How Are Kidney Stones Diagnosed?

The acute patient with kidney stones usually presents with classic symptoms of acute onset of pain, writhing, and vomiting. The presentation can be dramatic and the patient is often suffering. The health care professional can often make the diagnosis based on history and brief physical examination.

Physical examination is used to detect tenderness in the flank where the kidney is located. This is usually not present. Often the exam is meant to look for other potential problems including aortic aneurysm, gallbladder disease, appendicitis, and diverticulitis. In males, the scrotum may be examined to look for testicular torsion and in females a pelvic exam might be considered to evaluate causes for pelvic pain.

Often, the patient is treated for pain while the diagnosis is being made. Urinalysis is obtained not only to detect blood in the urine, but also white blood cells and bacteria that might be associated with an infection.

Imaging of the kidney is usually performed. At present two options are widely available.

• Computerized tomography (CT) of the abdomen is the most reliable way of making the diagnosis of a kidney stone. Added benefits include knowing the size and location of the stone or stones that can help plan treatment, plus being able to evaluate other organs within the abdominal cavity. However, the risk of CT is radiation.
• Ultrasound of the urinary tract including the kidneys, ureter, and bladder can detect a kidney stone as well as associated abnormalities. Swelling of the kidney (hydronephrosis), an indirect sign of obstruction from the stone, can be detected and it is often possible to visualize the stone.

Historically, intravenous pyelograms were performed to image the urinary tract. Dye was injected into a vein and serial X-rays were performed as the kidneys excreted the dye, revealing the anatomy and any abnormalities.

Blood tests may be appropriate depending upon specific situations. A complete blood count (CBC) may be considered if an infection is present in association with the stone. Electrolytes including potassium and kidney function tests (BUN, creatinine) may be done if there is concern about kidney failure.

In patients where the type of stone is not yet known (this includes all first time kidney stone patients), attempts will be made to capture the stone by having the patient strain urine at home. If the stone is found (and it may be difficult because it can be very small and almost imperceptible to the eye) it can be sent for analysis. Knowing the type of stone may be useful to help prevent the development of future stones.