6.3.4 Urinary Stones
Stones（calculi）may form in any part of the urinary tract（urolithiasis），but most arise in the kidney，a condition called nephrolithiasis.The stones generally form in the kidney and may move to the bladder.These stones may increase in size and obstruct urinary structures.If they lodge in the ureters，they cause intense throbbing pain called renal colic.Because urine is hindered from passing into the bladder，it flows backward（refluxes）into the renal pelvis and the tubules，causing them to dilate（hydronephrosis）.
Urolithiasis may be related to infection，irritation，diet，or hormone imbalances that lead to an increased level of calcium in the blood.Most urinary stones，or calculi，are formed of calcium salts，but they may be composed of other materials as well.Causes of stone formation include dehydration，infection，abnormal pH of urine，urinary stasis，and metabolic imbalances.Because they are radiopaque，stones can usually be seen on simple radiographs of the abdomen.Stones may dissolve and pass out of the body on their own.If not，they may be removed surgically in a lithotomy，or by using an endoscope.External shock waves are used to crush stones in the urinary tract in a procedure called extracorporeal（outside the body）shock wave lithotripsy.For larger stones，it may be necessary to break them into smaller pieces using an endoscope fitted with a laser beam before the fragments are removed.This procedure is called ureteroscopic stone removal，in which no incision is required.
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Task 6 Select the best answer according to the text.
1.Urolithiasis may be caused by all of the following conditions except________.
A.infection
B.urinary stasis
C.hormone imbalances
D.allergy
2.The term“lithotripsy”means________.
A.crushing of stone
B.formation of stone
C.measurement of stone
D.removal of stone
3.The word“lodge”probably means________.(https://www.daowen.com)
A.move
B.stuck
C.flow
D.drop
4.Formation of stones in kidneys might induce all of the following conditions except________.
A.a decreased level of calcium in the blood
B.renal colic
C.dilation of the renal pelvis
D.obstruction of urinary structures
5.________might be used to crush the stones in the urinary tract.
A.Endoscopy
B.Antibiotics
C.External shock waves
D.Physical exercise