What Are Renal Calculi? - Definition, Causes, Symptoms & Treatment

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  • 0:00 Definition of Renal Calculi
  • 1:01 Types and Causes of…
  • 2:41 Risk Factors for Renal Calculi
  • 3:20 Symptoms of Renal Calculi
  • 3:48 Treating Renal Calculi
  • 5:10 Lesson Summary
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Lesson Transcript
Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

Renal calculi are also known as kidney stones - almost 1 million people are treated for these each year in the USA. Read this lesson to learn about different types of kidney stones, why they form, and how they are treated.

Definition of Renal Calculi

My friend Liz has suffered from kidney stones as long as I've known her. I didn't understand how painful they were until she tried explaining it one time, and she described them as 'a fire in her lower back.' Ouch! Let's take a look at why kidney stones form and why they are so awful.

Renal calculi is the medical term used to describe kidney stones, which - in case you're lucky enough not to know - are small, hard deposits that form in the urine that are made up of mineral and acid salts. Though kidney stones form in the kidneys, they can be transported throughout the urinary tract, which includes the kidneys, ureters, bladder, and urethra. Kidney stones are most commonly found in people between the ages of 20-40, and about one million people are treated for them every year in the United States. They are problematic because they can block urine from leaving the body, causing kidney infections and damage, and they cause a lot of pain as they move around the body.

Types and Causes of Renal Calculi

Kidney stones form when there are more solid waste particles filtered by the kidneys than there is urine to dissolve them. When these wastes cannot dissolve, they stay in a solid form and are called kidney stones. Different types of kidney stones form based on the type of waste particle present.

The most common type of kidney stone is made of calcium. Calcium is the most abundant mineral found in the body. Specifically, kidney stones are made of calcium oxalate, phosphate, or maleate. The amount of calcium consumed in food doesn't affect the formation of kidney stones, but the amount of oxalate (natural substance found in some food items) in the diet does. Spinach, beets, nuts, and potato chips are all foods high in oxalate, which can increase the development of kidney stones.

Kidney stones can also be made of uric acid, and these are most commonly found in men and in people with conditions like gout or who are undergoing chemotherapy. Uric acid is produced when the body breaks down purines, which are substances found in certain foods. These usually form when someone isn't getting enough fluids or they are losing too much fluid.

Kidney stones made of struvite form due to an infection, most commonly a urinary tract infection. Struvite is a substance composed of magnesium, ammonium, and phosphate. Women are more at risk of this type than men.

A rare form of kidney stone made of cystine occurs in people with the genetic disorder cystinuria, where their kidneys excrete too much of certain amino acids. Other types of stones can form as a side effect of certain medications.

Risk Factors for Renal Calculi

Though none of these are direct causes of kidney stones, there are risk factors that can help identify who is most at risk for developing kidney stones:

  • Caucasians experience them more than African Americans
  • A personal or family history of kidney stones - once you have had them, you are more likely to have them again
  • Obesity
  • Gastric bypass surgery
  • Immobilization
  • Metabolic disorders
  • Anatomic kidney or urinary tract abnormalities
  • High blood pressure
  • Diet: high levels of protein, salt, or sugar can cause stones to form, as can dehydration because less urine is produced

Symptoms of Renal Calculi

The severe pain that kidney stones can cause is bad enough that it has its own name: renal colic. The pain is usually in the lower back or sides, below the rib cage, and it may come in waves and vary in intensity.

Other symptoms include restlessness, blood in the urine, nausea, vomiting, discolored urine, bad-smelling urine, chills, fever, difficulty urinating, or frequently feeling the urge to urinate but only producing a small amount.

Treating Renal Calculi

The type of treatment used depends on the type of kidney stone. If it's due to an infection, antibiotics may be used. Pain relievers and drinking of plenty of water can help a stone pass.

For smaller stones, a small wire with a camera on the end may be inserted through the urethra to the bladder so that the stone can be found and captured. This procedure is called a ureteroscopy. Medications, like alpha blockers, can be used to help the muscles relax, making the stone easier to pass.

For large stones, extracorporeal shock wave lithotripsy may be used. In this procedure, external sound waves are directed at the stone to try to break it up into smaller pieces that are easier to pass. This procedure can be painful and can produce bleeding in the abdomen or kidneys.

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