What is stone disease?Urinary calculi, solid particles in the kidneys, bladder, or ureter, are of various chemical compositions -- calcium o
What is stone disease?
Urinary calculi, solid particles in the kidneys, bladder, or ureter, are of various chemical compositions -- calcium oxalate, uric acid, cystine, and struvite.
Renal calculus disease is one of the most ancient afflictions of mankind and remains a common cause for both office and emergency room urologist's visits. Approximately one of eight Caucasian patients forms a urianry tract stone within their lifetime.
After an initial episode of renal calculus, the recurrence rate of these patients is about 50% in the ensuing decade. Men and patients with a family history of stone disease are three fold more likely to have a stone than the general population. The differences between genders may be diet, activity or gender related. Men have been shown to excrete more oxalate in their urine while women excrete more citrate accounting for some of the differences in stone production. Residents in more affluent Western societies with diets high in animal protein are at highest risk for renal calculi.Symptoms
Symptoms of renal stones may range from no symptoms, to hematuria, urinary obstruction, infection, to vague flank pain, to severe colicky pain that is not relieved with pain medication. These symtpoms can lead to urinary urgency, frequency, hematuria, and/or gastrointestinal upset. Stone formation increases significantly when urine volume is low because of dehydration and supersaturation of the urine.Treatment
With the development of extracorporeal shock wave lithotripsy (ESWL), small caliber endoscopes and safe percutaneous access to the upper urinary tract, the entire urinary tract can be assessed, visualized and treated with minimally invasive techniques. While treatment options continue to improve, many patients require advanced techniques for difficult stone management issues caused by stone type, location, size, and patient anatomical differences.Extracorporeal Shock Wave Lithotripsy (ESWL)
ESWL is a minimally invasive treatment that was introduced in 1980 after years of research between Dornier, Inc. and the University of Munich. This technology uses shock waves generated outside the body by a lithotripter and are then targeted by fluoroscopy or ultrasound to fragment stones within the urinary tract. Fragmentation occurs through tensile stress that removes surface material and pulverization of the stone through the application of multiple shock waves. The number of shock waves required for adequate stone fragmentation depends on the composition and size of the stone, the focal pressure, energy density, and fluid interface. Stones that fragment easily include calcium oxalate dihydrate, uric acid, and struvite. Stones that are difficult to fragment include calcium oxalate monohydrate, cystine, and calcium phosphate. The use of shock wave lithotripsy is dependant on the size, position, and anatomic features of the stone and is less effective with large stones and in obese patients due to difficulty in getting the stone into the focal point. Once a stone is adequately treated, the fragments can then be passed spontaneously from the urinary tract.Ureteroscopy
Rigid ureteroscopy has been used since the 1980s and was initially indicated for management of distal ureteral stones. The development of smaller semi-rigid ureteroscopes and more recently, flexible deflectable ureterorenoscopes, allows routine endoscopic evaluation of the entire urinary collecting system. Both rigid and flexible ureteroscopy are used for stone diagnosis and treatment, investigation of gross hematuria and positive urine cytology, fluguration of epithelial tumors and management of ureteral strictures, obstructed calices, and ureteropelvic junction (UPJ) obstruction. Indications for ureteroscopic stone management include ESWL failures, lower pole stones, and obesity. Small stones in the lower ureter, less than7 mm in diameter, can be extracted by a basket or forceps passed through a rigid scope that has been passed over a working guidewire or alongside a safety guidewire. Larger ureteral and intrarenal calculi can be treated with electrohydraulic or Holmium laser intracorporeal lithotripsy to fragment the stone(s) prior to passage or removal.Percutaneous Nephrolithotomy
Endoscopic or intracorporeal management of stones through a percutaneous tract into the renal collecting system is called percutaneous nephrolithotomy (PNL). This technique was developed in 1975 by Fernstrom and Johanson. It can be used for most renal and upper ureteral stones (such as stones within the lower pole calyx, within a calyceal diverticulum or a staghorn calculi) but is used mostly for large stones, greater than 2 cm that are not easily managed by ESWL or ureteroscopy, and as a salvage procedure for failed ESWL. PNL is performed under general anesthesia. The patient is placed in a prone, semi-prone, or flank position. A guidewire is then passed and the tract is dilated with graduated plastic dilators or a balloon dilator. A hollow plastic sheath is placed through the tract which a rigid or flexible nephroscope is passed. Stones less than 1 cm in size can be manually extracted through the plastic sheath using a grasping forceps. If the stones are larger than 1 cm, intracorporeal lithotripsy using ultrasonic, electrohydraulic or laser lithotripsy is performed.Open Lithotomy
Only 1% to 5% of stones require an open procedure for removal in the 21st century. Open procedures have been largely replaced by ESWL, ureteroscopy and PNL due to decreased postoperative morbidity, more rapid recovery, and shorter hospitalizations and comparable success rates. In the past, obesity was an indication for open surgery, although development of longer nephroscopes makes percutaneous procedures possible in even the morbidly obese individual. Most often open lithotomy is reserved for patients who have failed ESWL or PNL or who have abnormal anatomy. Branched or large stones may necessitate open surgical removal, while stones that may require multiple ESWL or PNL procedures may be better managed with open surgery in select cases. Finally, patients requiring partial or total nephrectomy for a nonfunctioning kidney, repair of a ureteropelvic obstruction or stenosis, or in need of other nonurologic surgery may be candidates for open surgery.Conclusion
First line therapy for urinary stones typically involves minimally invasive surgical procedures for obstructing stones that cause symptoms and do not pass spontaneously in a reasonable time. Treatment decisions are based upon suspected stone type, size, location, renal anatomy, and renal function. Morbidity, hospitalization, and cost are often reduced signficiantly with minimally invasive treatments such as extracorporeal shock wave lithotripsy, ureteroscopy, and percutaneous nephrolithotripsy; open surgical lithotomy is rare but indicated in select cases. Patients recover more quickly and have a quicker return to normal activity with the less-invasive surgical options that are available.