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Question 13#

The following are true of non-metallic ureteric stents, except:

a. They may encrust within a few weeks in patients with cystinuria and in pregnancy
b. They may be inserted to relieve obstruction in patients with pyonephrosis secondary to a proximal ureteric stone
c. Complications include encrustation and ureteric reflux
d. Indwell time should not exceed six months
e. Alpha-blocker medication has been shown to reduce stent symptoms

Correct Answer is D

Comment:

Answer D

Ureteric stents may be used to relieve ureteric obstruction or be inserted prophylactically where obstruction is anticipated; for example, prior to ESWL for large (>2 cm) renal stones or after ureteroscopy. Indications for stenting following ureteroscopy may be remembered using the acronym SPOILED (Solitary kidney, Perforated ureter, Obstructed kidney/Oedema, Infection, Large residual stone burden, Elective second procedure anticipated, Dilatation of ureteric orifice to more than 10 F).

Pyonephrosis may be relieved with either a ureteric stent or percutaneous nephrostomy (PCN). One of the advantages of PCN is that it may be inserted under local anaesthesia thereby obviating the  need for general anaesthesia in a patient who may be unstable due to sepsis or hyperkalaemia. That said, some clinicians will place stents without a GA, especially in women. Furthermore, a PCN may require less instrumentation of the urinary tract and reduce the risk of exacerbating sepsis. On the other hand, PCN requires the skills of an experienced interventional radiologist and where this expertise is not available a retrograde stent inserted by an experienced urologist may be a better option. The literature to date supports both methods of decompression.

Pearle randomised 42 patients with obstructing ureteric calculi to either PCN or retrograde ureteric stent. There were no significant differences in time to resolution of fever or white cell count. There was one failed PCN which was salvaged with a retrograde stent. Length of stay was longer for PCN but ureteric stent was twice as expensive. In another randomised controlled trial Mokhmalji found that PCN was superior to retrograde ureteric stent insertion. Failure rate was lower (0% vs. 20%), need for prolonged antibiotic therapy was reduced and PCN dwell time was less than for retrograde stents.

Ureteric stents may encrust rapidly in susceptible individuals but some may be left in-situ for one year; for example, the Percuflex® stent.

A systematic review and meta-analysis of five randomised placebo-controlled trials that included 461 patients suggested that administration of alpha-blockers reduced urinary symptom and body pain scores in patients with ureteric stents.