Urological Emergencies in Clinical Practice стр.117

Radiation doses of <100mGy are very unlikely to have an adverse effect on the fetus (Hellawell et al. 2002). In the United States, the National Council on Radiation Protection (NCRP) has stated, 'Fetal risk is considered to be negligible at <50 mGy when compared to the other risks of pregnancy, and the risk of malformations is significantly increased above control levels at doses >150mGy' (NCRP 1997). The American College of Obstetricians and Gynecologists (ACOG) has stated, 'X-ray exposure to

TABLE 8.1. Fetal radiation dose after various radiological investigations

Procedure

Fetal dose mGy (mean)

Risk of inducing fetal cancer (up to age 15 years)

KUB x-ray

1.4

IVU 6 shot

1.7

1 in 10,000

IVU 3 shot

   

CT—abdominal

 

CT—pelvic

 

Fluoroscopy for

0.4

1 in 42,000

JJ stent insertion

   

CT, computed tomography; IVU, intravenous urogram; JJ stent; KUB, kidney and urinary bladder.

8. URETERIC COLIC IN PREGNANCY 153

<50 mGy has not been associated with an increase in fetal anomalies or pregnancy loss' (ACOG 1995).

While these recommended maximum radiation levels are well above those occuring during even computed tomography (CT) scanning, and a dose of 50 mGy or less is regarded as safe, understandably there is a concern that any radiation dose exposes the fetus to some risk. For this reason every effort should be made to limit exposure of the fetus to radiation, to use alternative imaging tests where possible, and to minimise radiation exposure during treatment by JJ stent insertion or ureteroscopy. However, the pregnant woman may be reassured that the risk to her unborn child as a consequence of radiation exposure is likely to be minimal.

Investigations or treatment that involve exposure to ionizing radiation should not be withheld because of an unjustified fear of damaging the fetus. The risks associated with irradiating the fetus have to be balanced against the risks of missing the diagnosis of a stone obstructing the ureter and the difficulties and potential dangers of performing JJ stent insertion or ureteroscopy without the use of any (ionising radiation) imaging. While ureteroscopy can be performed without fluoroscopy (Rittenberg and Bagley 1988), most urologists nowadays perform the majority of their ureteroscopic work under fluoroscopic control, and may feel uncomfortable doing otherwise in a case that, as it involves a pregnant woman and an unborn baby, is already high risk. It is worth remembering that the radiation dose during fluoroscopy for JJ stent placement is very low (on the order of 0.4 mGy, and up to a maximum of 0.8 mGy) and that the dose used to assist ureteroscopy is likely to be little more than this.


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