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Struvite and Staghorn Calculi Treatment & Management

  • Author: Maxwell Meng, MD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
 
Updated: Nov 20, 2015
 

Medical Therapy

Staghorn calculi resulting from urease-producing bacteria are best managed with complete surgical removal of the stones. Medical therapy alone cannot rid the patient of struvite calculi and is typically adjunctive in nature. Nevertheless, nonsurgical measures may control life-threatening sequelae of untreated stones and may represent the best option in patients with significant comorbidities.

Urease inhibitors

The most successful method of oral chemolysis is with urease inhibitors. Acetohydroxamic acid (AHA) is the most widely used irreversible inhibitor of bacterial urease. AHA has a high renal clearance, can penetrate the bacterial cell wall, and acts synergistically with several antibiotics.

Although studies have demonstrated that AHA inhibition of bacterial urease decreases urinary alkalinity and ammonia levels even in the presence of infection, 20% of patients experience associated adverse effects. These include phlebitis, deep venous thrombosis, and hemolytic anemia. In addition, in patients with impaired renal function (serum creatinine level >2.5 mg/dL) has limited effectiveness and increased toxicity.

Other measures

Suppressive antibiotic therapy may prevent pyelonephritis and associated systemic infection and may help inhibit stone growth.

Sterilization of the urine with antimicrobial treatment alone can partially dissolve some struvite stones. However, only a single case report exists in the literature of prolonged oral antibiotic (dicloxacillin) therapy alone resulting in complete resolution of an infection stone.[12] Therefore, suppressive antibiotics should be viewed primarily as a means of inhibiting stone growth and as infection prophylaxis.

Dietary manipulation with a low-phosphorus, low-calcium diet and aluminum hydroxide gel (in an attempt to limit substrate [ie, phosphate] for struvite stones) has had only modest success and carries a significant risk of calcium abnormalities (hypercalciuria) and possible aluminum toxicity.

Other medical interventions, such as urinary acidification with oral ammonium chloride, have had limited long-term clinical utility.

Drug Category: Urine acidification agents - These agents reduce urine pH level.

Table. (Open Table in a new window)

Generic name Citric Acid, glucono-delta-lactone, and magnesium carbonate
Brand names Renacidin
Description Action on susceptible apatite calculi results from exchange of magnesium from irrigating solution for insoluble calcium contained in stone matrix or calcification. Magnesium salts thereby formed are soluble in gluconocitrate irrigating solution, resulting in dissolution of calculus. Struvite calculi are composed mainly of magnesium ammonium phosphates, which are solubilized by hemiacidrin due to acidic pH. Essential that patients be free from urinary tract infections prior to initiating chemolytic therapy. Used for local irrigation dissolution of renal calculi composed of apatite (a calcium carbonate-phosphate compound) or struvite (magnesium ammonium phosphates) in patients who are not candidates for surgical removal of calculi. Also used as adjunctive therapy to dissolve residual apatite or struvite calculi and fragments after surgery or to achieve partial dissolution of renal calculi to facilitate surgical removal.
Adult Dose Renal calculi:



Place nephrostomy tube at surgery or percutaneously to permit lavage of calculi; single catheter may be sufficient if calculus not obstructing ureter or ureteropelvic junction; in patients with obstructed ureter, a retrograde catheter can be placed through ureter to renal pelvis via a cystoscope (used to irrigate calculus while percutaneous nephrostomy tube used for drainage)



Pressure measurements are made under fluoroscopic guidance to ensure 2-3 mL/min can be infused without causing pain, pyelovenous or pyelotubular backflow, or manometric evidence of elevated pressure within collecting system



Postoperative patients:



Irrigation should not be started before fourth or fifth postoperative day; irrigation of renal pelvis is begun with sterile saline only after sterile urine demonstrated



Saline is infused at rate of 60 mL/h initially, and rate is increased until pain or an elevated pressure (25 cm water) appears or until maximum flow rate of 120 mL/h achieved; inspect site of insertion for leakage; if leakage occurs, irrigation is discontinued temporarily to allow for complete healing around nephrostomy tube; if no leakage or flank pain occurs, start irrigation with flow rate equal to maximum rate achieved with saline solution



Place clamp on inflow tube and instruct patients and nursing personnel to stop irrigating solution whenever pain develops; nursing personnel responsible for performing irrigation must be instructed concerning location of nephrostomy tube(s) and direction of flow of irrigating solution to ensure against misconnection of inflow and egress tubes



Perform nephrotomography periodically to assure proper placement of catheter tip and to assess efficacy; if stones fail to change size after several days of adequate irrigation, discontinue procedure; upon demonstration of complete dissolution of calculus, inflow tube is clamped and left in place for few days to ensure that no obstruction exists, after which time nephrostomy tube should be removed



Bladder calculi:



Instill 30 mL through urinary catheter into bladder; clamp catheter for 30-60 min and release clamp to drain; repeat 4-6 times/d; continuous drip through 3-way Foley catheter is alternative means of dissolving bladder stones; in presence of bladder spasm and associated high pressure reflux, all precautions required for irrigation of renal pelvis must be observed



Pediatric Dose Not established
Contraindications Urinary tract infections; presence of demonstrable urinary tract extravasation; ureteral catheters, nephrostomy or pyelostomy tubes, or renal lavage for dissolving calculi
Interactions May increase toxicity of magnesium-containing medications
Pregnancy C - Safety for use during pregnancy has not been established.
Precautions Fever, urinary tract infection, signs and symptoms consistent with urinary tract infection, persistent flank pain, or if hypermagnesemia or elevated serum creatinine level develops (urea-splitting bacteria reside within struvite and apatite stones and serve as source of infection); dissolution therapy in presence of infected urinary tract may lead to sepsis and death; severe hypermagnesemia has occurred



Caution when irrigating renal pelvis of patients with impaired renal function; severe hypermagnesemia may result in hyporeflexia, dyspnea, apnea, coma, cardiac arrest, and subsequent death; treatment should include discontinuation of therapy followed by treatment with IV calcium gluconate, fluids, and diuresis in severe cases



 

Table. (Open Table in a new window)

Generic name Suby solution G
Brand names Suby solution G
Description Used to dissolve phosphatic calculi or incrustations in the bladder and urethra.
Adult Dose 1-3 L qd by intermittent irrigation or by tidal instillation and drainage to allow continuous irrigation of bladder for periods of several hours; intermittent irrigation of bladder (after manner of intermittent peritoneal dialysis) may be preferred to promote longer contact of irrigant with bladder stones; tidal (continuous inflow and outflow) irrigation may be less efficient and require larger amounts of irrigation fluid
Pediatric Dose Administer as in adults
Contraindications Bladder infections, bleeding, ulcerations, or other open wounds; IV/IM/SC injections
Interactions None reported
Pregnancy C - Safety for use during pregnancy has not been established.
Precautions For use only in irrigation of lower urinary tract; not for dissolving phosphate calculi in renal pelvis (may cause back pressure that could reactivate existing pyelonephritis); repeated or continuous use may cause bleeding (irritating to urethra; after each treatment, irrigate with sterile saline or water); 4 cases of sudden death reported during lavage therapy with similarly acting solution; not to be used in place of other indicated measures, including correction of underlying metabolic disorders, surgical intervention, and treatment of infection

Drug Category: Urease inhibitors -These agents inhibit the hydrolysis of urea and the production of ammonia.

Table. (Open Table in a new window)

Generic name Acetohydroxamic acid
Brand names Lithostat
Description Reversibly inhibits bacterial enzyme urease, thereby inhibiting hydrolysis of urea and production of ammonia in urine infected with urea-splitting organisms. Reduced ammonia levels and decreased pH enhance effectiveness of antimicrobial agents and increase cure rate of these infections. Does not acidify urine directly, nor does it have direct antibacterial effect. In patients with urea-splitting urinary infections (often accompanied by struvite stone disease) that are recalcitrant to other management, reduces pathologically elevated urinary ammonia and pH levels.
Adult Dose 12 mg/kg/d PO tid/qid on empty stomach recommended initially; not to exceed 1.5 g/d
Pediatric Dose 10 mg/kg/d PO initially; monitor clinical condition and hematologic status; dosage titration may be required
Contraindications Patients whose physical state and disease are amenable to surgery or antimicrobial agents, urine is infected by non–urease-producing organisms, or renal function is poor (eg, serum creatinine >2.5 mg/dL or CrCl < 20 mL/min) and females without satisfactory method of contraception whose urinary infections can be controlled by culture-specific oral antimicrobial agents
Interactions Absorption of iron and AHA may be reduced from intestinal lumen when both drugs taken concomitantly (give iron IV when indicated)
Pregnancy X - Contraindicated in pregnancy
Precautions Bone marrow depression (ie, leukopenia, anemia, thrombocytopenia) has occurred in animals receiving large doses (never reported in humans); hemolysis with decrease in circulating red blood cells, hemoglobin levels, and hematocrit values also noted; in renal impairment, closely monitor patients and reduce daily dose to avoid excessive drug accumulation
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Surgical Therapy

In the past, removal of large complex renal calculi required either anatrophic nephrolithotomy (bivalving the kidney on the lateral aspect) or pyelolithotomy (opening the renal pelvis). These are both major open operations with attendant morbidity. Moreover, these procedures did not always ensure complete stone removal, with the incidence rate of residual fragments ranging from 12-36%.

The advent of minimally invasive modalities to treat renal stones revolutionized the approach to staghorn calculi. These include extracorporeal shockwave lithotripsy (SWL) and percutaneous nephrolithotomy (PNL).

Extracorporeal shockwave lithotripsy

SWL was introduced in 1982 and is used to fragment urinary stones in a variety of locations without requiring an incision or instrumentation of the urinary tract.

Struvite calculi are effectively broken by SWL because of the multiple laminations within the stones. However, even with excellent stone fragmentation by primary SWL, repeat therapy via SWL must be performed in 50% of patients because of a large stone burden. If multiple sessions are anticipated, the renal pelvis should be treated first. Real-time monitoring of stone fragmentation using fluoroscopy is important to target and shock all areas of the stone.

In addition, the potential for urinary obstruction during spontaneous stone passage usually requires the placement of an indwelling ureteral stent. In up to 40% of patients, a percutaneous nephrostomy (PCN) tube is subsequently required to allow adequate renal drainage.

If the renal infundibula are narrow, stone fragments that stem from SWL are unlikely to pass and remain in the calyces. Percutaneous nephrolithotomy (PNL) is the preferred surgical therapy in these cases. Large, wide infundibula that permit easy passage of fragments increase the stone-free rate and overall success of SWL treatment for staghorn calculi.

Percutaneous nephrolithotomy

PNL refers to the creation of a tract from the skin to the renal collecting system, thus permitting use of a nephroscope and instruments via this tract to fragment and remove stones. More recently, flexible ureteroscopes combined with small holmium laser fibers have allowed retrograde access to the kidney for stone destruction.

PNL was developed and popularized in the 1980s with the proliferation of miniaturized instruments. Access to the kidney is obtained under ultrasound or fluoroscopic guidance, and the tract is typically dilated to 24-30F. Through this tract, a rigid nephroscope is introduced to visualize the stone and collecting system and to guide fragmentation. Energy sources for this purpose include ultrasonic, electrohydraulic, and pneumatic lithotrites and laser.

The use of a flexible nephroscope allows examination of the entire kidney and helps ensure complete stone removal. Multiple PCN tracts may be used in cases of branched, complex staghorn calculi.

After PNL, a PCN tube is placed to optimize urinary and fragment drainage. The first photo below illustrates the results of the patient shown in the second image. Right PNL was performed via a single lower-pole access during a single session, rendering the patient stone free. The left stone was later treated using SWL.

Struvite and staghorn calculi. Plain abdominal rad Struvite and staghorn calculi. Plain abdominal radiograph of a 72-year-old woman. She underwent right percutaneous nephrolithotomy, with the path of renal access demonstrated by the remaining nephrostomy tube. She was rendered stone free in the single-session procedure.
Struvite and staghorn calculi. Plain abdominal rad Struvite and staghorn calculi. Plain abdominal radiograph demonstrating a right staghorn calculus and a smaller left renal pelvic stone. The patient is a 72-year-old woman.

Some practices have advocated placing the patient in a flexed prone or supine position in preference to a flat prone position, to more easily access the stone percutaneously and clear a larger stone burden. In addition to possibly improving stone clearance, these positions may provide better comfort for the surgeon during the procedure.[13, 14]

Other advances

Technologic advances have resulted in instruments that can reach the kidney from the urethral meatus. Both laser and electrohydraulic ureteroscopic lithotripsy are possible and can significantly fragment staghorn calculi.

Case reports describe a synchronous bidirectional technique that combines percutaneous nephroscopy and retrograde intrarenal surgery to successfully treat complex, branched staghorn calculi, lessening the need for multiple flank punctures. As with SWL, the passage of a large stone burden requires an indwelling ureteral stent, and multiple treatments may be required.

For both monotherapy SWL and retrograde ureteroscopic lithotripsy, rendering the patient stone free is difficult, especially in the setting of dilated collecting systems and dependent lower pole calyces.

Surgical principles

Although multiple surgical approaches to staghorn calculi are available, several principles must be kept in mind. First, complete removal of all stone material is the goal of any procedure. Simple debulking does not prevent future infections, stone formation, or impairment of renal function.

Second, the patient should be counseled that multiple interventions may be required. If ureteroscopy or SWL is the primary treatment modality, the need for subsequent SWL, ureteroscopy, or PNL must be discussed. Use of combination therapy is a reasonable approach to ensure removal of all residual fragments. An example of this is the so-called sandwich technique, with initial PNL followed by SWL and then second-look PNL. Patient outcomes have been demonstrated to improve with increasing PNL experience.

Third, the immediate use of adjunctive measures can be considered. Postoperative oral acetohydroxamic acid (AHA) and antibiotics may delay the regrowth of struvite stones. In addition, direct irrigation of the collecting system is possible through the nephrostomy tube after PNL.

Lavage chemolysis for residual fragments consists of acidification of the urine with solutions such as Suby G or hemiacidrin (Renacidin). Although in vitro and in vivo data support some efficacy of direct acidification and ion exchange of stone calcium for magnesium, caution must be used when performing irrigation to ensure sterile urine, low intrarenal pressure, and normal serum magnesium levels. Hypermagnesemia (and associated toxicity) is more common in patients with compromised renal function.

Recommendations

The American Urological Association Nephrolithiasis Clinical Guidelines Panel outlined general recommendations regarding the treatment of staghorn calculi in 1994[15] and updated them in 2005.[16] The report reviewed the advantages and disadvantages of all treatment modalities and presented evidence-based guidelines and options but did not represent absolute standards or unanimous opinions.

In essence, the procedure or combination of surgical techniques that presents the lowest morbidity to the patient but yields the highest stone-free rates should be chosen. The following four treatment modalities were identified:

  • Percutaneous nephrolithotomy monotherapy
  • Combination therapy of PNL and shock-wave lithotripsy (SWL)
  • SWL monotherapy
  • Open stone surgery

The report did not address retrograde approaches to staghorn calculi.

PNL yields the highest stone-free rate for large struvite staghorn calculi, and so should be the initial therapy in most cases, followed by SWL or repeat PNL as necessary. SWL monotherapy should be reserved for patients with smaller staghorn stones (<500 mm2 surface area). Although once the criterion standard, initial open surgery is typically not necessary unless the kidney requires complete removal, the intrarenal anatomy is not amenable to other approaches, or the stone cannot be expected to be removed by a reasonable number of minimally invasive procedures.

Although the treatment plan for each patient should be individualized, some prospective, randomized studies are confirming and solidifying the PNL-based recommendations outlined above. Al-Kohlany and colleagues evaluated PNL versus open stone surgery in 79 patients with 88 complete staghorn calculi, which is defined as a stone burden filling at least 80% of the entire collecting system.[17] Patients undergoing PNL suffered fewer intraoperative and postoperative complications and benefited additionally from shorter operative times, shorter hospital stays, and an earlier return to work, all while reaching comparable stone-free rates without worsening renal function.

A meta-analysis by Astroza et al of 1311 PNLs performed on patients with staghorn calculi found that higher stone-free rates were achieved in a shorter surgical time when patients are positioned in the prone position versus supine positioning. Complication rates were comparable for both positions.[18]

Meretyk et al compared SWL monotherapy to PNL combined with SWL for the treatment of complete staghorn calculi and highlighted the concern of SWL alone in cases of significant stone disease.[19] Patients undergoing SWL monotherapy displayed diminished stone-free rates yet experienced an increase in overall treatment time, unplanned ancillary procedures, and complications (sepsis, in particular).

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Preoperative Details

Patients rarely require additional procedures prior to removal of the stones; however, if the patient is uroseptic and has evidence of urinary obstruction (eg, hydronephrosis) or pyonephrosis, placement of a PCN tube or ureteral stent may be necessary. Only when the patient is clinically stable after adequate urinary drainage and administration of intravenous antibiotics should definitive surgical intervention for stone removal be performed.

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Intraoperative Details

In performing PNL and open stone removal, be aware of the potential for an underlying anatomic abnormality such as ureteropelvic junction obstruction or ureteral stricture. Their role in staghorn stone formation should be considered, but the abnormality may not be best addressed at the same setting. After the stone has been removed, subsequent treatment can correct the defect.

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Postoperative Details

In analyzing outcomes of the treatment modalities, important considerations are (1) the probability of being stone free and (2) the probability of undergoing secondary unplanned procedures. Thus, careful assessment of the postoperative stone status is important.

Plain abdominal radiography may help visualize large stone fragments after open surgery, PNL, and SWL. An advantage of PNL includes the ability to fill the collecting system with contrast and to perform antegrade nephrostography, typically 1-2 days after surgery if the patient remains afebrile. Evidence of significant residual stones or urinary obstruction may lead to second-look nephroscopy or maintenance of the nephrostomy tube, respectively.

Most patients are discharged in 3 days after PNL, without the need for percutaneous renal drainage. Secondary SWL is usually indicated if a stone (or multiple stones >1 cm) remains in peripheral calyces. This can be performed during the same hospitalization 1-2 days after the initial PNL.

In a review of 31 patients who underwent repeat PNL after prior failed attempts at percutaneous stone removal, Borofsky et al reported uniform success with salvage PNL. Most of the cases involved staghorn calculi, and in most cases, initial PNL failed because of unsuitable access to the stone. These authors concluded that in the hands of experienced surgeons, salvage PNL can have outcomes no different from those of primary PNL.[20]

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Follow-up

After all treatment modalities, the patient should be closely monitored for signs of infection, renal dysfunction, and bleeding.

Postoperative serum electrolyte evaluations, CBC counts, and creatinine studies should be performed. The patient should continue on the appropriate parenterally administered antibiotic. If an indwelling ureteral stent was placed prior to SWL, the patient should return for stent removal in 3-4 weeks.

Patients should be evaluated in an outpatient setting in 3 weeks after any surgery for staghorn stones. Renal ultrasonography, abdominal radiography, and serum creatinine studies are usually performed. In addition, if a preoperative metabolic evaluation of stone disease (24-h urine collection) was not performed, conduct one postoperatively once the patient is no longer hospitalized and on a controlled diet. Patients should be exhibiting no symptoms, eating their regular diet, and following their usual lifestyle activities when such a study is performed.

In a 2014 expert opinion guideline on medical management of kidney stones, the American Urological Association recommended that after removal of struvite stones, patients should be closely monitored for persistent or recurrent urinary tract infections with urease-producing organisms. Monitoring should include periodic urine culture. In some cases, long-term prophylactic antibiotic therapy may be appropriate for helping prevent recurrences.[21]

For patient education information, see Kidney Stones.

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Complications

Infectious complications, including pyelonephritis and sepsis, may occur after either open or noninvasive (ie, SWL) treatment. Typically, infections occur early after PNL, but they may be delayed after SWL, when stone passage and obstruction occur. The incidence of significant blood loss and the need for transfusion after SWL is low, probably well below 0.1%.

The authors' recent experience demonstrates a PNL-associated transfusion rate of less than 5%. Early recognition of bleeding after PNL is paramount. Venous bleeding can usually be managed by balloon tamponade or clamping of the PCN tube; arterial bleeding may necessitate renal arteriography and embolization (or rarely nephrectomy). However, kidney loss after percutaneous stone removal, although more common than after SWL, is rare (0.1%).

Overall, the mortality rate associated with staghorn stone treatment is extremely low (SWL, 0.06%; PNL, 0.1%; PNL and SWL, 0.2%) and is typically related to cardiac dysfunction. Although significant morbidity is encountered more often with open surgery and PNL, SWL is associated with both planned and unplanned secondary interventions.

Injury to adjacent organs, including the spleen, liver, colon, and lungs, has been reported with PNL. Knowledge of perirenal anatomy, prompt recognition, and appropriate intraoperative and perioperative management usually minimize associated morbidity. For example, placement of a chest tube effectively drains air and/or fluid from the pleural cavity. Supracostal renal access during PNL is associated with a greater likelihood of pulmonary complications.

Perforation of the renal pelvis may occur during PNL. Adequate visualization, careful intracorporeal lithotripsy, and sufficient irrigation drainage help reduce this complication. Typically, it is identified immediately, with evidence of urothelial disruption or perinephric fat. Recognition of this complication is important so that the surgery can be terminated, minimizing extravasation of irrigation fluid and the potential for significant fluid absorption and spread of infection. Placement of the PCN tube is sufficient to ensure urinary drainage and healing of the urothelium. The nephrostomy tube is kept in place for 3-4 weeks to ensure healing, at which time nephrostography is performed and repeat nephroscopy can be considered for residual stone fragments.

During PNL, irrigating fluid may also be absorbed through open venous sinuses; dilutional hyponatremia and hypothermia may result. Long-term complications of both open surgery and PNL include intrarenal stricture or stenosis of the collecting system. Infundibular stenosis was recently reported as a rare complication, typically within the first year after surgery, and was associated with more complex stones and PNL.

Treatment complications for staghorn stones

Complications include the following:

  • Perforation of the renal pelvis
  • Hydrothorax/pneumothorax
  • Perirenal hematoma
  • Significant blood loss
  • Vascular injury
  • Transfusion
  • Urinoma
  • Sepsis/pyelonephritis
  • Stent/nephrostomy tube migration
  • Renal impairment
  • Wound infection
  • Loss of kidney
  • Injury of adjacent organ (eg, spleen, liver, colon)
  • Deep vein thrombosis
  • Death
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Outcome and Prognosis

Multiple measures of treatment outcomes are available for evaluation. At best, monotherapy SWL for struvite staghorn stones yields stone-free rates of 60%. Residual fragments remain in 22-70% of patients, and re-treatment is necessary in 32-88% of patients.

In patients with a smaller stone burden (>500 mm2 surface area), stone-free rates may approach 90%. After monotherapy PNL, reported stone-free status is achieved in approximately 80% of patients. These outcomes are further improved in correlation to surgeon experience. Combining PNL with subsequent SWL yields stone-free rates comparable to those of PNL alone; this likely reflects the aggressiveness of the initial PNL and attempts to remove residual stones via flexible nephroscopy.

While the goal of the physician is to ensure stone-free status, patients are interested in direct outcomes. Prevention of patient symptoms and associated stone-related morbidity, such as infection, are important means of assessing treatment success. Studies have demonstrated that, even in the presence of small stone fragments after SWL monotherapy and perioperative antibiotics for 2 weeks, 86% of patients were cured of persistent infection. Conversely, achieving stone-free status does not ensure resolution of persistent urinary infections. Important considerations in these patients include anatomic abnormalities, neurogenic bladder, indwelling catheters, or urinary diversion. Long-term freedom from bacteriuria is probably not possible in these situations.

Potential deleterious effects of staghorn calculi and treatments for the stone have been a source of concern. However, studies have demonstrated the general safety of both SWL and PNL in the management of large stones, even with a solitary kidney and chronic renal insufficiency. Effects of SWL and PNL are minimal, with only slight decreases in renal function after intervention. Patients who progress to severe renal insufficiency associated with staghorn stones usually present initially with compromised renal function (serum creatinine level >3 mg/dL).

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Future and Controversies

Many aspects of struvite staghorn calculi require further study.

Standardized classification of renal anatomy and staghorn calculi may improve staging of the stones. This will allow more accurate comparison of treatment modalities. Also, uniform methods of reporting treatment outcomes are needed.

Determining which endpoints (eg, stone free, clearance of infection, preservation of renal function, resolution of symptoms) are most important is necessary. Elucidating some of these factors will help in selecting the appropriate surgical approach and goals of intervention. Continued technological advancements in minimally invasive instruments and increasing worldwide surgical PNL experience will continue to lessen the morbidity associated with staghorn calculi therapy.

A better understanding of the etiology of infection staghorn stones may direct rational treatment. The potential role of microorganisms, such as nanobacteria, must be defined. In addition, development of more effective medical treatments may significantly alter management strategies. Urease inhibitors with less toxicity may have increased general utility. Also, drugs effective in acidification of the urine could halt stone formation and growth even in the presence of persistent infection.

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Contributor Information and Disclosures
Author

Maxwell Meng, MD Associate Professor-in-Residence, Department of Urology, University of California, San Francisco, School of Medicine

Maxwell Meng, MD is a member of the following medical societies: American College of Surgeons, American Urological Association, Society of Urologic Oncology

Disclosure: Nothing to disclose.

Coauthor(s)

Marshall L Stoller, MD Professor and Vice Chairman, Medical Director of Urinary Stone Center, Department of Urology, University of California, San Francisco, School of Medicine

Marshall L Stoller, MD is a member of the following medical societies: American Urological Association

Disclosure: Nothing to disclose.

Thomas Chi, MD Assistant Professor, Department of Urology, University of California, San Francisco, School of Medicine

Thomas Chi, MD is a member of the following medical societies: American College of Surgeons, American Urological Association, Western Section of the American Urological Association

Disclosure: Received honoraria from Bard Medical for speaking and teaching.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Bradley Fields Schwartz, DO, FACS Professor of Urology, Director, Center for Laparoscopy and Endourology, Department of Surgery, Southern Illinois University School of Medicine

Bradley Fields Schwartz, DO, FACS is a member of the following medical societies: American College of Surgeons, Society of Laparoendoscopic Surgeons, Society of University Urologists, Association of Military Osteopathic Physicians and Surgeons, American Urological Association, Endourological Society

Disclosure: Nothing to disclose.

Additional Contributors

Martha K Terris, MD, FACS Professor, Department of Surgery, Section of Urology, Director, Urology Residency Training Program, Medical College of Georgia; Professor, Department of Physician Assistants, Medical College of Georgia School of Allied Health; Chief, Section of Urology, Augusta Veterans Affairs Medical Center

Martha K Terris, MD, FACS is a member of the following medical societies: American Cancer Society, Association of Women Surgeons, American Society of Clinical Oncology, Society of Urology Chairpersons and Program Directors, Society of Women in Urology, Society of Government Service Urologists, American College of Surgeons, American Institute of Ultrasound in Medicine, American Urological Association, New York Academy of Sciences, Society of University Urologists

Disclosure: Nothing to disclose.

Acknowledgements

Thomas Minor, MD Resident Physician, Department of Urology, University of California, San Francisco, School of Medicine

Thomas Minor, MD is a member of the following medical societies: American Urological Association

Disclosure: Nothing to disclose.

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  21. [Guideline] Medical Management of Kidney Stones. American Urological Association. Available at https://www.auanet.org/education/guidelines/management-kidney-stones.cfm. March 2014; Accessed: November 18, 2105.

  22. Gleason MJ, Griffith DP. Infection Stones. Resnick MI, Pak CY, eds. Urolithiasis: a Medical and Surgical Reference. Philadelphia, Pa: WB Saunders; 1990. 134-6.

  23. Griffith DP, Osborne CA. Infection (urease) stones. Miner Electrolyte Metab. 1987. 13(4):278-85. [Medline].

  24. Lam HS, Lingeman JE, Mosbaugh PG, Steele RE, Knapp PM, Scott JW, et al. Evolution of the technique of combination therapy for staghorn calculi: a decreasing role for extracorporeal shock wave lithotripsy. J Urol. 1992 Sep. 148(3 Pt 2):1058-62. [Medline].

  25. Lingeman JE, Lifshitz DA, Evan AP. Surgical management of urinary lithiasis. Walsh PC, Retik AB, Vaughan ED, Wein AJ, eds. Campbell's Urology. 8th ed. Philadelphia, Pa: WB Saunders; 2002. Vol 4: 3366-3370.

  26. McDougall EM, Liatsikos EN, Dinlenc CZ. Percutaneous approaches to the Upper Urinary Tract. Walsh PC, Retik AB, Vaughan ED, Wein AJ, eds. Campbell's Urology. 8th ed. Philadelphia, Pa: WB Saunders; 2002. Vol 4: 3320-40.

  27. Morey AF, Nitahara KS, McAninch JW. Modified anatrophic nephrolithotomy for management of staghorn calculi: is renal function preserved?. J Urol. 1999 Sep. 162(3 Pt 1):670-3. [Medline].

  28. Schwartz BF, Stoller ML. Nonsurgical management of infection-related renal calculi. Urol Clin North Am. 1999 Nov. 26(4):765-78, viii. [Medline].

  29. Suby HI, Albright F. Dissolution of Phosphatic Urinary Calculi by the Retrograde Introduction of a Citrate Solution Containing Magnesium. N Engl J Med. 1943. 228:81-91.

  30. Wang LP, Wong HY, Griffith DP. Treatment options in struvite stones. Urol Clin North Am. 1997 Feb. 24(1):149-62. [Medline].

 
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Struvite and staghorn calculi. Plain abdominal radiograph demonstrating a right staghorn calculus and a smaller left renal pelvic stone. The patient is a 72-year-old woman.
Struvite and staghorn calculi. Plain abdominal radiograph of a 72-year-old woman. She underwent right percutaneous nephrolithotomy, with the path of renal access demonstrated by the remaining nephrostomy tube. She was rendered stone free in the single-session procedure.
Table.
Generic name Citric Acid, glucono-delta-lactone, and magnesium carbonate
Brand names Renacidin
Description Action on susceptible apatite calculi results from exchange of magnesium from irrigating solution for insoluble calcium contained in stone matrix or calcification. Magnesium salts thereby formed are soluble in gluconocitrate irrigating solution, resulting in dissolution of calculus. Struvite calculi are composed mainly of magnesium ammonium phosphates, which are solubilized by hemiacidrin due to acidic pH. Essential that patients be free from urinary tract infections prior to initiating chemolytic therapy. Used for local irrigation dissolution of renal calculi composed of apatite (a calcium carbonate-phosphate compound) or struvite (magnesium ammonium phosphates) in patients who are not candidates for surgical removal of calculi. Also used as adjunctive therapy to dissolve residual apatite or struvite calculi and fragments after surgery or to achieve partial dissolution of renal calculi to facilitate surgical removal.
Adult Dose Renal calculi:



Place nephrostomy tube at surgery or percutaneously to permit lavage of calculi; single catheter may be sufficient if calculus not obstructing ureter or ureteropelvic junction; in patients with obstructed ureter, a retrograde catheter can be placed through ureter to renal pelvis via a cystoscope (used to irrigate calculus while percutaneous nephrostomy tube used for drainage)



Pressure measurements are made under fluoroscopic guidance to ensure 2-3 mL/min can be infused without causing pain, pyelovenous or pyelotubular backflow, or manometric evidence of elevated pressure within collecting system



Postoperative patients:



Irrigation should not be started before fourth or fifth postoperative day; irrigation of renal pelvis is begun with sterile saline only after sterile urine demonstrated



Saline is infused at rate of 60 mL/h initially, and rate is increased until pain or an elevated pressure (25 cm water) appears or until maximum flow rate of 120 mL/h achieved; inspect site of insertion for leakage; if leakage occurs, irrigation is discontinued temporarily to allow for complete healing around nephrostomy tube; if no leakage or flank pain occurs, start irrigation with flow rate equal to maximum rate achieved with saline solution



Place clamp on inflow tube and instruct patients and nursing personnel to stop irrigating solution whenever pain develops; nursing personnel responsible for performing irrigation must be instructed concerning location of nephrostomy tube(s) and direction of flow of irrigating solution to ensure against misconnection of inflow and egress tubes



Perform nephrotomography periodically to assure proper placement of catheter tip and to assess efficacy; if stones fail to change size after several days of adequate irrigation, discontinue procedure; upon demonstration of complete dissolution of calculus, inflow tube is clamped and left in place for few days to ensure that no obstruction exists, after which time nephrostomy tube should be removed



Bladder calculi:



Instill 30 mL through urinary catheter into bladder; clamp catheter for 30-60 min and release clamp to drain; repeat 4-6 times/d; continuous drip through 3-way Foley catheter is alternative means of dissolving bladder stones; in presence of bladder spasm and associated high pressure reflux, all precautions required for irrigation of renal pelvis must be observed



Pediatric Dose Not established
Contraindications Urinary tract infections; presence of demonstrable urinary tract extravasation; ureteral catheters, nephrostomy or pyelostomy tubes, or renal lavage for dissolving calculi
Interactions May increase toxicity of magnesium-containing medications
Pregnancy C - Safety for use during pregnancy has not been established.
Precautions Fever, urinary tract infection, signs and symptoms consistent with urinary tract infection, persistent flank pain, or if hypermagnesemia or elevated serum creatinine level develops (urea-splitting bacteria reside within struvite and apatite stones and serve as source of infection); dissolution therapy in presence of infected urinary tract may lead to sepsis and death; severe hypermagnesemia has occurred



Caution when irrigating renal pelvis of patients with impaired renal function; severe hypermagnesemia may result in hyporeflexia, dyspnea, apnea, coma, cardiac arrest, and subsequent death; treatment should include discontinuation of therapy followed by treatment with IV calcium gluconate, fluids, and diuresis in severe cases



Table.
Generic name Suby solution G
Brand names Suby solution G
Description Used to dissolve phosphatic calculi or incrustations in the bladder and urethra.
Adult Dose 1-3 L qd by intermittent irrigation or by tidal instillation and drainage to allow continuous irrigation of bladder for periods of several hours; intermittent irrigation of bladder (after manner of intermittent peritoneal dialysis) may be preferred to promote longer contact of irrigant with bladder stones; tidal (continuous inflow and outflow) irrigation may be less efficient and require larger amounts of irrigation fluid
Pediatric Dose Administer as in adults
Contraindications Bladder infections, bleeding, ulcerations, or other open wounds; IV/IM/SC injections
Interactions None reported
Pregnancy C - Safety for use during pregnancy has not been established.
Precautions For use only in irrigation of lower urinary tract; not for dissolving phosphate calculi in renal pelvis (may cause back pressure that could reactivate existing pyelonephritis); repeated or continuous use may cause bleeding (irritating to urethra; after each treatment, irrigate with sterile saline or water); 4 cases of sudden death reported during lavage therapy with similarly acting solution; not to be used in place of other indicated measures, including correction of underlying metabolic disorders, surgical intervention, and treatment of infection
Table.
Generic name Acetohydroxamic acid
Brand names Lithostat
Description Reversibly inhibits bacterial enzyme urease, thereby inhibiting hydrolysis of urea and production of ammonia in urine infected with urea-splitting organisms. Reduced ammonia levels and decreased pH enhance effectiveness of antimicrobial agents and increase cure rate of these infections. Does not acidify urine directly, nor does it have direct antibacterial effect. In patients with urea-splitting urinary infections (often accompanied by struvite stone disease) that are recalcitrant to other management, reduces pathologically elevated urinary ammonia and pH levels.
Adult Dose 12 mg/kg/d PO tid/qid on empty stomach recommended initially; not to exceed 1.5 g/d
Pediatric Dose 10 mg/kg/d PO initially; monitor clinical condition and hematologic status; dosage titration may be required
Contraindications Patients whose physical state and disease are amenable to surgery or antimicrobial agents, urine is infected by non–urease-producing organisms, or renal function is poor (eg, serum creatinine >2.5 mg/dL or CrCl < 20 mL/min) and females without satisfactory method of contraception whose urinary infections can be controlled by culture-specific oral antimicrobial agents
Interactions Absorption of iron and AHA may be reduced from intestinal lumen when both drugs taken concomitantly (give iron IV when indicated)
Pregnancy X - Contraindicated in pregnancy
Precautions Bone marrow depression (ie, leukopenia, anemia, thrombocytopenia) has occurred in animals receiving large doses (never reported in humans); hemolysis with decrease in circulating red blood cells, hemoglobin levels, and hematocrit values also noted; in renal impairment, closely monitor patients and reduce daily dose to avoid excessive drug accumulation
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