Renal cysts, or cystic kidney disease, as the name implies, is a general term for the presence of cystic lesions in the kidney that do not communicate with the outside world. Common renal cysts include simple renal cysts, parapelvic cysts, and polycystic kidneys, among others. With the popularization of physical examination and the wide application of ultrasound and CT, the detection rate of renal cyst disease has increased significantly and has become a more common kidney disease in clinical practice. Some kidney tumors (e.g. cystic kidney cancer) may appear like cystic structures due to the formation of necrosis and cavity inside the tumor, which should be differentiated from renal cysts.
Disease Classification
By etiology, most renal cysts are congenital (hereditary), while a few are acquired or uncharacterized.
Disease Profile
Solitary renal cyst (SRC) is the most common lesion in human kidney disease, which is the appearance of one or several cystic cavities of variable size and inaccessible to the outside world, filled with cystic fluid, in one or both kidneys.
Disease characteristics
The etiology is unclear. The majority of patients are adults, and it is rare in children. There are more males than females. The incidence increases with age, and about 50% of people over 50 years of age have one or more simple renal cysts, and the prevalence is as high as 90% in people over 70 years of age.
Simple renal cysts have a thin, transparent wall containing a yellowish, clear fluid, and if there has been inflammation, the wall may thicken, become fibrotic or even calcified. The cyst is not connected to the renal pelvis and the wall is lined with a single layer of flattened epithelial cells.
Smaller simple renal cysts grow slowly and have little impact on renal function and little chance of malignancy, and only require regular observation; for simple renal cysts larger than 4 cm in diameter, cysts that increase rapidly, or cysts with suspected malignancy, surgery should be considered.
Clinical manifestations
It is usually asymptomatic and is mostly found by chance during physical examination or imaging examination for other diseases. Some patients may experience “low back pain” on the affected side, which is often not directly caused by the kidney cyst. Some very large renal cysts, especially those with intracapsular hemorrhage or infection, can cause significant pain and discomfort in the lower back and abdomen. Some kidney cysts happen to compress the ureter or the neck of the calyx, which can cause hydronephrosis and secondary infection, followed by symptoms of back pain, fever, and urinary tract infection. Individual simple renal cysts can develop cyst wall carcinoma, the carcinoma rate is about 1%, and the possibility of carcinoma should be alerted when there is bleeding inside the cyst.
Examination means and identification
Ultrasound (or color ultrasound) of the abdomen is the first choice for physical examination, which can both detect kidney cysts and serve as a means of regular review. If the ultrasound result cannot accurately determine the nature of cysts, abdominal enhancement CT should be checked.
The focus of differentiation is to distinguish simple renal cysts from cystic tumors (such as cancerous cysts or internal necrotic tumors). In the former, there is a round homogeneous liquid dark area with no enhancement, thin wall, posterior wall echogenic enhancement and clear and smooth demarcation between the cyst and renal parenchyma under ultrasound and CT; in the latter, the cyst wall is irregular, there are tumor-like contents inside the cyst and there is enhancement inside the cyst. In the latter case, the cyst wall is irregular and there are tumor-like contents within the cyst, and there is enhancement within the cyst.
Treatment and prognosis
Simple renal cysts progress slowly and have a good prognosis, and those without conscious symptoms or compression and obstruction do not require surgical intervention or oral medication, and do not affect daily life.
The indications of simple renal cysts that are generally considered to require surgical treatment are
1, those with symptoms of pain and discomfort in the lower back and abdomen or those with high psychological pressure
2, those with cysts larger than 4 cm in diameter or those with a significant recent increase in volume
3, those with cysts producing symptoms of compression or hydronephrosis, or those with cysts secondary to bleeding, infection, rupture and other lesions.
4. Those who are suspected of cancerous changes.
Laparoscopic decompression of renal cysts is the main way of surgical treatment for renal cysts at present. This surgical modality is less traumatic, effective treatment, less risky, fast postoperative recovery, short hospital stay, beautiful incision healing, and low recurrence rate. The excised cyst wall should be sent for pathological examination to clarify its nature.
Treatment also includes ultrasound-guided cyst puncture and aspiration with injection of sclerosing agent (e.g. anhydrous alcohol), but this approach has a high risk of puncture and a high recurrence rate, and the damage caused by the injected sclerosing agent if it enters the renal pelvis and ureter is extremely serious and difficult to repair, and should not be recommended.