Over the years, the development of a detrusor pressure above 40 cm H₂O has been accepted as dangerous for the upper urinary tract. Studies have shown deterioration of renal function and complication development in groups with cystometric pressure above 40 cm H₂O [9]. But some caution is needed. It still has to be evaluated how important the time is that pressure remains above 40 cm H₂O, if repeated high pressures from overactive contractions are as harmful as high pressure from low compliance, and how UDT tracings represent what happens in the LUT in daily life. Figure 7.1 gives some tracings of pressure change during cystometry. It is uncertain which is the most dangerous, though one may assume the danger C > B > A. This has however not been studied.