Renal calculi are the most common cause of urinary obstruction. A renal calculus is a concentration of various mineral salts in the renal pelvis or the cuplike extension of the renal pelvis called the calyx of the kidney or elsewhere in the urinary tract. They can be small like a grain of sand or very large. Most stones develop in the kidney and are formed from calcium salts, uric acid, cystine, and struvite in descending order of frequency.
Renal calculi form as a result of a disturbance in the kidney’s delicate balancing act of preventing water loss while at the same time eliminating watersoluble mineral wastes. Many factors, such as prolonged dehydration or immobilization, can upset this balance. The balance also may be upset by underlying diseases, such as gout, hyperparathyroidism (disease caused by oversecretion of the parathyroid glands), Cushing syndrome, or urinary tract infections and neoplasms. A person may develop renal calculi because of an excessive intake of vitamin D or dietary calcium. The condition appears to be genetic for certain types of stones, with men much more commonly affected than women. In many instances, no specific cause can be pinpointed.
FIGURE. Location of calculi in the urinary tract.
Signs and Symptoms
A person having renal calculi may remain asymptomatic for long periods. If a stone or calculus fragment lodges in a ureter, however, the individual may complain of intense flank pain and urinary urgency. Classic ureteral colicky pain is manifested by acute, intermittent, and excruciating pain in the flank and upper outer quadrant of the abdomen on the affected side. If calculi are in the renal pelvis and calyces, the pain is duller and more constant. Back pain and severe abdominal pain may occur. Other presenting symptoms include nausea, vomiting, chills and fever, hematuria, and abdominal distention.
The history may reveal a familial tendency toward the formation of kidney stones. A urinalysis may be ordered to detect elevated levels of RBCs or WBCs in the urine or to check for the presence of protein, pus, and bacteria. CT scan and abdominal x-ray (or KUB) may be ordered to determine the locations of calculus formation. A noncontrast spiral CT scan of the ureters and kidneys is the preferred test for kidney stones. In this test, the scanner moves in a circle as the client moves through the machine. This test takes less time than a standard CT scan and provides better images of the kidneys and ureters. Blood testing may be helpful in confirming imbalances of minerals or the existence of other metabolic disorders.
Treatment is directed at clearing obstructive stones and preventing the formation of new ones. Increased fluid intake (greater than 3 L/day) may enhance elimination of stones in some cases, but large stones may require surgical intervention, especially if renal function is threatened. Ureteroscopic removal with the use of fluoroscopic guidance may be used to dilate the ureter to grasp and remove the stone. Techniques such as ultrasonic percutaneous lithotripsy and extracorporeal shock wave lithotripsy pulverize stones in place, allowing them to be passed in the urine or removed by suction. Lithotripsy via a ureteroscope can also be used to remove urethral stones. Antibiotics may be prescribed if it is determined that the calculus buildup is due to bacterial infection. Analgesics may be necessary for the relief of intense pain.
Complementary practitioners recommend drinking 8 or more glasses of water per day and eating a diet high in fiber and low in fat, with reduction of red meat consumption. Vitamins and minerals may be helpful especially when coordinated with the primary care provider. Relaxation techniques may be beneficial to deal with the pain.
Stress the importance of proper diet and completing any medicinal therapy. Explain any diagnostic or surgical procedures to clients. Encourage increased fluid intake.
The prognosis is good if urinary tract obstruction is prevented and underlying disorders are promptly treated. However, about 60% of people who have a calcium stone have further stone formation later.
An adequate daily fluid intake is the best way to minimize the chance of stone formation, especially among individuals at risk. Fruit juices, especially unsweetened cranberry and blueberry juice, help acidify urine and may help prevent the formation of renal calculi.