Pediatric Percutaneous Nephrolithotomy and CT vs IVP for Flank Pain Diagnosis

Two firsts are reviewed: an initial percutaneous nephrolithotomy procedure using smaller instrumentation and the first series in the urologic literature comparing noncontrast spiral computed tomography (CT) to intravenous pyelography (IVP) for evaluating patients with renal colic.

Percutaneous Nephrolithotomy in Infants and Preschool Age Children: Experience With a New Technique

Jackman SV, Hedican SP, Peters CA, Docimo SG.

Urology. 1998;52(4):697–701.

The treatment of complicated nephrolithiasis in the pediatric age group has lagged behind adult treatment in terms of the development of minimally invasive technology. Pediatric urologists have been reluctant to apply minimally invasive techniques to manage ureteropelvic junction (UPJ) obstruction and renal calculi.¹ The same criteria for percutaneous treatment of renal calculi applied to adults should be utilized in children. Percutaneous nephrolithotomy (PCNL) may be the treatment of choice in children who fail shockwave lithotripsy (SWL), fail ureteroscopy, or who have anatomic abnormalities such as UPJ obstruction that can be treated at the time of PCNL.² In addition, patients who have large stone volumes will have higher stone-free rates when treated with primary PCNL monotherapy, as compared with primary SWL.³ The development of smaller instrumentation and access equipment for PCNL in children thus far has not kept up with the need. The larger sheaths and endoscopes available to treat renal calculi in adults may be too large and overly traumatic in children—eg, a 24F nephrostomy sheath placed in an infant corresponds to a 72F sheath in adults. It is clear that the development of smaller nephrostomy sheaths and endoscopes for the management of complicated renal calculi has been needed.

The authors describe a technique for PCNL using a small vascular sheath that provides an 11F nephrostomy tract. They point out that the use of a smaller sheath may result in less renal trauma, fewer complications, possible shorter hospital stays, and, perhaps, less pain. This study of PCNL in 11 patients ranging in age from 2 to 6 years represents the initial experience with this technique. A 7F pediatric ureteroscope and a 9.5F flexible ureteroscope were used in 7 patients who had a variety of stones. Three patients were treated at a second-look procedure. Intracorporeal lithotripsy was performed using 1.9F and 3.0F electrohydraulic lithotripsy (EHL). The stone-free rate was 85%. No transfusions or other significant complications were reported in this study.

The significance of this article is 2-fold. First, it is clear that a number of complicated renal calculi in the pediatric age group can be cleared with minimal morbidity. Second, by using a small vascular sheath, adequate access to the collecting system can be obtained.

Percutaneous nephrolithotomy continues to play an important role in the treatment of renal calculi. Despite the initial enthusiasm for SWL, many complex renal stones do not respond to SWL monotherapy.⁴ The majority of renal calculi in adults and children can be cleared endoscopically. Rarely is open surgical intervention required⁵; however, many children with complex renal and ureteral calculi are still treated with open surgical removal. The enthusiasm for endoscopic treatment of urinary calculi has lagged behind that of adults,¹ in part due to technical considerations. Most nephroscopes and percutaneous access systems have been developed for use in adults. The authors of this article have developed a small sheath for the treatment of renal calculi in the pediatric age group. They have modified a vascular access sheath and applied this 11F peel-away sheath to the treatment of patients with upper tract calculi. The primary lithotrite used in this study, EHL, is effective, but it has been our experience that the holmium laser is more effective.

Although decreasing the size of the nephrostomy tract may decrease the morbidity of the procedure, an 11F nephrostomy tract may severely limit the ability to clear complex renal stones such as full or partial staghorn calculi. In this setting, we have used a 19F pediatric nephroscope and, using an Amplatz dilation system, placed a 24F nephrostomy sheath (Cook Urologic, Spencer, Ind).

Like other areas of surgery, one must weigh the benefits of less invasive techniques versus more traditional techniques. It is clear that percutaneous nephrolithotomy will continue to play an important role in the management of upper tract renal calculi. Children, like adults, should benefit from the techniques to treat stones in a less invasive fashion than open surgery. Improvements in instrumentation and other equipment (such as access kits) will need to be developed for children, allowing for the placement of smaller endoscopes and access sheaths.

A Comparison of Non-Contrast Computerized Tomography With Excretory Urography in the Assessment of Acute Flank Pain

Niall O, Russell J, MacGregor R, et al.

J Urol. 1999;161: 534–537.

Helical computed tomography (CT) was first introduced into clinical practice in the late 1980s.¹ The use of noncontrast CT scanning for the diagnosis of acute flank pain has been reported extensively in the radiology literature.² This study represents the first series in the urologic literature that compares noncontrast spiral CT scanning to intravenous pyelogram (IVP) in the evaluation of patients with renal colic.

At many large medical centers, noncontrast CT scanning is becoming the gold standard for the diagnosis of acute flank pain.³ The evaluation of acute flank pain in the emergency department has largely been done with the use of excretory urography (IVP); IVPs provide information about the presence or absence of obstruction and give qualitative information about renal function.² However, with the recent development of helical noncontrast CT scanning, IVPs may be used with less frequency in the future. This is due in part to some of the limitations associated with IVPs. Contrast allergy, the need for delayed imaging, and the presence of radiolucent calculi may hinder the ability to correctly diagnose the etiology of acute flank pain.

Noncontrast CT scanning allows direct cross-sectional imaging of the entire genitourinary system. This involves continuous translational motion of the patient through the gantry during simultaneous continuous rotation of the x-ray source in a helical path around the patient. The study can be completed in less than 2 minutes in some cases, but it may take as long as 10 minutes.

In this study, a total of 40 consecutive patients presenting to the emergency department with acute flank pain were enrolled. All patients were evaluated with noncontrast CT scans and a standard IVP. Treatment was determined by the urologist, who had access to the sets of films. Patients who were pregnant or had known contrast allergy were excluded from the study. At the completion of the study, all films were reviewed retrospectively and randomly by the same radiologist. CT scans were evaluated for the presence of calculi and secondary signs of obstruction, which include perinephric or periureteral stranding, dilation of the collecting system, or an increase in renal cortical thickness.⁴ IVPs were evaluated for the presence of ureteral calculi and obstruction. The presence of a stone was confirmed by passage or removal.

Calculi were confirmed in 28 of 40 patients. CT scanning had a sensitivity of 100% versus 64% for IVP. CT correctly demonstrated the absence of calculi in 11 of 12 patients, resulting in a specificity of 92% (Figure). This study and others confirm that noncontrast helical CT scanning is both sensitive and specific for the diagnosis of ureteral obstruction.⁵ In addition to demonstrating accuracy, CT scanning was completed in a mean time of 4 minutes versus a mean time of 63 minutes for an IVP. In 17 patients, additional pathology was defined, which included carcinoma of the cervix, carcinoma of the kidney, and gallstones.

Figure 1.

Noncontrast CT showed Increased diagnostic sersitivity versus IVP in a study of 40 patients presenting with a cute frank plan.³

There are limitations to noncontrast helical CT scanning. Initially, depending on the institutional costs, helical CT scanning may be more expensive than traditional IVP. However, the cost of the study is offset by rapid diagnosis and less time spent in the hospital. Noncontrast helical imaging does not provide any functional information. This modality cannot be used to evaluate stricture disease or transitional cell carcinoma of the ureter. A false-positive reading can be produced if the patient has phleboliths.

Despite these limitations, it is clear that noncontrast helical CT scanning will replace IVP in the evaluation of patients with acute renal colic. All types of ureteral calculi can be identified using this modality. In general, stones have a higher attenuation value (between 200 to 600 HU) that differentiates them from soft tissue.² The combination of a high attenuation calcification and 1 or more signs of obstruction is highly sensitive for the diagnosis of an obstructing calculus.