Pathology of urinary system stones

2021-01-26 12:00 AM

Crystals of normal substances are dissolved in urine, mainly calcium and oxalates. Besides these common substances, there are also Phosphate, Magnesium, Urat, Cystine.


Kidney stones and urinary system are the most common diseases of the urinary tract and are more common in men than women. Age is usually from 30 to 55, but can also be found in children (bladder stones). In industrialized countries, Unique Acid gravel tends to be more common in developing countries. In Vietnam, Ammonium-Magié-Phosphate (Struvit) gravel accounts for a higher percentage. Unreasonable diet (too much protein, carbohydrates, sodium, oxalate), urinary infections or living in hot, tropical regions, ... are favourable factors for urinary kidney stones. incurred. Calcium stones are usually contrasted stones, while urate and cystic stones are usually not.

According to the author Glenn. H. Preminger, the prevalence of urinary kidney stones in the world is about 3% of the population.

Causes and mechanisms of pathogenesis

The structure of the gravel

Bowman and Meckel studied urolithiasis and found that the stone had a unique property of two factors:

Mucoprotein, which acts as a glue that holds crystals together to form stones.

Crystals of normal substances are dissolved in urine, mainly calcium and oxalates. Besides these common substances, there are also Phosphate, Magnesium, Urat, Cystine.

Little is known about the role of Mucoprotein in the mechanism of stone formation.

It can be said that when the urine is concentrated or when the pH of the urine changes, the substances dissolved in the urine recrystallize into crystals, which will be eliminated along the urine stream. Mucoprotein ​​is required for the crystals to bond together to form a stone. Therefore, when testing urine, there are many Oxalate or Phosphate crystals, but the patient does not have urinary stones.

Favourable conditions for the stone generation

The most common condition is excessive concentration of urine.

Under normal conditions, if the following two conditions exist, the dissolved crystals can be deposited:

The solution is left to be quiet, not disturbed for a long time.

The solution contains foreign objects such as threads, dead cells, bacteria, ... then this object can become the nucleus for crystals to accumulate around to form stones.

In addition, when the solution is concentrated above the solubility margin above the saturation threshold, there will be the crystallization of the solutes.

The change in urine pH will make some specific solutes recrystallize specifically, under the effect of some types of bacteria (such as Proteus Mirabilis) secreting the enzyme urease that degrades urée into amoniaque, water. The urine will be alkaline (pH> 6.5) and as such, the Phosphate - Magié will recrystallize. Conversely, if the urine pH becomes acidic (pH <6), it is a favourable condition for urate to recrystallize.

Common types of urolithiasis

Stone calcium:

Accounting for 80 - 90% of the cases. The causes of increased calcium in urine are:

Parathyroid hyperthyroidism.

Large fractures and long-term immobility.

Take a lot of Vitamin D and Corticoids.

Metastasis of cancer through the bones, causing bone destruction.

There are also many cases where there is an increase in calcium concentration in the urine without finding a cause, encountered in 40-60% of cases. In addition, there may also be a high concentration of calcium in the urine but the concentration of calcium in the blood is still normal. The high concentration of calcium in the urine is not the deciding factor for urolithiasis, it is only a favourable factor.

Oxalate stones:

Occupying a high proportion in tropical countries like our country, oxalates often combine with calcium to form calcium oxalate stones.

Phosphate stones:

The most common type of phosphate stone is ammonium-magné-phosphate, accounting for about 5-15% of cases, large in size, coral-shaped, contrasted, formed by infection, especially by proteus.

The protéus bacteria have the enzyme uréase which decomposes the urea into amoniaque, so the urine will be alkaline, if the urine pH is above 7.0, the phosphate will precipitate.

acid uric stone:

Uric acid is easy to dissolve in an alkaline environment and easily crystallizes in an acid environment when the urine pH is below 6. Its causes are usually:

Uric acid is excreted too much in the urine.

Urine is too concentrated in case of dehydration caused by sweating while working in a hot environment.

Uric acid stones are more likely to appear when purine metabolism increases in the body. Causes that can increase purine metabolism:

Use a variety of foods containing high levels of purine such as pork belly, beef tripe, dried fish meat, mushrooms.

Gout (Goutte).

Decomposition of cancer when using chemotherapy drugs.

Cystine stones:

Formed due to a defect of the renal tubular reabsorption of the substance

Xystin is relatively rare in our country. Cystin stones are not contrasted.

Theory of stone formation

Up to now, there is still not a completely complete mechanism to explain the formation and development of stones in the urinary system. Many theories have been proposed, but they also do not explain all cases of stone formation. Therefore, the formation of stones is still considered to be a multi-factor process.

The Carr:

In people who often have recurrent stones, Carr found that at the ends of the manifolds, around the spines of the kidney there are small, round, hard stones. These aggregates are composed of calcium phosphate and mucoprotein.

Randall and the others:

If the kidney tower is normal, smooth, the stone would be difficult to combine, Randall said. On the contrary, if for some reason, such as in the case of pyelonephritis, altered pyelonephritis, the epidermis of the pyelonephronus inflamed, the calyx is eroded, the crystals will be precipitated in the calyx, forming calcified clusters, and then slough off and fall onto the sepals, forming small stones.

Necrosis of the kidney tower:

In some cases, such as diabetes, chronic urinary tract infections or in the case of prolonged analgesics, necrosis of the pyramids of the kidneys is found, and this is the nucleus for the crystals to deposit. gravel.


After the stone is formed, if the stone is small, the stone usually passes through the urine and is expelled. But if a stone gets stuck somewhere in the urinary tract, it will enlarge, block the flow of urine, and lead to stagnation and bulging above the block. Overtime will lead to complications:

Urinary retention.


Generate more stones.

It will eventually destroy the kidneys that produced it.

Causes of the stone being entangled

The shape and size of the stone:

A large, rough stone is easy to stick to the mucosa and become entangled.

On the urinary tract there are natural narrow spots due to the anatomical structure:

The pebble does not pass those narrow spaces, those narrow spaces are:

Ancient kidney radio.

Neck pelvis.

Narrow spots in the ureter.

In the lumbar region, the genital blood vessels (ovarian or testicular blood vessels) cross and where the ureter is often folded, the stone can become entangled.

The pelvic area, ureter cross some arteries such as the pelvic artery, the uterine bladder artery.

The area close to the bladder, the ureter crosses the vas deferens.

The ureter part in the inner bladder wall,

Therefore, ureteral stones often get entangled in the following segments:

A lumbar segment of the upper third of the ureter.

The paragraph in the baby's hip pelvis.

The inner segment of the bladder.

In the bladder:

The bladder neck is the main narrow spot. In men, the bladder neck has a prostate lining, so it is harder to pass in women.

In the urethra:

In women, the urethra has a no narrower and shorter place, so the stone is less likely to get entangled. In men, the urethra has three places that expand and the stone often goes in. The places are:

Prostate sinuses.


The bolt hole is near the stake hole.

The effect of the stone on the urinary tract

The urine comes from the pyelonephony to the bladder through peristalsis. Want to have a motive must have the following sequence:

Dilation of the anterior sphincter.

Contraction of the posterior sphincter.

Contraction of the longitudinal muscles.

This phenomenon must happen sequentially from top to bottom before the urine can go. Peristalsis starts from the kidney radio, spread to the renal pelvis and to the ureter. The apex of the calyx and the neck of the pelvis are the host sites of the peristaltic waves.

When a stone gets stuck inside the urinary tract, it affects the urinary tract in three stages:

Resistance phase:

The urinary tract above the stone strengthens the contractility to force the stone out. The ureter and renal pelvis above the stone are not yet dilated. There is a sudden increase in pressure in the pyelonephony station causing kidney cramping pain. Clinically at this stage, the patient often presents with typical renal cramps.

Expansion phase:

Usually, after about 3 months, if the stone cannot move, the ureter, renal pelvis and the kidney radio above the stone will be dilated, and the ureter's motility will decrease.

Complicated stage:

The stone will not move for a long time because it is attached to the mucosa, the ureter is thickly fibrous, and may be narrowed. Kidney function will be gradually reduced, kidney water retention, pus retention if there is an infection, stones remaining in the urinary tract are a favourable factor for recurrent infection, which will cause chronic pyelonephritis. and lead to chronic kidney failure. Bilateral ureteral stones can cause anuria due to obstruction.


Upper urinary tract stones

Includes kidney stones, renal pelvis, ureter. The common symptoms are:

Kidney cramping pain: appears suddenly, after exertion, starts in the lumbar fossa on one side, spreads forward, downward, the intensity of pain is usually strong, and there is no analgesic position. Two cases can be distinguished:

Kidney pain due to obstruction of the renal pelvis and calyx: pain in the lumbar fossa below the 12 ribs, extending forward towards the navel and pelvic fossa.

The pain of the ureter: comes from the fossa of the lumbar spread along the path of the ureter, down to the genital pelvic fossa and the inside of the thigh.

Common symptoms are nausea, vomiting, abdominal distension caused by paralysis. There may be malaria, tremors if there is a combined infection.

Examination of the back flank point pain, kidney vibration is very painful. The ureteral points press pain, can see large kidneys.

Note that there is no relationship between the size or the number of stones and the occurrence or intensity of pain in the kidneys. In some cases, the patient has no symptoms (silent stone), or has only vague signs such as dull pain in one or two lumbar areas.

Lower urinary tract stones

Includes bladder and urethral stones.

The bladder stone will irritate the bladder lining, causing burning, burning, and urination.

Primary mid-line obstruction.

Examination of the painful bladder point.

Urethral stones will cause urinary retention, physical examination often reveals bladder bridge, palpation along the urethra can see stones.


Urine test

Find cells and germs: The urine has a lot of red blood cells and white blood cells. Germs can be seen during Gram-staining and autofocus when complications of infection occur. Urine culture is required in case infection is suspected.

Sediment scanning: Oxalate, Phosphate, and Calcium crystals can be seen.

Urine pH: With urinary tract infection, the pH will rise above 6.5 because bacteria break down Urea into ammonia. When the pH is below 5.5, urate stones are more likely.

Albuminuria: Urinary tract infections have only a little Albuminuria. If there are many, glomerular pathology must be explored.


Detecting stones, kidney and ureter water retention, thin thickness of the kidney tissue owner. This test is often ordered first when urinary system stones are suspected because it is simple, inexpensive, non-invasive and can be repeated many times without harming the patient. Many cases of asymptomatic stones are found by chance on a routine screening scan or an ultrasound of the abdomen for another reason.

Abdominal X-ray preparation (ASP)

Locate the contrasting stone, giving it the size and number and its shape. Very valuable because most of the urinary system stones in Vietnam are contrast stones.

Intravenous urinary system (UIV)

Kidney shape, pyelonephropathy, ureter.

The location of stones in the urinary tract.

The degree of dilatation of the pyelonephric and ureter.

Contrast secretion function of the kidneys on each side.

X-ray of the kidney ureter upstream

Detecting unenhanced stones.

Valid in case of kidney mute on UIV film.

Downstream kidney ureter X-ray


Usually rarely used to diagnose stones, but endoscopy can intervene to remove stones.


Internally medical treatment

Treatment of kidney stones caused by stones:

Pain relief: Usually non-steroidal anti-inflammatory drugs work well in this case, can use Voltarene 75mg intravenous tube.

In the absence of an effect, Western authors often recommend the use of Morphine.

Smooth muscle relaxants: Intravenous administration of Buscopan, Drotaverine, ...

Reduce water intake.

Antibiotics, if there are signs of infection, pay attention to antibiotics that have an effect on gram-negative bacteria. 3rd generation cephalosporins, Quinolones and Aminoxides are commonly used, the dosage should be adjusted according to the degree of renal failure (if any) and aminozide should be avoided in renal failure (antibiotic nephrotoxicity).

Addresses the cause of ureter obstruction (stones, urinary tract malformations that cause fluid retention). Some cases of ureteral stones causing kidney pain that do not respond to medical treatment need to indicate early surgical intervention to resolve the obstruction. Depending on the patient's location, the number, size of the stone and the condition of the kidney function on each side to decide to minimize the drainage of the kidney pelvis through the skin or to intervene to remove the stone by emergency surgery.

Is it possible to use oral medicine to dissolve stones? This is a question that has long been considered by researchers. At present, it is concluded as follows:

For small and smooth pebbles:

Thanks to the peristalsis of the ureter the stone will move gradually to be expelled. This progressed naturally, not because the drug "eroded" the pebble as some people often think. However, the diuretic increases the flow of urine, the non-steroidal anti-inflammatory drug makes the ureter's mucosa not swollen, obstructing the movement of the stone, so it is good for the stone to move easily.

Only uric acid stones are soluble under the effect of the drug:

This is unenhanced gravel common in Western countries. Urine pH is usually very acid <6 stones will dissolve when we alkaline urine, treatment is as follows:

Diet: reduce protein, abstain from alcohol, beer, and tobacco.

Have the patient drink plenty of water per 2 litres of water per day

Alkaline urine with drugs:

Bicarbonate de Sodium 5 -10g/day.

Foncitril 4000: 1-4 capsules / day. This grade contains the chemicals citrate sodium, citrate potassium, critique acid, and trimethyl phloroglucinol.

Hungary produced with drugs such as Malurite and Magurlit is similar to Foncitril.

The attack dose of 3-4 tablets/day until pH> 7, then maintain 1-2 capsules/day and maintain urine pH and until ultrasound shows that the stone has dissolved.

Allopurinol (zyloric) : A purine inhibitor at a dose of 100-300mg per day, depending on the urine pH, used with Foncitril until the stone dissolves in the case of large stones, sometimes using the drug continuously for several weeks. side effects such as nausea, diarrhoea, pruritus, skin rash, impaired liver function. Should take the medicine after eating.

Treatment of combination drugs:

Thiazide diuretics will help the renal tubular calcium reabsorption often have to last for many months to have results like Hypo chlorothiazide (Esidrex) 1-2 tablets/day.

Vitamin B6 works well against the formation of oxalate stones (Prien research).

Medical treatment after the stone removal surgery

The problem of stone recurrence after surgery is extremely severe, the factors for stone recurrence are:

Postoperative gravel removal:

Factors that maintain urinary infections cause stone growth

A narrow spot in the urinary tract.

Urinary infections without complete treatment:

It is essential to best cure urinary tract infections with antibiotics

time map from 4-6 weeks.

Surgical treatment

Digging for gravel.

Other methods:

Laparoscopic surgery to remove stones.

Extracorporeal stones.

Get ureteral stones through the skin.

Preventive treatment

For patients to drink plenty of water, over 2.5 litres / day, drink evenly throughout the day.

About diet: depending on the nature of the stone, there are appropriate indications for each patient.

For calcium stones:

Exclude parathyroid adenoma.

Good treatment of bone marrow tumours.

Patients with increased calcinuria may be given a thiazide diuretic to reduce the concentration of calcium in the urine below 2 mmol / l.

For Oxalate stones:

Exclude foods rich in Oxalate such as spinach, Chocolate, ...

For Oxalate stones with increased urinary calcium and decreased blood phosphorus, Phosphorus can be added: 0.5 -1 g orally.

Cystine stones:

The diet is poor with sulphur-containing amine acids.