Kidney Stones and Cystic Fibrosis

Anyone who has had a kidney stone can tell you that it was one of the most painful events of their life. Nephrolithiasis is the process of forming a kidney stone, whereas nephrocalcinosis refers to the deposition of calcium oxalate and calcium phosphate, components of a kidney stone, into the kidney.

Prevalence of kidney stones with CF

Both nephrolithiasis and nephrocalcinosis are common in people with cystic fibrosis (CF). Nephrocalcinosis can be found up to 92 percent of people with CF. Three to 6 percent of people with CF can develop nephrolithiasis compared with 1-2 percent in the general population. Another study showed that 5.5 percent of people with cystic fibrosis had some sort of kidney stone disease, and 3.4 percent of these people had two or more episodes, with the median age of the first episode being 27 years old.^1,2

Risk factors

Besides cystic fibrosis, there are other risk factors for developing kidney stones. These include:³

• Geography. There seems to be a higher incidence of kidney stones in people in the Southeastern area of the United States. However, it is unclear why that is.
• Sex. After the age of 40, there are higher rates of kidney stones in men compared to women. However, before the age of 40, the incidence rates are similar.
• Age. The risk of kidney stones rises after the age of 40.
• Ethnicity. Kidney stones are most common in non-Hispanic white people, and least common in Asians and African-Americans.

What are signs and symptoms?

There are various signs and symptoms that can accompany kidney stones. The severity may depend on how big the stone is, or how lodged it is in the urinary tract. Some of these symptoms include:⁴

• Nausea and vomiting
• Brown, pink, or red urine
• Severe pain on the side and back, sometimes radiating to the groin
• Burning when urinating

Most kidney stones are not life threatening. Rarely, they can become lodged in the urinary tract and cause serious kidney infections. Nevertheless, it is important to see the doctor if any of these symptoms appear.

What causes kidney stones in cystic fibrosis?

There are a few proposed reasons explaining why kidney stone incidence is increased in people with CF. Some of these are:⁶

• Increased calcium oxalate excretion through the urine due to malabsorption. Calcium oxalate stones are the most common type of kidney stones. It is interesting to note that the increased excretion of oxalate is linked to the CF-related malabsorption; however, this effect is also seen in people who take replacement enzymes.⁵
• Change in gastrointestinal flora. People with CF are more likely to be on several rounds of antibiotics. Antibiotics can lead to a decreased breakdown of oxalate, resulting in more being excreted through the urine.

Preventing kidney stones

Diet plays a significant role in preventing kidney stones. For example, drinking less water, eating a diet low in calcium and potassium, and higher intake of oxalate, salt, sugar, and vitamin C can increase the risk of developing a stone. Higher animal protein intake and less fruit and vegetable consumption is also a contributing factor.⁷

Although the association between kidney stones and cystic fibrosis is not clear, spreading awareness of the link may prompt more people to seek medical care.