Low-Dose (10%) Computed Tomography May Be Inferior to Standard-Dose CT in the Evaluation of Acute Renal Colic in the Emergency Room Setting.

INTRODUCTION: Noncontrast CT is the standard of care to evaluate nephrolithiasis. We evaluated the performance of low-dose CT (LDCT) scan for evaluation of renal colic in the emergency room (ER). MATERIALS AND METHODS: Patients visiting the ER with suspected nephrolithiasis received a standard-dose CT (SDCT) and an LDCT. Two urologists read the LDCTs and later they read SDCTs. Stone information was recorded on a diagram of the renal system. Findings on SDCTs and LDCTs were correlated through side-by-side comparison of the diagrams. Later, the two urologists adjudicated all nonconcordance between SDCTs and LDCTs in an unblinded manner. RESULTS: Twenty-seven patients were included. SDCTs revealed 27 stones in 18 patients. Mean stone size was 3.81 mm. LDCTs revealed 27 stones in 18 patients with a mean stone size of 4.7 mm (p = 0.23). Overall sensitivity and specificity of LDCTs were 70% and 39%, respectively. There were eight false-positive and eight false-negative stones. All the false-positive stones on LDCTs were placed in the ureter, in which all of the corresponding SDCTs were visible calcifications outside the ureter. Of the eight false-negative stones on LDCTs, seven were visible calcifications on the SDCTs and the eighth stone was 1 mm and was not visible. CONCLUSION: LDCT may not perform well in the evaluation of suspected nephrolithiasis in the acute setting. LDCT scan accurately demonstrates calcifications; however, accurate placement of calcifications in or out of the urinary tract may be diminished due to impaired resolution of soft tissue structures.

Body mass index predicts outcome of ureteroscopy-assisted retrograde nephrostomy for percutaneous nephrolithotomy.

INTRODUCTION: Several clinical series of retrograde nephrostomy for percutaneous nephrolithotomy (PCNL) have been published over the past 30 years demonstrating good outcomes and safety. We previously reported our adaptation of the Lawson technique, wherein we deploy the puncture wire through a flexible ureteroscope. We herein aim to clarify the performance characteristics of this nephrostomy creation technique. MATERIALS AND METHODS: Institutional Review Board approval and informed consent were obtained. A ureteroscopy-assisted retrograde nephrostomy (UARN) procedure was performed as described previously. Data were collected prospectively. Multiple patient and operative factors were evaluated for association with UARN success and nephrostomy creation time: body mass index (BMI), skin-to-stone distance, Guy's score, Clinical Research of the Endourological Society nephrolithometric score, hydronephrosis, stone burden, location of nephrostomy, exit from a stone-bearing calix, and use of holmium laser to access calix. RESULTS: Nephrostomy was successful in 49/52 UARN procedures (94%). Only single access was placed: upper-18, mid-27, and lower-7. Median BMI was 29 kg/m(2) and median time for nephrostomy creation was 39 minutes. Fluoroscopy time for the entire PCNL including nephrostomy creation was 84 and 16 seconds for case numbers 1-25 and 26-52, respectively. By stepwise linear regression, variables correlating with nephrostomy creation time were BMI (r(2)=0.219), stone burden (r(2)=0.094), use of holmium laser to access calix (r(2)=0.104), and total r(2) linear=0.416. CONCLUSIONS: UARN is an intuitive safe procedure that offers dramatic reductions in fluoroscopy times. UARN is best suited to cases requiring only one nephrostomy tract. Upper pole access is commonly performed with a subcostal technique to navigate the puncture wire below the ribs. Increasing BMI best predicts longer nephrostomy creation times; procedure failure was associated with BMI exceeding 40 kg/m(2). UARN is a robust technique for nephrostomy creation in appropriately selected patients.

Flexible ureteroscopy-directed retrograde nephrostomy for percutaneous nephrolithotomy: description of a technique.

We describe flexible ureteroscopy-directed retrograde nephrostomy access using a puncture wire to achieve renal access. This is a natural extension of modern retrograde intrarenal surgical techniques and a modernization of the original Lawson technique for retrograde nephrostomy tract creation. In appropriately selected patients, this approach is safe and permits reduced radiation exposure. We believe this technique is easy to learn and may overcome the difficult learning curve of antegrade nephrostomy techniques faced by urologists who have not undergone subspecialty training in endourology.