11/12/2020
- Mechanisms of Stone Formation
(Kidney stones)
The mechanism of stone formation include nucleation of stone constituent crystals, their growth or aggregation to a size that can interact with some intrarenal structure, their retention within the kidney or renal collecting system and further aggregation and/or secondary nucleation to form the clinical stone. The crystals form either in renal tubular fluid or in the renal interstitial fluid that is supersaturated with respect to these constituents, which in turn may be a consequence of increased excretion of stone constituent molecules, reduced urine volume, an alteration in urine pH, or a combination of these factors. The urine and, presumably, the tubular fluid of stone formers is often more highly supersaturated than that of normal healthy adults, which favors nucleation and growth of crystals. Long-term accretion of additional elements, crystalline as well as organic matrix, produces the clinical stone.
Symptoms:
* Severe, sharp pain in the side and back, below the ribs
* Pain that radiates to the lower abdomen and groin
* Pain that comes in waves and fluctuates in intensity
* Pain or burning sensation while urinating
Other signs and symptoms may include:
* Pink, red or brown urine
* Cloudy or foul-smelling urine
* A persistent need to urinate, urinating more often than usual or urinating in small amounts
* Nausea and vomiting
* Fever and chills if an infection is present
- Urine pH
Highly acid urine leading to precipitation of uric acid crystals may not only lead to uric acid stone disease but may also enhance calcium oxalate crystallization due to heterogeneous crystallization, in which one type of crystal acts as a template, thereby promoting crystallization of a second type of crystal, as noted above. Highly alkaline urine may also promote secondary nucleation of calcium oxalate by precipitation of calcium phosphate.
Low pH cannot really be said to promote crystallization of cystine, as the solubility of this substance is minimal at most usual urinary pH values. On the other hand, the solubility of this substance, increases significantly at pH values in excess of 7.5. Commercial laboratories that market packages of urine stone chemistries consider stone risk to be minimal when urine pH is between 5.8–6.2, in one instance, or between 5.5–7.0 in another.
Risk factors
Factors that increase your risk of developing kidney stones include:
- Family or personal history. If someone in your family has had kidney stones, you're more likely to develop stones, too. If you've already had one or more kidney stones, you're at increased risk of developing another.
- Dehydration. Not drinking enough water each day can increase your risk of kidney stones. People who live in warm, dry climates and those who sweat a lot may be at higher risk than others.
- Certain diets. Eating a diet that's high in protein, sodium (salt) and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much salt in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones.
- Obesity. High body mass index (BMI), large waist size and weight gain have been linked to an increased risk of kidney stones.
- Digestive diseases and surgery. Gastric bypass surgery, inflammatory bowel disease or chronic diarrhea can cause changes in the digestive process that affect your absorption of calcium and water, increasing the amounts of stone-forming substances in your urine.
- Other medical conditions such as renal tubular acidosis, cystinuria, hyperparathyroidism and repeated urinary tract infections also can increase your risk of kidney stones.
- Certain supplements and medications, such as vitamin C, dietary supplements, laxatives (when used excessively), calcium-based antacids, and certain medications used to treat migraines or depression, can increase your risk of kidney stones.
Saleh M Al-bzour
