ultrasonography include its low cost and absence of radiation exposure. Ultrasound imaging is useful for detecting stones in situations where X-rays or CT scans are discouraged, such as in children or pregnant women. Despite these advantages, renal ultrasonography in 2009 was not considered a substitute for noncontrast helical CT scan in the initial diagnostic evaluation of urolithiasis. The main reason for this is that, compared with CT, renal ultrasonography more often fails to detect small stones (especially ureteral stones) and other serious disorders that could be causing the symptoms. On the contrary, a 2014 study suggested that ultrasonography should be used as the initial diagnostic imaging test, with further imaging studies be performed at the discretion of the physician on the basis of clinical judgment, and using ultrasonography rather than CT as an initial diagnostic test results in less radiation exposure and equally good outcome. Laboratory examination Laboratory investigations typically carried out include microscopic examination of the urine, which may show red blood cells, bacteria, leukocytes, urinary casts, and crystals; urine culture to identify any infecting organisms present in the urinary tract and sensitivity to determine the susceptibility of these organisms to specific antibiotics; complete blood count, looking for neutrophilia (increased neutrophil granulocyte count) suggestive of bacterial infection, as seen in the setting of struvite stones; renal function tests to look for abnormally high blood calcium levels (hypercalcemia); 24 hour urine collection to measure total daily urinary volume, magnesium, sodium, uric acid, calcium, citrate, oxalate, and phosphate; collection of stones (by urinating through a StoneScreen kidney stone collection cup or a simple tea strainer) is useful. Chemical analysis of collected stones can establish their composition, which in turn can help to guide future preventive and therapeutic management. Composition Calcium-containing stones By far, the most common type of kidney stones worldwide contains calcium. For example, calcium-containing stones represent about 80% of all cases in the United States; these typically contain calcium oxalate either alone or in combination with calcium phosphate in the form of apatite or brushite. Factors that promote the precipitation of oxalate crystals in the urine, such as primary hyperoxaluria, are associated with the development of calcium oxalate stones. The formation of calcium phosphate stones is associated with conditions such as hyperparathyroidism and renal tubular acidosis. Oxaluria is increased in patients with certain gastrointestinal disorders including inflammatory bowel disease such as Crohn's disease or in patients who have undergone