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Urolithiasis (urinary stone) is the most common reason for non-obstetrical abdominal pain in pregnant women. This occurs in almost one in 1,500 pregnant women. The stones occur in the ureter twice as often as in the kidney and affect both ureters in equal frequency. Almost 80 to 90 per cent urinary stones are diagnosed after the first trimester. Urolithiasis in pregnancy is often a diagnostic and therapeutic challenge; reasons include potential adverse effects of anaesthesia, radiation and surgery. There are some specific changes that occur during pregnancy that may affect the urinary tract leading to increased chances of problems with already present urinary stones. These changes can also increase the chance of formation of kidney stones. Also, later in pregnancy, the size and position of uterus can restrict the outflow of urine. The ureters get dilated in pregnancy and may not eliminate urine as efficiently and this may lead to hydronephrosis. The ureters increase in size (approx. 1 cm) due to increased renal vascular and interstitial volume during pregnancy. The collecting system and ureters also decrease their ability to contract, resulting in dilation and sometimes pain. The big concern of dilation is stagnant urine. If the urine is not fully eliminated, stone or infection can occur. These changes usually occur in the second trimester and subside after delivery. Also, during pregnancy the body tends to handle calcium less effectively, thereby leading to onset of kidney stones. Urinary tract infection, commonly seen during pregnancy, may also contribute to development of kidney stones. The need of the body for water also increases during pregnancy. Lack of fluid intake may lead to dehydration and contribute to kidney stone formation. Most of the stones (70-80 per cent) pass spontaneously with conservative treatment. However, if the stone does not pass, it may initiate premature labour, produce intractable pain, cause urinary tract infection, or interfere with the progress of normal labour. Investigating the renal stone during pregnancy is very difficult. X-rays are contraindicated. Renal ultrasonography is the first-line screening test for urolithiasis in pregnant patients. However, ultrasound doesn't always show the presence of stones. A urine test should be performed, but not all kidney stone problems will show up in urine. Intravenous pyelography (IVP) or CT scan is done in complex cases only. Ideally, no ionising radiation is to be used in the first or second trimesters. MRI has limited utility in such cases. Treatment of urinary stones in pregnancy ranges from conservative management (bed rest, adequate fluid intake, medications) to more invasive measures (stenting, ureteroscopy, percutaneous nephrolithotomy (PCNL). Extracorporeal shock wave lithotripsy (ESWL) is totally contraindicated during pregnancy. Surgical options are severely limited. Often, stent is placed, but it must be left for the remainder of pregnancy. Any type of manipulation in the bladder, pelvis, ureter or kidney could result in premature labour. With appropriate diagnosis and management, the outcome for both the mother and baby is usually good. — The writer is chairman and managing director, RG Stone Urology & Laparoscopy Hospital, New Delhi
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