Kidney Stone

A kidney stone is formed in the kidney. Small kidney stones are able to pass through the urinary system without being noticed. However, larger stones can obstruct the ureter. 

Causes
There are various types of stones, such as calcium stones, uric acid stones, and magnesium ammonium phosphate stones. Calcium stones are the most common type.

Some people are more likely to developing kidney stones than others. Some people have a genetic predisposition towards developing kidney stones. Other people have other medical conditions that predispose them to kidney stones, for example, having high calcium levels in the blood (hypercalcemia), or high uric acid levels in the blood (hyperuricemia).

Risk Factors
Those at highest risk are males over 30 years of age. A person is more likely to develop kidney stones if they have had a previous kidney stone, or if they have a family history of kidney stones. Having a low fluid intake increases the risk of kidney stones, as the urine will be low in volume and concentrated. Another risk factor for developing kidney stones is frequent upper urinary tract infections. 

Signs and Symptoms
A stone in the ureter causes a sudden onset of severe pain in the lower back (flank pain) which can radiate to the groin. The severity of pain can be variable, but most people describe it as excruciating. Due to the pain, the patient is often restless and distressed, unable to keep still due to the inability to find a comfortable position. They may be pale, cool and diaphoretic, and often nauseous. Due to the pain, they are usually tachycardic and hypertensive.

Classically the pain comes in waves, increases in severity, until it is severe, after which time it might ease for a short period, before returning again. However, for others the pain remains constant.

There is often blood in the urine (hematuria). This may be visible (macroscopic hematuria), or not visible to the naked eye (microscopic hematuria).

Investigations
Analysis of the urine should be performed, to examine for leucocytes, nitrites and blood. Hematuria is a frequent finding. Routine blood tests include renal function tests (creatinine and urea), electrolyte levels and white blood cell count.

Ultrasound can often confirm the presence of a stone. Abdominal x-ray can oEen confirm the presence of a stone, however not all stones are visible on x-ray.

Treatment
Many patients can be managed with good analgesia until the stone passes. Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective. Intravenous opiates (such as Morphine) are also often required. 

Good hydration is important, to keep the urinary system flushed. Often intravenous fluids are beneficial.

The majority of stones will pass naturally but if the stone does not pass naturally then it will need to be removed. The stone shall also need to be removed if there are complications, such as urinary infection.

There are some advanced methods of removing stones, such as using sound waves to break up the stone (shock wave lithotripsy). Another treatment is inserting a specialized instrument into the urethra and then into the ureter (ureteroscopy). However, if these methods are unavailable, or if the stone is exceptionally large, then conventional surgery can be performed.

Complications
Kidney stones can cause obstruction to the flow of urine. Static urine above the obstruction site can become infected, causing pyelonephritis.

Severe obstruction in the ureter can cause the urine to back up and eventually fill the kidney (hydronephrosis). If untreated, then it can cause irreversible loss of kidney function.