Difference Between Calcium Oxalate Monohydrate and Calcium Oxalate Dihydrate

Ever heard of kidney stones? These hard, painful masses can form in your kidneys when hard deposits "stick together" during urine production. Calcium oxalate dihydrate and calcium oxalate monohydrate are two common types of crystals that make up calcium oxalate kidney stones.

The Mayo Clinic defines a kidney stone as a hard deposit of minerals and salts that forms inside your kidney. Kidney stones vary in size from a grain of sand to larger than a marble and can be extremely painful. They are also common: Around 6 percent of women and 15 percent of men in industrialized countries will have one at some point during their life.

Small kidney stones may pass through your urine without causing symptoms. Potential symptoms of kidney stones include:

• Severe side and back pain, particularly below your ribs
• Fluctuating pain
• Pain during urination
• Urine that is red, pink or brown, or appears to have sediment in it
• Feeling a persistent need to urinate
• Nausea
• Vomiting

There are a variety of types of kidney stones. Calcium oxalate stones are the most common, forming when calcium crystallizes with oxalate (a substance found in some foods that is also created by the liver). Other kidney stone types include uric acid stones, struvite stones, cystine stones and calcium phosphate stones.

​Read more:​ Is It Normal to Have Sediment in Urine?

Some stones will pass naturally during urination, but others are too large to pass on their own. There are multiple options for treating kidney stones that you cannot "flush out" by drinking plenty of fluids:

• During a procedure called a percutaneous nephrolithotomy, a physician removes the kidney stone through an incision in your back. This is typically done under general anesthesia.

• In some cases, a doctor can insert a scope through your urethra and bladder to locate the stone, then break it into small, passable pieces using surgical tools. This can be done under general or local anesthesia.

• Extracorporeal shock wave lithotripsy, also known as ESWL or lithotripsy. This procedure uses soundwaves to break down the kidney stones into little pieces, small enough for you to pass naturally. This can be done under sedation or anesthesia.

The University of Chicago explains that calcium oxalate kidney stones form when calcium combines with oxalate, also called oxalic acid. There are two possible combinations: Calcium oxalate monohydrate and calcium oxalate dihydrate.

Calcium oxalate monohydrate and calcium oxalate dihydrate are similar crystals save for the fact that calcium oxalate monohydrate is associated with one water molecule and calcium oxalate dihydrate is associated with two. Calcium oxalate monohydrate crystals are harder than calcium oxalate dihydrate crystals, which makes it more difficult to break them up using lithotripsy.

According to Harvard Health, a few factors can increase your risk of developing calcium oxalate kidney stones, including:

• A low volume of urine
• High levels of calcium in your urine
• High levels of oxalate in your urine
• Low levels of citrate in your urine

Plus, some medical conditions increase your risk of calcium oxalate kidney stones, such as:

• Bowel diseases
• Kidney problems
• High levels of uric acid in the blood
• Hyperparathyroidism, which happens when one of your four parathyroid glands secretes too much parathyroid hormone

Two things can contribute to the formation of uric acid stones: High levels of uric acid in the urine, and an acid urine pH level of 5.5 or below. Urine acidity levels can be affected by a diet high in animal proteins and medical conditions such as gout. Gout is a type of inflammatory arthritis, and people with gout may experience small, painful crystals forming in their joints.

Cystine stones are caused by a genetic condition called cystinuria. This inherited disease prevents the body from reabsorbing an amino acid called cystine, so cystine builds up in your urine and can form crystals or stones. Around 1 in 7,000 people has cystinuria.

Struvite stones are typically caused by urinary tract infections. Calcium phosphate stones are linked to a high sodium intake and a high intake of calcium.

If you are prone to calcium oxalate kidney stones, your doctor may suggest cutting down on oxalate-rich foods to lower the levels of oxalate in your urine. According to the Cleveland Clinic and the National Kidney Foundation, foods to avoid on a low-oxalate diet include:

• Spinach
• Beetroot
• Rhubarb
• Swiss chard
• Nuts
• Nut butters
• Potato chips
• Bran flakes
• Miso
• Tahini
• Sesame seeds
• Buckwheat flour

The Cleveland Clinic also explains that most plant foods contain oxalate, so it's not possible to avoid it completely. Instead, you should just aim to scale back your intake.

​Read more:​ Diet for Calcium Oxalate Crystals in the Urine

The National Institutes of Health says that staying hydrated is the No. 1 thing you can do to prevent kidney stones. Drinking plenty of water can help dilute your urine, which lessens the likelihood of calcium and oxalate sticking together to form kidney stones. Pay close attention to your daily water intake, and pack your diet with water-rich foods like cucumber, watermelon, tomatoes and celery.

Though it sounds counterintuitive, try combining oxalate-rich foods with calcium-rich foods at meals if you are prone to calcium oxalate kidney stones. The National Kidney Foundation explains that this makes the calcium and oxalate more likely to bind together in your stomach long before reaching your kidneys, thus decreasing your likelihood of developing calcium oxalate stones.

Another kidney stone prevention trick is to decrease the sodium in your diet. The American Heart Association recommends consuming not more than 2,300 milligrams of sodium per day for adults, noting that an ideal number would be 1,500 milligrams or below. And yet, the average American consumes 3,400 milligrams of sodium daily.

​Read more:​ How Can I Tell When My Body Is Hydrated?