Ultrasound of non-organic retroperitoneal masses

Comprehensive ultrasound examination of non-organ retroperitoneal formations

The retroperitoneal space is located between the posterior leaflet of the parietal peritoneum and the posterior wall of the abdominal cavity, which is formed by the bodies of the vertebrae, the four lower ribs and the preperitoneal fascia covering the crura of the diaphragm, the quadratus lumborum and the iliac muscles. The upper boundary of the space is the diaphragm, the lower boundary is the promontory and the innominate line, and the lateral boundaries are the inflection points of the parietal peritoneum.

In the retroperitoneal space, in the tissue stratified by fascia, are the kidneys with ureters, adrenal glands, abdominal aorta with large branches, inferior vena cava with a number of large tributaries, ascending lumbar veins, initial sections of vv. Azygos and hemiazygos, autonomic nerve plexuses, lumbar section of the sympathetic nervous system. Retroperitoneal organs also include the duodenum (except for the initial section), pancreas (except for the tail). The above determines the diversity of clinical forms and differences in the genesis of primary non-organ retroperitoneal tumors.

Summarizing the data on the characteristics of non-organ retroperitoneal formations (NRP), it should be noted that:

1. There is no specific clinical picture of NZO. The diversity of clinical signs of the disease is due to the fact that NZO can spread from the diaphragm to the small pelvis, and only the localization of the tumor determines the development of pathognomonic clinical symptoms.
2. The leading characteristics of the general condition are signs of tumor intoxication and weight loss. The discrepancy between the large size of the tumor and the low degree of its impact on the body over a long period of time is a characteristic feature of NZO.

It is generally accepted that B-mode ultrasound is a screening method in the diagnosis of abdominal and retroperitoneal tumors. Based on the B-mode examination data, it is possible to obtain information about the size, shape, and structure of the tumor. Despite the fact that there are different points of view in the literature, B-mode ultrasound data provide fairly specific information about the structure of individual nosological forms of NZO, such as tumors from adipose tissue, some neurogenic formations, and teratomas.

To clarify the location of the neoplasm and resolve the issue of its resectability, V.V. Tsvirkun proposed a scheme for dividing the retroperitoneal space into 5 zones, numbered clockwise:

1. between the diaphragm above, the aorta on the left, the left renal artery below and the lateral abdominal wall on the right;
2. between the left renal artery above, the aorta on the left, the left iliac artery below and the lateral abdominal wall on the right;
3. pelvic - below the iliac arteries and the innominate line;
4. between the right common iliac artery below, the infrarenal segment of the aorta on the right, the lateral abdominal wall on the left and the right renal artery above;
5. between the right renal artery below, the suprarenal segments of the aorta on the right, the lateral wall on the left and the right dome of the diaphragm above.

Based on the ultrasound image of the main arteries and veins, it is necessary to analyze their anatomical location and course relative to the neoplasm. In this case, the anatomical course of the vessels may have the following options: unchanged, changed, or located in the structure of the neoplasm. Registration of the LSC allows us to judge the state of hemodynamics in the studied vessels, taking into account the presence or absence of local changes in blood flow. Thus, according to the data of Yu.A. Stepanova, among 60 studied NZO, changes in the anatomical course of the vessels were detected in 76.7% of observations, of which 65.9% of patients were diagnosed with hemodynamically significant extravasal compression in this area. In case of recurrent tumors, changes in the anatomical course of the main vessels are possible.

The vessels encircling the tumor are visualized only in case of malignant genesis of the tumor. The source of these vessels can be the lumbar arteries, inferior vena cava, iliac arteries and veins. The examined vessels with a diameter of 1.5-3.0 mm are represented by arteries with collateral blood flow and veins with a monophasic blood flow spectrum. However, in case of large tumors, polycyclic and/or multinodular form, difficulties may arise in determining the presence and recording the anatomical course of the vessels. encircling the tumor. In some cases, the lumbar and iliac vessels are the source of vessels involved in the blood supply to the NZO. Using the CDC and/or EDC mode, it is possible to trace their anatomical course to the tumor. register the diameter (1.5-5.0 mm), and determine the nature and magnitude of the blood flow.

Diagnostics of various variants of intratumoral angioarchitectonics is one of the interesting and poorly studied issues. When interpreting the angioarchitectonics data of NZO, the degree of their vascularization should be assessed. NZO can be hypervascular, hypo- and avascular. The degree of vascularization depends on the type, size of the tumor and the nature of its blood supply. We compared the results of morphological examination of non-organ tumors and color Doppler scanning data. The data we obtained allowed us to analyze the angioarchitectonics of retroperitoneal formations of various genesis and to identify some of their features. Thus, the analysis of the angioarchitectonics of 80 NZO, according to Yu.A. Stepanova, showed that intratumor blood flow is not detected in lipoma. The following tendencies are observed in liposarcoma: when the tumor size is less than 5.0 cm, data on the presence of intratumoral blood flow were not obtained in any observation, but as the tumor increases, single arteries with collateral blood flow and veins are detected. Large tumors are predominantly hypervascular. Numerous arteries and veins are recorded in them. Recurrent tumors are usually hypervascular. The vascular network inside the tumor increases with each new relapse. Apparently, this circumstance can explain the absence of foci of decay in liposarcoma, unlike leiomyosarcoma. The intratumoral network inside leiomyosarcoma is represented by arteries and veins, but it is insignificant even when the tumor size is more than 15.0 cm. Intratumoral blood flow was not detected in hemangiomas, lymphangiomas, and in systemic diseases. In malignant morphological forms, arterial and venous blood flow was diagnosed in patients with rhabdomyosarcoma, hemangiasarcoma, lymphangiosarcoma, mesenchymoma, neurosarcoma, and tumors of unknown genesis. The described ultrasound images at the level of tumor vessels abound in various variants, which is associated with the diversity of morphological types of tumors, different genesis, and individual features of their blood supply.

Summarizing the presented data on the possibilities of color Doppler scanning in examining patients with NZO, it should be emphasized that the method allows to specify the localization of the neoplasm and determine the relationship with the main vessels, identify the sources and routes of blood supply to neoplasms, it is one of the leading methods in assessing regional angioarchitectonics in the NZO zone. Such a volume of information on the anatomical and functional state of the arteries and veins of the abdominal cavity and retroperitoneal space helps surgeons decide on the nature and scope of surgical intervention in this category of patients.

However, CDS also has its limitations: ultrasound imaging of the vascular system is only possible in individual segments; if the blood flow velocity in a vessel is low, it is not possible to trace its anatomical course.

Three-dimensional reconstruction of ultrasound images includes examination in B-mode, ultrasound angiography mode, and a combination of B-mode and ultrasound angiography. The use of three-dimensional reconstruction in B-mode when examining patients with NZO allows for the following: a clearer image of the structural features of the formations being examined due to the transparency of the image; a greater volume of information about the condition of adjacent tissues and structures due to their unification into a single visual array; advantages in assessing the marginal zone and shape of the pathological focus.

Such information allows us to clarify the details of the structural features of the neoplasm, however, the data obtained using a combination of B-mode and ultrasound angiography are of great clinical significance.

Three-dimensional reconstruction using a combination of B-mode and ultrasound angiography allows visualization of major vessels over a greater length, in some cases tracing the anatomical course that is not determined by color Doppler scanning. The ability to visualize medium- and small-caliber vessels is especially improved, which allows more thorough tracing of their anatomical course. This information is especially important in diagnosing vessels involved in the blood supply of the neoplasm and vessels enveloping it, as well as intratumor vessels. Using a combination of B-mode and ultrasound angiography allows for correct correlation of the anatomical location of vessels relative to the tumor and obtaining a complete picture of the angio-architectonics of non-organ retroperitoneal formations. Color Doppler scanning and three-dimensional reconstruction complement each other, which gives grounds to propose these two methods for complex use in ultrasound examination of patients with non-organ retroperitoneal formations.

Analyzing our material based on the results of examination of patients with NZO using three-dimensional reconstruction, we believe that the indication for three-dimensional reconstruction is to clarify the anatomical features and location of the vascular system in the area of the non-organ retroperitoneal formation.

Thus, the use of the latest ultrasound technologies - color Doppler scanning and three-dimensional reconstruction of abdominal vessels - has shown that non-invasive ultrasound diagnostics is reaching a qualitatively new level, allowing participation in the selection of treatment tactics for patients.