Kidney stones, as the name implies, are “stones” that have grown inside the kidneys. Of all the organs in the urinary system, the kidneys are usually the site of stone formation. Kidney stones are one of the most common diseases of the urinary system, and one in 20 people may develop kidney stones. There are dozens of known kidney stone components. Stones are usually classified clinically into four major categories: calcium-containing stones, infected stones, uric acid stones, and cystine stones. There are many causes of kidney stones, including genetic, metabolic, infectious, environmental, dietary, anatomical, and pharmacological factors, among others.
Although kidney stones are a benign disease, they may sometimes block the urinary tract obstructing the discharge of urine, causing pain, hydronephrosis, and in severe cases, uremia or even tumors.
Kidney stones are characterized by complex etiology, diverse components, non-specific symptoms, and multiple and highly specialized treatment methods. In particular, the treatment should be based on the different conditions of the stone to develop different strategies and choose the best method. Therefore, when you have kidney stones, you need to go to a regular hospital for consultation and treatment.
Stone composition
There are dozens of known components of kidney stones. The stones are usually classified into four major categories: calcium stones, infectious stones, uric acid stones and cystine stones. 80% of kidney stones are calcium stones, mainly calcium oxalate and calcium phosphate. Infectious stones account for about 10%, and the main component is ammonium magnesium phosphate. Uric acid stones account for about 10%, and the incidence of uric acid stones has been gradually increasing in recent years. Cystine stones account for only about 1% of all stones. In addition, there are some drug stones and stromal stones. Clinically, most stones contain more than one component.
Etiology and pathogenesis
There are many causes of kidney stones, including genetic, metabolic, infectious, environmental, dietary, anatomical, and pharmacological factors. The pathogenesis is also very complex. We can briefly introduce the formation of kidney stones by understanding the composition of urine. The main function of urination is to excrete various wastes produced by metabolism. A person excretes about 1500ml of urine every day, taking away about 30g-50g of waste products. These wastes include: urea, uric acid, creatinine, various acids (hydrogen ions, lactic acid, glucuronic acid, beta-hydroxybutyric acid, oxalic acid, citric acid, etc.), and various salts (calcium, phosphorus, magnesium, potassium, sodium, ammonia, chloride, etc.). The concentration of these substances in urine is high, but the human kidneys can keep these substances in balance and excrete them from the body in a dissolved state. If there is too little urine, the less soluble of these substances, such as calcium oxalate, calcium phosphate, uric acid, and magnesium ammonium phosphate, will form crystals – tiny stones. Usually, these tiny stones are excreted unknowingly. The formation of these stones is caused by the alteration of certain components of the urine, the disturbance of the balance of the urine, the formation of microscopic stones, and the growth of the crystals under the long-term action of pathogenic factors, and eventually the development of clinically significant kidney stones.
Clinical manifestations
Prevalent groups
Young adults are the most prevalent group: the peak age of onset is 20-50 years old, which means that they are more likely to occur in the workforce in the prime of life, with men being 2-3 times more likely than women; the incidence of kidney stones in children is very low.
Symptoms
The symptoms of kidney stones are diverse.
(1) Lumbar colic: renal colic is a typical symptom of kidney stone, usually occurs suddenly after exercise or at night with severe pain on one side of the lower back, because it hurts too much often described as “knife-like”, at the same time can appear pain in the lower abdomen and inner thighs, nausea and vomiting, pale face, etc.. The patient is restless and in great pain. The cause of renal colic is a kidney stone blocking the renal pelvis or ureter in the process of expulsion. Many patients present with hidden pain and swelling in the lower back. After the pain, some patients can find the stone expelled with urine.
(2) Hematuria: About 80% of patients with stones present with hematuria, only some of which can be detected visually as red urine, and most of which can only be detected by laboratory tests.
(3) Asymptomatic: Many patients find kidney stones by chance during physical examination without any symptoms.
(4) Hydronephrosis: stones block the renal pelvis and ureter and cause hydronephrosis due to poor urine drainage. Some hydronephrosis can have no symptoms. Long-term hydronephrosis can cause impaired kidney function on the affected side. Severe bilateral hydronephrosis may lead to uremia.
(5) Fever: Kidney stones can be caused by bacterial infections (infectious stones) or can induce bacterial infections that lead to fever. Because the stones obstruct the urinary drainage, bacteria cannot be excreted in time, which can lead to sepsis in severe cases and endanger life.
Diagnosis Differential diagnosis
Diagnosis
Ultrasound can be used for the initial diagnosis of kidney stones. Because ultrasound is simple, quick, inexpensive and without radiation, it is usually used as the first choice for routine diagnosis. Urological X-rays can also be used as a preliminary test and for review after treatment, but it is important to note that 1 in 10 kidney stones do not show up on X-rays, often called “negative stones”. Because “bright spots” on ultrasound or X-rays are not always stones, CT and intravenous urography (IVU) are needed to confirm the diagnosis of kidney stones.
Through these “films”, it should be clear whether there are kidney stones, as well as the location, size and number of stones, whether they are combined with hydronephrosis, preliminary determination of kidney function, and whether there are urinary system malformations.
In addition, urine and blood tests should be performed to analyze the composition of the stones, so as to understand the causes of kidney stones and whether they are combined with infection, and to provide a basis for treatment and preventive measures.
Differential diagnosis
Renal tuberculosis, renal tumor, hemangioma, gallbladder stone, lymph node calcification, etc. may appear as “bright spots” in the upper abdomen on the X-ray and need to be differentiated. The diagnosis can be clarified by CT.
First aid measures
If you encounter the following conditions, you should go to the hospital for emergency treatment as soon as possible.
(1) Renal colic: give antispasmodic and analgesic treatment.
(2) Infection with high fever: Give antibiotics and antipyretic treatment, and more importantly, drain the pus from the kidney by placing ureteral stent or nephrostomy as soon as possible.
(3) Anuria: If uremia has occurred and the body is in critical condition, dialysis treatment is required. If the condition is stable, it is also necessary to place a ureteral stent or renal puncture fistula to temporarily drain urine and protect kidney function.
Treatment
The goal of treating kidney stones is to remove the stones, keep the urinary tract open, and allow the urinary system to function properly.
The method of stone removal needs to be based on the location, number, size, kidney function, whether there are combined anatomical abnormalities, whether there are combined infections, and physical status of the stones. Generally speaking, for kidney stones below 5mm, conservative treatment or observation is the main treatment. 5mm~2cm kidney stones, extracorporeal lithotripsy is preferred. It is especially important to note that extracorporeal lithotripsy should not be performed based on only one ultrasound result or X-ray, but should be performed after a clear diagnosis. percutaneous nephrolithotomy is preferred for kidney stones above 2cm. Peking University First Hospital and Peking University Institute of Urology first started to perform extracorporeal lithotripsy and minimally invasive treatment of kidney stones including percutaneous nephrolithotomy in China in the 1980s, and have nearly 30 years of experience. The use of open surgery for stone extraction has become less and less common. When combined with anatomical abnormalities of the urinary system, open surgery can be performed to treat anatomical abnormalities while extracting stones.
After treatment of stones, it is important to perform a careful review to clarify whether the stones are completely expelled. This is very important.
Prognosis of the disease
About 50% of patients with kidney stones recur within 10 years, so stone prevention is very important.
In the case of hydronephrosis caused by stone obstruction, if the obstruction is prolonged, the hydronephrosis may be completely relieved after stone removal and the kidney function remains normal; if the obstruction is prolonged, the hydronephrosis may be partially relieved after stone removal and the damaged kidney function may be difficult to recover.
Disease prevention
The prevention of kidney stones focuses on finding the cause of the stones and treating the cause or intervening. If a kidney stone is caused by a parathyroid tumor combined with hyperparathyroidism, the parathyroid adenoma can be surgically removed. Kidney stones caused by narrowing of the ureteral junction of the renal pelvis should undergo junctional plasty surgery. Other congenital and hereditary metabolic factors should be guided accordingly according to their specific conditions.
Dietary modification is an important element in the prevention of stone recurrence. For patients with calcium oxalate stones, the intake of foods that tend to produce oxalic acid, such as spinach, amaranth, hollow cabbage and mustard, should be reduced, and the intake of large amounts of vitamin C should be avoided. For the elderly, calcium supplementation is generally not restricted, but it should be done at the same time as eating. It is not reasonable to say that spinach and tofu should not be eaten. Nowadays, the incidence of uric acid stones is increasing year by year and is related to the excessive intake of meat and fat by modern people. Patients with uric acid stones should eat less purine-producing foods such as animal offal, seafood, beef and lamb, boiled soups, nuts, etc.
Drinking water is also an important part of preventing the recurrence of stones. Patients with stones are advised to drink more than 4000ml of fluid daily and keep the urine very dilute by excreting more than 1500ml of urine per day. The recommended daily urine volume for patients with uric acid stones is above 2000ml and for patients with cystine stones is above 3000ml. The main types of water to drink are plain water, pure water, mineral water, light tea water, orange juice & watermelon are good ways to ingest water. Be proactive in drinking water and distribute it evenly throughout the day.
Medications: Patients with uric acid stones and cystine stones can take alkaline medications to improve the pH of urine, increase the solubility of uric acid and cystine, and reduce their chances of recurrence.
Proper exercise facilitates the expulsion of smaller stones.
Regular review is an important part of the follow-up.