Kidney and ureteral stones: when to treat them and how to prevent them

What stones are and what renal colic is

Stones, also called calculi or urolithiasis, form when certain substances in the urine clump together and crystallise. They can stay in the kidney without causing any trouble for years, or move down the ureter, the tube that carries urine from the kidney to the bladder.

If the stone blocks the ureter, urine cannot flow properly and renal colic begins: a severe pain in the back or side, which may spread towards the groin and comes and goes. Nausea or vomiting, needing to pass urine often or seeing blood in the urine are common.

To confirm the stone and see its size and position, an ultrasound scan or a low-dose CT scan is used. Those findings decide what to do.

During an attack of colic

The European guidelines recommend anti-inflammatories (NSAIDs) or metamizole, and paracetamol, as the first choice for pain. Anti-inflammatories are not suitable for everyone, for example if you have kidney, stomach or heart problems. Only take what your doctor has advised.

If the pain does not settle with treatment, or if there is a fever, the blockage needs to be relieved. I explain this in When to seek help.

Do they pass on their own?

Many small stones in the ureter pass on their own in the urine. According to the studies collected in the European guidelines:

• Stones smaller than 5 mm pass on their own in about 3 out of 4 cases; if they are close to the bladder, in about 9 out of 10.
• Stones of 5 mm or more pass on their own in about 6 out of 10 cases. The larger the stone, the less likely this is.
• On average they take about 2 to 3 weeks, although everyone is different.

While you wait, your urologist may suggest a medicine that relaxes the ureter (an alpha-blocker). It helps mainly with stones of 5 to 10 mm close to the bladder. For this use it is prescribed off-label, that is, outside the medicine's official indications, and it can cause dizziness on standing up or a blocked nose.

If the stone comes out, keep it (you can pass urine through a strainer) and bring it to your appointment: analysing it helps to prevent the next one.

When they need treatment

A stone in the ureter is treated if it has little chance of passing on its own, if the pain cannot be controlled, if the blockage does not clear over time or if the kidney is working less well. Also when there is only one kidney or there are stones on both sides.

A stone in the kidney is treated if it grows, causes a blockage, causes infections or pain, or if your health or circumstances make it advisable: for example, if your job or your travel make an attack of colic risky. A small stone that causes no trouble can be monitored. This is decided with you.

If a stone is blocking the kidney and there is an infection, a drain is placed first so that urine can flow: a double-J stent on the inside, or a nephrostomy, a thin tube that comes out through the back. Antibiotics are given and the stone is treated once the infection has cleared.

Treatment options

The choice depends on the size, position and hardness of the stone, on your body and on your health:

Shock waves (ESWL)

From outside the body, a machine sends waves that break the stone into fragments, which then pass out in the urine. It needs no cuts and no general anaesthesia, and you go home the same day. It works well for stones up to about 2 cm, except some in the lower part of the kidney and very hard ones. Sometimes more than one session is needed. It is not used in pregnancy, if there are clotting problems, an uncontrolled urinary infection, a blockage below the stone or an aneurysm close to it, or when obesity or the shape of the skeleton prevents the waves from being aimed at it.

Laser ureteroscopy

Through the urethra, without cuts, a thin instrument with a camera is passed up to the stone, in the ureter or inside the kidney (flexible ureteroscopy). A holmium or thulium laser breaks it into fragments or dust, and the larger pieces are removed. It is done under general or spinal anaesthesia and you usually go home the same day or the next. Compared with shock waves, it leaves you stone-free after a single session more often, at the cost of slightly more complications.

Percutaneous surgery (PCNL)

For large kidney stones, over 2 cm, it is the first choice in the European guidelines. Under general anaesthesia, the kidney is entered through a small opening in the back or side and the stone is broken up and removed. It requires a short hospital stay.

Another approach, such as laparoscopy, is rarely needed. The techniques available depend on each centre.

The double-J stent

It is a thin, flexible tube that runs on the inside, from the kidney to the bladder, and lets urine through. It cannot be seen from outside. It is placed to relieve a blockage or after some treatments, but not always: after an uncomplicated ureteroscopy the European guidelines recommend not leaving one in.

While you have it, there may be discomfort in your side when passing urine, urgency, going to the toilet more often or some blood in the urine. An alpha-blocker can ease this. The stent is temporary: it must be removed or changed on the planned date. If you have one and do not know when it is due to come out, ask.

Side effects and risks

• Shock waves. Blood in the urine and pain in the first few days are common. The fragments can cause colic as they pass and sometimes build up in the ureter and need treatment. A kidney haematoma with symptoms is rare: about 2 cases in 1,000.
• Ureteroscopy. Most complications are mild. A urinary infection can occur and, less often, a generalised infection (up to 5 in 100). Over time, the ureter may narrow in about 3 to 5 in 100.
• Percutaneous surgery. In a review of almost 12,000 patients, around 1 in 10 had a fever and about 7 in 100 needed a blood transfusion. Injuries to nearby organs are rare.
• Remaining fragments. After any technique, fragments may remain; they may pass on their own, grow or need further treatment.

Tell us if you take anticoagulants or antiplatelet drugs: shock waves and percutaneous surgery usually require stopping or adjusting them.

How to avoid another attack of colic

Stones can form again. These general measures apply to most people:

• Water. Drink 2.5 to 3 litres a day, spread through the day and mainly water, so that you pass more than 2.5 litres of urine. If your doctor has asked you to limit fluids because of a heart or kidney problem, follow their advice.
• Salt. No more than 4 to 5 grams a day, including the salt already in food.
• Animal protein. No excess of meat, fish or eggs: the guidelines suggest 0.8 to 1 gram per kilo of body weight a day.
• Calcium. Do not cut it out: a normal amount of calcium in your diet (1 to 1.2 grams a day, for example from dairy products) is protective. Take supplements only if advised to.
• Diet and habits. Plenty of vegetables and fruit, a healthy weight, physical activity, fewer fizzy drinks and less alcohol, and no excess vitamin C supplements.

Stone analysis is recommended in all cases. If the risk of recurrence is high, blood tests and a 24-hour urine collection are done, no earlier than 20 days after the colic and preferably at around 3 months. Depending on the results, there may be specific measures or medication.

Where it is treated

In private practice, Urología Mínimamente Invasiva (UMI) offers treatment adapted and tailored to each individual case.

When to seek help

• Seek urgent medical attention if you have a fever or chills with colic or with a stone that is causing a blockage, if the pain does not settle with the pain relief you have been advised to take, if you have only one kidney and get colic, if you are not passing any urine or if vomiting stops you from taking your medication.
• Book a priority appointment with your doctor if you have a double-J stent and do not know when it is due to be removed, if a stone has not passed after a few weeks or if a stone has been found and you do not know whether it needs treatment.

There is more detail in the warning signs.

Frequently asked questions