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Urinary tract obstruction and its relief
History and examination (including PR in both genders) is essential. Apart from patients with paraplegia, most patients with acute retention are well aware of the problem. Catheterisation usually relieves urethral obstruction (full bladder on palpation and gentle percussion), but occasionally suprapubic catheterisation may be necessary.
Patients with ureteric obstruction may present with rather non-specific back pain and the diagnosis should be considered in all oliguric patients without another obvious cause. Ultrasound is usually diagnostic, and treatment involves either surgical or percutaneous radiologically guided tube decompression.
Perspective: complications following relief of obstruction
Haematuria.
The shrinking wall of a chronically distended bladder may bleed, leading to rather alarming frank haematuria, which rarely may be exsanguinating. This usually clears within a day or so, and the management is supportive – transfusion is sometimes required. There are recommendations to relieve obstruction by gradual emptying of the bladder (release a certain volume, clamp for a while and then release a bit more) but the evidence that this makes a difference, although very weak, does not provide much support for the practice1 It is probably reasonable to consider emptying a massively distended chronic bladder retention in stages, but worry less about doing this for acute retention.
Hypotension and sodium balance
The other problem is hypotension and sodium shifts related to volume and salt loss from the post-obstructive diuresis. This is multifactorial, with proposed mechanisms including osmotic diuresis (urea), saline diuresis and nephrogenic diabetes insipidus. By the time the situation is recognised, considerable metabolic chaos may have arisen, either because of practically no replacement therapy, or because of replacement with inappropriate fluids. Check the electrolytes regularly and manage appropriately. Saline replacement is a good start.
Wu M-Y, Chang J-R, Lee Y-K, Lin P-C, Tsai T-Y. The Effect and Safety of Rapid and Gradual Urinary Decompression in Urine Retention: A Systematic Review and Meta-Analysis. Medicina. 2022; 58(10):1441. https://doi.org/10.3390/medicina58101441 ↩