Kidney stone disease (nephrolithiasis) is a condition characterized by the occurrence and the presence of calculi stones in the urinary tract.
Kidney stone disease is a common disorder which can affect people of different ethnic groups, age, and sexes, although usually older people tend to face problems associated with kidney stones. It was estimated that approximately 10% of people have a large kidney stone at some point in their life. Kidney stones may be different in size, from sand-like small particles to large round stones which can block the urine outflow. Some stones, known as the staghorn calculi, fill the whole kidney pelvis and the calyces. When a stone blocks the ureter, it causes an acute attack of severe lower back pain irradiating to the groin which comes and goes as the stones move in the urinary tract.
- Diet high in protein and/or sodium, low in calcium;
- Diseases affecting the ileum or resection of the gut;
- Renal tubular acidosis;
- Familial hypercalciuria;
- Medullary sponge kidney;
- Primary oxaluria;
Calculi are aggregates of various minerals, their structure depends on the urine pH; substances dissolved in urine become solid again under certain circumstances and form the stones. Calcium oxalate stones are the most common, less common are calcium phosphate, uric acid stones, struvite (magnesium ammonium phosphate) and cystine stones. A mixture of different crystal types also happens (for example, some stones are composed of calcium oxalate and calcium phosphate). In rare cases, kidney stones are built of some medications such as acyclovir, indinavir or triamterene.
- Dietary risk factors
High dietary animal protein, oxalate, sodium, sucrose, and fructose are associated with an increased risk of developing kidney stones. On the other hand, a diet rich in calcium, potassium, and phylate is known to decrease the risk.
- Nondietary risk factors
Age, race, body size and environmental factors are thought to be related to the risk of developing kidney stones. Stone disease is more common among middle-aged white men. Obesity also increases the risk. Other important risk factors are working in a hot environment or lack of ready access to water or a bathroom.
- Urinary risk factors
Urine volume may influence the kidney stones formation – lower urine volume increases the risk of lithogenesis. Higher excretion of calcium with the urine is also known to increase the likelihood of the urine stones. High urine oxalate excretion also increases the risk of calcium oxalate stone formation. Urine pH changes the solubility of minerals in the urine and thus may both increase or decrease the risk of developing kidney stones.
- Genetic risk factors
Individuals with a family history of kidney stone disease are more likely to have urinary stones themselves. Such genetic disorders as primary hyperoxaluria and cystinuria.
For a long time, kidney stones remain asymptomatic and are referred to as “silent stones” until it suddenly blocks the urine outflow through the ureter and injures the urinary tract, causing acute loin pain radiating to the groin, testis or labia and bloody urine – this is known as the renal or ureteric colic. The pain is very intense, increases gradually and worsens during attacks, therefore, a person is restless and worried. In-between the attacks, pain in the back is dull. Sometimes a person has a profuse sweating and pale skin. Vomiting and nausea also develop. Typically, pain occurs abruptly, sometimes at night and awakes a person. Urinary urgency and frequency may also bother. Of note, the symptom severity does not correlate with the size of the stone/stones.
The white blood cell count may be increased during the attack of ureteric colic. Urinalysis reveals the presence of red blood cells and white blood cells in the urine and sometimes salt crystals. An ultrasound examination may be used to confirm the diagnosis, although CT is more sensitive.
Treatment of renal colic should be initiated immediately. As renal colic is very painful – nonsteroidal anti-inflammatory drugs or even narcotic analgetics to relieve the pain.
Stones with a diameter of less than 4 mm may pass spontaneously. Other stones have to be removed surgically – fragmented with a laser via percutaneous nephrolithotomy or with an ultrasonic disaggregator. Extracorporeal shock wave lithotripsy may also be used to break the big stone into small pieces which can path through the urinary system easily.
Diclofenac may be administered orally or as a suppository (100 mg) – typically it is enough, although sometimes the administration of morphine or pethidine is required.
Dietary modifications are helpful to prevent calcium stone formation. Increased fluid intake up to 3-4 L distributed throughout a day is recommended. Sodium intake should be restricted. Food rich in oxalates (spinach, rhubarb) should be avoided. On the other hand, calcium intake has to be enough, whereas calcium supplements should be avoided or taken only together with the meals.
Vitamin C or vitamin D supplements should be avoided.
Thiazide diuretics may be administered to reduce calcium excretion. Allopurinol is recommended if urate excretion is high.