Surgical Thresholds for Kidney Stones

Table of Contents

Introduction to Kidney Stones

Most patients are aware that many kidney stones will pass spontaneously without surgical intervention over a period of several days to several weeks. Many theories exist concerning the cause of the colicky pain associated with a stone’s passage.

However, not all stones will pass spontaneously, or may take a prolonged period of time during which the patient is experiencing significant discomfort. In addition, a small but therefore increased percentage of patients may, as a direct or indirect result of the presence of the stone in the urinary tract, develop a sudden, life-threatening local or systemic infectious process. In some cases, due to the physical size of the stone, along with clinical features of stone size and location, it may be known unequivocally that the stone will not pass spontaneously without causing prolonged significant discomfort to the patient, or represents a clear and definite medical threat to the patient.

Thus, the patient is often faced with three basic treatment options: a medically assisted passage of the stone as an outpatient, a surgical intervention designed to remove the stone completely from the urinary system, or observation only by follow-up of the patient’s symptoms.

In an age of expanding medical technology and increasing patient awareness, dialogue between the medical practitioner and the informed patient is becoming increasingly important. Many individuals are concerned about the formation of a single episode of a kidney stone in their life. The patient desires prompt and effective treatment to eliminate the initial episode, as well as future episodes. Many questions, often with many differing answers and often incorrect information, typically evolve from the patient that can only be answered satisfactorily by a dialogue between patient and well-trained professional. Patient knowledge of what contributes to kidney stone formation, as well as possible measures to diminish the likelihood of formation, is not only service-worthy, but changes in the patient’s lifestyle based on this dialogue can impact favorably on future stone formation.

Definition and Types of Kidney Stones

Urinary stone disease can be classified into different types according to several mineral compositions. 65-70% of all urinary stones are calcium oxalate concretions, which is the highest type of urinary stone incidence. Calcium phosphate occurs in 5-10% of urinary stones. In a development period, these urinary stones can be set up urinary pH. Uric (urate) acid-based concretions and cysteine concretions make up the remaining 10% of urinary stones and are minor mineral compositions. Struvite and Staghorn stones with magnesium ammonium phosphate and calcium carbonate apatite contents are recognized in 1-2% of urinary stones. These compounds are located in alkaline urine. There are also several non-calcium nonprotein compounds included, such as drug metabolism, infection, and idiopathic recurrent with a decreasing ratio.

Urinary stone is a urinary crystalline concretion that is formed by the treatment on the contrary of urinary role or impedance of urinary excretion and can occur in urinary organs. Sizes of urinary stones can vary and can form a single stone or multiple stones. Single urinary stones are located in places of the whole urinary system such as renal pelvic calyces, urinary ureter, and bladder pelvis. Urinary stones, which comprise 80-85% of all cases that slowly grow up in a few years, can certainly occur again if the primary cause or another cause appears. The overall incidence of urinary stones is observed between 2% and 15% in all people of society. The prevalence of urinary stones in males is higher than females, with a ratio of 50.5% to 49.5%. It can be recognized predominantly between adulthood and elderly in younger adults, especially at approximately 35 years old. The prevalence of urinary stone at the time of life becomes 75-80%. Studies in various countries have shown that the diversity in the rate of urinary stone disease is also related to racial origin or dietary habits.

Non-Surgical Treatment Options

In the absence of conditions that might contraindicate alkali therapy, patients with uric acid stones, who are able to tolerate this, should have alkali supplementation. Mid-afternoon pH monitoring may be used to track the urine pH response to a single morning dose of alkali (as a check of compliance) and to determine whether there is overcompensation (i.e., urine apparent pH over 6.5). For those who don’t respond adequately, increased doses of potassium citrate or sodium bicarbonate may be considered. In patients with hypocitraturia and a threshold of urinary citrate of <350 mg/day, supplemental citrate is recommended. In cases of severe hypocitraturia combined with volume depletion, simple hydration, diuretics, or thiazide-like agents may be used first to expand the extracellular volume before repletion with citrate. The use of acetazolamide and allopurinol may assist in the management of these patients.

There are several methods that may be utilized to treat renal stones non-surgically. These methods are not mutually exclusive, and they may be combined when appropriate for the specific patient and the stone concerned. The passage of stones can be facilitated by increasing urine volume and by expanding ureteral and renal pelvis pressure to encourage stone passage. Many objects have been ingested under the belief that they will hasten stone passage or even dissolve stones once they reach the bladder, but none have been demonstrated to actually accomplish this. Some have been shown to increase the risk of stone formation. Alcohol and other metabolic stresses should be minimized, and patients with hyperparathyroidism should be treated appropriately. Alkali therapy plays a key role in the management of most types of stones.

Medication and Pain Management

The way in which the stone is removed can vary a great deal. The following are common ways to remove a stone. A stone may be removed with a small tube (stent) going through the bladder and into the ureter that has been used to help the stone pass using a small, rigid instrument that goes through a viewing tube placed in the urethra. This treatment is not usually offered to very young patients with large stones or medical problems that are hard to manage, such as infections, prostate bleeding, or a low platelet count. A laser may be used to remove a stone. In this procedure, a very thin viewing tube is passed through the urethra and into the stones. The stone is then shattered with a laser and the pieces are washed out. This is often done as an outpatient so that the person can go home again after about half an hour. The person has no incisions and requires a stent or other ways to help drain the urine.

If the kidney stone does not pass, antibiotics may be needed to prevent an infection. The drugs tamsulosin (Flomax) and terazosin (Hytrin) are used to help the ureter relax and the stone pass. Some people have severe pain even though they know that they have passed a stone. Patients may be given strong pain relief for a few weeks. If the pain does not go away, the doctor may decide to ask a urologist to look for the stone. There are a number of factors that can influence the decision as to where the stone is to be found. Any patient with a urinary infection with a stone in the kidney is more likely to have the stone shattered so that all the urine can be drained. If, for some reason, the stone does not pass naturally, surgery may be needed to remove the stone and ensure that the ureter is not blocked

Medication and Pain Management

The way in which the stone is removed can vary a great deal. The following are common ways to remove a stone. A stone may be removed with a small tube (stent) going through the bladder and into the ureter that has been used to help the stone pass using a small, rigid instrument that goes through a viewing tube placed in the urethra. This treatment is not usually offered to very young patients with large stones or medical problems that are hard to manage, such as infections, prostate bleeding, or a low platelet count. A laser may be used to remove a stone. In this procedure, a very thin viewing tube is passed through the urethra and into the stones. The stone is then shattered with a laser and the pieces are washed out. This is often done as an outpatient so that the person can go home again after about half an hour. The person has no incisions and requires a stent or other ways to help drain the urine.

If the kidney stone does not pass, antibiotics may be needed to prevent an infection. The drugs tamsulosin (Flomax) and terazosin (Hytrin) are used to help the ureter relax and the stone pass. Some people have severe pain even though they know that they have passed a stone. Patients may be given strong pain relief for a few weeks. If the pain does not go away, the doctor may decide to ask a urologist to look for the stone. There are a number of factors that can influence the decision as to where the stone is to be found. Any patient with a urinary infection with a stone in the kidney is more likely to have the stone shattered so that all the urine can be drained. If, for some reason, the stone does not pass naturally, surgery may be needed to remove the stone and ensure that the ureter is not blocked.

Indications for Surgical Intervention

Before the patient is definitively treated, it is the surgeon’s responsibility to seek and correct the metabolic disturbance that led to calculus formation. Unfortunately, only approximately 25% of patients undergo metabolic evaluation after stone passage. The value of such testing is demonstrated by the high percentage of abnormal compositions identified in patients that do undergo metabolic testing, upwards of 90% in one large population. The decision to treat further stone formers with conservative versus aggressive measures is influenced greatly by metabolic testing. Currently, there is no consensus on which patients mandate metabolic testing. Practices differ widely from no metabolic work-up to a blanket metabolic evaluation for all new stone formers. Under debate is the clinical significance of small renal calculi (defined based on their diameter, usually considered to be less than 7 mm or sometimes less than 4 mm). Unlike the situation in bladder calculi, trends have emerged in the management of individual anatomy and stone burden as well as renal function.

In most cases, surgical intervention for urinary calculi is elective. Theoretically, most large renal stones might pass if given ample time (two to three months). However, pain control, lost time from work, liability concerns, and patient desires for aggressive treatment to prevent further episodes limit the time that can be allowed for ureteral stone passage. The physicians’ challenge then is to select patients appropriate for observation, ureteral stent placement, ESWL, or ureteroscopy. Renal pelvic and lower pole calculi evaporate more slowly, and the decompression afforded by a ureteral stent may be required. The exception to this thought process is in the febrile patient. Any obstructed upper third of the ureter should be quickly drained, and the offending calculus should be expeditiously removed. In addition, progressive unilateral obstructing stones that occur in the setting of a solitary functional kidney may require prompt intervention.

Size Criteria for Surgery

Currently, the guidelines for active therapy are that direct intervention is recommended when stones may produce symptoms and clinical complications or when stones are considered likely to remain stable. Informed consent is a key concept in the active surveillance of kidney stones. The patient must be aware of the possible consequences when recommendation is made not to actively intervene at the time of urinary stone diagnosis. Stones ≤4 mm have a high likelihood of spontaneous passage, and the odds of a stone of this size becoming obstructive are minor. Small calculi are usually not treated unless compelling symptoms justify treatment. On the other hand, patients with stones >1 cm may require early surgery to relieve the obstruction. If definitive treatment is undertaken, there should be no lingering doubt as to treatment completeness. Remnants that are left behind may grow in size, leading to a lowering of the upper urinary tract and obstruction. Renal stones can form at any location along the urinary drainage pathway, from the renal papillae to the urethra, and treatment of the stone should involve removal and clearance from the entire urinary tract.

The technical feasibility and clinical significance of surgical intervention is contingent upon a case-specific determination as to which stone(s) should be removed. Dissolution of all urinary calculi would be a preferable alternative to invasive surgery, but the long-term treatment course is difficult to predict. When the secondary disorders that led to nephrolithiasis cannot be completely resolved, the long-term potential for new stone formation is high, and dissolution of a single large stone can lead to urinary outflow obstruction. A pragmatic approach is to consider the natural history of calcified urinary concretions. Stones measuring ≥10 mm are unlikely to pass out of the body without intervention. Stones ≤5 mm can often spontaneously exit and are unlikely to be a source of urinary complications.

Surgical Procedures for Kidney Stones

The current combined modalities, such as laparoscopy and robotic surgery, have several advantages over traditional surgical methods. Laparoscopic and robotic surgeries are especially suitable for the treatment of lower pole, large, and/or multiple kidney stones where PCNL cannot be performed, and flexible and semi-rigid ureteroscopy may not be effective. Sufficient expertise on laparoscopic and robotic surgeries should be available for the selection of treatment methods. This chapter will review not only PCNL and SWL but also advanced and combined surgical treatment methods. Future directions for developments in these treatment areas are discussed.

In recent years, the majority of larger kidney stones have been treated with PCNL, which is currently the primary surgical intervention method for kidney stones. However, traditional surgical intervention is associated with many complications and a long convalescent phase, while the minimally invasive surgical modalities, such as laparoscopy and robotic surgery, are associated with relatively small trauma and quick recovery. The surgical instrument, treatment method, and other measures for the kidney stones include careful decision-making on intervention timing, intervention goal, and indication for surgery and workup prior to surgery. In recent years, there have been technical advances in instruments, surgical methods, and perioperative supportive care.

Surgical procedures may be needed when a kidney stone does not pass on its own, is not amenable to treatment with extracorporeal shock wave lithotripsy, or cannot be removed with a ureteroscope, either because of anatomic considerations or because the procedure is not technically possible in order to safeguard kidney function. In addition, surgery is required more frequently for lower pole, larger, and hard calculi

Extracorporeal Shock Wave Lithotripsy (ESWL)

ESWL is not painful, but it may result in bruising on the back or abdomen and blood in the urine. In addition, there is usually discomfort as the stone fragments pass through the urinary tract during the days following treatment. ESWL requires some exposure to diagnostic x-rays. ESWL may not be suitable for very obese individuals. A shock wave lithotripsy procedure may be performed under a local or general anesthetic, depending on the stone condition and patient preference. In addition to spinal anesthesia, ESWL may be performed using IV sedation (conscious anesthesia), or under general anesthesia, although local anesthesia may be an option in certain cases. In general, shock wave lithotripsy is considered the safest, least invasive, and cost-effective treatment for kidney stones.

Extracorporeal shock wave lithotripsy (ESWL) is the least invasive treatment for kidney stones. Shock waves are used to break stones into tiny fragments that can pass through the ureter and out of the body. ESWL has a success rate of about 70% for small stones and is most effective for stones in the kidneys and upper ureter. A lithotripsy procedure involves the use of high-energy shock waves to fragment and disintegrate kidney stones. Once the stone has been reduced to fragments, they are then able to pass through the rest of the urinary tract. ESWL is not very effective at treating very large, hard or cystine stones.

Recovery and Complications

As with all surgeries, there are potential complications that can follow stone extraction. Pain is the most frequently encountered problem, which can be managed with the pills that the urologist prescribes. Additionally, bleeding is common during stone removal, due to the excessive dilation of the kidney with the nephroscope. Blood in urine is normal, and it may be misleading to note that it turns bright red at the end of urination, therefore confirming the ureteral stent functionality. It is also possible for blood clots to obstruct the stent, causing urine to back up into the kidney and triggering the cycle of pain and nausea. If this occurs, it can be managed by asking a nurse or friend to gently tap the region under your ribs while standing. However, it is advisable that you call your doctor and schedule an urgent appointment. Small bits of stone can block the percutaneous nephrolithotomy tube, and sometimes the surgeon inserts a fine tube through the skin to milk the drainage, and to make sure that the nephrostomy is functioning properly. The fact that you have a stent in place already creates an alternative drainage system, so there are no reasons to worry for your welfare.

Upon being transferred to the recovery room, the nursing staff will use what are known as surgical drain clamps to prevent vessel kinking, which mimics the function of the stent and allows for the swift resumption of normal urine flow. Generally, after two hours of unimpeded urine flow, the urinary catheter is gently removed and you can return home, accompanied by a family member or friend. It is important to place the kidney on the side that you undergo the surgery because the gravitational force will create gentle pressure on the kidney, facilitating the draining process. You will be provided with tissue and narcotics, and it is recommended that you either sleep or recline in an armchair until the next day, as the majority of patients feel excessively tired. The day after the surgery, it is important to take a short walk as much as tolerated, in order to stretch your muscles and promote digestion. If you feel the need to urinate, you must do so by sitting in order to avoid the risk of sudden tachycardia and fainting. At the end of the day, despite the remaining discomfort, it is a good sign if you feel reasonably well, as this is indicative of good stone fragmentation and drainage.

Most people who undergo surgical intervention on their kidney stones require minimal use of narcotic medications and are discharged on the same day or the day following the surgery, in stable condition and with minimal pain. This is a multistep process which begins while you are still in the operating room. Following general anesthesia, a tube called a ureteral stent is placed within your urinary tract in order to facilitate the drainage of the kidney and to allow for the passage of stone fragments. Additionally, the stent causes the drainage of the blood clots which the surgeon might have otherwise evacuated via the operating nephroscope, thus avoiding unnecessary manipulation of the kidney and ureter, which in turn reduces the risk of bleeding and potential strictures. Therefore, the stent placement is a beneficial procedure which minimizes the complications of percutaneous nephrolithotomy.

Post-Surgery Care

The surgical incisions are covered with adhesive strips, gauze, and a clear plastic with a small hole that is removed after a normal shower. The patient should avoid contact with the sun and with scented lotions or oils to the area for several weeks. Serious complications that can result from surgical removal of kidney stones include urine leakage from the kidney and subsequent abscess formation or further renal damage and bleeding. The last side effect can lead to anemia and a decrease in blood pressure, and metal coils can be used as a temporary solution to bleeding. The most common side effects after surgical removal of kidney stones are frequency, urgency, and burning on urination, which can be treated symptomatically with pyridium. Cefadroxil can be prescribed if burning is associated with an infection.

The patient is instructed to drink a significant amount of fluids over the next two weeks. The reason for the increased fluid intake is that the kidneys are easily blocked following surgical removal of stones. This blockade can be caused by edema or excessive blood clots. Pain is controlled by pain medication, and the patient is encouraged to ambulate in bed and sit on the side of the bed, and later ambulate in the room. Care should be taken to help the patient to and from the bathroom, since balance can be affected from the narcotics and other medications. The kidneys are difficult to irritate with any substance that the patient eats, since filtration is the one part of the body that is always functioning. Care must also be taken to ensure regular and frequent voiding to enhance passage of debris and to prevent bladder distention.

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