Nephrostomy urinary diversion is widely available (Fig. 8.3), can be done rapidly, provides good pain relief, drains infected urine if present, and has a low risk of inducing miscarriage or preterm labour (Kavoussi et al. 1992). These advantages must be weighed against the fact that there is a small risk (in the order of 1%) of heavy bleeding, requiring embolisation and/or blood transfusion during nephrostomy insertion, and of septicaemic shock occurring after insertion (2-4%; Ho and Cowan 2002, Ramchandani 2001) (see Chapter 10). Furthermore, the nephros-tomy tube may be required for some months, particularly when it is inserted at a relatively early stage in the pregnancy. It can be uncomfortable, may block or become infected, and may need to be changed several times during the remaining pregnancy.
JJ stents overcome some of the problems of nephrostomy tube drainage. They can be placed under local anaesthetic or with light sedation with low doses of pethidine and diazemuls using either ultrasound guidance or limited periods of fluoroscopy (Hellawell et al. 2002, Stothers et al. 1992) (see Chapter 10). They
8. URETERIC COLIC IN PREGNANCY 157
FIGURE 8.3. Nephrostomy urinary diversion.
are an effective way of managing the pain of obstructing stones. They may be a more comfortable form of urinary diversion than percutaneous tube drainage, though many patients develop 'stent symptoms' (frequency, urgency, and bladder pain), which can be so bothersome that in some cases the stent has to be removed (Hellawell et al. 2002).
158 J. REYNARD
In two series totalling 20 pregnant women who underwent JJ stent placement (all under local anaesthetic or with sedoan-algesia), at between 6 to 36 weeks' gestation (mean 31 weeks), there were no cases of premature labour (Hellawell et al. 2002, Stothers et al. 1992).
The hypercalciuria of pregnancy may make stent encrustation and blockage more likely, and as a consequence it has been suggested that stents should be changed every 6 to 8 weeks to prevent the occurrence of blockage from encrustation (Kavoussi et al. 1992). However, in a contemporary series where stent insertion was performed at an average of 28 weeks of gestation for obstructing ureteric stones, stent replacement was not required in any patient (Hellawell et al. 2002), and in a slightly older series, only 1 of 13 stents required replacement because of ongoing pain (presumably indicating obstruction) (Stothers et al. 1992). It may well be, therefore, that regular stent changes, at least when using contemporary stents, are not required. Avoiding the need to change JJ stents is clearly desirable, as this is technically more challenging than replacing a percutaneous nephrostomy tube (though the difficulty of placement and replacement depend on the availability of local expertise). Therefore, one might be more inclined to recommend nephrostomy tube drainage in very early pregnancy, rather than a JJ stent where frequent changes of the latter might, at least in theory, be required throughout the remaining pregnancy (Denstedt and Razvi 1992).