What is a renal cyst?

Renal cyst is a general term for cystic masses of different sizes in the kidney that do not communicate with the outside world. Common renal cysts can be divided into adult polycystic kidney, simple renal cyst and acquired renal cyst.

Polycystic kidney in adults is a congenital genetic disease. The renal parenchyma is filled with numerous circular cysts of different sizes, which are not connected with the outside world. Cyst contains liquid, which is invisible to the naked eye and can reach several centimeters in size, so it is called polycystic kidney. It is characterized by increased nocturia, low back pain and hypertension. Urine test has hematuria and a small amount of proteinuria, which often develops slowly into chronic renal failure. Kidney calculi patients accounted for 10%, and polycystic liver patients accounted for 30%. With the help of B-ultrasound and intravenous pyelography, experienced doctors can make a diagnosis.

Simple renal cyst may be a congenital anomaly, which is unilateral or bilateral, with one or several annular cavities of different sizes that are not connected with the outside world, and most of them are unilateral, so it is called simple renal cyst. Its incidence can increase with age, and 50% of people over 50 years old can find this cyst by B-ultrasound. Diagnosis can be made by B-ultrasound and CT.

Acquired renal cysts mainly occur after uremia or dialysis treatment. It has nothing to do with age, but with the time of hemodialysis. There are no renal cysts in the kidney. According to the literature, if the dialysis time exceeds 3 years, most patients will have cysts. A kidney has at least 4 cysts, most of which are 2 ~ 3 cm in diameter. Some cysts can be infected or even cancerous, and can be diagnosed by B-ultrasound or CT examination.

abstract

Simple renal cyst is usually unilateral and single, but it can also be multiple or small-chambered, and rarely occurs bilaterally. Compared with polycystic kidney disease, it is different in clinical and pathological manifestations.

Treatment measures

(1) Special handling:

① When the first diagnosis cannot be made by excretory urography, renal tomography, ultrasound image and CT, angiography and percutaneous cyst aspiration can be selected as the next diagnostic means, which can be carried out under the supervision of X-ray fluorescent screen or ultrasound image. It is an encouraging sign to find clear cystic fluid, but the aspiration fluid should still be examined by cytology. The fat content should also be determined, and the increase of fat content is consistent with the diagnosis of tumor. Then the cystic fluid is completely discharged and replaced by contrast agent. Then take photos at different positions to show the smoothness of the capsule wall and whether there are any vegetation. Injecting 3ml of iodine ester into the capsule cavity before withdrawing the contrast agent will reduce the changes caused by liquid accumulation. Bean 198 1 introduces that 95% alcohol is injected into empty capsules. Through this method, he only found 1 recurrence in 29 patients. If the cyst is simply emptied, most of it will recur. If the aspiration fluid contains blood, surgical exploration can be considered, so the lesion is serious and even cancerous.

② If the diagnosis is clear, the cyst can be preserved. After all, it is rare for the cyst to damage the kidney.

③ When the diagnosis is still in doubt, surgical exploration can be considered. Ambrose et al. preferred surgical exploration in 197 1 year, when most cysts were diagnosed. In that 55 operation they performed. 5 cases were diagnosed as canceration, accounting for 9%. Usually only the extrarenal part of the cyst is removed. Nephrectomy is also an indication if the kidney is seriously damaged, but it is rare.

(2) Treatment of complications: When cyst is complicated with infection, we should strengthen antibiotic treatment, although Muther and Bennett found that the concentration of antibiotics in cyst fluid is very low. So it is often necessary to drain through this puncture. If puncture and drainage failed, surgical removal of the extrarenal part of the cyst wall and drainage were also proved to be effective. When hydronephrosis occurs, removing the cyst wall that causes obstruction can relieve ureteral obstruction. Pyelonephritis involving the kidney suggests urinary tract obstruction, and then ureteral drainage is not smooth. After cyst removal, urinary tract pressure is naturally reduced, thus making antibacterial treatment more effective.

pathogenesis

Whether simple renal cyst is congenital or acquired is still unknown. Its origin may be similar to polycystic kidney, but the degree is different. On the other hand, animals can suffer from simple renal cysts by causing renal tubular obstruction and ischemia. This shows that this kind of lesion can also be obtained. With the enlargement of cyst, basal compression can damage renal parenchyma, but not renal function. The site where the solitary cyst occurs can just press the ureter, thus causing progressive hydronephrosis, and then infection can occur. Feiner, Katz and Gallo 1980 noted that acquired renal cyst disease is very common in long-term dialysis patients. In kessel and Tynes 198 1 year, 2 cases of renal cysts resolved spontaneously.

pathological change

Simple renal cysts often involve the lower pole of the kidney. The average diameter of symptomatic cysts is about 10 cm, but a few cysts can be large enough to fill the lateral abdomen. Cysts usually contain transparent amber cystic fluid. The cyst wall is very thin, and the cyst is often in the shape of "blue dome". Occasionally, calcification of the cyst wall can be seen. About 5% cysts contain bloody cystic fluid, and half of them may have papillary carcinoma on the wall. Simple renal cyst usually occurs on the surface of the kidney, but it can also be located in the deep. When the cyst is located in the deep part, its cyst wall is closely connected with the epithelial inner wall of renal pelvis and calyx, which is very difficult to separate, but the cyst is not connected with renal pelvis. Microscopic examination showed that there were severe fibrosis and vitreous degeneration in the capsule wall, and calcified areas were also seen, and the adjacent renal tissues were also compressed to cause fibrosis. Many simple renal cysts in children have been reported, but giant cysts are still rare in children. At this point, we must first rule out the possibility of cancer. In urography, multilocular renal cysts may be confused with tumors. Ultrasound images can be diagnosed, and occasionally CT and MRI are needed.

clinical picture

(1) Symptoms: Common pain is located in the lateral abdomen and back, usually accompanied by intermittent dull pain. When bleeding causes the cyst wall to expand, sudden and severe pain may occur. Occasionally, gastrointestinal symptoms appear, but it is suspected that it is peptic ulcer or gallbladder disease. Patients can find abdominal masses by themselves, although such large cysts are rare. When cysts are infected, patients often complain of hypochondriac pain, general malaise and fever.

(2) Physical signs: Physical examination is mostly normal, and the renal area can be touched or tapped occasionally. If the cyst is infected, there may be tenderness in the lateral abdomen and abdomen.

(3) Laboratory examination: urine analysis is normal. Hematuria under microscope is rare. Renal function is normal unless the cyst is multiple or bilateral (rare). Even if the surface of one kidney is extensively damaged, the contralateral kidney can still maintain normal total renal function due to compensatory hypertrophy.

(4)X-ray examination: On the plain film of abdomen, a part of kidney shadow is often seen to be enlarged or there is a compressive mass on it. The weight or position of cyst can cause renal torsion and abnormal renal axis. Sometimes strip calcification can be seen at the edge of the mass. Excretory urography can be used for diagnosis. 1 ~ 2 minutes after intravenous injection of contrast agent, the density of renal parenchymal blood vessels increased, but the space occupied by cysts did not increase because there were no blood vessels in cysts. Continuous urography showed a mass. One or more renal calices or renal pelvis around cysts are often widened, flattened or even disappeared due to depression or bending. Oblique or lateral radiographs are also helpful for diagnosis. When the mass occupies the lower pole of the kidney, the upper ureter will shift to the spine. The kidney itself will also rotate. Through the radiolucent sac fluid or see psoas major. When routine urography can not effectively distinguish opaque renal parenchyma, renal tomography can increase the contrast between renal parenchyma with blood vessels and cysts. Occasionally, renal parenchymal tumors are relatively avascular and easily confused with cysts. In a few cases, tumors can also occur on the cyst wall, which requires further differential diagnosis and examination.

(5)CT scan: CT is the most accurate in differentiating renal cyst from tumor. The density of cystic fluid is similar to that of water, while that of tumor is similar to that of normal renal parenchyma. After intravenous injection of contrast agent, the renal parenchyma became denser, but the cyst was still unaffected. The boundary between cyst wall and renal parenchyma is clear, but there is no boundary between tumor and renal parenchyma. The cyst wall is thin, but the tumor is not. In differentiating cyst from tumor, CT is superior to puncture and aspiration in many aspects.

(6) Ultrasound examination of kidney: Ultrasound examination occupies a large proportion when non-invasive diagnostic techniques are used to distinguish renal cysts from solid masses. When the ultrasound examination finds that it conforms to the cyst image, the cyst can be punctured and the cyst fluid can be sucked under the supervision of the ultrasound image.

(7) Isotope scanning: Linear scanning can show the outline of mass, but it is difficult to distinguish cyst from tumor. Avascular masses can be shown by technetium scanning photography.

(8) Percutaneous cyst aspiration under cyst photography: When the above examination still has doubts about the differentiation between cyst and tumor, puncture aspiration should be performed.

complication

Spontaneous infection is rare in simple renal cyst, but once it happens, it is difficult to distinguish it from renal carbuncle. Sometimes there will be bleeding in the cyst, and when it happens suddenly, it will cause severe pain. The bleeding may come from the accompanying cancer on the cyst wall. When the cyst is located in the lower pole of the kidney and close to the ureter, it can aggravate hydronephrosis, and the pressure of urine on the renal pelvis can cause back pain. This obstruction can also lead to kidney infection.

differential diagnosis

(1) Renal cell carcinoma: It is a space occupying lesion, but it is easy to occur in the deep part, thus causing more obvious curvature of renal calyx. Hematuria is common, but cysts are uncommon. When renal parenchymal tumor compresses psoas major muscle, muscle margin can not be seen on abdominal plain film, but cysts can still be seen. Evidence of metastasis (such as weight loss, fatigue, enlarged clavicular lymph nodes, and metastatic nodules on chest film), polycythemia, hypercalcemia, and accelerated erythrocyte sedimentation rate all suggest cancer. Remember, the cyst wall will also become cancerous. If the renal vein is blocked by cancer, excretory urography will be unclear or even unable to develop. Ultrasound images and CT are usually used for differential diagnosis. Angiography and renal tomography can show that there is a "pond" with dense contrast agent in the tumor, which is rich in blood vessels, but the cyst density is not affected. It is wise to assume that all renal space-occupying lesions are cancers until they are proved to be other diseases.

(2) Polycystic kidney: As shown by urography, the disease is almost bilateral, and the diffuse distortion of renal calices and renal pelvis has become its law. Simple renal cysts are mostly isolated and solitary. Polycystic kidney is often accompanied by renal insufficiency and hypertension, while renal cyst is not.

(3) Renal carbuncle: This disease is rare. When collecting medical history, it can be found that there was a history of skin infection several weeks before sudden fever and local pain. Urography showed that the lesions were similar to cysts and tumors, but affected by perinephritis, the outline of kidney and the shadow of psoas major were blurred. At this time, the kidneys are mostly fixed. It can be confirmed by comparing the position of the kidney when the patient is supine and upright. Angiography can show no vascular lesions. Gallium -67 scan can show the inflammatory nature of the lesion, but the infected simple renal cyst can also have similar manifestations.

(4) Hydronephrosis: Symptoms and signs can be completely consistent with simple renal cysts, but urography is completely different. Cyst causes renal deformation, while hydronephrosis is manifested as dilatation of renal calices and renal pelvis caused by obstruction. Acute or subacute hydronephrosis often produces more limited pain due to the increase of intrarenal pressure, and its manifestations are easy to be complicated with infection.

(5) Extrarenal tumors (such as adrenal gland and mixed retroperitoneal sarcoma): can displace the kidney, but rarely invade the kidney and deform the renal calices.

(6) Echinococcosis: When the cyst is not communicated with the renal pelvis, it is difficult to distinguish it from simple renal cyst, because there will be no echinococcosis and its larvae in urine. X-ray examination often found calcification on the wall of renal hydatid cyst. Skin allergy test is helpful for the diagnosis of diseases.

prognosis

Ultrasound images and CT scans are extremely accurate in diagnosing simple renal cysts. Ultrasound imaging is a good method, and the swelling is reviewed every year to observe the changes of its size, shape and internal texture. When there is cancer, CT scanning is feasible, and if diagnosis is needed, puncture and aspiration of cystic fluid can be performed. Most cysts have a good prognosis.

Renal cysts include solitary renal cysts, congenital polycystic kidney and congenital multiple renal cysts. Patients usually have no symptoms, and only one or several cysts grow on the kidney through B-ultrasound examination. A few people can also have multiple cysts, but it is rare to have cysts on both sides. The wall of this cyst is very thin, and the cyst is a transparent yellowish liquid. Most cysts are as big as walnuts. The etiology of renal cyst is not very clear, and it is generally considered to belong to renal degeneration, so the patients are mostly elderly. Small cysts do not cause any symptoms. Recently, due to the extensive development of B-ultrasound examination, the number of renal cysts has also increased.

Main clinical symptoms of renal cyst

Most renal cysts are asymptomatic. Some patients may have the following symptoms due to the cyst itself, increased pressure in the cyst, infection and other reasons.

① Lumbar and abdominal discomfort or pain: It is caused by swelling and expansion of the kidney, which increases the tension of the renal capsule, pulls the renal pedicle, or oppresses adjacent organs. In addition, polycystic kidney disease leads to high water content, heavy weight, falling and pulling, and also causes low back pain. Pain manifests as dull pain and dull pain, which is fixed on one side or both sides and radiates to the lower part and back. If there is intra-capsular bleeding or secondary infection, the pain will suddenly increase. If the urinary tract is blocked by blood clots after stones or bleeding, renal colic will occur.

② Hematuria: It can be manifested as microscopic hematuria or gross hematuria. Seizures are periodic. Low back pain is often aggravated during the attack, and strenuous exercise, trauma and infection can all be induced or aggravated. The cause of bleeding is that there are many arteries under the capsule wall. Due to pressure increase or infection, the blood vessels in the capsule wall rupture and bleed due to overstretching.

③ Abdominal mass: sometimes it is the main reason for patients to see a doctor, and 60% ~ 80% of patients can touch the swollen kidney. Generally speaking, the bigger the kidney, the worse the renal function.

④ Proteinuria: Generally, the amount is not much, and the urine in 24 hours will not exceed 2g. Nephrotic syndrome does not occur in many cases.

⑤ Hypertension: The solid cyst compresses the kidney, causing renal ischemia and increasing renin secretion, causing hypertension. When the renal function is normal, more than 50% patients have developed hypertension, and when the renal function is decreased, the incidence of hypertension is higher.

⑥ Decreased renal function: Due to the occupation and oppression of cysts, the normal renal tissue decreased obviously, and the renal function decreased gradually.

Examination method of renal cyst

Reliable methods include X-ray, renal B-ultrasound, radionuclide scanning and CT examination. In the case of renal cyst, urinary X-ray can show that the renal pelvis and calyx are compressed and deformed, but the edges are smooth and undamaged. Renal cyst is not a tumor, but it is easily confused with tumor, so it is very important to distinguish renal cyst from renal malignant tumor. The differential method between them can be renal parenchyma tomography or renal arteriography. Renal parenchyma tomography showed that the cyst image was shallow and the tumor image was deep; During renal arteriography, the blood vessels in the cyst were sparse and there was no contrast agent concentration, while the renal malignant tumor was rich in blood vessels and had contrast agent concentration. When the cyst is suspected to be malignant, puncture can be performed to extract the cyst fluid for routine examination and exfoliated cell examination; Contrast media can also be injected into the cyst to check whether there is a tumor on the cyst wall. B-ultrasound and CT can easily distinguish renal cysts from renal solid tumors, and are ideal examination methods.

Treatment of renal cyst

At present, there is no specific method to treat renal cyst at the medical level. For small renal cysts, there is no need to do any treatment when they are asymptomatic, but they should be reviewed regularly to see if the cysts continue to grow. Asymptomatic patients should regularly check their urine, including urine routine and urine culture, and check their renal function every six months to one year, including the clearance rate of endogenous creatinine. Because infection is an important reason for the deterioration of this disease, do not carry out urinary tract traumatic examination unless it is very necessary. Renal cyst puncture has little effect, which is not only easy to relapse, but also can not delay the occurrence of renal function damage after long-term observation. Surgical removal of cysts is not an easy task, because cysts on the surface of the kidney can be removed, but cysts buried in the deep part of the kidney are quite difficult to remove. When the tumor is large and may become malignant, surgical exploration can be carried out. If it is proved to be a benign cyst, the cyst wall on the surface of the kidney can be removed, and the edge of the cyst can be sutured continuously with catgut, and the remaining cyst wall can be coated with iodine tincture. Nephrectomy is feasible if the renal parenchyma on one side is extensively destroyed and the renal function on the other side is normal.