Urolithiasis refers to the condition where there is the formation of urinary stones as well as their location in the urinary system. While the term urolithiasis refers to those stones that are in the ureter, nephrolithiasis also known as renal calculus refers to those stones that are found in the kidney, and cystolithiasis (vesical calculi) refers to the stones that are formed or located into the urinary bladder (Pearle, Calhoun, & Curhan, 2007).
The urinary stones also known as calculi refer to the hardened mineral deposits forming in the kidney. The stones originate as microscopic after which they develop into stones after some time. The stones may contain various chemical combinations with most stones containing calcium in combination with either phosphate or oxalate. There are other stones although not common that are caused by infections that affect the urinary tract. This type of stone is referred to as infection stone or struvite. In addition, uric acid stones and cystine stones are found in the urinary tract but are very rare (Brisbane Urology Clinic, 2012).
Epidemiologically, urolithiasis differs in incidence and prevalence, sex and age distribution, stone composition and location. In the United States, the annual incidence of kidney stones is about 0.5%, and the prevalence is roughly above 5.2% (Moe, 2006). The total treatment cost for urolithiasis $2.1 billion every year (Monga, 2011). Between 65 and 80% of those people having kidney stones are men with most stones that are found in women being as a result of either metabolic defect or infection. Most men experience kidney stones at an age of between 30 and 40 years while women have their first episode at an older age than men. The rate of recurrence is estimated at more than 50% over a 10 year period and 75% over a 20-year period (Moe, 2006). For children, the age at which urolithiasis first occurs ranges from 5 to 15 years of age. Differences in the epidemiology of urolithiasis geographically have been explained in terms of climate factors, race, and diet differences.
Urolithiasis mainly affects white patients although, in the recent past, there has been an increase in the urolithiasis incidence in other populations. The incidences are greater among the white males than they are among black males. The risk of having the disease is lowest among the African Americans (1.7%) followed by Mexican American (2.6%) and highest among the Caucasians (5.9%) (Trinchieri, 2008). Infection incidences of urolithiasis have been on the increase with incidences of infection in women increasing from 15.5 to 27.6/100 000 between 1999 and 2009. Infection incidences in men within the same period increased from 7.8 to 12.1/100 000 (Sammon, et al., 2012).
Urinary stones normally are a result of a delicate balance breakdown. The kidneys have to preserve water, though they have to eliminate materials with a low solubility. These two opposing demands have to be balanced in the course of adaptation to climate, diet, as well as substances that suppress crystallization of calcium salts together with others that bind calcium insoluble complexes. These prophylactic mechanisms are less than perfect. When the urine turns supersaturated with insoluble materials, due to excessive excretion rates and/or extreme water conservation, there is the formation of crystals and may develop and combine to create a stone.
The common -most kidney stone type comprises calcium in combination with either phosphate or oxalate. Approximately 75% of kidney stones are calcium stones. Other compounds that may form stones in the urinary tract are magnesium ammonium phosphate, uric acid, and the amino acid cystine.
Dehydration from strenuous exercise or reduced fluid intake with no sufficient replacement of fluid raises the kidney stones risk. Urine flow obstruction can also cause stone formation. In this case, climate can be a risk factor for development of kidney stone, as hot and dry areas residents are more probable to become dehydrated and susceptible to stone formation. Kidney stones may also arise from urinary tract infection, and this is known as infection or struvite stones. Metabolic abnormalities, including inherited metabolism disorders, can change the urine composition and raise an individual's stone formation risk.
There are several risk factors that have been are recognized to cause a rise in the risk of developing urinary stones. These factors include disease conditions such as hypertension, gout, and hyperparathyroidism. People who have a family history of incidents of kidney stones are at a greater risk of developing the disorder than those from family with no history of the disease. Other factors include immobilization, metabolic disorders that may increase the rate of solute excretion such as hypercalciuria, chronic metabolic acidosis, and hyperuricosuria. People who are relatively dehydrated are at a higher risk than those who are well hydrated. Citrate deficiency in the urine also increases the risk. Those people taking certain medications such as diuretics, vitamin D supplements among others are more susceptible to urolithiasis. In addition, men are at a higher risk of the disease than women (Jackson, 2012).
When the urine turns supersaturated with a single or more calculogenic substances, a seed crystal may form via nucleation. Heterogeneous nucleation goes on more quickly than homogeneous nucleation since it needs less energy. Bonding to cells on the renal papilla surface, a seed crystal can develop and combine into an organized mass. Based on the crystal’s chemical composition, the process of stone-forming may go on more quickly when the pH of urine is unusually high or low.
Urine supersaturation with respect to a calculogenic compound is dependent on pH. For instance, at a neutral pH, the uric acid solubility in urine is 158 mg/100 ml. Lowering the pH to 5.0 reduces the uric acid solubility to below 8 mg/100 ml. The uric acid stones formation needs a combination of low urine pH and hyperuricosuria. Hyperuricosuria alone is not linked to the formation of uric acid stone under alkaline pH of urine. Urine supersaturation is a requisite, though not an adequate condition for any urinary calculus development. Supersaturation is probably the fundamental cause of cystine and uric acid stones, though calcium-based stones may have a more complex cause.
Normal urine comprises chelating agents, like citrate, which suppress the nucleation, development, as well as aggregation of calcium-containing crystals. Other endogenous inhibitors are calgranulin, nephrocalcin, glycosaminoglycans, Tamm-Horsfall protein, uropontin, prothrombin F1 peptide, as well as bikunin. The biochemical action mechanisms of these substances have not yet been methodically clarified. Nevertheless, when these substances go down below their usual proportions, stones may form from a crystal aggregation (Coe, Evan, & Worcester, 2005).
Kidney stones frequently arise from a blend of factors, rather than one, clear cause. Stones occur commonly in persons who take high animal protein diet or those who do not take adequate calcium or water (Preminger, 2007). They may be as a result of a fundamental metabolic condition, like acidosis of distal renal tubular (Moe, 2006).
The clinical presentations of urolithiasis include sharp, acute and spasm-like pain that is felt in the flank and hematuria. There may be pain that starts in the loin moving to the groin, with loin or renal angle tenderness (Brisbane Urology Clinic, 2012). Stones that are in motion cause more pain than the stones that are static. From the ureter, the pain radiates down to scrotum, testis, and labia or to the interior thigh. The pain is more constant although periods of relief may be experienced before the pain returns. The patients may feel changes in pain as the stone moves with most patients being able to point the point at which pain is high. This point has a high correlation with the position where the stone is currently located. Patients pay experience tachycardia, nausea, diaphoresis, vomiting, and tachypnea, which make them typically uncomfortable. Other symptoms that may be observed include rigors and fever, dysuria, and urinary retention (Jackson, 2012).
Urolithiasis diagnosis starts with a focus on the history of the patient. Key elements that are of interest include past incidents of calculi and family history of the disease, evolution and duration of the symptoms, and signs, as well as the symptoms of sepsis. Use of physical examination is usually used as a valuable way of ruling out chances of nonurologic disease. Urinalysis test is usually recommended for all patients who are suspected of having calculi. Other than the typical microhematuria, other crucial parameters such as the presence of crystals and urine pH that may help in the identification of stone composition. Acidic urine is usually present in patients with uric acid stones while alkaline urine is present in patients with stone formation that results from infections. Urine culture is routinely performed in order to identify the bacteria causing the disease and plan for the appropriate therapy (López & Hoppe, 2010).
Abdominal ultrasonography may be performed to visualize ureteral stone through ultrasound. However, abdominal ultrasonography has very limited use in the both in diagnosis, as well as management of urolithiasis. Although there are various advantages that make ultrasonography widely used in the kidney stone diagnosis including being readily available, sensitive to renal calculi, and quickly performed and sensitive to renal calculi, the technique is virtually not very sensitive to ureteral stones (Yilmaz, et al., 1998). The ultrasound is highly sensitive in hydronephrosis examination, which may be an indication of ureteral obstruction manifestation. The test is, however, limited in defining the nature or level of obstruction. The technique is also useful in renal parenchymal processes assessment.
The other technique in urolithiasis diagnosis is the plain-film radiography of the ureters, kidneys, and bladder. This test may be sufficient to show the location and size of radiopaque urinary calculi. Radiography is able to detect those stones that are composed of calcium like the calcium oxalate and calcium phosphate stones. Stones that have less radiopaque calculi such as those that are mainly made up of magnesium or cystine ammonium phosphate are not easily detected using plain-film radiographs.
Intravenous pyelography is the other diagnostic procedure that has been considered to be the imaging modality for diagnosis of urinary tract calculi. This technique provides useful information concerning the stone such as the location, size, and radiodensity. The technique is also able to give information on the environment of the stone such as degree of obstruction and the calyceal anatomy, and the contralateral renal unit. Advantages of this technique include being widely available, and the interpretation of the results obtained being well standardized. Using this imaging modality may help in easily distinguishing ureteral calculi from nonurologic radiopacities. When compared with abdominal ultrasonography and plain-film radiography, intravenous pyelography shows greater sensitivity and specificity in detecting renal calculi.
In the initial renal colic assessment, noncontrast helical CT has been the technique that is increasingly used. The imaging modality is accurate and fast and identifies all forms of stones in all locations. Noncontrast helical CT is very sensitive and specific, and this suggests that the technique has the capability of excluding stones in patients who have abdominal pain in a definitive manner. Although the cost of noncontrast helical CT is higher than that of intravenous pyelography, the high cost is certainly balanced the faster and more definitive diagnosis (Portis & Sundaram, 2001).
In the treatment of urolithiasis, pain relief is the initial therapeutic step especially in patients having an acute stone episode. Medication using non-steroidal anti-inflammatory drugs abbreviated NSAIDs have been indicated to be effective in most patients having acute stone colic. These drugs are given in the form of diclofenac PR or IM and help to relief the severe pain. Opioid is also used in the treatment of urolithiasis. NSAIDs are known to be more effective in treating this condition and have reduced chances to cause nausea. It is also important to provide rehydration and anti-emetics therapy when needed. After treatment, most patients will have their stones passing spontaneously by the third week after starting medication.
Unless in cases where the patients are not able to manage pain or the patients have shown signs of obstruction or infection, conservative management may be continued for up to three weeks. In order to facilitate stone passage, medical expulsive therapy may be applied. This is also useful in cases where no obvious reason is available to call for an immediate surgical to remove the stone. Some of the medications that are applied include alpha-blockers such as tamsulosin and channel blockers such as nifedipine. A corticosteroid may be added in case alpha-blocker is used. Surgical procedures may also be applied since approximately 1 in 5 stones may not pass spontaneously. In case the ureter is blocked, a JJ stent is in most cases introduced using a cystoscope to prevent the ureter from contracting. This helps to reduce the pain and at the same time buy time until measures that are more definitive are taken (Jackson, 2012).
Prevention measures that are there for urolithiasis incidents mainly focus on preventing the recurrence of renal stones, which is very common. It is, therefore, recommended that patients who have had renal stone to adapt various lifestyle measures that will enable them prevent or delay any renal urolithiasis recurrence. Some of these lifestyle measures include increased fluid intake in order to maintain a urine output of between 2 to 3 liters in a day, reduce intake of salt, reduce the amount of animal proteins taken, reduce intake of oxalate rich food such as rhubarb, chocolate, and nuts, as well as urate-rich food such as offal and certain fish. It is also important to maintain intake of calcium at levels that are normal since lowering intake enhances calcium oxalate excretion. Medications to prevent future incidents are sometimes provided depending on the stone composition. For example, thiazide diuretics are given for calcium stones, allopurinols are given for uric acid stones while calcium citrate is given for oxalate stones (Jackson, 2012).
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