In clinical practice, a renal cyst (or renal cyst) typically refers to a simple renal cyst. It is the most common lesion in human kidney disease, ranking first in incidence among cystic kidney diseases. Cysts are generally unilateral and solitary, though multiple or bilateral cysts can occur, which is rare. The cause is still unclear. Patients are generally asymptomatic and are often discovered during health checkups or ultrasound or CT scans for other illnesses. The most common clinical manifestations are abdominal pain or distension on the affected side, and may also include hematuria, abdominal mass, fever, and general malaise. It rarely affects renal function and has a low chance of malignancy.
Epidemiology
Contagious
Not contagious.
Incidence
Simple renal cysts are the most common lesion in human kidney disease, ranking first in incidence among cystic kidney diseases. The incidence of simple renal cysts is approximately 10% in individuals aged 30 to 40 years, rising to over 50% in individuals aged 80 and older. Among children undergoing renal ultrasound examinations for various reasons, the incidence of simple renal cysts is between 1% and 2%.
Incidence trend
The incidence rate gradually increases with age.
High-risk population
It can occur at any age and is rare in children. The incidence of renal cysts varies between men and women, with more cases in men than in women, with a male-to-female ratio of 1.6:1 to 1.8:1.
Causes
Overview
The etiology of simple renal cysts is not fully understood, but their development is currently believed to be related to a variety of acquired factors. Cysts often originate in the renal tubules (especially the proximal tubules) and are connected to the tubules, possibly due to nephron obstruction caused by some reason. Some renal cysts have unknown origins and are not connected to the tubules, indicating that they originate from sources other than the tubules and may be related to factors such as epithelial cell proliferation and secretion. Cyst fluid contains epidermal growth factor (ECF), insulin-like growth factor-1 (IGF-1), and an active substance that promotes cyst formation. These substances promote epithelial cell proliferation, leading to cyst formation.
symptom
Overview
Simple renal cysts are usually less than 2 cm in diameter and are generally asymptomatic. However, symptoms often develop when the cyst reaches 4 cm in diameter. Because larger cysts pull outward on the renal capsule or compress the renal parenchyma inward, patients often experience pain in the affected side of the abdomen or back, primarily characterized by distension. If excessive bleeding within the cyst causes the cyst wall to swell and the capsule to compress, severe flank pain may occur. Secondary infection can lead to increased pain, fever, and general malaise. Some patients may also experience gross or microscopic hematuria. Large cysts may present as a palpable abdominal mass. This mass can compress the ureter or calyceal neck, causing obstruction. Prolonged obstruction can lead to infection, resulting in flank pain, fever, pyuria, and leukocytosis. If the cyst compresses adjacent blood vessels, renal hypertension may develop. Furthermore, due to elevated levels of erythropoietin in the cyst fluid, polycythemia vera may develop.
complication
1. Renal hypertension
Renal hypertension, also known as renovascular hypertension, is high blood pressure caused by kidney disease and can usually be controlled with antihypertensive medication. While there are usually no symptoms, when blood pressure is severely elevated, patients may experience headaches, confusion, blurred vision, double vision, and pink blood in the urine.
2. Ureteral or calyceal obstruction
During acute attacks, patients may experience flank pain or typical renal colic. Chronic obstruction is often less pronounced, sometimes with dull flank pain or hematuria. Intermittent hydronephrosis can cause alternating oliguria and polyuria.
examine
Scheduled inspection
Patients experiencing abdominal or back pain, hematuria, or abdominal masses should seek medical attention promptly. The doctor will first perform a physical examination to assess any abnormalities. They may then recommend ultrasound, CT scans, and cyst fluid aspiration to further confirm the diagnosis.
Physical examination
The doctor will perform a palpation examination on the patient’s abdomen. If the cyst is large, an abdominal mass may be felt.
Laboratory tests
When ultrasound or CT scans suspect malignancy, puncture can be performed under ultrasound or CT guidance. Cytological and biochemical examinations are performed on the cyst fluid. When a secondary tumor develops in the cyst wall, the cyst fluid is bloody or dark brown, with a significant increase in fat and other components. Cytological examinations often reveal cancer cells. The tumor marker CA50 level is elevated. Inflammatory cystic fluid is turbid and dark, with moderate increases in fat and protein content, and significantly increased levels of amylase and LDH. Inflammatory cells may be present, and bacterial culture may reveal pathogenic bacteria. After the cyst fluid is extracted, a contrast agent may be injected to further understand the condition of the cyst wall and determine whether a tumor is present.
Imaging examinations
1. Ultrasound
Diagnosis of renal cysts is sensitive and reliable, making it the preferred method. Typical sonographic features include round or oval, fluid-filled, echo-free areas within the renal parenchyma or subcapsular space, with thin walls and smooth edges and increased echogenicity posteriorly. Even very small cysts can be detected.
2. CT
It can accurately reflect the positional relationship between the cyst and the surrounding structures. The imaging shows that the cyst is a uniform, round, low-density structure with sharp boundaries and a clear boundary with the adjacent renal parenchyma.
diagnosis
Diagnostic principles
The diagnosis is generally based on symptoms such as pain in the affected side of the abdomen or back, hematuria, and other symptoms, combined with ultrasound, CT, and other auxiliary examination results. During the diagnosis process, the doctor needs to differentiate it from hydronephrosis and polycystic kidney disease.
Differential diagnosis
1. Hydronephrosis
Clinical manifestations can be similar to those of simple cysts, but hydronephrosis often has an obstructive etiology, making it more susceptible to secondary infection, and symptoms are more pronounced during acute obstruction. For example, hydronephrosis caused by urinary tract stones may present with renal colic, hematuria, and urinary tract irritation. Imaging studies show distinct imaging features, each useful for distinguishing the two.
2. Polycystic kidney disease
If the patient has multiple cysts, it is sometimes necessary to differentiate it from polycystic kidney disease. If there is no family history and the number of cysts is easy to count, it is not polycystic kidney disease.
3. Multilocular renal cysts
The main symptoms are abdominal discomfort, abdominal mass, and occasional hematuria. Ultrasound and CT scans reveal a cystic mass within the renal parenchyma. However, the cyst is internally divided into multiple fluid-filled dark areas.
4. Kidney abscess
Typically, there are systemic manifestations of acute infection, such as high fever, chills, severe pain in the renal region on one side, muscle tension, and palpable percussion tenderness at the costovertebral angle. Leukocytosis, white blood cells in the urine, and positive bacterial cultures are present. Intravenous ultrasound (IVU) reveals compression or filling defects in the renal pelvis and calyces. Ultrasound reveals fluid-filled dark areas in the renal region and the primary lesion that may cause pyonephrosis. Aspiration can yield pus.
treat
Treatment principles
Simple renal cysts rarely affect renal function and have a low risk of malignant transformation. Therefore, asymptomatic and uncomplicated patients do not require treatment. However, patients experiencing pain, discomfort, urinary tract obstruction, infection, bleeding, hypertension, tumors, or cysts that are at risk of rupture or have already ruptured should seek prompt treatment. Surgery is the primary treatment option.
Drug treatment
There is currently no effective drug treatment.
Related drugs
None
Surgical treatment
1. Renal cyst puncture and sclerotherapy
(1) Indications: For larger cysts with a diameter >5 cm, puncture and fluid extraction can be considered, and a sclerosing agent such as anhydrous ethanol can be injected to prevent recurrence.
(2) Principle of surgery: The cyst fluid is secreted by the epithelial cells of the cyst wall. The sclerosant acts on the cells, changing the ratio of biological membrane proteins and lipids, causing abnormal amino acid transport and calcium ion influx, which in turn leads to the death of cyst epithelial cells and the loss of secretory function. The cyst then shrinks and eventually disappears.
(3) Surgical procedure: Usually performed under the guidance of B-ultrasound, the patient takes the prone or healthy side decubitus position, with a pillow under the abdomen to stabilize the kidney. B-ultrasound is performed to locate the cysts, determine the location, number and size of the cysts, and determine the location, angle and depth of the puncture point under B-ultrasound. Routine skin disinfection, sterile drapes are applied, and local anesthesia is performed. After the operation, the patient rests in bed and a urine routine test is required. If there is pain, redness or swelling at the puncture site, the patient should be informed immediately and the appropriate treatment should be given.
(4) Note: Parapelvic cysts and renal cysts that are connected to the renal pelvis are not suitable for cyst puncture and sclerotherapy.
2. Surgery
Surgical treatment should be considered for giant cysts with a diameter exceeding 10 cm and a volume exceeding 500 ml, cysts suspected of being cancerous, or cysts that recur after puncture.
Treatment cycle
The treatment cycle is affected by factors such as the severity of the disease, treatment plan, treatment timing, age and physical condition, and may vary from person to person.
Treatment costs
There may be significant individual differences in treatment costs, and the specific costs are related to the selected hospital, treatment plan, medical insurance policy, etc.
Prognosis
General prognosis
Simple renal cysts generally have no clinical symptoms, do not affect renal function, have a good prognosis, and do not affect the patient’s life expectancy. However, if symptoms do appear and treatment is not timely, various complications such as renal hypertension and ureteral or calyceal obstruction may occur, seriously affecting the patient’s quality of life.
Hazards
After symptoms appear, if not treated promptly, various complications such as renal hypertension, ureteral or renal calyx obstruction may occur.
Curative
Active treatment of this disease can effectively relieve symptoms and improve prognosis.
Recurrent
This disease may recur after cyst puncture and sclerotherapy.
daily
Overview
Patients with renal cysts should pay attention to daily care, get enough rest, maintain a good attitude, actively prevent and treat infection, and follow the doctor’s orders for regular checkups so that the doctor can understand changes in the condition in a timely manner and adjust the treatment plan.
Postoperative care
1. While still awake from general anesthesia, the patient should lie supine without a pillow, with the head tilted to one side. On the day of surgery, after waking from general anesthesia, the patient should lie supine or in a lateral position. One day after surgery, the patient should assume a semi-recumbent position and move around in bed. Two to three days after surgery, the patient may move around the bedside with assistance. Four days after surgery, the patient may move around the room with assistance, gradually increasing their range of motion.
2. Replace damp, contaminated bedding and patient clothing promptly, keep bed units and patient clothing clean and tidy, and prevent the formation of bedsores.
3. Keep the area around the surgical incision clean and dry, and take anti-infection drugs as prescribed by the doctor to prevent infection. If signs of inflammation such as redness, swelling, heat, and pain appear near the surgical incision, seek medical attention immediately.
Life Management
1. Live a regular life, ensure adequate sleep and avoid fatigue.
2. Maintain a relaxed and happy mood and avoid emotional stimulation such as tension and anxiety.
3. Avoid the use of nephrotoxic drugs.
4. Increase exercise appropriately, such as walking, swimming, jogging, and Tai Chi, to improve immunity. Avoid strenuous physical activity and abdominal trauma.
5. Actively prevent and treat infection, such as taking a shower, urinating and cleaning the vulva immediately after sexual intercourse, paying attention to the hygiene of the vulva, avoiding catheterization and other urinary tract instrument examinations as much as possible, not holding urine, wiping backwards with toilet paper after defecation, etc.
6. Pay attention to controlling blood pressure.
Follow-up Instructions
Follow the doctor’s advice for regular checkups, generally once every six months. The checkups include blood pressure, urine routine, renal function and B-ultrasound examinations.
diet
Dietary adjustment
Patients with renal cysts should eat foods high in high-quality protein, supplement with high-fiber and high-vitamin foods, and maintain a low-fat, moderately sugary diet to ensure adequate nutritional intake. They should also develop good eating habits, such as chewing slowly, eating in moderation, paying attention to food hygiene, and avoiding overeating.
Dietary recommendations
1. Do not be picky about food. You can eat whole grains, fresh vegetables and fruits, lean meat of beef, mutton and pork, eggs, milk, fish and shrimp, etc.
2. Adjust salt intake according to the patient’s condition and renal function.
Dietary taboos
1. Controlling protein (low-protein diet in renal failure) plays an important role in reducing the burden on the kidneys, reducing the production of uremic toxins, and alleviating the condition.
2. Avoid spicy foods such as chili peppers.
3. Avoid alcohol and smoking (including passive smoking).
4. Avoid “irritating foods” such as chocolate, coffee, sea fish, shrimp, crab, etc.
5. Avoid overly salty foods, especially pickled foods.
6. Avoid contaminated food such as unhygienic food, rotten food, leftovers, etc.
7. Avoid barbecued foods.
8. People with renal insufficiency or uremia should also avoid eating beans and their products, and limit their intake of high-protein animal foods and greasy foods.
prevention
Preventive measures
The cause of renal cysts is still unclear and there are no special preventive measures.
Medical Guide
Outpatient indications
1. Recurring side or back pain;
2. Accompanied by severe pain in the waist;
3. Accompanied by fever and general discomfort;
4. With hematuria and pyuria;
5. Other persistent or progressive symptoms and signs occur, affecting normal life.
All of the above require timely treatment at regular medical institutions or hospitals.
Treatment department
1. The first department to visit is usually the Nephrology Department.
2. If surgical treatment is required, go to the urology department for treatment.
Medical preparation
1. Make an appointment in advance and bring your ID card, medical insurance card, medical card, etc.
2. On the day of the appointment, you can wear loose clothes to facilitate the physical examination.
3. If you have had medical treatment recently, please bring relevant medical records, examination reports, laboratory test results, etc.
4. If you have taken some medicine to relieve symptoms recently, you can bring the medicine box with you.
5. Family members can be arranged to accompany the patient to seek medical treatment.
6. Prepare a list of questions you want to ask in advance.
Questions your doctor may ask
1. What symptoms do you have now?
2. When did the symptoms begin? Have they gotten worse or better? What causes them?
3. Do you have any other discomfort?
4. Have you had similar symptoms before?
5. Do you have kidney disease?
6. Have you been exposed to nephrotoxic substances recently?
7. Do you have any other illnesses?
8. What are your eating habits like?
9. Have you ever received treatment? What was the treatment process like? What were the results?
What questions can patients ask?
1. Is my condition serious?
2. What could be the reason?
3. What tests do I need to do?
4. What treatments are available? Which one do you recommend? Does hospitalization require treatment?
5. Are there any risks in surgical treatment?
6. Are these covered by medical insurance?
7. I have other diseases. Will they affect my treatment?
8. How effective is the treatment? Is it hereditary? Will it recur?
9. What should I pay attention to in my daily life?
10. Do I need a follow-up examination? How often should I have one? What should I expect?