There is no need to encourage the patient to drink copious amounts of fluids or to give them large volumes of fluids intravenously, in the hope that this will 'flush' the stone out. Renal
3. NONTRAUMATIC RENAL EMERGENCIES 27
blood flow and urine output from the affected kidney will tend to fall during an episode of acute partial obstruction due to a stone, and any excess fluid that is excreted will tend to cause a greater degree of hydronephrosis in the affected kidney, which will make ureteric peristalsis even less efficient than it already is. Remember, peristalsis, the forward propulsion of a bolus of urine down the ureter, can occur only if the walls of the ureter above the bolus of urine can coapt, i.e., close firmly together. If they cannot, as occurs in a ureter distended with urine, the bolus of urine cannot move distally. This is why insertion of a percutaneous nephrostomy tube can restore efficient peristalsis. By draining the hydronephrosis and hydroureter, it allows the ureteric wall to coapt and thus encourages a return to normal peristaltic function.
In many instances, small ureteric stones pass spontaneously given a period of 'watchful waiting' with analgesic supplements for exacerbations of pain. Accurate determination of stone size (on plain abdominal x-ray if the stone is so visible or by CTU) can help predict the chances that the stone will pass out of the ureter and into the bladder; 95% of stones measuring 5 mm or less pass spontaneously (Segura et al. 1997). However, it never ceases to amaze us that stones much larger than 5 mm do, from time to time, drop harmlessly out of the ureter, and that others that are only 4 mm in diameter stubbornly remain in the ureter.
Whether patients opt for watchful waiting or active intervention will, to a certain extent, depend on other factors, such as their job. Young, active patients may be very keen to opt for surgical treatment because they need to get back to work or their child-care duties, whereas some patients will be happy to sit things out. Discuss the options with patients so they are able to make a rational decision.