Renal angiolipoma is a tumor formation of unclear etiology, mainly of a benign nature. Invasive growth into the vessels or germination of the organ capsule is extremely rare. It usually proceeds asymptomatically. With a size of more than 4 centimeters, lower back pain, hematuria, detection by palpation are possible, with neoplasia of more than 5 cm, there is a risk of spontaneous rupture with the development of retroperitoneal bleeding and the clinical picture of an “acute abdomen”. Diagnosis is made by ultrasound, MSCT, MRI, radiopaque angiography, biopsy with histological examination of tissues. In asymptomatic forms, treatment is limited to observation, surgical removal is performed according to indications.
ICD 10
D30.0 Benign neoplasm of the kidney
Meaning
Renal angiolipoma is a benign tumor that includes blood vessels, adipose tissue and a certain number of smooth muscle cells. The latter circumstance became the basis for the synonymous name of this formation – angiomyolipoma. It is a fairly common tumor lesion of the excretory system, but exact statistics are unknown due to the large number of asymptomatic forms of pathology.
The tumor affects women much more often than men, the share of the latter among registered patients is about 20%. It can be detected at any age, but most often the patients are adults 40-50 years old and older. It is not known for sure whether this is due to the late appearance of the formation or to its slow growth and delayed detection.
Causes
The etiology of renal angiolipoma remains unclear, it is not even known for certain whether it has a congenital or acquired character. It was possible to establish a relationship between the development of a tumor and some genetic diseases (tuberous sclerosis), but the clinical course of these forms differs significantly from sporadic formations. Based on the long-term study of many patients, several possible mechanisms for the development of angiolipoma and theories regarding the causes of its occurrence have been proposed:
- Chronic inflammation. Neoplasm is quite often combined with chronic glomerulonephritis, pyelonephritis, urolithiasis, which indicates the possible influence of inflammation on the development of pathology. Opponents of this opinion point out that the tumor itself can become the primary provoking factor of these conditions.
- The effect of endocrine disruptions. Renal angiolipoma is often registered in women during the menopausal period, when global hormonal changes occur in the body. Cases of a sharp acceleration of the growth of education during pregnancy are described, which is also explained by the influence of a changed hormonal background. However, whether such changes cause a kidney tumor or stimulate the growth of an existing one is not reliably clarified.
- Hereditary factor. Pathology accompanies at least one genetic disease – Bourneville-Pringle disease, in which multiple angiolipomas occur in both kidneys. Regarding sporadic forms of clear hereditary transmission, it was not possible to fix.
- Viral etiology. It is assumed that this type of tumor growth can be stimulated by a certain type of viruses. But to date, this theory has not been confirmed experimentally.
In the scientific community, there is a generally accepted opinion regarding the main risk factors for the occurrence of this tumor, which include female sex, pregnancy, menopause, hormonal failures, increased levels of female sex hormones in men. The combination of these circumstances with inflammatory or metabolic lesions of the excretory system organs significantly increases the likelihood of developing a benign neoplasm.
Pathogenesis
The pathogenesis of renal angiolipoma has been studied a little better than the causes that cause its development, but there are many “white spots” in relation to this process. It is assumed that a tumor is formed from perivascular epithelioid cells surrounding the blood vessels of the kidneys. Its growth has an expansive character – the formation presses on the surrounding structures of the excretory organs and deforms them. With small sizes (up to 30-40 mm), this does not affect the functions of the excretory system, therefore it does not manifest itself with subjective and clinical symptoms. The appearance of signs of invasive growth (vascular germination with the development of thrombosis, going beyond the renal capsule) indicates the malignancy of the neoplasm. Very rarely, this can result in metastases to regional lymph nodes.
An increase in angiolipoma over 40-50 mm leads to compression of nerve trunks, which causes pain syndrome. Tumor vessels are untenable and often damaged, blood from them first enters the cup-pelvic system of the kidney, and from there into the urine, leading to the development of hematuria. With a significant size of the neoplasm, in the case of mechanical loads (sudden movements, lifting weights), a tumor rupture may occur with the occurrence of bleeding. The condition is accompanied by severe anemia, severe abdominal pain, rigidity of the abdominal muscles and requires urgent surgical intervention.
Classification
The widespread prevalence of pathology against the background of poorly understood causes of its development has led to the development of numerous classification systems – based on sensitivity to hormones, the presence of invasive growth, age of occurrence and other criteria. None of the listed systems has received wide and generally accepted distribution, as they have a lot of disadvantages. In modern urology, only one classification of renal angiolipoma is used, where the well-known etiological factor of its development is taken as a basis:
- 1 Sporadic type. It is the most common, accounting for 75-80% of all cases of the disease. Neoplasia is determined by random ultrasound examination of the organs of the urinary system, has a small size, is characterized by expansive growth, asymptomatic course. The defeat is always one-sided, the formation is solitary.
- 2 Hereditary type. Includes tumors accompanying genetic diseases. Usually this is the Burneville-Pringle syndrome (tuberous sclerosis) – an autosomal genetic pathology from the group of phacomatoses. It is accompanied by multiple bilateral angiomyolipomas of the kidneys and causes about 20% of cases of such formations.
- Type 3 with an unclear etiology. It is rarely diagnosed (about 1-5% of cases), includes all other types of angiolipes of the excretory system. It includes multiple sporadic neoplasms, tumors with invasive growth, neoplasia, accompanying other oncological diseases of the kidneys.
Symptoms
Due to the absence of pain receptors in the renal parenchyma, the disease is characterized mainly by an asymptomatic course. There are cases of arterial hypertension of renal genesis in patients with small neoplasms, but it may be due to other mechanisms. Obvious symptoms appear at the moment when the tumor begins to exert pressure on the kidney capsule, equipped with nerve endings. This is manifested by prolonged pulling pains in the lower back, at first without a certain irradiation in any direction. As the renal angiolipoma progresses, the pain concentrates on the side of the affected organ.
Simultaneously with the pain syndrome, hematuria occurs, which is first determined only by laboratory examination of urine, and then becomes visible to the naked eye. The long course of the disease leads to the development of anemia and hypoalbuminemia. Sometimes there is a difficulty in the outflow of urine due to the blockage of the angiomyolipoma site with the development of renal colic. A sharp increase in pain, its spread to the entire abdominal area, pallor and tachycardia are signs of rupture of the neoplasm and retroperitoneal bleeding. With such symptoms, the patient must be urgently taken to a hospital for surgical care.
The duration of the pathology is long – the asymptomatic stage can take many years, last until the death of the patient due to natural causes. The period from the appearance of the first painful sensations to the occurrence of macrohematuria also takes many months and even years. The slow progression and insignificance of angiomyolipoma manifestations, on the one hand, make it possible to prescribe long–term follow-up instead of surgical treatment, and on the other hand, lead to late referral of patients to a specialist.
Complications
The most common complication of renal angiolipoma is tumor rupture – neoplasia is rich in vessels with fragile walls, so their damage leads to copious, long-lasting bleeding. Hemorrhage occurs in the retroperitoneal space or (less often) in the heart, manifests itself with hematuria, threatens to develop shock as a result of blood loss and irritation of the peritoneum. A rare form of a long–term complication of pathology is malignancy of the tumor – it acquires an invasive nature of growth and the ability to metastasize. As a result of the germination of the walls of venous vessels, their embolism and circulatory disorders in the kidneys are possible.
Diagnostics
The urologist is engaged in determining the presence of a neoplasm and its type in close cooperation with an oncologist. Often, renal angiolipoma is detected accidentally during preventive ultrasound or other diagnostic manipulations, in which the structure of the excretory organs is evaluated. A number of techniques are used to clarify the nature of the formation, its size, localization, and relationship with surrounding tissues:
- Palpatory examination. If the angiomyolipoma has a size of more than 5 centimeters, it can be detected with the usual palpation of the patient’s kidneys. In addition to confirming the presence of neoplasia, this method does not provide any other data.
- Ultrasound examinations. Ultrasound of the kidneys detects a tumor in the form of a homogeneous echogenic formation of various sizes. By means of dopplerography (ultrasound of the kidneys), it is possible to confirm the vascular nature of the neoplasm, to identify possible damage and rupture of blood vessels.
- Multispiral computed tomography. MSCT of the kidneys with contrast is the gold standard in determining the position and size of an angiolipoma. In case of a planned operation to remove a tumor, such a study, in the absence of contraindications, is included in the mandatory preoperative preparation.
- Magnetic resonance imaging. Kidney MRI is used as an alternative to MSCT in preparation for surgery or to determine the size and structure of neoplasia. Angiomyolipoma is detected as a moderately hyperdensive rounded formation in the kidney.
- Kidney biopsy and histological examination. It is a standard for clarifying the nature of the tumor, often used for final confirmation of the diagnosis. Sampling is carried out by means of endoscopic equipment under the control of ultrasound or X-ray techniques. Microscopy reveals vascular and fatty components with an admixture of smooth muscle fibers.
- Genetic research. It is carried out in case of suspicion of the presence of tuberous sclerosis. Diagnosis consists in automatic sequencing of the sequences of the TSC1 and TSC2 genes, mutations of which lead to the development of Bourneville-Pringle disease.
Basic clinical tests (examination of blood, urine, measurement of blood pressure, assessment of functional activity of the kidneys) play a secondary role in the diagnosis of pathology. With the asymptomatic presence of renal angiolipoma, these studies practically do not indicate the disease. In the case of pronounced tumor sizes, hematuria and proteinuria are detected in the blood test, a blood test reveals iron deficiency anemia. Blood biochemistry may confirm the presence of hypoalbuminemia.
Treatment
With angiomyolipoma sizes of 40-50 millimeters, the absence of severe anemia and hematuria, treatment is not prescribed – it is recommended only to be monitored by a urologist or nephrologist once every six months with a preventive ultrasound. It is shown that the optimal drinking regime is observed, the load on the excretory system is reduced, in the presence of concomitant kidney diseases – their proper full-fledged treatment. If the renal angiolipoma has a significant size or becomes the cause of disorders (pain, anemia), surgical removal of the neoplasm is prescribed. The type and volume of the operation depends on a number of factors:
- Endoscopic selective angioembolization. It is the least invasive intervention in which ligation or laser coagulation of the vessels feeding the tumor is performed. The method is quite effective in terms of reducing the size of the formation, but the prospects for its complete elimination are quite low. It can be produced at any size of the tumor.
- Removal of a part of the kidney. It can be performed in endoscopic and open (classical) versions. The surgeon resects the kidney with the removal of the area including the angiomyolipoma and sutures the remaining part of the organ. The technique is used for the size of the formation from 5 to 8 centimeters.
- Removal of the kidney. Nephrectomy of an organ affected by a tumor is performed with giant (over 10 centimeters) angiolipomas, their multiple nature, signs of invasive growth or damage to the kidney as a result of rupture. The operation is justified only if there is a second functioning kidney.
The method of surgical treatment may vary depending on the size of the angiolipoma, the presence of concomitant disorders, and the patient’s condition. Urgent life-saving surgery to stop retroperitoneal bleeding on the background of a tumor rupture is also often accompanied by its removal. In rare cases of metastasis to the lymph nodes, they are also removed. There are no conservative methods of treatment with kidney angiomyolipes.
Prognosis and prevention
Renal angiolipoma is characterized by a favorable prognosis due to its extremely slow development and the benign nature of growth. Appointed after the detection of the tumor and confirmation of its type, observation by a nephrologist allows you to detect any negative changes in the course of pathology in a timely manner. Due to this, surgical elimination is carried out on time, before the development of severe complications. According to statistics, surgical treatment is required for less than a third of all patients observed by a specialist for this reason. In other patients, the neoplasm does not manifest itself throughout life.