Renal stones-Basic understanding and causes

Urinary stones are very common and roughly one in every twenty individuals forming a stone at some point of their life. At a given point of time kidney stone disease affects an estimated 1% to 15%of population. Stone occurrence is relatively uncommon before age of 20, but peaks in incidence in the fourth to sixth decades of life.
Urinary stones can cause excruciating pain or obstruct the flow of urine. Obstructed urinary flow can lead to infection or damage to kidney, also known as Obstructive Nephropathy. Therefore, prompt diagnosis and treatment is imperative for renal stone disease.

What is renal stone disease?

Stones forming in relation to the urinary system are called renal or urinary stones. Urine is a solution, which is composed of water with various waste products and body toxins dissolved in it, after being filtered from the bloodstream by the kidneys. Under normal circumstances, these waste products remain fully dissolved in the water, which imparts the urine its’ normal transparent and light yellow colour. Sometimes, however, urine can become supersaturated with any of these several substances, causing them to precipitate as crystals suspended in the water. Multiple crystals then aggregate over time to form urinary stone.

Renal stones
Urinary tract stones

Why do stones form in urinary system?

Urinary stones form by a process of super-saturation and crystallisation. A solution is made up of solid particles or solute dissolved in a liquid, referred to a solvent. The solutes can be dissolved only to a particular amount called saturation point or limit. If the concentration of a substance in a solution is above the saturation point, the solution is said to be supersaturated and leads to the growth of crystals. This super-saturation can be caused by excess amounts of solutes which in urinary stones are calcium, uric acids, oxalates etc., or decreased amount of solvent, that is the water content of urine.
Therefore, urinary factors favouring stone formation, including low volume, increased calcium, oxalate, phosphate and uric acid, dehydration, abnormal pH, and a diet high in protein. All these factors increase calcium oxalate super saturation thereby favouring crystal formation. If these conditions persists, then crystals aggregate and form stone.

What are the risk factors of urinary stones?

Men are affected two to three times more frequently than women. The geographic distribution of stone disease tends to roughly follow environmental risk factors with a higher prevalence of stone disease being found in hot, arid, or dry climates such as the mountains, desert, or tropical areas. Seasonal variation in stone disease is related to temperature, peaks in the summer months. This is because of dehydration and associated concentrated urine in individuals from such regions.
Geographic differences in the incidence of stone disease have also been ascribed to differences in the mineral and electrolyte content of water in different areas.                  Heat exposure and dehydration also constitute occupational risk factors for stone disease as well. Those exposed to high temperatures exhibited lower urine volumes and pH, higher uric acid levels, and higher urine specific gravity, leading to higher urinary saturation of uric acid and calcium.
Individuals with sedentary occupations have been found to carry an increased risk of stone formation. Increased risk of stone disease in affluent individuals, countries, and societies, which may be reflective of a more indulgent diet and lifestyle.
People who have higher Body Mass Index and Weight carries risk of stone disease which is directly proportional to the weight and body mass index in both sexes, although the magnitude of the association is greater in women than men.

What are the types of Urinary system stones?

Calcium stones are the most common stones and usually occur in form of calcium oxalate or calcium phosphate. Increased calcium intake, Vitamin D overdose, intestinal bypass surgery and certain metabolic diseases increase calcium and oxalate levels in urine.
Uric acid stones are common in individuals who drink less fluids, eat a high protein diet or have gout which causes excess of uric acid.
Struvite stones form in response to urine infections. In favourable circumstances, these stones can grow rapidly to a very large size. These stones develop jagged edges, which are very traumatic and can cause appearance of blood in urine.
Cystine stones are relatively uncommon and are found in individuals with Cystinuria, a condition associated with excess excretion of an amino acid, Cystine.

Are gallbladder and kidney stones same?

It is general belief that these two stone are one and they form because of similar reasons. This is not true, even though the concept of solvent and solute is the same. There are two different organs systems involved as Gallbladder stone forms in the digestive tract and renal stones form in relation to the urinary system. Gallbladder stones generally are made up of cholesterol whereas renal stone are made up of calcium.
The symptomatology is also different, in gall bladder stone the pain is in right upper abdomen, just below the rib cage and is associated with indigestion and heaviness in abdomen after meals. Renal stones cause pain in right or left side of loin, depending upon the side of kidney involved, along with vomiting, blood in urine and urinary discomfort. Stone in the ureter or urinary bladder may cause pain in the lower abdomen or groin. The surgical treatment is also different. In gall stone disease, gallbladder is removed along with the stones, whereas in kidney stone only stone is removed.

Disclaimer: This is for the general awareness of the patients and cannot replace expert medical advice. Patient treatments need to be individualised and that can be decided based on clinical examination and evaluation by a trained physician.

About the authorDr. Darshan Kumar is a Urologist and Andrologist in Gurgaon, India. Dr. Darshan Kumar is a specialist in Endourological surgery for renal stone disease and laparoscopy surgery.

Dr. Darshan Kumar
Dr. Darshan Kumar  MCh, Urology

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2 thoughts on “Renal stones-Basic understanding and causes

  1. Very informative article. Good to know that gall bladder n urine stones are different as everyone thinks its the same. The article throws light on diff. type of stone n their causes wgich is good to know as prevention.

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