New and Evolving Concepts in the Imaging and Management of Urolithiasis: Urologists’ Perspective

Abstract

Urolithiasis is a universal problem that has become increasingly prevalent in the United States and has a high rate of recurrence. Imaging of urolithiasis has evolved over the years due to technologic advances and a better understanding of the disease process. Computed tomography (CT) has been the investigation of choice for the evaluation of urinary stone disease. The emergence of multidetector CT and the recent introduction of dual-energy CT have further reinforced the superiority of this modality over other imaging techniques in the management of urolithiasis. Multidetector CT is not limited to simply helping make an accurate diagnosis in patients with stone disease; it is also useful in the assessment of stone burden, composition, and fragility, findings that are helpful in determining appropriate treatment strategies. In addition, multidetector CT is a valuable tool in the follow-up of patients after urologic intervention or institution of medical therapy. Familiarity with recent technologic developments will help radiologists meet the growing expectations of urologists in this setting. In addition, radiologists should be aware of the radiation risks inherent in the imaging of patients with urolithiasis and take appropriate measures to minimize this risk and optimize image quality.

Urinary Obstruction, Stone Disease, and Infection

“…Less common compositions include protein matrix, cystine, brushite, or stones due to drug-related therapies such as indinavir. Even though most stones are visible on CT, the struvite stones and uric acid stones are radiolucent on radiography [22]. Due to the difference in composition of renal stones, there is a wide variation in the attenuation on multidetector CT. For example, calcium monohydrate and brushite measure 1700-2800 HU, calcium phosphate 1200-1600 HU, cystine 600-1100 HU, struvite 600-900 HU, and uric acid 200-450 HU [23][24][25].…”

“…Uric acid stones are managed with medical therapy. Cystine-and calcium-based stones cannot be easily fragmented with shock wave lithotripsy (SWL) [22].…”

Urolithiasis: An Update on Diagnostic Modalities and Treatment Protocols

“…Haematuria and infection are also common symptoms associated with renal stone disease. Urinary tract infection (UTI) may be a result of stone obstruction or may be the cause of magnesium ammonium phosphate (struvite) stones also called the infection stones [17][18][19] . Fever, chills and pus formation are usually associated with infection stones [17,20,21] .…”

“…dumbbell shaped calcium oxalate monohydrate crystals (COM), tetrahedral or bipyramidal shaped calcium oxalate dihydrate crystals (COD), calcium phosphate stones appear narrow and elongated, struvite stones appear as coffin lid like rectangular prisms, uric acid stones appear like yellow or reddish brown diamond shaped crystals (rhomboidal) or as needles, cystine stones appear hexagonal [24,26,28,29] while 2,8-dihydroxyadenine stones appear as brown colored spherical crystals [30] . Evaluation of urine for presence of components such as calcium, creatinine, sodium, phosphate, oxalate, citrate, magnesium, uric acid and cystine helps in the determination of the causal metabolic abnormalities and risk factors [18] .…”

Dual Energy CT Application in the Abdomen

“…Because of the measurable Zeff differences obtained from renal stones of sufficient size, categorization of the dominant stone composition is possible (uric acid, cystine and calcium) [22].…”