Disease etiology
The etiology of gallbladder polyp-like lesions is not clear, but it is generally believed that the occurrence of the disease is closely related to chronic inflammation, among which inflammatory polyps and adenomatous hyperplasia are both inflammatory reactive lesions, and cholesterol polyps are the result of systemic lipid metabolism disorders and local inflammatory response of the gallbladder.
Pathophysiology
The pathology is classified into two categories: non-neoplastic lesions and neoplastic lesions, the latter being subdivided into benign and malignant.
I. Non-neoplastic polyps
1, cholesterol polyps: cholesterol polyps are the most common among non-neoplastic lesions. They are followed by inflammatory polyps, adenomatous hyperplasia and adenomyoma. Cholesterol polyp is a local manifestation of abnormal cholesterol metabolism, which is caused by the precipitation of cholesterol-like lipids in the blood and phagocytosis by the tissue cells of the gallbladder wall. Histologically, polyps consist of an accumulation of foamy histiocytes covered by a single layer of columnar epithelium with connective tissue tips, microvessels, and branching villi-like projections. The pathology of cholesterol polyps is characterized by multiple small polyps. In contrast, neoplastic polyps tend to be single. Cholesterol polyps are brittle and thin, easily separated from the mucosa, without intestinal metaplasia or atypical hyperplasia, and without other stromal components. The inflammation, if any, is mild and no carcinoma has been reported so far. Regarding cholesterol polyps and cholesterolosis, some believe that they are the same disease, while others believe that cholesterolosis is the cause of cholesterol polyps. Cholesterol deposited in macrophages in the lamina propria of gallbladder mucosa gradually protrudes to the mucosal surface, prompting the mucosal epithelium to proliferate, increasing the ro-A sinus and thickening the muscle layer to form polyps; however, some people think that the two are not related.
2, inflammatory polyps: due to chronic inflammatory stimulation, can be solitary, or multiple, generally 3-5 mm in size, thick or inconspicuous tip, similar in color to the adjacent mucosa or slightly red, solitary or multiple broad-based nodules. Histology showed focal glandular epithelial hyperplasia with vascular connective tissue mesenchyme and marked inflammatory cell inflammatory polyps, granulomas due to inflammatory stimulation, and marked inflammation of the gallbladder wall surrounding the polyps. No carcinogenesis has been reported, but from the study of carcinogenesis of gallbladder cancer combined with gallstone, it is believed that bacterial chronic cholecystitis may be one of the factors, so the inflammatory polyps cannot be relaxed to observe.
Adenomatous hyperplasia and adenomyoma: Adenomatous hyperplasia is a kind of hypertrophic lesion of gallbladder wall caused by the proliferation of gallbladder epithelium and smooth muscle, which is divided into 3 types.
(1) Limited type: cone cap-shaped thickening at the base of the gallbladder.
(2) Segmental type: localized thickening of the cystic wall protrudes into the lumen to form the “triangular sign”, diffuse centripetal thickening, unevenness of the inner wall, narrowing of the lumen, sometimes accompanied by stones, and hypercontraction of the gallbladder as shown by lipid meal test.
(3) Extensive type: the gallbladder wall is extensively hypertrophied, the inner wall is uneven, and the dilated ro-A sinus is visible in the wall as a small cystic hypoechoic area. The hyperplasia of the epithelium is most evident in the center of the lesion, and the surrounding glands are often cystically dilated and filled with mucus, with calcium deposits in the dilated glands. Adenomatous hyperplasia and adenomyosis are both proliferative lesions that are neither inflammatory nor neoplastic. The former are soft yellow warts, about 5 mm in diameter, solitary or multiple. They consist of abundant connective tissue containing smooth muscle bundles and cupped cells, with surface epithelial hyperplasia and intestinal metaplasia. In the latter case, there are localized changes in the mucosal epithelium, myofibrillar hyperplasia and limited adenomyosis, also known as adenomyomatosis. Both of these lesions may be cancerous.
Tumor polyp: adenoma is the main benign lesion, while malignant is mainly gallbladder cancer.
1.Adenoma: Adenoma is mostly a single tipped polyp. According to the appearance, it can be divided into papillary or non-papillary, and the malignancy rate is about 30%. Papillary adenomas can be subdivided into two types: tipped and non-tipped. Microscopically, they are branching or dendritic structures with thin vascular connective tissue tissues, attached to the wall of gallbladder, covered by a single layer of cuboidal or columnar epithelium, and migrating well with the surrounding normal gallbladder mucosa epithelium. Most of the non-papillary adenomas have tissues, and most of the hyperplastic glands are seen microscopically surrounded by a moderate amount of connective tissue mesenchyme, and occasionally the glands show cystic expansion. This type of adenoma is dominated by tubular proliferation of glands, hence the name adenoductal adenoma, and sometimes intestinal epithelial metaplasia of cupular or basal granular cells is seen. The incidence of adenoma is very low, and although it has the possibility of cancer, it does not pose a clinical threat.
2.Benign mesenchymal tissue tumor: benign mesenchymal tissue tumor is a benign tumor of gallbladder derived from supporting tissue. They mainly include fibroma, smooth muscle tumor, hemangioma, lipoma, mucinous tumor, nerve sheath tumor, etc.
Adenocarcinoma: Adenocarcinoma is divided into papillary type, nodular type and infiltrative type. The first two types of adenocarcinoma are bulging lesions with a diameter of <20 mm, while the infiltrating type is not a polyp and most of them are >20 mm in diameter. Most of the papillary type adenocarcinomas are confined to the mucosa and muscular layer and have a better prognosis.
III. Diagnosis
Gallbladder polyps often have no clinical symptoms or mild symptoms. The diagnosis mainly relies on imaging. There are many diagnostic methods for gallbladder polyp-like lesions, such as oral cholecystography, ultrasound, CT, magnetic resonance imaging (MRCP), intracavitary ultrasound (EUS), etc. However, the most important means to diagnose gallbladder polyps is still ultrasound.
1.B ultrasound examination
Ultrasound typically shows strong or slightly strong echogenic clusters in the wall of the gallbladder in the form of points, small pieces or sheets, followed by no acoustic shadowing, spherical, mulberry, papillary and nodular prominence, and even the tips of polyps. CT can clearly show the location, size, number of gallbladder polyps and local changes of gallbladder wall, which is a simple and reliable diagnostic method.
2.Three-dimensional ultrasound imaging
It can make the gallbladder have a three-dimensional sense of spatial orientation, good sound transmission, and the effect of direct view of the gallbladder profile, which can make up for some shortcomings of two-dimensional imaging. It can not only observe the size and shape of gallbladder polyps, but also distinguish the relationship between polyps and gallbladder wall, especially the polyps in the posterior wall of gallbladder. 2D imaging often cannot clearly distinguish whether there is a tip and the scope and depth of the tip attached to the gallbladder wall. Three-dimensional reconstruction can observe the continuity of the lesion and the surface of the lesion through the rotation of different sections, which can help to improve the differentiation between gallbladder polyps and adenoma or cancer of gallbladder.
3.Endoscopic ultrasound
That is, transendoscopic ultrasound scan, which is a tiny ultrasound probe placed at the top of the endoscope with a high frequency probe, inserting the endoscope into the digestive tract and entering the duodenal jugular after this probe is closer to the gallbladder, which can exclude the influence of intestinal gas interference or bile viscosity. Endoscopic ultrasound can divide the gallbladder wall into 3 layers, the inner layer is the highly echogenic mucosa and submucosa, the middle layer is the hypoechoic muscle fiber layer, and the outer layer is the highly echogenic subplasma and plasma membrane layer. In the case of polyp-like lesions, the 3 layers of the cystic wall are clearly visible, while in the case of gallbladder cancer, the 3 layers of the cystic wall have different degrees of infiltration and destruction. Most of the early gallbladder cancers develop under the cover of lesions such as stones and polyps, and lack of characteristic sonographic manifestations in early stages makes identification difficult. However, endoscopic ultrasonography can help the differential diagnosis by observing the relationship between polyp-like lesions and gallbladder wall.
4.CT simulation endoscopy technique
The imaging principle of CT simulation endoscopy is to use the computer software function to post-process the image data obtained from the spiral CT volume scan to reconstruct a three-dimensional image of the inner surface of the cavity organ, similar to that seen by endoscopy. Biliary CT simulation endoscopy technology has also begun to be used in clinical applications. the value of clinical applications of CT simulation endoscopy technology.
1, CT simulation gallbladder endoscopy can clearly display the normal anatomical structure in the gallbladder cavity.
2, CT simulation endoscopy technology can clearly display the size of gallbladder polyps, the smallest visible 1, 5mm × 2, 2mm × 2, 5mm, can be more accurately observed polyp growth site, morphology, surface, substrate and other image changes, and color ultrasound and surgical pathology is basically the same.
3.It can accurately observe the single polyp of gallbladder.
The advantages of CTVE in the diagnosis of gallbladder polyp examination are more prominent, but there are also some shortcomings.
1.The polyps with flat and wide base are not well displayed, and the roughness of the gallbladder wall may affect the detection of small polyps.
2. Patients with iodine allergy are not suitable for this test and are susceptible to iodine concentration in the gallbladder.
Differential diagnosis
Color Doppler ultrasound shows high-speed arterial blood flow signal in the mass and gallbladder wall, which is an important differentiating feature of primary gallbladder cancer from benign masses and metastatic cancer. For example, blood flow in cholesterol polyps is linear with <500px/s, while blood flow in gallbladder cancer is mostly dendritic with flow velocity >500px/s.
The positive rate of finding cancer cells in bile for early-stage gallbladder cancer is 64%, while the positive rate in the diseased gallbladder wall is 91%. Therefore, it is emphasized to selectively puncture the diseased wall tissue under B ultrasound guidance. The concentration of carcinoembryonic antigen was also measured during gallbladder aspiration, and the increase in concentration was statistically significant compared with that of simple gallbladder stones, which also has auxiliary diagnostic value.