An assistant professor of Medicine in the Nephrology Division, Boston University School of Medicine, Boston Medical Centre, Massachusetts, U.S.A., Dr Titilayo Ilori, tells ALEXANDER OKERE about the causes and management of kidney stones
what are kidney stones?
Kidney stones are solid deposits of salts and minerals that form inside the body. They are also called renal calculi, nephrolithiasis or urolithiasis.
How dangerous are kidney stones and at what point can they lead to kidney damage?
The stones themselves may not be dangerous but when they pass through the ureter, they can be very painful. Usually, if they are recognised on time, they cause no permanent damage. Recurrent kidney stones or obstructing stones (especially bilaterally or in the presence of another compromise to the kidney) may cause renal damage.
Are they fatal?
They are not fatal except when they cause obstruction that is not quickly relieved.
Are there different types of kidney stones?
Yes, there are.
What are they and can you explain their causes?
The majority of the stones we see as clinicians are calcium stones. Usually, calcium stones occur as calcium oxalate stones. Interestingly, oxalate is found in many healthy foods like nuts, vegetables (spinach for example) and chocolate. Oxalate may also independently increase the risk of kidney disease. Other stones from calcium include calcium phosphate, which occurs with certain medications such as topiramate, a medication used to treat migraines. Uric acid stones may occur when individuals lose too much fluid, or in diabetes or metabolic syndrome. Struvite stones occur when an individual has a urinary tract infection. Cystine stones form in people with cystinuria, which causes kidneys to excrete excessive amino acids.
Should one consider reducing or avoiding the consumption of peanuts, chocolate and potato chips, which are said to also cause kidney stones?
A high salt diet, a high protein and sugar diet increase the risk of kidney stones. Overall, eat healthy but, perhaps, a dietary modification should occur if the person gets the first kidney stone. Potato chips are high in salt and are generally not very healthy. Chocolate may have high oxalate and so do some vegetables. Overall, a healthy diet is vital.
What are the risk factors for kidney stones?
The risk factors for kidney stones include volume depletion, diet, personal or family history, obesity. Depletion occurs when an individual does not drink enough water, especially in places where the weather is hot. High salt and sugary diets and a diet high in protein, all place individuals at risk of kidney stones. Individuals who have had kidney stones are more likely to get a repeat episode. Family history of kidney disease places individuals at an increased risk of kidney stones. Obesity places individuals at increased risk of kidney stones.
There are other risk factors, like gastrointestinal disease and surgery. Inflammatory bowel disease, chronic diarrhoea and gastric bypass disease may all increase the risk for kidney stones because they may affect calcium and water absorption. Other diseases, like renal tubular acidosis, cystinuria, hyperparathyroidism and recurrent urinary tract infections, are risk factors. Medications and supplements, such as vitamin C, topiramate, antacids (calcium based), water pills and excessive use of laxatives, are also included.
Which categories of individuals are more likely to develop kidney stones?
Non-Hispanic white individuals are more likely to have kidney stones than other ethnicities. Also, men are more likely than women to get kidney stones.
Children are usually advised to chew hard food before swallowing. Is avoiding kidney stones part of the reasons for this advice?
I don’t think the chewing of food has anything to do with the stones. That probably is more related to choking as a hazard for little children.
What are the first signs that show a person has kidney stones?
Small stones may not have any symptoms and may move through the urinary tract unnoticed. But larger stones may present with nausea or vomiting, pain with urination, blood in urine and abdominal or back pain.
At what stage is diagnosis for kidney stones necessary?
Usually people come to the hospital for pain and that is how they discover they have kidney stones. Smaller kidney stones with no symptoms are usually noticed on ultrasound or CT scans, as an incidental finding. Urine tests, blood tests and x-rays may also be needed. Treatment for kidney stones depends on the size and composition of the stone, whether it is blocking the urinary tract (obstruction) or whether it is causing pain.
Urinary tract obstruction is said to be a major problem caused by kidney stones. Are there tests that can confirm or rule out urinary tract obstruction?
Yes. An ultrasound scan or a CT scan confirms obstruction.
Are there easy ways to prevent kidney stones?
Kidney stones can be prevented by drinking enough water (eight to 12 cups per day) except for those with advanced kidney disease. Individuals should moderate protein diet by limiting the consumption of meat and eggs. More plant protein is advised. Reduce packaged and processed foods.
Patients with severe cases of COVID-19 may develop an acute form of kidney disease. The exact mechanism for this disease is not clear but contributors to kidney disease include low blood flow to the kidneys, intense systemic inflammation and muscle breakdown. We suspect that the virus may be directly causing injury to the kidney but this is still being studied.
Do these adverse effects persist in a survivor or remain permanent?
The long-term outcomes of COVID-19 are not yet understood and many studies are investigating what the specific long and short-term effects on COVID-19 are.
Is it true that survivors are likely to require dialysis in future due to the impact left by the virus?
Usually, acute kidney injury is a bad sign in a COVID-19 patient. Some patients may recover from the disease but the likelihood of recovering from kidney injury or moving on to dialysis or transplantation is not clear.
What are obvious signs of COVID-19-related problems a survivor should look out for?
A study from Wuhan, China, published in The Lancet, looked at the survivors of COVID-19 at the six-month mark and found 75 per cent of patients were struggling with fatigue, depression and diminished lung function. These ‘long-haul’ symptoms include fatigue, insomnia, depression and anxiety in addition to the reduced lung function.
How can these be managed?
It is probably best to contact your doctor if you are having any of these symptoms
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