Kidney stones and renal colic

By Cristiano Antonino On Dec 4, 2022

What is kidney stones and what are kidney stones: kidney stones, whose medical term nephrolithiasis (or lithiasis) comes from the Greek and means ‘stones in the kidney’, is a disease of the urinary tract characterised by the formation of stones

Technically, kidney stones are hard aggregates of crystals

They are formed from various chemical substances such as calcium (calcium oxalate or calcium phosphate), less commonly from uric acid.

They are therefore real stones resulting from deposits of mineral salts that separate from urine within the urinary tract or in the kidneys.

They originate as microscopic particles but over time grow to varying sizes ranging from a few millimetres up to 6-7 centimetres in diameter.

When the stones are very small and manage to pass through the urinary tract, they are expelled spontaneously by the body, sometimes with the help of medication if necessary.

When, on the other hand, the stones are larger, they can be deposited in the kidneys, ureters and bladder, and surgery may be required for expulsion.

Incidence of kidney stones

Lithiasis, or kidney stones, is a disease of great social impact due to its high frequency.

Worldwide, its prevalence varies widely depending on diet, lifestyle, socio-economic and environmental conditions: recently, an upward trend in prevalence has been noted, especially in industrialised countries, probably due to a diet rich in animal protein.

According to the Guidelines for Urinary Tract Calculosis of the Italian Urology Association (AURO), 2007, the male/female incidence ratio is close to 2/1 probably due to the role of female sex hormones in decreasing urinary excretion of oxalate.

Calcium oxalate stones are more frequent in younger subjects, while mixed stones and uric acid stones tend to occur in older age.

What are the causes and risk factors of kidney stones?

Kidney stones form in the case of hypercalciuria (a hereditary disease involving increased absorption of calcium in food), hyperoxaluria (high levels of oxalate) or hyperuricosuria (a disorder of uric acid metabolism) associated with a lack of citrate and so much water in the kidneys that the substances dissolved in urine cannot be diluted efficiently.

The kidneys, in fact, must produce sufficient water to be able to remove excess waste from the blood, maintain a stable ratio of salts in the blood as well as produce hormones.

Other secondary causes can also be responsible for the formation of kidney stones, including:

urinary tract infections
renal cystic disease
chronic inflammation of the intestines
metabolic disorders (e.g. hyperthyroidism)

Among the risk factors, diet can be considered an important element in kidney stone formation.

A diet rich in meat, in fact, induces urinary oversaturation of uric acid which, favoured by hyperuricemia and uricosuria, low pH and insufficient fluid intake, promotes crystallisation of calcium oxalate.

Obesity and an increased body mass index (BMI) are also related to nephrolithiasis.

Even some drugs can precipitate directly into the urine to form an initial crystalline aggregation nucleus.

Signs and symptoms of renal colic

Renal colic occurs when the stone moves with a sudden, stabbing pain that starts in the back and reaches the lower abdomen.

Most often it radiates down the ipsilateral leg and in men it may even affect the testicle.

It is often accompanied by nausea, vomiting and a feverish state.

Those who have experienced it compare the pain of a kidney stone to a gunshot wound, and there are those who consider it only inferior to childbirth because it is so severe that it dulls the breath.

Other symptoms of kidney stones can be:

blood in the urine (red, pink or brown urine)
vomiting
nausea
frequent need to urinate

Diagnosis of kidney stones

To diagnose kidney stones, examinations are performed that can provide information on the location and size of the stone and whether it is obstructing the outflow of urine into the bladder:

direct urinary tract X-ray
renal and bladder ultrasound
uro-CT
haematochemical tests (creatinine and azotemia), which show the status of renal function

Prevention of kidney stones

Kidney stone formation can be prevented by adopting healthy eating habits.

First of all, the diet must be adjusted according to the type of stone.

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In any case, it is important to reduce salt in food and avoid convenience foods that contain plenty of it.

Cold cuts and sausages, anchovies, shrimps, mussels, cabbage, peas, asparagus, spinach, tea, hazelnuts, chocolate, fruit juices should be avoided.

Hydration is essential: to prevent the formation of stones and, if they already exist, to help expel them, you should drink at least 2 litres of water a day, preferring water with a low sodium and calcium content; carbonated water should be avoided as it can acidify the urine.

How to treat kidney stones

Decisions about the treatment of kidney stones are influenced by the size, location and shape of the stones.

Most stones smaller than 4 mm in diameter manage to pass through the urinary tract and be spontaneously expelled.

However, spontaneous stone expulsion and assessment of kidney function should be confirmed by medical investigation.

Expelled stones should also be analysed.

Non-steroidal anti-inflammatory drugs (NSAIDs) are the main therapy in cases of inflammation and pain.

Anti-spastic drugs can be combined with these to reduce colic.

For larger stones, surgery may be necessary

Lithotripsy, i.e. stone crushing, can be performed extracorporeally by bombarding the stones with shock waves that shatter the stones into very small sizes to facilitate their expulsion.

Percutaneous lithotripsy is the treatment of first choice for kidney stones larger than 2 cm in diameter.

Open’ surgery, on the other hand, is indicated in particularly challenging situations.

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