Indications for Intervention to Relieve Obstruction and/or Remove the Stone
1. Pain that fails to respond to analgesics, or that initially does so but then recurs and cannot be controlled with additional pain relief, is an indication for drainage of the kidney (by JJ stent insertion or percutaneous nephrostomy) or emergency definitive treatment of the stone.
2. Where there is an associated fever, one should have a low threshold for draining the kidney, and this is usually done by percutaneous nephrostomy.
3. Where renal function is impaired because of the stone (solitary kidney obstructed by a stone, bilateral ureteric stones,
28 J. REYNARD
or preexisting renal impairment that gets worse as a consequence of a ureteric stone), the threshold for intervention is lower.
4. Obstruction unrelieved for >4 weeks can result in long-term loss of renal function. In a study of 239 patients presenting with unilateral ureteric stones, after 2 weeks the stones were still present in 143 patients (Holm-Nielsen et al. 1981). Of these 143 patients, 50% had renal obstruction defined by isotope renogra-phy; 11 of 31 patients (35%) with obstruction for >4 weeks developed varying degrees of irreversible renal damage. The problem with current imaging for stones, which nowadays is essentially CTU, is the absence of any information on the presence of renal obstruction (most urologists do not routinely obtain isotope renograms in patients with ureteric colic). However, what we do know from the Holm-Nielsen study is that only 50% of patients with ureteric stones that are still present at 2 weeks, have reno-graphic evidence of obstruction. It seems reasonable to limit the period of watchful waiting for spontaneous stone passage to approximately 4 weeks and to intervene to remove the stone or drain the kidney (by, for example, JJ stent placement) if it has not passed at this time.
5. Personal or occupational reasons. As stated above, some patients will not be able to wait for spontaneous stone passage and therefore may accept the risks associated with active intervention. The classic example would be the airline pilot who is unable to fly until he is stone free.