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Renal calculi

Kidney stones, also known as nephrolithiases, urolithiases or renal calculi, are solid accretions (crystals) of dissolved minerals in urine found inside the kidneys or ureters. They vary in size from as small as a grain of sand to as large as a golf ball. more...

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Kidney stones typically leave the body in the urine stream; if they grow relatively large before passing (on the order of millimeters), obstruction of a ureter and distention with urine can cause severe pain most commonly felt in the flank, lower abdomen and groin.


Conventional wisdom has held that consumption of too much calcium can aggravate the development of kidney stones, since the most common type of stone is calcium oxalate. However, strong evidence has accumulated demonstrating that low-calcium diets are associated with higher stone risk and vice-versa for the typical stone former.

Other examples of kidney stones include struvite (magnesium, ammonium and phosphate), uric acid, calcium phosphate, or cystine (the amino acid found only in people suffering from cystinuria). The formation of struvite stones is associated with the presence of urease splitting bacteria (Klebsiella, Serratia, Proteus, Providencia species) which can split urea into ammonia, most commonly Proteus mirabilis.


Kidney stones are usually idiopathic and asymptomatic until they obstruct the flow of urine. Symptoms can include acute flank pain (renal colic), nausea and vomiting, restlessness, dull pain, hematuria, and possibly fever if infection is present. Acute renal colic is described as one of the worst types of pain that a patient can suffer from. But there are also people who have no symptoms until their urine turns bloody—this may be the first symptom of a kidney stone.

Diagnosis & Investigation

Diagnosis is usually made on the basis of the location and severity of the pain, which is typically colic in nature (comes and goes in spasmodic waves). Radiological imaging is used to confirm the diagnosis and a number of other tests can be undertaken to help establish both the possible cause and consequences of the stone.

The relatively dense calcium renders these stones radio-opaque and they can be detected by a traditional X-ray of the abdomen that includes Kidneys, Ureters and Bladder—KUB. This may be followed by an IVP (Intravenous Pyelogram) which requires roughly about 50ml of a special dye to be injected into the bloodstream that goes straight to the kidneys and helps outline any stone on a repeated X-ray. Computed tomography, a specialized X-ray, is by far the most accurate diagnostic test for the detection of kidney stones.

Investigations typically carried out include:

  • Culture of a urine sample to exclude urine infection (either as a differential cause of the patient's pain, or secondary to the presence of a stone)
  • Blood tests: Full blood count for the presence of a raised white cell count (Neutrophilia) suggestive of infection, a check of renal function and if raised blood calcium blood levels (hypercalcaemia).
  • 24 hour urine collection to measure total daily urinary calcium, oxalate and phiosphate.


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Treatment options for ureteral calculi - Tips from Other Journals
From American Family Physician, 11/1/91

Extracorporeal shock-wave lithotripsy and endourologic procedures have been the methods of choice for the treatment of upper urinary track calculi. Patients with stones in the middle to lower region of the ureter have generally been treated with endourologic procedures, but second-generation lithotriptors are now being used for the in situ treatment of stones throughout the ureter. Netto and colleagues conducted a retrospective analysis to compare the efficacy of extracorporeal shock-wave lithotripsy with that of endourologic procedures in the treatment of ureteral calculi.

The study included 307 patients who underwent one of these procedures over a two-year period: 236 patients were treated with endourologic procedures, including percutaneous renal access and transurethral urethroscopy, and 71 patients were treated with lithotripsy. Stones were categorized into three groups according to size: less than 1 cm, 1 to 2 cm and larger than 2 cm. The mean stone size in the patients who underwent endourologic procedures was 1.12 cm, and the mean stone size in the patients who underwent lithotripsy was 1.03 cm. Follow-up studies, consisting of ultrasonography or plain films, or both, were performed one day, one month and three months after the initial procedure. Successful treatment was defined as complete resolution of all calculous material as demonstrated on the imaging study.

The success rate was 93.6 percent in the endourologic group and 90.1 percent in the lithotripsy group. Stone size was not a factor in the success rate in the endourologic group. However, in the lithotripsy group, the stone-free rate was 93.5 percent in the patients with stones less than 1 cm in size and 66.6 percent in the patients with stones greater than 2 cm.

The length of hospitalization was shorter in the lithotripsy group than in the endourologic group. However, retreatment was necessary in eight (11.2 percent) of the patients in the lithotripsy group, while retreatment was unnecessary in the patients in the endourologic group. Better results were obtained with lithotripsy for stones located in the upper and middle region of the ureter if the stones were less than 1 cm in size, while better results were obtained in the endourologic group for stones located in the lower and middle region of the ureter if the stones were greater than 1 cm in size.

The authors conclude that in sity treatment of upper ureteral calculi with extracorporeal shock-wave lithotripsy has a high success rate. Fewer complications and a shorter hospital stay were associated with the use of lithotripsy for calculi in the mid-ureteral area, but the retreatment rate was higher than in the endourologic group. Lower ureteral calculi should be treated endoscopically. (Journal of Urology, July 1991, vol. 146, p. 5.)

COPYRIGHT 1991 American Academy of Family Physicians
COPYRIGHT 2004 Gale Group

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