If you don't know about these rare causes of retention, you won't think to ask the relevant questions. Missing the diagnosis
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in such cases can have profound implications for the patient (and for you!). One should have a low threshold for arranging an urgent magnetic resonance imaging (MRI) scan of the thoracic, lumbar, and sacral cord, and of the cauda equina in patients who present in urinary retention with these additional symptoms or signs.
Risk Factors for Postoperative Retention
Postoperative retention may be precipitated by instrumentation of the lower urinary tract; surgery to the perineum or anorec-tum; gynaecological surgery; bladder overdistention; reduced sensation of bladder fullness; preexisting prostatic obstruction; and epidural anaesthesia. Postpartum urinary retention is not uncommon, particularly with epidural anaesthesia and instrumental delivery.
Urinary Retention: Initial Management
Urethral catheterisation is the mainstay of initial management of urinary retention. This relieves the pain of the overdistended bladder. If it is not possible to pass a catheter urethrally, then a suprapubic catheter will be required. Record the volume drained—this confirms the diagnosis, determines subsequent management, and provides prognostic information with regard to outcome from this treatment.
IS IT ACUTE OR CHRONIC RETENTION?
There is a group of elderly men who are in urinary retention, but who are not aware of it. This is so-called high-pressure chronic retention. Mitchell (1984) defined high-pressure chronic retention of urine as maintenance of voiding, with a bladder volume of >800 mL and an intravesical pressure above 30 cm H2O, often accompanied by hydronephrosis (Abrams et al. 1978, George et al. 1983). Over time this leads to renal failure. The patient continues to void spontaneously and will often have no sensation of incomplete emptying. His bladder seems to be insensitive to the gross distention. Often the first presenting symptom is bed-wetting. This is such an unpleasant and disruptive symptom that it will cause most people to visit their doctor. In such cases inspection of the abdomen will show gross distention of the bladder, which may be confirmed by palpation and percussion of the tense bladder.