Kidney stones (renal calculi) are hard masses formed by minerals and salts that cannot dissolve in the urine. They combine to form solid aggregates of various sizes that remain in the kidney. In most cases, kidney stones are non-symptomatic because they do not obstruct the kidney. However, they can migrate through the ureter (the tube that carries urine from the kidney to the bladder) and block the regular urine passage. The obstruction of the ureter and the consequent increase in kidney pressure is a painful situation that can start renal colic, which is the main symptom of stone disease.
When the water intake is too low, the urine becomes too concentrated, allowing minerals to crystallize and stick together. However, they can arise because of a wrong diet, excess body weight, some medical conditions, and certain supplements and medications.
Most kidney stones pass through the ureter, bladder and urethra and go out of the body independently with or without treatment. In a few cases, the stone gets stuck in the ureter and requires a procedure under general anaesthesia.
How and why do kidney stones form? It is a common query when the patient wants to know how to prevent further painful renal colics or, in the worst case, an invasive procedure. Effective prevention starts with knowledge of the risk factors to proactively modify some aspects of our lifestyle. The causes of kidney stone are the following:
What we eat and drink can affect the chance of forming kidney stones. One of the common causes is high levels of calcium in the urine (or hypercalciuria).
It is not always due to dietary calcium. If we lower the amount of calcium on our diet rarely, we stop stones formation. By restricting dietary calcium, we can affect bone health, and we may even increase kidney stone risk. Then, to prevent kidney stone disease, we limit the dietary calcium intake only in clear overload cases.
Instead of lowering dietary calcium intake, we may reduce the urine calcium level by decreasing sodium (salt) intake. A good action then is to avoid salty food. By lowering salt in the diet, we reduce urine calcium, and we effectively prevent the calcium stones from forming.
Moreover, because oxalate is a component of the most common type of kidney stone (calcium oxalate), eating foods rich in oxalate can raise our risk of kidney stones.
A diet high in animal protein can raise the urine’s acid levels promoting calcium oxalate and uric acid stones. The breakdown of meat into uric acid also increases the chance that both calcium and uric acid stones will form.
Obese patients usually have lousy diet habits that make them at risk of having diet imbalance and increased risk of stone formation. That is why obesity is a risk factor for stones. Moreover, obesity may change urine acid levels, which is another recognized risk factor for urinary stones.
The parathyroid glands control most of the metabolism of calcium. Abnormal growth of these glans causes high calcium levels in the blood and urine.
Crohn’s disease and ulcerative colitis or surgeries to treat obesity (gastric bypass surgery) can raise the risk of forming calcium oxalate kidney stones. These conditions may cause diarrhea and/or excessive oxalate absorption from the intestine, resulting in an increased amount of oxalate in the urine. Low urine volume (caused by diarrhoea and dehydration) and high urine oxalate levels both promote the formation of calcium oxalate stones.
Some medications, supplements may increase the risk of forming stones.
The risk of having kidney stones is much higher if parents or siblings have already had a history of kidney stones.
Kidney stones are not symptomatic when they are small and remain in the kidney. However, when they migrate down through the ureter, the main symptom is renal colic.
Other symptoms include:
We detect most kidney stones casually during health checks. In renal colic, a US scan and urine analysis are enough to diagnose a ureteric stone migrated from the kidney. If this diagnostic is not sufficient, we use the CT scan reaching a diagnostic rate close to 100%. This radiologic examination allows us to measure the stone density that helps to plan the best treatment when the stone does not pass on its own.
Treatment depends on stone composition and site. Moreover, the treatment decision may be influenced by how effective is pain treatment, the failure of conservative treatment and complications.
Small stones are likely to pass on their own. We do not recommend treating aggressively with the procedure. In this case, pain control and observation is the only appropriate treatment.
We consider it safe to wait up to 4-6 weeks for the stone to pass if:
The most common medication prescribed to increase the stone expulsion rate is Tamsulosin (a muscle relaxant that makes easier expulsion). Painkillers and anti-nausea medicines may help to treat the symptoms while waiting for spontaneous stone clearance.
We need a more aggressive procedure if:
Shock Wave Lithotripsy (SWL) is the less invasive procedure done on local anaesthesia or general analgesia. We use it mainly to treat kidney stones. With this technique, shock waves, generated externally, are focused on the stone by US or X-ray guidance. During the treatment, the stone breaks into small pieces that can pass out in the urine over a few weeks.
The limitations of SWL are hard stones (CT scan measures the stone hardness), more than 15 mm in size, stones composed of cystine and calcium phosphate. Sometimes, we need more sessions to get rid of the stone.
With this procedure, we usually discharge the patient the same day, and he can resume the regular daily activities the following day. Sometimes, some fragment resulting from the treatment is relatively too large, it blocks the ureter, and we need to do an additional procedure to remove it from the ureter.
Although SWL is time tested and considered very safe, it can still cause side effects:
Ureteroscopy (URS) or Retrograde Intra Renal Surgery (RIRS) are procedures more invasive than SWL. We use URS and RIRS to treat kidney and ureteric stones, usually under general anaesthesia. With a rigid or flexible ureteroscope, we navigate endoscopically (without any skin incision) through the ureter up to the kidney. We use a laser to break the stone in small fragments or dust.
After the procedure, we need to place a temporary stent in the ureter to keep it patent and drain possible residual stone fragments and dust. The ureteral stent is a tiny plastic tube entirely within the body without an external bag for urine collection. We usually remove It in 7 to 10 days during cystoscopy.
We discharge the patient the same day, and the patient can resume the regular daily activities the day after. Sometimes we prescribe some mild painkiller and or anticholinergic to prevent bladder contractures’ discomfort due to the stent.
URS and RIRS are safe procedures, and the complications are rare:
Percutaneous Lithotripsy (PCNL) is more invasive than SWL and URS/RIRS but allow us to treat large kidney stones under general anaesthesia best. The endoscopic access to the kidney takes place through a half-inch incision in the lumbar area. By the rigid telescope (or nephroscope) with US and X-Ray guidance, we proceed through the flank and kidney until reaching the stone. At this point, we use laser or electro-hydraulic energy to break the stone.
After the procedure, we leave a nephrostomy into the kidney to drain urine into a collecting bag and prevent active bleeding.
We discharge the patient the day after the procedure.
We plan the post-operative radiology check in the following days after surgery to evaluate the stone fragments’ complete removal. Sometimes we need a second look when the treated stone is too large.
The patient usually resumes his regular daily activities in one or two weeks.
We rarely do open, laparoscopic or robotic surgery to remove stones. However, we consider doing these procedures when the previous ones fail.