty tissue) are used. In the diagnosis of liver cirrhosis, the informative value of radiological diagnostic methods is significantly higher. A distinction is made between macronodular, micronodular, and mixed forms of cirrhosis. In micro-nodular cirrhosis the liver is reduced in size and significantly thickened, and there is little regenerative activity. In macronodular cirrhosis there are multiple nodules of regeneration, some of them multilobular, with septa. The main criteria for diagnosis of cirrhosis are a reduction in liver size (the liver may be enlarged in the initial stages of the disease), the detection of multiple nodules of regeneration, the presence of signs of portal hypertension, splenomegaly and ascites. CT, ultrasound and MRI are the most diagnostic tools. Evaluation of the portal vein and hepatic vein blood flow pattern by ultrasound Doppler imaging may help to assess the degree of venous blood flow abnormality in the organ. Sometimes it is necessary to differentiate between hepatic cell carcinoma and regenerative nodules in cirrhosis. In difficult to diagnose cases a puncture biopsy is used. It can be performed under ultrasound or CT scanning to increase the accuracy of the biopsy and reduce the risk of complications. In a number of liver diseases associated with metabolic abnormalities, radiotherapy can provide specific symptoms to facilitate diagnosis. Examples include Konovalov-Wilson disease and haemochromatosis. Hepatocerebral dystrophy (Konovalov-Wilson disease) is caused by disorders of copper metabolism, which is deposited in the liver, kidneys and brain. Examination of the liver reveals various degrees of hepatitis or cirrhosis. Most important, however, is the characteristic increase in the density of the liver parenchyma on CT scan (or increased signal intensity on MRI). This is due to the increased content of copper ions in the organ. In hemochromatosis (primary or secondary) there is an increased accumulation of iron in the cells of the reticuloendothelial system. Correspondingly the character of liver CT scan images (increased density) and MRI signal changes (low signal intensity from liver parenchyma both on T1 and T2-weighted images). The latter is explained by peculiarities of magnetic properties of iron oxides in cells of reticuloendothelial system. Diagnostics and differential diagnostics of volumetric liver neoplasms is extremely important. These include simple liver cysts, parasitic diseases, abscesses, echinococcosis and alveococcosis, metastases of organ tumors, and primary liver tumors. Simple liver cysts are quite common. On ultrasound and tomography images, they are of various sizes, have thin walls, and
© C.Y. Kazakaov, C.D. Muratova, S.I. Akbarov, X.T. Yusufzoda, 2022.
have homogeneous contents with characteristics characteristic of a fluid with a density close to water. There are no vessels inside the cysts. The contents of simple cysts are not reinforced by the administration of a contrast agent. Liver cysts occur in 20-40% of patients with polycystic kidney disease. All radiodiagnostic techniques -ultrasound, CT, MRI - allow liver cysts to be detected with a high degree of accuracy. Liver abscesses can have different origins. The most common are microbial (E. coli, streptococcus, anaerobic infection) and parasitic (ame-bic) liver abscesses. Infective abscesses can occur after liver trauma, surgery, cholangitis, sepsis, and portal vein phlebitis. Doppler ultrasound shows increased vascularisation of the capsule, no signal from the blood flow inside the abscess cavity. On ultrasound, the liver abscess appears as a round structure with a dense, jagged capsule with thick walls and an irregular inner surface. A dense liquid content is present inside, and there may be gas. Amebic abscesses are characterized by a thick capsule with multiple internal membranes, no gas accumulation within the abscess, and often multiple lesions. A similar picture is obtained using CT and MRI scans. In doubtful cases, intravenous contrast is resorted to. Contrast enhancement of the abscess capsule and detection of gas bubbles in the abscess cavity allows a correct diagnosis. Radiological diagnostic techniques (most often CT scan and ultrasound) are used to perform various manipulations to treat abscesses, such as puncture and drainage. The liver, spleen and lungs are the main organs of dissemination of echinococcus and alveococcus larvae. Lesions of other organs (kidneys, moths, heart, etc.) are much rarer. Initially, after infection, the cysts are small (2-3 mm) and difficult to identify. As they grow, diagnosis becomes easier. For all methods, the most characteristic feature of echinococcosis is the presence of cysts of varying sizes with clear, thin and smooth walls in the liver. The diagnosis of echinococcosis is facilitated if daughter cysts are found inside or outside the mass. In 30% of cases of echino-coccosis, the walls of the cyst are calcified. If the parasite has died, there is often partial or complete detachment of the inner membrane, which becomes clearly visible inside the cystic cavity. In alveococcosis the cysts are multiple, with indistinct contours due to infiltrative growth with inflammatory and necrotic reactions at the periphery of the cysts. The density inside the cyst is higher than in echinococcosis. Therefore, the mass may resemble a growing tumour. Focal liver lesions include benign and malignant liver tumors and metastases of organ tumors to the liver. Among benign tumors, hemangiomas, focal nodular hyperplasia, and hepatic adenomas are the most common. Haemangioma is the most common benign liver tumour. It occurs in 1 -5% of the adult population. In the vast majority of cases hemangiomas are found incidentally by ultrasound or CT scan of the liver. Very rarely giant (>10 cm) hemangiomas can present with clinical symptoms due to compression, thrombosis, or hemorrhage. On ultrasound, a haemangioma appears as a round mass with multiple small vessel signals within the tumour. On the CT scan, hemangiomas typically appear as round, low-density masses with clear contours. If a hemangioma-like mass is detected, intravenous contrast is mandatory. A characteristic feature of hemangiomas is the centripetal (peripheral to central) sequence of filling the hemangioma with contrast media. In MRI, because of the long relaxation time on T2-weighted images, the tumour is characterised by a very bright image against a darker liver parenchyma. In dynamic contrast-enhanced MRI with gadolinium, the pattern of contrast filling of the tumour is the same as in CT scanning. Large hemangiomas can have an atypical appearance - extended central areas that do not or do not accumulate contrast (scarring, hyalinosis). In rare cases, liver scintigraphy with labelled red blood cells or angiography is used to diagnose haemangiomas. Focal nodular hyperplasia is a rare benign liver tumour that usually occurs in young women (up to 75% of cases). It consists of hepatocytes, kupffer cells and bile ducts. There is usually a scar in the central part of the liver, from which septa (septa) branch off. It can be multiple. On imaging, this tumour is characterised by the absence of a capsule, a homogeneous structure, and hypervascularity. Without contrast enhancement, the tumour usually has the same signal characteristics as the liver parenchyma. A large tumour can cause hepatic vascular abnormalities. This tumour is hypervascular, and it is well-detected on a dynamic CT or contrast-enhanced MRI in the arterial phase. A hypointense central rumen is usually clearly visible, which accumulates contrast media in the lag phase, while the tumour parenchyma becomes barely distinguishable from the normal liver. An adenoma is a rare benign liver tumour consisting of hepatocytes. It is supplied by one or more accessory branches of the renal artery. On ultrasound, CT or MRI, it looks like a large mass, often surrounded by a thin pseudocapsule (a zone of fibrosis). Areas of haemorrhage can be seen in the tumour tissue, and there is no central rumen. On contrast-enhanced CT and MRI, the adenoma contrasts predominantly in the arterial phase. There is a non-homogeneous increase in density. It is sometimes difficult to differentiate between adenoma and hepatocellular carcinoma. Malignant liver tumours are divided into primary and secondary (metastases). Among malignant tumors, hepatoma (hepatocellular cancer) is common, and cholangiocarcinoma (cholangiocel-lular cancer) is less common. Hepatocellular cancer (hepatoma) is the most common primary liver tumour. Patients with cirrhosis, hepatitis B and C, or haemochromatosis are at increased risk of developing a hepatoma. A distinction is made between nodular (solitary), multinodular, and diffuse forms of the disease. Invasion of the tumor into portal and hepatic veins is common (up to 30% of cases). Hepatoma may metastasize to other organs (lungs, bones, lymph nodes). The images of hepatoma obtained by radiological methods of diagnosis are quite diverse. The tumour is characterised by non-homogeneous internal structures, intratumoural septa, central scar, necrotic or cystic areas, capsule, and presence of daughter nodes may be detected. The tumour may infiltrate blood vessels, have
calcium inclusions, and be accompanied by ascites. Hepatomas are usually characterized by increased vasculari-zation and arterio-venous shunts. For this reason, they are best seen in the arterial phase when performing ultra-sound-doppler imaging, angiography or CT or MRI with contrast. In the diagnosis of hepatoma, radiological methods allow the size and location of the tumour and reveal local intrahepatic metastases and hepatic vein invasion. This information is very important in determining treatment and prognosis. Cholangiocellular cancer (cholangio-carcinoma) is a malignancy growing from the intrahepatic bile ducts. On ultrasound or CT scan it can appear as hypodense (hypointense on MRI) or as a multifocal mass with infiltrative growth along the bile ducts. The most striking manifestation of the disease is a marked dilation of intrahepatic bile ducts above the place of their obstruction by a tumor and contrasting of a tissue of a mass. CT, MRI and especially MR cholangiography facilitate diagnostics of tumorous affection of bile ducts. Cholangiocarcinoma affecting area of intrahepatic bile ducts fusion and causing their obstruction is called Clatzkin's tumour. The disease should be differentiated from cases of benign congenital cystic dilatation of the bile ducts (Caroli disease). Among all focal liver lesions, the detection of malignant liver metastases is of great importance. The detection of even a single small metastasis to the liver changes the stage of the process and, therefore, the choice of therapy and the prognosis of the disease. All methods of modern radiodiagnostics allow visualisation of liver metastases. Their sensitivity and specificity range from 7590% and depend on the characteristics of the method itself, the method of examination, histological structure, vascularisation and the size of the lesions. Most commonly, ultrasound is indicated as an initial examination. In complicated situations, the diagnostic algorithm is extended. A CT scan with multiphasic contrast and/or an MRI scan (also with contrast) are performed. Liver metastases are found in about 30-40% of patients who die of malignant disease. The most common sources of liver metastases are intestinal, gastric, pancreatic, lung, and breast cancer. Tumours from other organs may also metastasize to the liver. On ultrasound and tomography, liver metastases can be seen as multiple soft tissue lesions (penny symptom). Depending on the histology of the primary lesion, they can be hypervascular or hypovascular (most often). The appearance of metastatic foci on CT scans and the change in their density (intensity on MRI) during contrast exposure largely depend on the vascularisation. Occasionally there are metastases with calcinates or with a marked cystic component. In doubtful cases, PET or 18-FDG PET/CT can help in the diagnosis of metastatic lesions. Radiological methods are important in the diagnosis of portal hypertension. Portal hypertension syndrome occurs in a number of diseases: thrombosis and compression of the portal vein and its branches, cirrhosis, cholangitis, congestive heart failure and other diseases. It is therefore mandatory to examine and describe the vascular condition of the liver and spleen when examining the abdominal organs. Portal hypertension is diagnosed on the basis of portal vein enlargement, detection of collateral varices, splenomegaly, and ascites. When portal vein thrombosis or Budd-Chiari syndrome (hepatic vein thrombosis) is diagnosed, an angiographic CT or MRI scan plays a major role. Ultrasound Doppler can determine the velocity and direction of blood flow in the portal and splenic veins. Diseases of the spleen are much less common than those of the liver. Diagnosis is by ultrasound and CT scan, less commonly by MRI. Benign tumours such as hamartomas and haemangiomas can occur in the spleen. Metastases and lymphoproliferative diseases (lymphogranulomatosis, lymphoma) are the most common malignancies. Primary malignant tumours of the spleen are very rare. The principles of diagnosing spleen lesions are the same as those of the liver. Trauma to the spleen leads to bruising and rupture of the organ. Accurate information about the condition of the spleen influences the choice of treatment. Diagnosis is usually urgent. Therefore, ultrasound and CT scanning are of prime importance. Both ultrasound and CT scans can quickly provide comprehensive information. Embologenic infarcts of the spleen in the acute stage are well detected by contrast-enhanced CT or MRI. In the chronic stage, calcinates can be detected by CT at infarct sites.
Conclusions: Despite advances in radiology diagnosis, there is still no single universal method of diagnosing abdominal diseases. Their choice and method of examination largely depend on the nature of the suspected disease, the severity of the process and the leading clinical syndrome. However, it is clear that the role of ultrasound and CT scanning continues to increase. These techniques are increasingly used in acute, emergency situations, and have also begun to be used for the examination of hollow organs (intestine, stomach). MRI and PET are of great importance in the diagnosis and differential diagnosis of liver tumours.
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SARDOR YUSUFKAZAKAOV- master of radiation diagnostics and therapy department, Samarkand State Medical Institute.
MURATOVA SEVARA DILSHOD KIZI - resident at the department of radiation diagnostics and therapy, Samarkand State Medical Institute.
AKBAROVSARDOR IKROM UGLI - resident at the department of postgraduate education in medical radiology, Samarkand State Medical Institute.
YUSUFZODA HOSIYAT TURONKIZI - resident at the department of postgraduate education in medical radiology, Samarkand State Medical Institute.