Diagnosing Renal Lithiasis

Medical history. This provides information on the family history (40-50% of cases), eating habits, medicines taken, diseases predisposing to urinary lithiasis, environmental factors (work stress, climate, job, etc.), and whether the lithiasis is recurrent, i.e. whether there have been previous episodes. 

Urine and blood test. This is performed to assess the presence of erythrocytes (red blood cells), leukocytes (white blood cells), crystals, bacteria, and biochemical parameters in the urine and also in the blood (pH, creatinine, albumin, urea, and ions). Patients with a high risk of recurring lithiasis are asked for a specific metabolic blood and urine study. 

Simple abdominal X-ray. The goal is to see any opacities that suggest the presence of stones in the urinary system. The renal areas, the ureteral trajectories, and the bladder area are studied. It allows the detection of calcium-containing stones. The higher the calcium content of the stone, the greater the opacity and the more easily it can be seen on the X-ray. 90% of stones are radiopaque, in other words, visible on X-rays. The drawbacks of this type of test are that stones smaller than 2 mm in size are not visible, nor are radiolucent stones (uric acid). Furthermore, the interposition of gas from the intestines and bone tissue can prevent the stones being visible.

Ultrasound. This is a harmless, non-invasive test. Lithiasis is detected via ultrasound. It is the most suitable test for pregnant patients as it uses no contrast or ionising radiation. Another advantage is that it can be performed at the beginning of the acute phase of renal colic and as many times as needed during follow-up. It provides morphological, not functional, information on the kidney. It is able to detect very small stones in the kidney between 2 and 3 millimeters. However the lumbar and pelvic ureter is not very accessible due to the interposition of gas from the intestinal loops. It also detects the dilation of the urinary tract due to the obstruction caused by the stone. 

Non-contrast CT scan. This is the reference test that provides the greatest precision when it comes to the location of the stones, their size and hardness in Hounsfield Units (HU). It takes just a few minutes (5 minutes). It is capable of detecting almost all types of calculi, including radiolucent ones and those down to 2 millimetres in size. If required, contrast can be used to detect diseases other than urinary lithiasis.