The incidence of gallstones in pregnancy has been reported to be 4% to 12% (1).  Choledocholithiasis requiring therapeutic intervention during pregnancy is rare, estimated at one in 1200 deliveries (2).  However, choledocholithiasis may lead to cholangitis and/or gallstone pancreatitis, both of which can be detrimental to the health of both the mother and the fetus.  For example, gallstone pancreatitis is associated with maternal and fetal mortality rates of up to 15% and 60%, respectively (3).

Open cholecystectomy and common bile duct exploration have been reported in older series to carry a high risk of fetal loss (2).  More recent case series have shown that laparoscopic cholecystectomy carries a significantly decreased risk of spontaneous abortion in the first trimester and pre-term labor in the third trimester, though it is advocated that laparoscopic cholecystectomy should be performed either in the second trimester or early in the third (1, 2) (Visual 1).  There have been case reports describing management of choledocholithiasis during pregnancy by performing magnetic resonance cholangiography, followed by laparoscopic common bile duct stone removal or laparoscopic cholecystectomy if the common bile duct is free of filling defects (4).

The most commonly reported management in the literature, however, has been endoscopic retrograde cholangiopancreatography (ERCP).  This was first reported by Baillie et al. in 1990, who described five pregnant women with choledocholithiasis who underwent ERCP with endoscopic biliary sphincterotomy for choledocholithiasis and went on to have normal babies (5).  Several other case series have subsequently demonstrated that ERCP can be safely and successfully performed during any trimester of pregnancy (Visual 2) (6).  The largest series (7) included 23 pregnant women at six different centers who underwent 29 ERCPs (15 in the first trimester, 8 in the second, and 6 in the third).  Indications were choledocholithiasis in 19 patients, cholestasis in two, and recurrent pancreatitis in two.  Fifteen patients underwent biliary sphincterotomy, and four underwent biliary stent placement.  Long-term follow-up showed two elective abortions, one unrelated spontaneous abortion, and one infant death 26 hours after delivery after three ERCPs for pancreatic stent placement, each complicated by pancreatitis.  Tham et al. (2) reported on 15 pregnant women who underwent ERCP (one in the first trimester, 5 in the second, and 9 in the third).  Indications were gallstone pancreatitis in 6 patients, choledocholithiasis on ultrasound in 5, elevated liver enzymes and a dilated common bile duct on ultrasound in 2, abdominal pain and gallstones in one patient, and chronic pancreatitis with intractable pain and a pseudocyst on magnetic resonance imaging in one.  Findings and outcomes are outlined (Visual 3).  Labor did not occur within one month of any ERCP, and all who had delivered by the time of the study (11 out of 15) had healthy babies.  The mean fluoroscopy time was 3.2 minutes (range 1.1-6.1 minutes).  The estimated average fetal radiation dose was 310 ± 164 mrad (range 102-577 mrad).  The most recently published study (6) involved 17 pregnant women who underwent ERCP for gallstone pancreatitis (10 patients), choledocholithiasis (5 patients), and cholangitis (2 patients).  The mean gestational age was 18.6 weeks (range 5-33 weeks).  All underwent sphincterotomy.  Complications included post-sphincterotomy bleeding controlled with hemo-clip placement in one patient and mild post-ERCP pancreatitis in one patient.  Preeclampsia developed in two patients in the third trimester, and labor was induced in both.  Thirteen of the 15 patients who delivered were confirmed to have healthy babies (one was still pregnant at the time of publication, and the other was lost to follow-up).  Mean fluoroscopy time was 14 seconds (range 1-48 seconds), and estimated mean fetal radiation dose was 40 mrad (range 1-180 mrad).     
 

Kahaleh et al. demonstrated a correlation between fluoroscopy time and estimated fetal radiation exposure, but the correlation was not entirely linear (Visual 4).  However, all radiation doses were within 200 mrad at fluoroscopy times within one minute. 

There is agreement that radiation exposure to the fetus should be minimized by shielding the pelvis and lower abdomen with lead, minimizing fluoroscopy time, and obtaining hard copy radiographs only when essential, i.e., for a cholangiogram after direct cannulation of the common bile duct with a sphincterotome and aspiration of bile to verify position.  However, some have advocated eliminating radiation exposure altogether by cannulating the common bile duct with a sphincterotome over a guidewire that can be fixed in place, performing sphincterotomy, exchanging the sphincterotome for an extraction balloon catheter over the guidewire, and sweeping the bile duct without a cholangiogram to extract any stones (3).  This technique obviously provides no knowledge of the anatomy of the ductal system and whether all stones have been delivered.

Most do advocate that biliary sphincterotomy and stone extraction be performed rather than biliary stent placement, as this obviates the need for a second procedure and, without the introduced risk of stent occlusion, may be associated with a lower probability of cholangitis.  It should, however, be noted that Farca et al. placed 10-French biliary stents without sphincterotomy in ten patients, all of whom had uncomplicated pregnancies (8).  All underwent repeat ERCP with stent extraction and sphincterotomy post-partum; eight had stones extracted.  In two patients the stent remained in place for 7 and 8 months, respectively, without the development of cholangitis.

Potential risks to the fetus from specific medications should also be factored (9). Meperidine is category B and does not appear to be teratogenic.  It is preferred over fentanyl (category C), which is embryocidal in rats but does appear safe in humans in low doses.  Benzodiazepines, including midazolam, are considered category D; midazolam, however, has not been associated with congenital abnormalities and is preferred when sedation with meperidine is inadequate.  Propofol, glucagon, and topical anesthetics are considered category B.                

Patient positioning for ERCP is dependent on the time of pregnancy at which it is performed.  The patient may have difficulty maintaining a prone position when she is in the second or third trimester of pregnancy.  In this situation, the procedure may need to be performed with the patient in the left lateral position.  It is advised that the patient not be completely supine, as the gravid uterus can compress the great vessels and cause maternal hypotension and decreased placental perfusion (9).  However, all patients in the study by Kahelah et al. underwent ERCP while supine, which did not appear to adversely affect the outcome of pregnancy.

As amniotic fluid can conduct electrical current to the fetus, the uterus should not lie in between the sphincterotome and the grounding pad (9). 

Our patient underwent ERCP for symptomatic choledocholithiasis.  She was placed in the prone position at a slight left lateral tilt during the procedure.  Her pelvis and lower abdomen were shielded with lead.  The common bile duct was directly and deeply cannulated with a short-nose traction sphincterotome pre-loaded with a guidewire.  The guidewire was passed into the bile duct, and a biliary sphincterotomy was performed over the guidewire.  The sphincterotome was then exchanged for an adjustable 15 mm extraction balloon catheter.  A partial occlusion cholangiogram was then obtained which showed an 8 mm filling defect in the distal common bile duct.  Balloon sweep readily delivered the stone.  No further filling defects were seen on repeat occlusion cholangiogram.  Total fluoroscopy time was 13 seconds.  A total of 1 mg of midazolam and 100 mg of meperidine was administered.  Fetal monitoring was normal both before and after the procedure.  The patient underwent uncomplicated laparoscopic cholecystectomy two days later and was discharged on the following day.