KIDNEY STONES - a patient's guide
- Kidney and bladder stones are a common problem
- Up to 15 percent of people will experience stones during their lives
- The problem is more common among men
- Symptoms include excruciating pain in the side, radiating towards the groin
- Strong painkillers are necessary to ease the pain
- An x-ray or ultrasound will confirm the presence of stones
- Small stones will pass without any intervention
- Shock wave treatment is recommended for most large stones
Background and history:
The cause of the stones remains relatively speculative.
As urinary constituents are similar in each kidney, why do stones commonly present on only one side? Also, why don't small stones pass uneventfully down the ureter early on? And why do some individuals develop very large stones that almost fill the kidney, and others, multiple small stones? There is considerable speculation regarding the phenomena.
Stones have plagued civilisations for thousands of years, and Hypocrates referred to the practice of cutting for stones by wandering "lithotomists".
Urinary stones (calculus/calculi) are common.
Approximately 10-15% of all individuals will experience stone disease. The male to female ratio is approximately 3:1, with women having a higher incidence of infectious stones.
The specific stone incidence: calcium oxalate is approximately 1/3, mixed stones 1/3, struvite stones (magnesium amonium phosphate) approximately 20%, uric acid approximately 5%, calcium 5-10%, calcium phosphate 5%, cystine approximately 2%, and miscellaneous rare stones zanthine xylocates, triamtyline, dihydroxy adenocine.
The theories are complex and incomplete.
Urine stones are crystallized aggregates, composed of various quantities of crystalloid and organic matrix. Stone formation requires supersaturated urine (very strong), which in turn is dependent on urinary pH (acidity level), solute concentration, and the presence of various aggregators and inhibitors of crystallization.
Factors influencing stone formation:
1. Genetic - various rare enzymatic disorders can predispose to stone formation.
These include cystinuria, renal tubular acidosis, abnormal purine metabolism, leesch-nyhan syndrome.
2. Diet - it is thought in patients predisposed to stone formation, that low fluid intake, or more specifically, production of concentrated urine is more likely to result in stone formation. Specific excesses of animal fat may predispose to uric acid stones, and leafy vegetables possibly to oxylate stones.
3. Environmental - stones are most common in the warmest areas of the world. This is probably related to relative dehydration and reduction in urinary volume, leading to increased urinary concentration.
Signs and symptoms:
The most common presenting sign of stones is of severe pain in the flank (side), that can radiate down into the groin and through into the back. The pain may also be felt in the testicle or labia. The pain is often the most severe pain the patient has experienced, and is commonly associated with nausea, vomiting and restlessness.
This group of symptoms is often called "renal colic".
This pain usually results from a calculus that has impacted in the ureter, and is therefore obstructing the urine flow from the kidney, resulting in back pressure and swelling of the affected kidney.
The pain may be colicky and intermittent. Stones in the kidney may be associated with a similar pain, but less severe in nature than with stones in the ureter.
Ureteral stones that lodge near the distal end of the ureter, i.e. in the ureter as it is passing into the bladder wall may cause severe urinary frequency and urgency in addition to "renal colic".
Patients may also experience microscopic or macroscopic haematuria (blood in urine).
If infection is present with or without obstruction, there may be fever in addition to the pain.
Bladder stones typically cause severe irritative bladder symptoms and pain radiating to the tip of the urethra or penis. The urine flow may suddenly cut off as the stone lodges at the bladder outlet. Pain associated with this inability to urinate is often referred to as "strangury".
Other conditions causing obstruction of the urinary tract can cause similar symptoms, but generally the pain is not as severe as with acute renal colic.
Management of pain:
Analgesia (pain relief): With renal colic simple analgesia is not often effective, however paracetamol is worth taking if that is all that is available. Anti-inflammatory medication often provides good pain relief, but if a patient is vomiting this may need to be given either as an intramuscular injection or as a suppository.
If anti-inflammatories do not provide sufficient pain relief, opiate medication, usually as an intramuscular injection of pethidine, often with an anti-emetic, e.g. Stemitil may be required.
Physical examination is required to rule out other causes of pain in a similar location, e.g. appendicitis, cholecystitis (gallstones), pyelonephritis and (rarely) ectopic pregnancy.
The urine should be examined, as usually there is microscopic blood visible in the urine. The urine should also be sent for culture, to see if an infection is present.
The diagnosis of kidney or bladder stone is confirmed with a plain x-ray or urinary ultrasound, or intravenous urography (IVU).
A plain X-ray will detect approximately 90% of stones, however some stones are radiolucent and will be missed with a plain X-ray. Also phleboliths (calcification in pelvic veins) can cause confusion on a plain abdominal film.
In addition to demonstrating the presence of a stone, an IVU demonstrates what the degree of obstruction is to the kidney, and also gives good anatomical detail regarding the kidney and ureter, which may be important in determining which method of treatment should be used, if intervention is required.
A urinary tract ultrasound is often helpful, and is a very sensitive examination for demonstrating the presence of stones in the kidney. However, most stones in the ureter tube are not identified on ultrasound, although if the stone is causing obstruction, the kidney above the stone may be swollen (hydronephrotic), which can be detected with ultrasound.
Generally however if the kidney is hydronephrotic an IVU is often done to determine the site and cause of the obstruction.
An ultrasound is the investigation of choice in patients with poor renal function, or those who have an allergy to the contrast media. In addition, ultrasound may be useful to differentiate radiolucent stones (which don't show on x-rays), which appear as "filling defects" in the renal pelvis on an IVU.
Management of stones:
There are several factors influencing the choice of management for renal and ureteric stones. These include the stone factors - location of the stones and physical features of the kidney/ureter.
Most patients do not require admission to hospital with the acute episode, but may require an intramuscular injection of anti-inflammatory drugs or pethidine to control the pain.
If the pain is persistent or nausea and vomiting continue, patients may require admission to hospital.
If there is urinary infection or fever associated with the pain, patients need urgent admission to hospital.
Most small stones (less than 5mm) pass spontaneously, without intervention, however they may take several days or months to pass. Generally the pain secondary to these stones is intermittent, and providing progress down the ureter is seen with small stones, intervention is usually not required.
The indications for intervention are - a persistent high-grade kidney obstruction:
- unrelenting pain
- infection in an obstructed system
- obstruction of a solitary kidney (rare)
Social circumstances do dictate intervention to a certain extent, and professions requiring stone-free kidneys, e.g. airline pilots are patients that clearly cannot work with a stone present.
Surgical management of stones:
There are a variety of options for treating larger stones that do not pass down the urinary tract spontaneously. These include:
1. Extracorporeal shock wave lithotripsy (ESWL), or shock wave treatment. This is the procedure of choice for managing most renal stones under 2-3cm in diameter, and for stones in the upper ureter. This procedure is done with either injected pain relief and sedation, or general anaesthetic. Ultrasound waves are focused on the stone, and several thousand shocks are applied. The success rate from this treatment is relatively high, with 60-70% of stones being well fragmented. The advantage of this procedure is that it is non-invasive, although it can cause some bruising to the skin, and sometimes blood occurs in the urine. The stone fragments can take several weeks to pass after the treatment, and can occasionally obstruct the ureter and cause pain as they pass. Occasionally additional procedures with ureteroscopy (placing a telescope into the bladder and up the ureter to remove impacted fragments of stone) may be required.
2. Percutaneous nephrolithotomy - this involves placing a telescope into the kidney through the back whilst under a general anaesthetic. Stones can then be directly removed, or if too large, fragmented into small pieces and removed with various ultrasound probes or a laser fibre. This is the treatment of choice for relatively large stones, (greater than 2cm in diameter), or stones in the lower part of the kidney, i.e. "lower pole calyx", which would not drain well with ESWL.
Stones impacted in the upper ureter are more safely managed with ESWL, however stones in the lower ureter are best managed with ureteroscopy (placing a telescope into the bladder and up the ureter to remove a stone), which has a higher success rate.