Causes of kidney stones.
1. Excessive accumulation of oxalic acid
The large accumulation of oxalic acid in the body is one of the factors that lead to kidney and urine stones. Such as spinach, beans, grapes, cocoa, tea, oranges, tomatoes, potatoes, plums, bamboo shoots and other things that people generally love to eat, is precisely the food containing high oxalic acid. Doctors found through research: 200 grams of spinach, containing 725.6 mg of oxalic acid, if a person will eat all 200 grams of spinach at once, 8 hours after eating, check the urinary excretion of oxalic acid for 20 to 25 mg, equivalent to the average total amount of oxalic acid excreted by normal people in 24 hours.
2, purine metabolism malfunction
Animal offal, seafood, peanuts, beans, spinach, etc., all contain more purine components. After purine enters the body, it has to be metabolized, and the end product of its metabolism is uric acid. Uric acid can contribute to the precipitation of oxalate in the urine. If too much purine-rich food is consumed at one time, and the metabolism of purine is out of order, oxalate will be deposited in the urine to form urinary stones.
3, too much fat intake
All kinds of animal meat, especially fatty pork, are fatty foods. Eat more fat in the body is bound to increase, fat will reduce the intestinal can be combined with calcium, thus causing an increase in the absorption of oxalate, if once the excretory function failure, such as sweating, drinking less water, less urine, kidney stones are likely to be formed in this case.
4. Excess protein
Laboratory analysis of kidney stone components revealed that calcium oxalate accounted for 87.5% of the stones. The source of such a large proportion of calcium oxalate is because protein contains oxalic acid in addition to the raw materials DD glycine, hydroxyproline, protein can also promote the intestinal function of calcium absorption. If high protein foods are often consumed in excess, it will lead to a general increase in the composition of calcium, oxalic acid and uric acid in the kidneys and urine. If the excess calcium, oxalic acid and uric acid are not discharged from the body through the kidney function in a timely and effective manner, the conditions for kidney stones and ureteral calculi will be formed. This is the main reason for the increased incidence of kidney stones in economically developed countries in the world today.
5.Sugar increase
Sugar is an important nutrient for the human body and should be added regularly in moderation, but increasing too much at once, especially lactose, will also create conditions for stone formation. Beijing Military General Hospital urology experts pointed out: whether normal people or stone patients, after consuming 100 grams of sucrose, after 2 hours to check their urine, found that the urinary concentration of calcium and oxalic acid are rising, if lactose, it can promote the absorption of calcium, more likely to lead to the accumulation of calcium oxalate in the body and the formation of urinary stones.
What tests should be done for kidney stones?
Laboratory tests.
(1) Urinalysis can be divided into general examination and special examination.
(1) General examination is mainly for urine routine: it includes pH, relative density (specific gravity), red blood cells, pus cells, protein, sugar, crystals and so on. Hematuria, crystalluria and pus cells can be found in the urine of patients with urinary stones. The pH of urine is often indicative of a certain type of stone: patients with calcium phosphate and carbonate apatite stones often have a urine pH higher than 7.0, while patients with uric acid, cystine and calcium oxalate stones often have a urine pH less than 5.5. Microscopic hematuria or hematuria in the naked eye is seen. However, hematuria is absent in 15% of patients. In non-infected stones, mild pusuria may be present.
(2) Special tests include.
(1) Urine crystallography: fresh urine should be retained. If benzene-like cystine crystals are seen to suggest possible cystine stones; if uric acid crystals are found in the urine, they often suggest possible uric acid stones; if envelope-like crystals are found, they may be calcium oxalate dihydrate stones; coffin lid-like crystals are magnesium ammonium phosphate crystals; sulfonamide crystals will be found in the urine of patients suspected of having sulfonamide stones.
② Urine bacterial culture: colonies >105/ml are considered positive. Drug sensitivity testing then provides information on the most effective antibiotic. A urine culture with urea-producing bacteria is likely to have the presence of infected stones.
③ 24h urine test: 24h urine must be collected correctly and urine measurement should be accurate. The content of the test includes: 24h urine calcium, phosphorus, magnesium, citrate, uric acid, oxalic acid, cystine, etc.
2.Blood biochemical examination
(1) Normal adult serum calcium is 2.13-2.6 mmol/L (8.5-10.4 mg/dl) and inorganic phosphorus is 0.87-1.45 mmol/L (2.7-4.5 mg/dl). In patients with primary hyperparathyroidism, serum calcium is higher than normal, often above 2.75 mmol/L (11 mg/dl), and is accompanied by a decrease in serum inorganic phosphorus.
(2) Serum uric acid should not exceed z416.36mmol/L (7mg/dl) in normal adult men and 386.62mmoL/L (6.5mg/dl) in women. When this value is exceeded, it is considered hyperuricemia. Patients with gout have increased blood uric acid.
(3) Kidney stones with renal dysfunction often have acidosis, when serum electrolytes are changed, serum sodium and carbon dioxide binding capacity is reduced, and blood potassium is increased to varying degrees. Hypokalemia and hyperchloremic acidosis may occur in renal tubular acidosis.
(4) The measurement of urea nitrogen and creatinine can understand the renal function of the patient. When the renal function is impaired, the urea nitrogen and creatinine in the blood can be increased to different degrees.
In conclusion, blood and urine tests in patients with urinary stones can help to understand the renal function, the presence of co-infection, the possible types of stones and the causes of stones, and can be useful in guiding the treatment and prevention of stones.
Imaging tests.
1.X-ray examination X-ray examination is the most important method to diagnose urinary tract stones.
It includes abdominal plain film, excretory urography, retrograde pyelogram, or percutaneous nephrostomy, etc.
(1) Urethral plain film: Urethral X-ray is the most basic method to diagnose urinary tract stones. According to the opaque X-ray shadows of kidney, ureter, bladder and urethra, the diagnosis of stone can be made initially. The calcium content of stones varies, as does the degree of transmission to X-rays. About 40% of stones can be determined by the dense shadow shown on radiographs. Calcium oxalate stones are the most radiopaque; magnesium ammonium phosphate is the next most common radiopaque stone. Cystine stones are slightly impervious to X-rays because of their sulfur content. However, indinavir stones and some stromal stones can be visualized on plain CT films. Renal calcification is common in medullary spongy kidneys (close to deposition in dilated collecting ducts). It can also be compared with the density of the lumbar transverse process and a diagnosis can be made. There are also 10% of non-calcium stones that are not easily detected by radiographs.
Calcified shadows in the abdomen can be confused with urinary tract stones. These calcified shadows are mainly.
(i) dirt and gas in the intestinal tract.
(ii) Calcified shadows in the mesenteric lymph nodes.
(iii) Bone island formation in the skeletal part (e.g. sacroiliac joint area), calcification of the 11th and 12th rib cartilage.
(iv) “Venous stone” shadow formed by calcification of veins in the pelvic region.
⑤ Foreign body interference (e.g. buttons, knots on trouser belts, etc.) outside the body.
(6) Barium that is not excreted after barium examination of the digestive tract.
(2) Excretory urography: Excretory urography can further confirm the relationship between the opaque X-ray shadow and the urinary tract on the X-ray plain film, and also reveal the delayed development of the upper urinary tract on the affected side; the enlarged kidney shadow; the dilated and tortuous ureter above the renal pelvis and obstruction, and other changes, and understand the function of the kidney accordingly. If necessary, it is necessary to extend the time of the imaging in order to achieve satisfactory visualization of the affected side. For stones in the ureteral wall, the image of the filling bladder may mask the stone, so the patient may be asked to take the film after urination. Stones that can be X-rayed may appear as filling defects on IVU films. The IVU film can also reveal the morphology of the kidney and the presence or absence of malformations. The IVU can also show the relationship between stones in the diverticulum of the renal calyces and the collecting system.
(3) X-ray angiography in acute renal colic: For patients who cannot be diagnosed clearly by routine examination, such as emergency nephrography showing obstructive nephrography, excretory urography can be performed immediately. As long as the necessary preparations are made (such as pain relief for the patient) and the time of imaging is extended appropriately, most patients can obtain a clear diagnosis. The main manifestations are: delayed visualization of the affected kidney (usually achieved at 120-240 min), increase in kidney volume, and obstruction of the excretion of the contrast agent at the site of the stone. Accordingly, the diagnosis of stones can be clarified.
The mechanisms of emergency urography are.
(i) In acute obstruction of the upper urinary tract on one side, the compensatory function of the kidney on the healthy side does not appear quickly, allowing the contrast agent to remain in the bloodstream for a longer period of time.
②After acute ureteral obstruction, reflux occurs within the kidney on the affected side. On the one hand, it reduces the pressure of the upper urinary tract on the affected side, improves the blood circulation of the renal cortex and maintains the function of the renal unit for a longer period of time; on the other hand, it makes the urine retained above the obstruction site constantly renewed and gets the contrast agent from the blood, which finally makes the site above the obstruction clearly visualized after a period of time.
(4) Retrograde contrast: Retrograde contrast is needed to assist in the diagnosis in the following cases.
(① When excretory urography is unsatisfactory for various reasons.
(ii) when excretory urography reveals lesions in the kidney or ureter and further clarification of the site, extent and nature of the lesion is needed.
③when negative stones and polyps are suspected in the kidney
(iv) Before surgery for certain renal deerstalker-type stones, retrograde contrast can help to understand the relationship between the stone and the renal pelvis and calyces. The contrast agent may be pantothenic glucosamine or air. With the continuous progress of diagnostic techniques, the use of retrograde imaging has been greatly reduced.
(5) Renal puncture angiography: In case of failure of retrograde angiography, renal puncture angiography can be performed. Because it may cause some complications, it is rarely used now.
2.Nephrogram is a safe, reliable, simple and painless method to diagnose urinary tract obstruction.
It can understand the function of the divided kidney and the patency of the upper urinary tract on each side, and serve as an indicator to understand the development of the disease and observe the efficacy of treatment. Its sensitivity is much higher than that of excretory urography. The diuretic nephrogram can differentiate between functional obstruction and mechanical obstruction. In acute renal colic, if there are red cells in the urine routine but no stone shadows in the KUB, and the diagnosis is not clear, a diuretic nephrogram can be performed urgently. If there is an obstructive nephrogram on the affected side, it can be determined that there is an obstruction in the upper urinary tract on the affected side, and it can be distinguished from other acute abdominal diseases.
3.Ultrasound examination can diagnose whether there are stones in the kidney and whether there are other combined lesions.
Determine whether there is hydronephrosis in the kidney. In particular, it can detect urinary tract stones that can be X-rayed, and it can also provide some evidence of kidney damage caused by stones and the etiology of certain stones. However, ultrasound also has some limitations. It cannot identify calcifications in the kidney from stones, visualize the relationship between stones and the kidney, or see the specific effects of stones on the kidney, and more importantly, ultrasound cannot provide sufficient evidence on how to treat stones. Approximately more than 1/4 of patients with normal ultrasound are diagnosed with ureteral stones at the time of IVU examination. Therefore, ultrasound can only be used as an adjunct or screening test for the diagnosis of urinary stones. After ultrasound reveals the presence of stones, further tests, such as excretory urography, should be performed.
4.CT examination is not necessary for all patients with urinary stones.
CT examination can show the size and outline of kidney, kidney stone, hydronephrosis, renal parenchymal lesion and renal parenchyma remaining, also can identify renal cyst or hydronephrosis; can identify the lesion of urinary tract obstruction caused outside the urinary tract such as retroperitoneal tumor, pelvic tumor, etc.; enhanced imaging can understand the function of the kidney; for acute renal failure caused by stone, CT can help to establish the diagnosis. Therefore, CT is required only for negative stones that do not show up on X-ray and for patients with urinary stones whose diagnosis cannot be established by routine examination and thus affects the choice of surgical approach. Non-enhanced spiral CT is used because the information can be stored and reconstructed. It is faster, less expensive, has no side effects of contrast agents, has a lower radiation dose, and can be differentiated from other diseases of the abdomen that are easily confused with renal colic (e.g. appendicitis, ovarian cysts, etc.). The sensitivity of diagnosing renal and ureteral stones is between 96% and 100%, and the specificity is between 92% and 97%. Spiral CT scans the area from the glabella to below the pubic symphysis. On spiral CT films, all stones are high density and can show hydronephrosis and the thickness of the renal cortex.
5.Magnetic resonance magnetic resonance urography is effective in diagnosing urinary tract dilatation.
It is effective in diagnosing 96% of urinary tract obstruction, especially for those with impaired renal function, contrast allergy, and contraindication to X-ray examination. It is also suitable for pregnant women and children. Stones all show low signal on MRI. However, they need to be differentiated from blood clots based on medical history and other imaging data. Magnetic resonance urography images water-bearing organs by a heavy T2-weighted effect. This technique is very sensitive to slow or stopped flowing fluids (such as brain crest fluid, bile, urine, etc.) and shows high signal; while substantial organs and flowing fluids show low signal to achieve the clear effect of water imaging. This technique does not use contrast agents, has no radiation, has the advantages of safety and easy operation, and can obtain similar effects to excretory urography. On magnetic resonance urography, kidney stones and bladder stones are shown as low signal and show a filling defect compared to the surrounding urine high signal. However, it also needs to be differentiated from blood clots and tumors. In addition to the obstruction caused by ureteral stones, magnetic resonance urography is also good for the diagnosis of other causes of upper urinary tract obstruction (such as pelvic-ureteral junction stenosis), ureteral cysts, and ectopic openings in the ureter.
What diseases are kidney stones easily confused with?
1. Gallstones gallstones can cause biliary colic, which is easily confused with right-sided renal colic.
When gallstones are combined with cholecystitis, there may be persistent pain in the right upper abdomen, with paroxysmal intensification and positive Murphy’s sign. Sometimes there may be an enlarged gallbladder under the right costal margin that is painful to touch and moves with inspiration, or a mass wrapped in a large omentum with unclear borders and little mobility that is painful to touch. Routine urinalysis is usually normal in patients with gallstones, and ultrasound examination can confirm the diagnosis.
2, renal tuberculosis kidney stones combined with obstruction and infection should be differentiated from renal tuberculosis.
Kidney tuberculosis often has chronic and stubborn bladder irritation symptoms, no significant effect by general antibiotic treatment; pus cells in the urine, while ordinary urine culture without bacterial growth; sometimes accompanied by pulmonary tuberculosis or small tuberculosis lesions in the kidney; cystoscopy can be seen congested edema, tuberculosis nodules, tuberculosis ulcers, tuberculosis granuloma and scar formation and other lesions, especially in the bladder triangle and near the ureteral opening lesions are obvious. The ureteral orifice is often cavernous and sometimes cloudy urine discharge is seen. Calcified renal tuberculosis is seen on plain radiographs as extensive calcification throughout the kidney, and in focal cases, speckled calcified shadows are seen in the kidney. In severe cases, renal occlusion, cavity formation, irregular enlargement of renal calyces and renal pelvis, or deformation.
The incidence of spongy kidney is 1/5000, the patient’s renal medullary collecting duct is cystic expansion, the general appearance of sponge-like.
Bilateral renal lesions are present in 70% of cases, with one to several papillae involved in each kidney. The disease is present at birth but is asymptomatic and is usually not detected until the age of 40 to 50 years due to the development of stones or infectious comorbidities. Prolonged urinary retention due to dilated collecting ducts, combined with frequent combined hypercalcemia, is responsible for the development of stones and infections. Renal tubular concentration and acidification are often impaired. Abdominal plain radiographs reveal normal or mildly enlarged kidneys of normal size and clusters of multiple stones (arranged radially in the papillary area) within the kidney. Intravenous pyelogram shows fan-like cystic dilatation of the medullary collecting ducts as a basis for the diagnosis of this disease.
4. Renal pelvis tumors are mostly papillary tumors.
There is often no obvious boundary between benign and malignant, and the metastatic pathway is the same as that of renal cancer; because of the thin wall of the renal pelvis and abundant surrounding lymphatic tissue, there are often early lymphatic metastases. The disease mostly occurs after the age of 40, and is more common in men than women. In the early stage, the disease is characterized by painless hematuria without obvious masses; in the late stage, masses may appear when the tumor increases and causes obstruction. Tumor cells are sometimes seen on urine sediment examination, and blood spraying from the ureteral orifice on the affected side can be seen on cystoscopy during hematuria. CT and ultrasound can help to differentiate.
5, biliary ascariasis kidney stone patients presenting with renal colic should be distinguished from biliary ascariasis.
The main manifestation of biliary ascariasis is the paroxysmal “drill-like” severe colic under the saber, which is characterized by sudden onset and rapid relief. During the attack, the patient often tosses and turns, sweats all over the body, and even turns pale and has cold limbs, and is often accompanied by nausea and vomiting, and the vomit may contain bile or even roundworms. In between attacks, the pain can disappear completely. Ultrasound can make a clear diagnosis.
6, acute appendicitis right kidney stone patients with renal colic, should pay attention to differentiate from acute appendicitis.
Metastatic right lower abdominal pain is a characteristic of acute appendicitis. 70% to 80% of patients feel pain in the upper abdomen at the beginning of the attack, and then it shifts to the right lower abdomen a few hours to a dozen hours later. The upper abdominal pain is generally thought to be caused by visceral nerve reflexes, while the right lower abdominal pain is due to inflammation irritating the right lower abdomen. The abdominal signs of acute appendicitis are manifested by limited fixed and obvious pressure points in the right lower abdomen, when the pressure pain is fixed in the right lower abdomen before the abdominal pain has shifted to the right lower abdomen, which is of diagnostic importance. If the symptoms are atypical or the location of the appendix is abnormal, other symptoms and signs should be referred for differentiation. If it is difficult to confirm the diagnosis for a while, close observation and comprehensive analysis should be made to reduce misdiagnosis.
7, acute pancreatitis abdominal pain is the main symptom of acute pancreatitis.
Abdominal pain often begins in the upper abdomen, but can be limited to the right or left upper abdomen, depending on the site of lesion invasion. If the lesion of the head of the pancreas is combined with biliary tract disorders, in addition to right upper abdominal pain, it may radiate to the right shoulder or right lumbar region; when the inflammation mainly invades the tail of the pancreas, the epigastric pain may radiate to the back of the left shoulder. The nature and intensity of pain is mostly consistent with the extent of the lesion. Edematous pancreatitis is mostly persistent pain, which can be accompanied by paroxysmal aggravation and is mostly tolerable; hemorrhagic or necrotizing pancreatitis is mostly severe pain like cutting, which is not easily relieved by general analgesics, and shock can occur in severe cases. According to the history, signs and blood and urine amylase measurement, the diagnosis of most acute pancreatitis can generally be established.
8, Ovarian cysts twisted kidney stones female patients presenting with renal colic should be distinguished from ovarian cysts twisted.
The typical symptoms of ovarian cyst torsion are sudden onset of severe abdominal pain and even shock, nausea and vomiting. Gynecologic examination reveals a painful, tense mass with limited muscle tension. If the torsion occurs slowly, the pain is mild, and sometimes the torsion can reset itself and the pain is relieved.
9. Lymph node calcification can be misdiagnosed as kidney stone if it is located in the kidney area.
Lymph node calcification is a round granular dense shadow, internally heterogeneous, and multiple, scattered, intravenous urographic film plus lateral film can help to distinguish from kidney stones.
10. Other kidney stones.
It should also be differentiated from other related diseases that cause low back pain and abdominal pain. Such as ruptured ectopic pregnancy, gastritis, gastric ulcer and other diseases.