Evaluation of bladder emptying disorders

The evaluation of bladder emptying disorders is a urodynamic assessment specifically directed at the analysis of the voiding phase. It aims to identify the cause of difficulties in expelling urine, which may be related to a mechanical obstacle (obstruction), a lack of contraction strength of the bladder (detrusor underactivity) or a disorder of coordination between the bladder and the sphincter (dyssynergia). Bladder outlet obstruction is the most common cause in men, mainly related to benign prostatic hyperplasia or urethral strictures. It is characterised by high detrusor pressure combined with a low flow rate. The pressure-flow study is the key test for confirming the diagnosis and quantifying the degree of obstruction. Detrusor underactivity manifests as insufficient contraction pressure and a low flow rate. It may be of neurological origin (diabetes, neuropathy), drug-related or linked to ageing. Its diagnosis is essential because it contraindicates certain deobstruction operations that could worsen the retention. Detrusor-sphincter dyssynergia, common in neurological conditions, combines a contraction of the detrusor with a paradoxical contraction of the sphincter during voiding. Its diagnosis relies on the combination of cystometry and perineal electromyography. Management involves self-catheterisation, sphincteric botulinum toxin or neuromodulation.