Kidney and ureteral stones

What is a kidney stone?

NIDDK describes kidney stones as hard, pebble-like pieces that form in the kidney when there is too much of certain minerals in the urine. They range from a grain of sand to a pea, and only rarely reach the size of a golf ball. A small stone may pass quietly. Severe pain usually begins when a stone gets stuck in the urinary tract and blocks the way.

According to NIDDK, about 11 percent of men and 6 percent of women in the United States have had at least one stone. This figure is for the US and says nothing about Iran, but it shows how common the problem is.

There are four main types. Calcium stones are the most common, and most of them are calcium oxalate. Uric acid stones form when the urine is too acidic. Struvite stones follow a urinary infection and can grow quickly. Cystine stones come from an inherited disorder.

Symptoms

The NHS describes the pain like this: it starts in the flank or back and may spread to the groin, testicle or genital area. It comes and goes, with severe spells alternating with milder or pain-free periods. It may come with nausea or vomiting, frequent urination, cloudy urine, and fever or feeling hot and shivery.

Stone pain starts in the flank. Pain that starts suddenly in the testicle itself is a different matter: it may be testicular torsion, and you need to go to an emergency department at once (urgent signs).

A small stone sitting in the kidney that has not moved sometimes causes no symptoms at all and is only seen on an ultrasound or CT done for another reason.

When not to wait

The NHS says that if you think you have a stone and the pain is severe, or you have fever and chills, you should get urgent help. Have severe pain seen the same day. Do not leave fever or chills with flank pain until tomorrow; go to an emergency department, because a stone blocking the urine flow together with infection is dangerous. The EAU calls an obstructed kidney with signs of infection a urological emergency, recommends draining the urinary tract urgently and says definitive stone treatment should wait until the infection settles. The same guideline says that urgent imaging is needed if you have fever or only one kidney.

Having a single kidney, or pain with fever, are among the situations listed in urgent signs. If you become confused or suddenly feel much worse, call 115 (Iran’s emergency number). If you are outside Iran, call your local emergency number.

How is it diagnosed?

The doctor asks about your symptoms, medical conditions, medicines, diet and family history. The NHS says a urine or blood test is sometimes needed as well. For severe pain, adults have a CT scan; pregnant women and children under 16 have an ultrasound.

The EAU guideline puts ultrasound first and says that, to confirm a stone in someone with sudden flank pain, a non-contrast CT follows. The same guideline says the radiation risk can be reduced with low-dose CT. If a stone comes out and you have been asked to keep it, store it in a clean container. The NHS and NIDDK write that the lab then tells you what type of stone it is. Preparing for imaging and urine tests is covered in the test preparation guide.

Treatment

Treatment depends on the size, location and type of the stone (NIDDK), and the decision belongs to the urologist. The options run from simple to more complex.

Waiting and follow-up. For a newly diagnosed ureteral stone with no reason to remove it, the EAU puts regular follow-up first. In that guideline’s data, spontaneous passage is reported at about 75 percent for stones under 5 mm and about 62 percent for stones of 5 mm and larger. The details are in the article Will my stone pass on its own?. The NHS says passing a stone can be painful and take a few weeks, and advises drinking plenty of fluids. Pain relief, anti-sickness medicine and sometimes a medicine to help the stone pass are prescribed by the doctor; do not choose the name or amount yourself. For lower ureteral stones between 5 and 10 mm, the EAU lists a group of medicines called alpha-blockers as one option and states that this use is outside the drug’s official label. The Cochrane review (2020) says these medicines may help fragments pass after lithotripsy, but the certainty of that evidence is low.

Active removal. The EAU lists these reasons: a stone unlikely to pass on its own, pain that does not settle even with adequate painkillers, persistent blockage, and kidney failure (including blockage of both sides or a single kidney). The methods, according to the NHS and NIDDK:

• Extracorporeal shock wave lithotripsy (ESWL): shock waves from outside the body break the stone, and the fragments pass with the urine. The NHS says no anaesthetic is needed and the patient stays awake; NIDDK says numbing medicine may be given. This difference depends on the treatment centre.
• Ureteroscopy: a thin tube goes up through the urethra and bladder to remove or break the stone. According to NIDDK it is done in hospital under anaesthesia, and the patient usually goes home the same day.
• PCNL: an instrument enters the kidney through a small cut in the back, used for larger stones. NIDDK says a stay of a few days in hospital may be needed.

After some procedures a soft tube called a stent (a double-J catheter) is left in the ureter. The EAU says it is not needed in an uncomplicated case after ureteroscopy and is recommended for people at risk of complications. Living with a stent is covered in the stent and catheter guide. If you are going to have an operation or procedure, read the before a procedure guide.

After the stone has passed or been removed, it is sent for analysis. NIDDK says a 24-hour urine collection may also be requested, because a low urine volume and a high amount of minerals raise the risk of a new stone.

Preventing the next stone

NIDDK says having one stone makes another more likely. The NHS considers the risk higher in people who drink too little, eat a high-protein, low-fibre diet, are inactive, have repeated urinary infections, or have stones in the family. The good news is that a few simple steps help.

• Water. NIDDK considers water the most important step. The NHS suggests 2.5 to 3 litres of fluid a day for adults, and the EAU sets the target as a 24-hour urine volume above 2.5 litres. The EAU writes that more water reduces stone recurrence: in its data, 15 fewer stone events per 100 people over five years. If you have kidney or heart disease, adjust your fluid amount with your doctor. Urine colour is a simple guide; dark urine means drink more (NHS).
• Salt. The NHS says adults should eat less than 6 g a day. The EAU suggests about 4 to 5 g or less, because a lot of salt raises urine calcium and lowers citrate.
• Calcium. Do not cut it. The EAU stresses that calcium should not be restricted without a strong reason, and calcium tablets are not routinely recommended either.
• Animal protein. For calcium and uric acid stones, NIDDK advises eating less of it. The amount, and what to eat instead, should be set by your doctor or a dietitian.
• Oxalate. For calcium oxalate stones, NIDDK advises limiting foods high in oxalate such as nuts, peanuts, rhubarb, spinach and wheat bran. It is better to first know what type your stone is.
• Drinks and weight. The EAU recommends fewer sugary drinks and keeping a reasonable weight. The NHS suggests mixing water with fresh lemon juice. The NHS also points out that you should not overhaul your diet without your doctor’s advice.

A daily routine is described in the stone prevention guide. If your stone is uric acid, cystine or struvite, the advice differs and should be coordinated with your doctor.

A reminder

This page is for general information and does not replace an examination and imaging. The decision about waiting, medicines or a procedure to remove a stone depends on its size, its location and your overall health.