Role of Non-contrast MDCT in the Assessment of Upper Urinary Tract Calculi Post ESWL to Predict Its Success Rate

Urinary stones are a common disease affecting one in 11 people . Their clinical presentation varies from being silent to severe loin pain owing to urinary obstruction. Currently, ESWL is the treatment of choice for most renal calculi ⩽30 mm, with success rates of 60-99%. Although many treatment options exist, ESWL has the advantages of simplicity and non-invasiveness. In contrast, failure of a first ESWL attempt requires a follow-up ESWL procedure, or an alternative procedure, both of which increase medical costs.

Advancements in imaging have significantly contributed to this process. In the mid- 1990s, computed tomography (CT) began to replace intravenous urography (IVU), abdominal films (KUB), and ultrasound (US) in stone diagnosis. Studies demonstrated that CT had superior sensitivity and specificity for stone diagnosis compared to the aforementioned modalities. Now non-contrast multidetector CT (NC-MDCT) is the gold standard for the detection of urinary system calculi. CT is also clinically useful as it can show alternate renal and non-renal pathology if present.

Many factors have been reported to predict ESWL outcome, such as skin-to-stone distance (SSD), stone size, stone location, multiplicity, the energy used, and Hounsfield Unit (HU) values measured by non-contrast computed tomography (NCCT).